CT OF SEVERAL FACTORS ON WHITENESS OF CUCUMBER PICKLE TlSSUE. THE EFFE Thesis for the Degree of Ph. D. MECHIGAN STATE UNWERSITY Paui Joseph Feilers 1964 [HESIS Ill!IllllI/lllflfllllllfllIll/WWII!!! Ill/lllllllllll g 3 12 3 10457 6305 This is to certify that the thesis entitled THE EFFECT OF SEVERAL FACTORS OH l-IIIITEIESS OF CUCUl-IBER PICKLE TISSUE presented by Paul Joseph Fellers * has been accepted towards fulfillment oi the requirements for P11.D. degree in Food Science Date November 30, 1964 0-169 LIBRARY Michigan State University ABSTRACT THE EFFECT OF SEVERAL FACTORS ON WHITENESS OF CUCUMBER PICKLE TISSUE by Paul Joseph Fellers Studies were made to determine the effect of several factors on loss of whiteness or deve10pment of translucency in cucumbers and their manufactured products. Loss of flesh whiteness was shown to vary directly with the loss of entrapped intercellular gas. At some low critical amount of gas left in the tissue, total translucency to the eye was found to result. Loss of tissue gas was attributed to many factors, most of which would in some manner affect permea- bility or porosity of the tissue. Tangible factors found to aid in the desirable preservation of flesh whiteness of fresh pickles included: blanching whole cucumbers, not blanching cut cucumbers, maintaining in—the-jar vacuums and pressures as close to atmospheric pressure as POSSibleI presence of sucrose and acetic acid in covering liquids, limited use of sodium chloride in covering liquids, adequate pasteurization to prevent spoilage and inactivate pectino- lYtic enzymes, avoiding regular refrigerated storage or refriger" ated controlled atmosphere storage of raw fruit if possible and Paul Joseph Fellers :if fruit are refrigerated use of the fruit as soon as {Massible after removal from storage, use of cool storage temperatures for in-the—jar pickles, and gentle handling of the raw product. Many of the mechanisms and probable mechanisms and relationships between several factors and their various effects on loss of whiteness from cucumber or pickle tissue are discussed. The roles of diffusion,solubility, buoyancy and amount of gas in cucumbers are discussed relative to loss of flesh whiteness. Photomicrographs clearly show cucumber tissue in various stages of translucency; other photographs show pictorially the effect of several factors on loss of flesh whiteness. THE EFFECT OF SEVERAL FACTORS ON WHITENESS OF CUCUMBER PICKLE TISSUE BY Paul Joseph Fellers A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Food Science 1964 ACKNOWLEDGMENTS The author is sincerely grateful to the many persons ‘who have helped in the preparation and presentation of this research. The author is especially indebted to his major professor, Professor I. J. Pflug, for inspiring guidance and generous sharing of a fine philosophy during the course of this investigation. Thanks are also extended to Professor C. L. Bedford (Food Science), Professor A. M. Pearson (Food Science), Professor L. W. Mericle (Botany and Plant PathologY), and Professor D. H. Dewey (Horticulture) for serving on the guidance committee. Grateful acknowledgment is also due Professor B. S. Schweigert, Chairman, Food Science Department and to the Michigan State University Agricultural Experiment Station for their interest and support of this program. The assistance of the Auntihnufs Foods,Division of the Borden Co., Croswell, Michigan; Dailey Pickle Co., Saginaw, Michigan; H. W. Madison Co., Medina, Ohio; Whitecap Co., Division of Continental Can Co., Inc., Chicago, Illinois; Brockway Glass Co., Brockway, Pennsylvania; and the Michigan State University Horticulture Department is gratefully acknowledged. ii The help and encouragement that only a wife can give during such an undertaking is acknowledged. This dissertation is dedicated to my mother and to the memory of my father who through their example instilled in their children the desire for knowledge. iii TABLE OF CONTENTS Page INTRODUCTION . . . . . . . . . . . . . . . . . . . . . 1 REVIEW OF LITERATURE . . . . . . . . . . . . . . . . . 3 Fresh-Pack Pickle Considerations . . . . . . . . . 3 Fermented Pickle Considerations . . . . . . . . . 6 Enzymatic Considerations . . . . . . . . . . . . . lO Histological and Microscopic Considerations . . . 13 Chemical Additive Considerations . . . . . . . . . l7 Nonenzymatic Oxidation Considerations . . . . . . 18 Anatomy of the Cucumber Fruit . . . . . . . . . . l9 EXPERIMENTAL PROCEDURE . . . . . . . . .-. . . . . . . 20 Raw Materials . . . . . . . . . . . . . . . . . . 20 Packing Procedure . . . . . . . . . . . . . . . . 20 Thermal Process . . . . . . . . . . . . . . . . . 22 Storage . . . . . . . . . . . . . . . . . . . . . 22 Product Evaluation . . . . . . . . . . . . . . . . 22 STUDIES CONDUCTED . . . . . . . . . . . . . . . . . . 23 I. Restatement of the Problem . . . . . . . . 23 II. Effect of Several Factors on Loss of Whiteness from Fresh Pickle Flesh: A General Preliminary Treatise . . . . . 26 III. Histological and Microscopic Examination of Raw and Processed Cucumber Tissue . . 29 IV. Effect of Blanching on the Curing of Pickling Cucumbers Made into Salt Stock . . . . . . . . . . . . . . . . . 37 V. Effect of Blanching Whole Cucumbers on Whiteness of Sweet Fresh Cucumber Slices and Spears . . . . . . . . . . . 42 VI. Effect of Blanching Cut Cucumbers on Loss of Tissue Whiteness . . . . . . . . 47 VII. Effect of Processing Temperature and Time and Storage Conditions on White- ness of Sweet Fresh Cucumber Spears . . 50 iv VIII. IX. XI. XII. XIII. XIV. XVII. XVIII. XIX. XX. XXI. Effect of Pasteurization on Loss of Gas from Pickle Tissue . . . . . . . Effect of Salt- Acid and Salt or Acid Only Covering Brines on Loss of White- ness from Fresh Pickle Flesh . . . . . A Study of the Diffusion Rate of Salt- Acid Brine into Whole Fresh Cucumber Pickles . . . . . . . . . . . . . . . Effect of Several Chemicals on Preservation of Whiteness of Fresh Pickle Flesh . . . . . . . . . . . . . Estimation of Gaseous Volume in Cucumber Tissue . . . . . . . . . . . . . . Actual Measurement of the Amount of Gas in Cucumber Flesh . . . . . . . . . . Studies on the Effect of Vacuum Infil- tration on Loss of Whiteness of Cucumber Tissue . . . . . . . . . . . A Study of the Relationship between Vacuum and Loss of Cucumber Tissue Gas Effect of In-the-Jar Vacuum on Loss of Flesh Whiteness from Fresh Pickle Products . . . . . . . . . . . . . . . Effect of Pressure in Excess of Atmos- pheric on Whiteness of Cucumber Flesh Storage of Pickling Cucumbers: Effect on Flesh Whiteness . . . . . . . . . . Effect of Storage Temperature and Time on Loss of Whiteness from Commercially Processed Fresh Sweet Cucumber Cross- cuts . . . . . . . . . . . . . . . . . Effect of Freezing on Raw Cucumber Tissue . . . . . . . . . . . . . . . Effect of Light on Whiteness of Fresh Pickle Flesh . . . . . . . . . . . . . GENERAL DISCUSSION . . . . . . . . . . . . . . . . SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . LITERATURE CITED . . . . . . . . . . . . . . . . . . Page 61 65 69 76 83 86 89 94 97 103 106 113 121 123 125 142 150 Table 10.1 11.1 11.2 LIST OF TABLES Effect of several variables on loss of whiteness from fresh pickle flesh Effect of blanch treatment on the curing and firmness of salt stock pickles (barrel fermentations) . . . . . . Effect of blanch treatment on the curing and firmness of pickles cured in 5 per cent salt brine at about BOOF (gallon jar fermentations) . . . . . . . . . Effect of blanching cut cucumber stock on loss of tissue whiteness in fresh pickle slices made from the blanched stock . . Whiteness evaluation of all sweet fresh pickle spear treatments . . . . . . . Effect of pasteurization and subsequent storage on loss of gas from raw and pasteurized pickle flesh . . . . . Development of translucency in fresh pickle slices in storage as affected by three covering liquids . . . . . . . . . The pathways of sodium chloride and acetic acid in pasteurized fresh whole pickles Effect of alum and calcium chloride on retention of flesh whiteness in fresh dill pickle slices stored at 75-850F . Effect of several chemicals on retention of flesh whiteness in fresh cucumber dill spears stored at 75—850F . . . . . vi Page 26 39 4O 48 52 62 67 7O 77 78 Table 11.3 12.1 13.1 14.1 14.2 14.3 15.1 16.1 17.1 18.1 Page Effect of adding pectinolytic enzyme inhibitor to covering brines to control translucency in fresh cucumber dill slices . . . . . . . . . . . . . . . . . . 81 An indication of the percentage of gas to be found in several localities of the cucumber . . . . . . . . . . . . . . . . . 84 A comparison of two methods for estimating gaseous percent of cucumber tissue . . . . 87 Estimated translucency in wedges of a slicing variety of cucumber exposed to one minute of vacuum infiltration with water, the vacuums progressing from 0 to 28 inches of mercury . . . . . . . . . . . 90 Effect of 2 minutes of 28 inches of mercury vacuum using different infiltration mediums on loss of whiteness, texture, and weight of raw cucumber tissue . . . . . 92 Development of translucency in cucumber tissue as a result of decreasing vacuum in a vacuum infiltration system at one minute intervals from a maximum of 28 inches of mercury . . . . . . . . . . . . . 93 Loss of gas from raw cucumber tissue as a function of the degree of vacuum applied . 94 Estimated percent of tissue translucency in fresh pickles as a function of initial in-the-jar vacuum and type of covering liquid . . . . . . . . . . . . . . . . . . 99 The effect of 15 pounds of air pressure for 5 and 15 minutes on loss of whiteness and texture of the flesh of a slicing variety of cucumber immersed in different cover— ing liquids and air . . . . . . . . . . . . 104 Degree of flesh translucency in fresh dill spears stored at room temperature for about six months after packing. Spears were prepared from SMR 15, number 3 size cucumbers taken out of CA storage . . . . . 108 vii Table Page 19.1 Effect of storage temperature and time on the loss of whiteness from commercially line-packed fresh sweet cucumber cross cuts . . . . . . . . . . . . . . . . . . . 114 viii Figure 3.1 3.4 3.5 LIST OF FIGURES Page Commercial fresh dill spears purchased from a local supermarket in September, 1963 and photographed then; packed in 1962 (left), in 1963 (right) . . . . . . . 25 Commercial fresh sweet spears purchased from a local supermarket in September, 1963 and photographed then; packed in 1962 (left), in 1963 (right) . . . . . . . 25 Fresh hand section of raw fleshy parenchyma tissue from a number 2,SMR 58 cucumber showing abundance of intercellular gas (dark areas) . . . . . . . . . . . . . . . 31 Fresh hand section of same tissue as shown ,in Figure 3.1 after vacuum infiltration. NOte intact cells and complete absence of gas. Tissue appeared translucent to the naked eye . . . . . . . . . . . . . . . . . 31 Fresh hand section of fleshy parenchyma tissue of 11 month old fresh dill pickle slice which showed nearly total trans- lucency to the naked eye. Note remnants of original intercellular tissue gas (dark areas) . . . . . . . . . . . . . . . 33 Hand drawn microscope fields of partially translucent raw cucumber tissue immersed in 15% salt brine for about 2 hours. Note intercellular gas (dark areas) and intercellular spaces no longer occupied by gas . . . . . . . . . . . . . . . . . . 33 Fresh hand section of the edge of the trans- lucent area (light area) beneath a spine spot and opaque white tissue having inter— cellular gas (dark area) . . . . . . . . . 34 ix Figure 3.6 5.1 Photomicrograph of central seed cavity tissue of a cucumber showing diverse tissue forms and characteristics (105x) . Cucumber slices showing opaque whiteness and translucency (curing) . . . . . . . Typical pickles fermented in gallon jars in 19° salometer salt brine for 11 days at about 80°F. Left: unblanched and most translucent or cured; center; blanched 6 min at 180°F; right; blanched 10 min at 180°F . . . . . . . . . . . . . Typical beneficial effect of blanch treat- ment on retaining whiteness of fresh sweet slices stored 2 years; unblanched (left), 5 min blanch at 160°F (right) . Typical beneficial effect of blanch treat- ment on retaining whiteness of fresh sweet spears stored 2 years$ unblanched (left), 5 min blanch at 160 F (right) . Unblanched (left) versus blanched for 2 min at 1800F in cut condition (right) packed in standard brine and stored 3 months at about 80°F . . . . . . . . . . . . . Typical results for nearly normal pasteuri— zation (left) versus overpasteurization (right) on flesh translucency after 16 months of 72°F storage . . . . . . . . . Development of translucency in fresh sweet pickle spears stored at 72°F as a function of pasteurization time at 180°F . . . . . . Development of translucency in fresh sweet pickle spears as a function of storage temperature. Heat processes of either 180°F for 25 min, 189°F for 20 min, or 198°F for 16 min can be applied to the data . . . . . . . . . . . . . . . . . . . Normal fresh dill spears (left) compared with typical microbiologically spoiled fresh dill spears (right) . . . . . . . . . . Page 34 36 41 44 44 49 54 55 58 60 Figure 10.1 10.2 10.3 11.1 11.2 15.1 16.1 18.1 Page An indication of the changes in in—the- jar pressures of commercially packed fresh pickles . . . . . . . . . . . . . . . 64 Development of translucency in slices covered with (left to right) 5% salt- l.4% acetic acid, 1.4% acetic acid, and 5% salt solutions after 3 months of about 80°F Storage . . . . . . . . . . . . 66 Diffusion of sodium chloride in fresh whole dill pickles . . . . . . . . . . . . . . . 71 Diffusion of sodium chloride and acetic acid from a covering brine into fresh whole dill pickles as measured in the brine . . . . . . . . . . . . . . . . . . . 72 Diffusion of acetic acid and sodium chloride from a covering brine into fresh whole dill pickles as measured in the pickle flesh . . . . . . . . . . . . . . . . . . . 73 Effect of adding 0, 100 and 500 ppm (left to right) sodium bisulfite to standard covering brine on development of trans— lucency after 81 days storage at about 80°F . . . . . . . . . . . . . . . . . . . 82 More severe bottom translucency than the top as a result of brine stratification: sodium bisulfite treated pickles (left), regular fresh sweet spears (right) . . . . 82 Gain in weight of cucumber tissue (an esti- mation of tissue volume occupied by gas) as a function of increasing vacuum infil- tration values . . . . . . . . . . . . . . 96 Effect of 5, l6 and 26 inches of initial in- the-jar vacuum (left to right respectively) on development of translucency after 3 months of about 80°F storage. Also note 1/4 in. cold-welded Copper tubing vacuum seals . . . . . . . . . . . . . . . . . . . lOO Severe spine spot deterioration as the re— sult of microbiological action during ex— cessively long refrigerated storage . . . . 109 xi Figure 18.2 18.3 18.4 19.1 19.2 19.3 19.4 Fresh dill spears made from cucumbers in refrigerated storage too long showing deep translucent areas beneath spine spots . . . . . . . . . . . . . . . Six month old fresh dill spears made from CA fruit, 10% C02 - 3% 02 (left), 5% C02 — 5% 02 (right) at 34oF for 4 weeks showing translucent areas beneath the spine spots . Six month old fresh dill spears made from CA fruit (5% C02 - 5% 02) stored 2 weeks at 40°F showing translucency resulting from not using cucumbers soon enough after removing from storage (right) com- pared with immediately used fruit (left) Quality of line-packed fresh sweet pickle slices stored at several temperatures for 19 months . . . . . . . . . . . . Quality of line—packed fresh dill pickle spears stored at several temperatures for 19 months . . . . . . . . . . Degree of translucency attained in com- mercially line-packed fresh sweet cucumber slices as a function of storage time and temperature . . . . . . . . . A graphic method of predicting the per- missible storage temperature and time to prOduce sweet cucumber slices of three levels or degrees of translucency xii Page 109 111 111 115 115 117 118 INTRODUCTION Prior to the middle 1930's, information of a scien- tific nature regarding the manufacture of fresh pickles (refers to products manufactured from cucumbers Cucumis sativis L.) was scanty. Fresh pickle products were probably made before that time, both in the home and industrially. But as Etchells and Jones (1951) have suggested, ". . . the details concerning manufacture were presumed to be based on a very secret process which certainly was not available to the industry as a group." The publication of a paper by Etchells (1938) on the rate of heat penetration in fresh pickles was the beginning of a scientific basis for the principles involved in the fresh pickle industry. Because of the large size of the fresh pickle pack (now comprising about 50 per cent of the entire pack in the state of Michigan) the problem of translucency or loss of whiteness associated with ageing of fresh-pack pickle products is great in magnitude. In the processed pickle pack (pickles made from salt stock), the pickles in their preparation have undergone a lactic acid fermentation under high salt conditions, result- ing in a "cured look" or totally translucent appearance. The cured look is accepted by consumers for processed fermented pickles, but when fresh-pack pickles, characterized by a bright white appearance, gradually lose their highly acceptable fresh appearance and start taking on a partially cured look, consumer preference is radically reduced. Each fall when both year old and new fresh pickles are available, quality extremes can often be seen on grocer's shelves. Even for the nondiscerning eye one may easily divide jars into quality categories of excellent—-those jars belonging to the then current summer's pack and poor-—those jars be- longing to the preceding year's pack. With a clearer understanding and knowledge gained through studies of the factors and mechanisms involved in the loss of whiteness in raw, salt-cured, and fresh pickles, it was hoped that optimum production conditions could be established for quality fresh cucumber pickles. These fresh pickles would be able to maintain desirable fresh whiteness characteristics for a maximum period of time after packing. Of course, texture (crispness), skin color, and other quality factors would be expected to retain their normal quality level. REVIEW OF LITERATURE Fresh-Pack Pickle Considerations One of the first references to consider the appear— ance of fresh-pack pickles was that made by Etchells (1938). He was describing the then relatively new pasteurized product as retaining ". . . the fresh characteristics over a period of several months' storage” as compared with unpasteurized pickles ". . . a clear, flabby, unpalatable product which has lost all of its fresh texture and appearance." Loss of whiteness phenomena in fresh pickles was early associated with storage of the product. Etchells and Goresline (1940), found no difference in general appearance of cucumber pickles in 68° to 76%?storage after 3 months, but noted that some of the slices lost some of their white- ness after 4 months. After 6 months there was a ". . tendency for the slices to take on a solid, translucent appearance denoting loss of air or whiteness." They ob- served further that during storage, loss of whiteness oc- curred in the slices from the center outward. The best heat process given the pickles was such that the contents of the jars maintained l60°F for 20 minutes. Nicholas and Pflug (1960) studied the effect of storage temperature on the quality of fresh pickles. ...,.~: A u.-on“‘ ‘. v..- ,_‘:r “cw. - . “vrey ‘ . ‘.->~%. .44 They stored three different fresh cucumber products at five storage temperatures ranging from 40 to lOOOF. A lucid description of the inside appearance of fresh cucumbers was given by Nicholas and Pflug as follows: "The inside surface of the cut, fresh cucumber is bright, white, and opague but under adverse conditions loses its brightness, becomes darker, and appears translucent. The property described here as translucent can also be called a cured look." The important observations from Nicholas and Pflug's (1960) study were that: 1. Storage at 40°F even after 388 days resulted in high quality pickles. 2. Deterioration followed more or less a set pattern for the storage temperature range 720 to 1000 with variation only in the rate of deterioration. This observation led to the presentation of a method de— signed by Nicholas and Pflug to be able to predict quality as a function of storage temperature. 3. The dill spears showed noticeable deterioration earlier than sweet spears, but darkening of the sweet spears was greater after 388 days. 4. Loss of texture was evidenced with increasing storage temperature and probably with storage time. 5. Darkening of the pickle product was more marked when the covering liquor contained sucrose. 6. It was deemed important to cool fresh pickle products rapidly and store them at the lowest practical temperatures (preferably under 72°F) for maintenance of high quality. The relation between final jar vacuum and loss of whiteness in fresh pickles was first shown by Etchells and Ohmer (1941) who ". . . consistently found that jars with a final vacuum somewhat in excess of 10 inches of mercury will lose their attractive whiteness and take on the appearance of cured cucumbers within a very short time after being opened (5 to 10 minutes)." They recommended that "[for manu- facturers] . . . the final vacuum obtained should be only sufficient for the adequate closure of the jar during pasteurization." The phenomena was explained on the basis of a gas exchange relationship. Etchells and Jones (1944) confirmed the above results. They illustrated jars of fresh pickle slices having vacuums of 9 and 15 inches; the jars were shown side by side unopened, after being Opened 10 minutes, and after being opened 2 hours. At the present time the industry attempts to regulate the manufacturing process so that the final vacuum is less than 10 inches (Valentine, 1963). Esselen and Anderson (1956) reported loss of white- ness or a "grayish appearance" in fresh pickles after 6 Inonths of storage; the pickles were manufactured from cucum— Ibers stored longer than 6 days at 35°F or room temperature '0 'u prior to packing. Esselen and Anderson further observed 35°F storage of the raw fruit as resulting in a greater amount of whiteness loss in the finished pickles. It should be noted that Long Green variety, a slicing or salad type, was uti- lized for all the tests. Furthermore, fruit was 5 days in transport before storage tests began. A relatively new concept in storing cucumbers for fresh pickle products has been described by Olthof (1959 and 1960) in Holland. The raw cucumbers were placed in 1aquered steel drums and covered with 25 grain (2.5 per cent) acetic acid. The drums were sealed, pasteurized for 60 min in a 185°F water bath, and cooled. When needed, the drums were opened; "pickles" were removed and repacked in 1 liter jars, then repasteurized in 176° water for 15 min and cooled. The final product was described as ". . . somewhat raw and showed a very good consistence." 'Pflug and Fellers (1964) are currently conducting studies on a promising new method of preserving cucumbers in a fresh, nonfermented condition in which blanched fruit are immersed in a salt-acid solution and held under refrigerated conditions for several months. Fermented Pickle Considerations The word "cure" is not clearly defined when used in reference to pickles. The end result of curing (olive green skin; dull, translucent, or lack of white flesh) is more -r If a obvious. "Fully cured" may also denote the relatively stable or deterioration resistent state in which the pickle exists after brining. Actually, curing is the all encompassing re- sult of those physical, chemical and biological changes in- volved in the transformation of a raw cucumber to a cured salt stock pickle existing in a state of semipreservation. Thus, when Fabian and Bryan (1932) referred to low— or high— salt curing, the entire salt stock process was implied: whereas, loss of whiteness of the flesh as a result of curing was implied when Fabian and Bryan stated ". . . they [referring to cucumbers] cure and ferment more slowly." Thus, we can see that the word "cure" may denote an entire process, a state of perservation, loss of whiteness of the flesh, or combinations of these. As an added note of interest, "cure" or "curing" and all that is implied is generally associated with the manu- facture of salt stock or processed fermented pickles, not with fresh pickles, except when loss of whiteness is ex- plicitly indicated. Fabian and Bryan (1932) found lowesalt curing (re- ferring to salt stock having an initial brine concentration of 300 salometer or about 8 per cent by weight of salt at . 60°F) to result in rapid curing as compared with slower cur- ing in high-salt curing (referring to salt stock having an initial brine concentration of 400 salometer or about 10.5 per cent salt by weight at 60°F). Furthermore, the high-salt cure apparently produced a firmer and better overall pickle than the low-salt cure. Pederson and Ward (1949), working with salt concentrations from 2 to 15 per cent in the manu- facture of salt stock, found more rapid curing and more rapid texture changes in the lower concentration brines. These results were basically in agreement with those reported by Fabian and Bryan (1932). There are many other factors affecting curing. Pederson and Ward (1949) suggested that curing ". . . may require a week or two or several months, depending on the size of the stock and the rate of fermentation." Pederson and Albury (1950) showed temperature of the brine used in salt stock manufacture to be of primary importance to the rate of curing. At 45° and 50°F, curing was markedly re- tarded, and 65°F showed a slower rate than 75°F. It was concluded that 75° to 86°F appeared to produce the best fermentations and most cured (translucent) pickles. The preceding data are not at all surprising in view of the '5 listed by Meyer and Anderson (1952) for general Q18 reactions such as may occur in the curing process. (The Q18 of any process is defined as the number of times that the rate increases with an 18°F (10°C) rise in temperature.) A Q of 2 or 3 was given for uncatalyzed chemical reactions, 18 1.4“to 2.0 for most enzymatic reactions, and 1.2 to 1.3 for diffusion. As early as 1929, Dillman cited cold weather as greatly slowing down the curing process. The number of studies on the relations existing be- tweenlnicroorganisms and their role in salt stock manufacture are voluminous. Needless to say, bacteria, yeasts, molds, and their enzymes have a great deal to do with the curing of pickles. A recent study (Pederson and Albury, 1961) em— ployed pure culture inoculation techniques in pickle fermen- tations. Use of the heterofermenters (bacteria capable of producing lactic, formic and acetic acids, ethyl alcohol, and carbon dioxide from sugars) Lactobacillus brevis, and Leuconostoc mesenteroides resulted in more nearly typical fully cured pickles than the homofermenters (bacteria capable of producing principally lactic acid from sugars) Lactobacil— lus plantarum, Pediococcus cerevisiae, and Streptococcus faecalis. It was found with both pickle and sauerkraut fermentations that raw flavor and texture of the products were retained to a large degree when L. plantarum was used. Furthermore, it was observed that low volatile acid coupled with low pH in relation to total acid accompanied these fermentations. Pederson and Albury theorized ". . . that the chemical and physical changes in cucumbers during a hetero- fermentation differ in some way from those in a homofermentation." Descriptions of the curing process are abundant in the literature (Fabian and Wickerham, 1935; Jones, 1940; Jones and Etchells, 1943; Etchells and Jones, 1943; Demain and Phaff, 1957; and Binsted, Devey, and Dakin, 1962). However, specifics in regard to - pagan tubing -,'-R J- h— it”... n «a. . A . . ‘3'.v‘ II. II) ’eL ~§ p n». ‘- 10 loss of whiteness are nearly nonexistent. According to the above workers the action of the brine on the cucumbers at first is to cause more rapid withdrawal of water from the cucumber than brine penetration into the flesh. The result is immediate shrinkage. The cells are more or less semi- permeable initially, thereby setting the stage for osmotic action when brine is placed in contact with the cucumber. The high moisture content of cucumbers, which assays 94 to 95% according to Camillo, Hoppert, and Fabian (1942), is of some interest here. Jones and Etchells (1943) state ". . . the brine al- so causes the cells of the cucumber tissue to become perme- able. This disorganization of the tissue permits the diffusion of the soluble cellular constituents such as sugar and other organic substances from the cucumber into the brine, and of salt from the brine into the cucumbers." As soon as sugars and other nutrients are available in the brine, microbial growth commences. As the microbes increase in number, the products of fermentation begin building up, types and amounts depending on the flora present and other factors. Enzymatic considerations Enzymes have been incriminated as softening agents. ,Demain and Phaff (1957), in their comprehensive review of the softening problem, conclude for sources of enzymes "L 11 ". . . the most promising possibilities seem to be from molds, the cucumber, and its accessory parts." Bell, Etchells and Jones (1950) demonstrated polygalacturonase and pectinesterase activity in curing brines. Etchells, Bell, and Jones (1955) associated pectinase and cellulase with cucumber salt stock softening. Recently, Porter and Schwartz (1962) isolated and described the pectinase and cellulase inhibiting tannins of grape leaves first dis- covered by Bell and Etchells (1958). Just what effect(s), if any, enzymes have on loss of whiteness from cucumber flesh has never been discussed in the literature. If pectic and cellulosic substances are degraded in the tissue, then one may reason that permeability of the tissue will change and diffusion will be enhanced because of the roles of these substances on the cell walls—-the pectic substances being cementing substances and the primary com- ponent of the middle lamella with cellulose being the chief component of plant cell walls (Esau, 1960). Loss of whiteness in fermented pickles has never been compared with loss of whiteness in fresh pack. The reason for this probably lies in the fact that a fully cured, translucent pickle is desirable in the former case while a white fleshed pickle is desirable in the latter case. Various enzymes have been of some concern for their deleterious affect on quality of pasteurized pickles. l l,’ ‘\ .‘~ e.~ g. .“ ,"‘ ‘ u ..,'.I ..‘~ 6"“ 1,”, ‘ b ,5“- 12 Anderson, Ruder, Esselen, Nebesky, and Labbee (1951) found ". . . that a much more severe heat treatment is required for the complete destruction of peroxidase than for micro— biological control" in pasteurized fresh whole pickles. Their tests showed a certain critical value of peroxidase concentration below which pickles did not develop off- flavors and other deterioration in storage. Nebesky, Esselen, and Fellers (1950) found high peroxidase activity in repre- sentative commercial samples of kosher style dill pickles and moderate activity in processed dill pickles. Nicholas and Pflug's (1961) data indicate peroxidase activity in fresh pickles given a heat treatment of 63 min at 180°F, a heat process far more severe than that given in commercial practice. Nebesky, Esselen and Fellers (1950) listed other enzyme systems such as polyphenolase, catalase, phosphatase, ascorbic acid oxidase, and pectinase known to be present in raw cucumbers. Bell (1951) has pointed out that the ripe cucumber fruit shows strong pectolytic enzyme activity. Esselen and Anderson (1952) reported pectin polygalacturonase activity in genuine dill pickles packed in quart jars to be zero at a pasteurization treatment of 30 min in a 180°F water bath with slight activity noted at 25 min. A final consideration of the enzyme picture is the recent discovery (Gizis, 1964) and isolation of an extremely heat resistant polygalacturonase enzyme (212°F for 35 min . pour»;- _ .- ,.a...\-\ . n .A-n .v'r —\ .ueogfi v ...vo-.a \.--h w”- . . .I ‘u.,‘ L I. Q'oou a I o “V‘Aq .- vv. .1» .4 --n.~.A ' .- ~-~'..'. . . ‘~e- \ ‘~§ .. ‘ ‘u \. \ VV . .“ V.‘ u e 13 required for inactivation). The enzyme was found in straw- berries and was shown to catalyze the hydrolysis of pectins, pectates, and protopectins. Maximum activity was indicated as lying between pH values 4.5 and 5.5 with no activity re- corded below a pH of 3 or over 8. The presence of this enzyme in cucumbers or pickles was not investigated. Histological and Microscopic Considerations Fabian and Johnson (1938) presented data on cucumber histology along with several hand drawn colored plates illustrating various tissue. Ruthenium red, a more or less specific dye for pectic material, was used extensively in their studies. Kertesz (1951), commenting on the limitations of stains for use with pectic substances, stated ". . . that in spite of these limitations, ruthenium red is still the best stain recommended for the observation of pectic con— stituents of plants under the microscope." Fabian and Johnson (1938) found: (1) An increase in pectic material in salt cured pickles as compared with normal pickles. (It was surmised that the pectic materials became more hydrophylic during fermentation.) (2) A diminution of pectic materials in slippery pickles and a total absence of pectic substances in mushy pickles. (3) A total absence of pectic material in pickles that had been placed in an enzyme solution from Which bacteria had been removed. (4) A great deal of pectic material in pickles preserved in 2.2 per cent hydrochloric ‘ 11 n. '1 3.4 ' ‘1 III A“ u an. by. .-'.A.-,. \ v‘e‘V-U tutu a .g-odv cypnpy- nus.- 'n-b—b Il~~ \ aw”... - V 0 ~, \ " 5.- "e. . _' u.‘.- 3: ..~~ ". n“‘ a \ u (I) 14 acid ". . . owing to the hydrolysis of the protopectin in the cell walls to a more soluble form of pectin." (5) Some structural weakening of pickles held 2 years in acetic and lactic acid. (6) Structural weakening of cooked pickles preserved in acetic acid. Chemical analyses of spoiled pickles (Fabian and Johnson, 1938) showed insoluble pectic material broken down to soluble forms by the action of enzymes. Also, the pectic materials were found to break down only as far as the pectic acid stage. The experiments of Fabian and Johnson indicate that heat, acids, and action of enzymes are deleterious to pickle texture. Etchells, Bell, Monroe, Masley and Demain (1958), in agreement with Fabian and Johnson, showed a slow loss of tissue strength in plant materials preserved in dilute acetic acid. Results indicated hydrolysis of the structural components due either to the low pH of the medium, or through the action of hydrolytic enzymes secreted by the tissue microorganisms. In a discussion of the effect of processing tech— niques on histological changes in fruits and vegetables, weier and Stocking (1949) stated, "Any food processing tech- nique which alters the permeability of the protoplasm, the ability of solutes to be retained within the cell, the elasticity of the cell wall, or the colloidal nature of the cell contents will alter the water retaining power of the cell, and possibly the crispness of the final product." .-:1 - u-.4 “a u.' a n. 15 Weier and Stocking made reference to the white chalky cast being imparted to the processed food by the presence of en- trapped air and stated that "Processing techniques may variously alter the proportion of air filled spaces in the tissue and consequently change the general appearance of the product as well as possibly its storage life." Weier and Stocking (1949) found that blanching (l) expanded the air resulting in its loss from the cut surfaces (2) caused leakage of cell sap from the dead cells into intercellular spaces and (3) softened the cell walls until they became pliable, thus, allowing sap to fill the spaces given up by the lost gas. Kertesz (l951),commenting on the effect of heat on various plant constituents, said that ". . . proteins may be coagulated and practically all tissue components which are copolymers, such as proteins, hemicelluloses, starch, pectic substances, etc., are slowly degraded during continued appli- cation of heat . . . and that heat alone changes water in- soluble pectic constituents of plants (protopectin, etc.) into soluble ones." Reeve and Leinbach (1953) reviewed the literature on the effects of heat on fruit (especially apple) and vegetable structure. Changes in the middle lamellae pectins, expansion and escape of intercellular gases, size of cells, intercellu- lar spaces, and cell turgor pressures were discussed. They (Reeve and Leinbach, 1953; and Reeve, 1953) investigated the ,,__- -. .- ch‘h'; v..--‘. . nu: ‘.~.. V '9. . ."1‘ 16 role of heat and effect of intercellular spaces on the structure of apples. Vacuum infiltration techniques were used extensively in their experiments. Most saucing apples were found to undergo total cell separation (but not rupture) when.vacuum infiltrated with either cold water or calcium chloride solution. The observation was made that most middle lamellae materials appeared to be removed or solu— bilized when cell separation was noticed. Vacuum infiltration methods (Reeve, 1953) were used to estimate the total intercellular space per unit volume of tissue. The percentage of intercellular spaces on flesh tissue was found to average between 20 and 25 per cent de- pending on variety. It was pointed out by Reeve that "the open tissue structure of apples has some bearing upon both fresh storage and processing treatments." Intercellular gas appears to be intimately involved in the whiteness associ— ated with raw cucumbers and fresh pickles as much as with apples. Joffe (1959) studied the softening problem in fresh cucumber pickles. Joffee lists 4 basic changes associated ‘with softening: "(1) Cellular changes in shape, dimension, and wall thickness. (2) Intercellular changes in absorbed gas and space volume. (3) Pectic changes. (4) Changes due to osmotic effects." Histological examination of heat processed fresh pickles (Jeffe, 1959; 250-300 micron sections) showed cell wall thinning, intercellular gas loss, l7 intercellular space enlargement, loss of cell turgidity, and granulation of the nucleus. Chemical Additive Considerations The effects of acids on cucumber structure has al- ready been reviewed. One of the first scientific treatises on the home preparation of pickles was that by Joslyn and Cruess (1929). The practice of heating pickles in the presence of vinegar and copper salts to secure a desirable green color was re- garded as intolerable because of the poisonous nature of the copper salts produced. Alum (potassium aluminum sulfate) has been regarded as a texture improver of doubtful expediency (Joslyn and Cruess, 1959; Valentine, 1963). No literature could be found proving one way or another the assumed role (that of making the pickle crisper) of alum as used in both fermented and fresh pickles and/or other products. Matz (1962) sug- gests that "in the case of pickles, it [alum] probably acts by complexing with the pectic substances, particularly those in the middle lamellae." The use of calcium chloride as a firming agent in pickles has never been fully investigated (to the author's knowledge). Lowe (1955) lists frozen apple slices, canned tomatoes and various types of pickles as foods in which calcium chloride has been used. A concentration of about 18 14 g (3974 ppm) of calcium chloride per gallon of pickles and brine was given by Lowe as an amount used in the manu— facture of cucumber pickles. Kertesz (1939) concluded that the calcium combined with pectic acid to form an insoluble calcium pectate gel which in turn acted as a binding agent for adjoining cells. Sodium chloride was found by Kertesz (1939) to soften tomatoes when used in soaking operations. He at- tributed the weakened tomato structure to replacement of the naturally occurring calcium and magnesium of the tissue with sodium. The effect(s), if any, of alum, calcium chloride, and/or sodium chloride on loss of whiteness of cucumbers has never been established. Nonenzymatic Oxidation Considerations Deuel (1943) revealed that pectin and cellulose could be oxidized by ascorbic acid in a nonenzymatic system. In a very recent study, Dakin (1963) reported on the nonenzymatic oxidative degradation of cellulose in red cabbage--shredded and preserved in acetic acid. Inhibitors of the reaction included sulfur dioxide (100 ppm), iodine, ethylenediamine tetraacetic acid, pyrophosphates, alcohol, formaldehyde, and phosphomolybdic acid. Dakin found a change of protopectin to soluble pectin accompanying the cellulose degradation, and concluded that this was due to q- i 19 either an oxidative factor affecting protopectin but not pectin, or that the insolubility of the protopectin was in some way connected with cellulose. Anatomy of the Cucumber Fruit The cucumber (Cucumis sativis L.) is a member of the cucurbitaceae family (Hayward, 1938). The cucumber fruit develops from an epigynous flower, the ovary being inferior. The ovary is tricarpellate. Occasionally, however, the pistil may consist of four carpels with a resultant four— celled ovary. The three (or four) placentae from which the ovules arise lie in parallel ridges along the length of the ovary wall (parietal placentation). There are numerous flat seeds in each locule. The flesh of the fruit is chiefly mesocarp and endocarp. Large parenchymatous cells comprise the fleshy tissue. Vascular bundles are located throughout the flesh. \- EXPERIMENTAL PROCEDURE Raw Materials Pickling cucumbers were procured from any of several locations in Michigan depending on availability of product and/or particular requirements of the particular experiment. If fruit came from any distance, closed transportation was used. Generally, fruit was utilized immediately upon arrival at the laboratory-—occasionally, however, it was found necessary to hold fruit for a short time and this was done at 40°F. A 40°F walk—in refrigerator was always avail- able for such storage as was required. SMR 15 and SMR 58, two commonly grown Michigan pickling cucumber varieties, were used for most of the studies. Cucumbers were graded normally prior to reaching East Lansing. For purposes of this thesis, the size desig- nations 2 and 3 will be used—-respective diameters being roughly about 1-1/16 to 1-1/4 in. and 1-1/2 to 1—3/4 in. Slicing or salad varieties of cucumbers used in the studies were procured from local supermarkets. Packing Procedure Basic fresh packs were whole dills, dill or sweet spears, and dill or sweet slices or crosscuts. Whole dills 20 21 were made from number 2 size fruit, spears and slices from 2's or 3’s. Raw product was washed with cold water for five minutes in a tumble action washing machine. If a blanch treatment was required, cucumbers were placed in cotton sacks and immersed in a hot water bath automatically maintained at the desired temperature. After the required length of time, fruit was removed and placed in cold water. No holding treatments were used. Quart size jars (screw—top or twist—off) of whole dills were packed to a net weight of 21 oz. The most common jar sizes used for spears and slices included 16-, 23-, and 28-02 twist-off type. Spears were prepared by cutting off the cucumber ends in a wooden box template designed to give uniform length to the spears, then the fruit was cut longi- tudinally into four or six wedges or spears depending on the size of the fruit. Spears were packed with the skin side facing toward the inside. A hand Operated mechanical slicer was used to prepare the slices. The two ends of the cucumber were discarded. For all whole dills and many of the spear and slice packs, a standard covering brine of 5 per cent common salt and 1.4 per cent acetic acid was used. Common sweet liquors included 50 per cent sucrose and 2.8 per cent acetic acid with or without 3 or 5 per cent salt. Occasionally, 1 ml of a soluble dill oil-brine mixture (supplied by the J. Stange w~ 22 Company, Chicago, Illinois) was added to the covering liquid for the dill packs. Thermal Process Jars were placed in wire baskets and lowered into an automatically controlled constant temperature water bath most generally maintained at 180°Fil/2o. After pasteuri- zation, the baskets of jars were removed to a water spray which was initially kept warm to eliminate thermal shock but which was manually turned colder after a few minutes; cool- ing was continued until an approximate jar temperature of 90°F was reached. Storage Most jars were stored in closed cases. Storage temperatures of 40, 60, 72, 86 and 99°F were constant. Room temperature storage ranged from about 75 to 85°F. Product Evaluation Subjective measurement of pickle flesh translucency was made since degree of translucency could be easily per- ceived by the human eye. Evaluations were made periodically during the storage period in order to follow any quality changes. STUDIES CONDUCTED I. Restatement of the Problem To discern more precisely why consumers rated down fresh pickles which had lost some or all of their whiteness was the object of this study. A consumer type of evaluation was carried out on commercial sweet and dill pickle spears obtained from a local supermarket in the fall of 1963. Two jars of each product were purchased representing the then current 1963 pack and two jars representing the 1962 pack. Twenty persons were asked to state a preference (if there was a preference) for one jar over another, and further, to express the reasons for their choice. Jars of the given product in each of the two cases represented dif- ferent years of packing (although the evaluator was not told this). Without exception the 20 persons chose the then current 1963 pack as being preferred for both the sweet and the dill spears. Figures 1.1 and 1.2 show the products as evaluated by the panel. The appearance attributes in order of the most to the least number of times mentioned are as follows: for the 1963 pack--firmer (crisper), better color, fresher, more appetizing; for the 1962 pack--look aged or 23 24 older, softer (poorer texture), off-color (translucent, not as bright colored), overcooked. One further observation made by several members of the panel was that the 1962 sweet spears, in general, showed an overall better appearance than the 1962 dill spears. Apparently this was due to a lesser degree of translucency in the sweet spears. From these data it has been shown that the consumer prefers a bright, white, fresh looking, firm and crispy looking fresh cucumber pickle product. 25 Figure 1.1. Commercial fresh dill spears purchased from a local supermarket in September, 1963 and photographed then; packed in 1962 (left), in 1963 (right). 1?:LSJUre 1.2. Commercial fresh sweet spears purchased from a local supermarket in September, 1963 and photographed then; packed in 1962 (left), in 1963 (right). 26 II. Effect of Several Factors on Loss of Whiteness from Fresh Pickle Flesh: A General Preliminary Treatise Introduction An initial study was set up to obtain information of a general nature relative to the problem of loss of white- ness from.fresh pickle flesh. Experimental Procedure All of the product was prepared as indicated in the general experimental procedure section; the exceptions being noted in Table 2.1. Variously treated products were rated for degree of translucency on a scale from 1 to 8 as described in Table 2.1. Results and Discussion Several generalities may be drawn from the data presented in Table 2.1: 1. Any covering liquid containing sucrose acted to preserve whiteness of the flesh more so than covering liquids containing no sucrose. 2. The only exception to the first generality was the straight acetic acid covering liquid which produced markedly white fleshed pickles, even after 9 months at the 99°F elevated storage temperature. 27 .omouosm monocmp 05m “UHUM UHuomH mmuocop ma “@Hom UHuoom monocmp o wocoosHmcmuoImoImoume mo COHpmHuomme I I I I e H e 04m v.HIuHmm m. mumwmm I I I I e H v ooo unspoum Hob Amov musumummEmB mmmuoum nocmHm mnmmHm meon amonm Eoum mmmcman3 mo mon co mmHanum> Hmum>om mo pommmm H.~ mHnma en. a. nah 28 3. Retention of flesh whiteness was greater at lower storage temperatures and shorter storage times. 4. Use of lactic acid in place of acetic acid produced no significant effect on flesh whiteness. 5. Blanching of whole pickles at 150°F produced no significant effect on flesh whiteness at the storage temperatures and times used in this study. It may be seen that four months at 99°F is approxi- mately equivalent to nine months at 72°F storage temperature in regard to the degree of translucency attained in the pickle flesh. This phenomenon is discussed later. The significant observation regarding the "protec- tive action" of sucrose on flesh whiteness had been observed earlier. When the translucency problem was first considered, a survey of pickles on the store shelves revealed sweet packs as having superior whiteness quality to the dill packs. The marked retention of flesh whiteness as the direct result of using 1.4 per cent acetic acid covering solution is also fully discussed in another section. 29 III. Histological and Microscopic Examination of Raw and Processed Cucumber Tissue Introduction Microscopic studies on raw cucumber and pickle tissue which had undergone various treatments was thought to be important in any problem relating to product deterioration. Experimental Procedure Cucumber tissue from both pickling and slicing varieties, mature and immature fruit, raw and variously processed fruit, and cucumbers subjected to various treat- ments were examined microscopically. Generally, hand sections were taken from pertinent areas of the cucumber tissue. Sections were either: (1) not stained at all, (2) stained with safranin, rutheniwn red, or crystal violet, or (3) cleared with a hypochlorite solution, then stained. Some of the sections were run through the alcohol dehydration series followed by the xylene series, then mounted on glass slides using neutral balsam in xylene. Some of the non- dehydrated, stained and unstained, fresh sections were mounted in plain water on glass slides for immediate photo- graphing or in glycerin for later photographing. Microtechnique methods used were generally according to Sass (1958). 30 The ruthenium red staining solution was made by simply placing a small crystal of ruthenium red in a watch glass with enough water to achieve a pink solution. This solution had to be filtered before using. Results and Discussion Figure 3.1 illustrates an untreated, white appearing, fresh, hand section of fleshy parenchymatous tissue taken from a number 2 size SMR 58 cucumber. The individual cells are obliterated by the abundance of intercellular gas ap- pearing as dark areas. Figure 3.2 shows a fresh section taken from the same area of the cucumber after vacuum infil- tration. The cellular outlines are very visible in the vacuum infiltrated tissue and no intercellular gas may be _observed. Cell walls can be seen to remain intact. The flesh had appeared totally translucent to the naked eye at the time of sectioning. Figure 3.3 illustrates a fresh section of fleshy parenchyma tissue taken from pasteurized fresh dill pickle slices after about 11 months in storage at room temperature. The fleshy parenchyma tissue showed nearly total trans- lucency to the naked eye at the time of sectioning, but the seed cavity area and a ring around the slice about 1/8 in. deep beneath the skin showed total translucency. As can be seen from the photomicrograph, cells are intact and a nearly complete absence of gas is noted. The few dark areas near Figure 3.1. Fresh hand section of raw fleshy parenchyma tissue from a number 2 SMR 58 cucumber showing abundance of intercellular gas (dark areas). Figure 3.2. Fresh hand section of same tissue as shown in Figure 3.1 after vacuum infiltration. Note intact cells and complete absence of gas. Tissue appeared translucent to the naked eye. .1- p... o‘- 7‘ |.' ‘~ 32 the center of the photograph clearly show some remnants of the tissue's original entrapped intercellular gas. Figure 3.4 shows two hand drawn microscope fields (magnified about 200x) of partially translucent raw cucumber tissue that had been immersed as slices in a 15 per cent mflt brine for about 2 hours. Some gas (colored dark and located intercellularly) remained in the tissue and several intercellular spaces without gas can plainly be seen. The cellular constituents show severe plasmolysis due to the high salt concentration of the covering brine. In the illustration of the hand section shown in Figure 3.5, the line of demarkation between gasless (light cmlored area) and gas- in (dark colored area) tissue can Clearly be seen. The gasless tissue represents the trans— lucent areas pictured elsewhere in this thesis (Figures 18.2 and 18.3). These areas, which are often observed beneath Warts or spine spots of cucumbers stored under refrigeration before processing, were unquestionably the result of some- thing such as an advancing front of an enzyme reaction originating at the spine spot. The enzyme would act to make the tissue gas-permeable as the tissue was enveloped. The central seed cavity area of the cucumber ex- hibits a diversity of cell forms or characteristics (Figure 3.6). The tissue in this case was cleared, safranin Stained, dehydrated and mounted permanently. This central area is almost always the first to show signs of tissue 33 Figure 3.3. Fresh hand section of fleshy parenchyma tissue of 11 month old fresh dill pickle slice which showed nearly total translucency to the naked eye. Note remnants of original intercellular tissue gas (dark areas). Figure 3.4. Hand drawn microscope fields of partially translucent raw cucumber tissue immersed in 15% salt brine for about 2 hours. Note inter— cellular gas (dark areas) and intercellular spaces no longer occupied by gas. Fresh hand section of the edge of the trans- lucent area (light area) beneath a spine spot and opaque white tissue having intercellular gas (dark area). Figure 3.6. Photomicrograph of central seed cavity tissue of a cucumber showing diverse tissue forms and characteristics (105x). .vee . n..n I." l n 35 translucency in fresh pickles. Microscopic examination of the central tissue revealed the presence of much less gas and smaller intercellular spaces than fleshy parenchyma tissue, thin cell walls, a rather loose cell structure, and diverse cellular forms and types. Figure 3.7 shows the opaque white (uncured) and translucent (cured) flesh conditions referred to in this study and throughout this thesis. 36 ? ' r. u I , Row (4...); Cereal -ingure 3.7. Cucumber slices showing opaque whiteness and translucency (curing). 37 Effect of Blanching on the Curing of Pickling Cucumbers _Made into Salt Stock IV. Introduction A study of the curing process associated with manu- facture of salt stock was deemed valuable since curing is also a process involving loss of gas from the tissue. Experimental Procedure Two separate studies were carried out in consecutive SMR 15 cucumbers. In the first years using number 3 size, study, two 55-gallon barrels were filled with cucumbers with enough allowance made for the addition of about one bushel Of blanched fruit per barrel. Barrels were located at the lflichigan State University horticultural farm. Four 20- ENDund lots of cucumbers were blanched as follows: 20 min in 1E30°F water, and 2, 4, and 6 min in 180°F water. Cooling 10218 effected rapidly after blanching by placing the cotton Seacks of warm fruit into cold water._ Each lot was divided irrto two lO-pound batches, each of which was placed in a C<>1rton bag, labeled, and one bag representing each of the ft>LLr blanch treatments placed in each of the two 55-gallon baJi‘rltels for regular salt stock treatment (final salometer of 60° 3). Barrels were put down on August 21, 1962 and the Pi-c2]<1e evaluations made January 9, 1963. Degree of cure and fl*t?hnness were noted at that time. 38 In the second study three gallon jars were filled with cucumbers which were blanch treated as follows: zero blanch (control), 6 min in 180°F water, and 10 min in 180°F water. A 5 per cent salt covering brine was added; storage was at about 80°F. A quality evaluation of these pickles was made 11 days after preparation. Titratable acidity of the brines was determined using standard sodium hydroxide and phenolphthalein indicator. Results and Discussion In all blanch treatments there was a certain small percentage of uncured flesh in each fruit after 141 days in salt stock. The blanch treatments ranged from an average high of 7.5 per cent uncured flesh (excluding seed cavity éarea) for the 20 min blanch at 160°F to an average low of 53.5 per cent for the 180°F blanch treatments for 2 min (frable 4.1). The control pickles remaining in the barrels registered total translucency. Poor pickle texture (loss of firmness) was found to k>€3 associated with the 6 min blanch at 180°F; a moderate 1~°Ss of texture was noted for the pickles subjected to the 4 min blanch at 180°F (Table 4.1). The results of the second study (Table 4.2) paral— 1e:Led those obtained in the first. The salometer of the feEJE1menting brine in the gallon jars was about 19° for the 11‘ «days of curing time. Figure 4.1 illustrates the greater 39 whiteness or uncured pickle flesh of the blanch treatments compared with the control. The very severe bloating (an indirect result of blanching in this case) is also clearly in evidence. Total titratable acidity of the brines indi- cates nearly equal fermentations to have been effected in the three treatments. Table 4.1. Effect of blanch treatment on the curing and firmness of salt stock pickles (barrel fermentations) Quality Evaluation After 141 Days Approximate % of Blanch Treatment White Tissue Re- —r 0 Barrel maining (Excluding subjective Temp. ( F) Min No. seed Cavity Area) Firmness Control --- l 0 very firm 2 0 very firm 160 20 1 5 very firm 2 10 very firm 180 2 1 3 very firm 2 2 very firm 180 4 1 4 moderately firm 2 3 moderately firm 180 6 1 5 slightly firm 2 4 soft The results obtained definitely establish that the a£3£>1ication of heat in the form of a blanch treatment to raw pj~<2kling cucumbers prior to salting or making salt stock re- S‘Jul.ts in poorly cured pickles. It seems plausible that the h‘E’Eit substantially reduced the activity of pectinolytic and ~0— ,.,. nunci got-u a - cur ly-v. «,4 a,. .- er... ‘n’. u“. ‘ 40 other degrading enzymes which Bell (1951) has shown to be present in the pickle flesh. This action could have re- sulted in securing the pectinaceous cell cementing sub- stances until the enzymes produced in the brine by micro- organisms and/or by cucumber flowers (Etchells, Bell, and Jones, 1955) managed to diffuse in to finally effect a cure by degrading or solubilizing the cell cementing substances to allow escape of the tissue gas between the cells. Another effect of the blanch might have been to shrink the outer layers of cells causing a physical blockade for tissue gas and preserving tissue whiteness somewhat. This situation could also give rise to movement of some tissue gas to the center of the cucumber, hence the bloating Observed in blanched fruit. Ifiible 4.2. Effect of blanch treatment on the curing and firmness of pickles cured in 5 per cent salt brine at about 80°F (gallon jar fermentations) Quality Evaluation After 11 Days IBJanch Approx. % Total Treatment of White Titratable at: 180°F Tissue Acidity , Subjective Bloaters (nfixfi Remainingat as % Lactic Firmness (%) Acid \ ‘:<>r1trol 30 0.51 very firm 10 6 80 0.46 very firm 100 3L0 90 0.54 moderately 100 firm \ aExcluding seed cavity area. 41 Figure 4.1. Typical pickles fermented in gallon jars in 19 salometer salt brine for 11 days at about 80°F. Left: unblanched and most translucent or cured; center: blanched 6 min at 180°F; right: blanched 10 min at 180°F. 42 V. Effect of Blanchinq7Whole Cucumbers on Whiteness of Sweet Fresh Cucumber Slices and Spears Experimental Procedure Variety SMR 15, number 3 size cucumbers were pro— cured from Mason, Michigan, August 22, 1961, held overnight at 40°F and packed the next day. Standard packing pro- cedures were generally followed. Whole cucumbers were divided into 6 lots, each lot enough to make two pint jars each of slices and spears having blanching times of 0, 2, 5, 9, l4 and 20 min at 160°F. Slices were packed at 265 g per jar; 320 g per jar for spears, and all covered with 50° Brix-2.8 per cent acetic acid syrup. No color or flavoring ingredients were added. Jars were heat processed for 40 min in a 180°F waterbath, then spray cooled. Jars were cased and stored at room temperature. For both slices and spears, a general subjective evaluation for whiteness was made every 30 days over a 10 month period, with intermittent evaluations being made after that up to 24 months. Results and Discussion Up to 10 months storage time revealed only slight differences between treatments in flesh whiteness. Zero min ‘blanch slices and spears showed the most yellow tinged dull flesh with 2 and 5 min treatments showing less. Twenty min 43 blanch treatments appeared whitest and brightest with 14 and 9 min treatments also rating high. Areas of flesh translucency after 10 months of stor- age were only slight, appearing in the central seed areas and peripheries. Since the unblanched pickles registered no peripheral type of translucency, blanching was assumed re- sponsible. Most likely, bruised areas, the result of handling practices, indirectly contributed to the condition. The author has upon occasion witnessed severe peripheral translucency in fresh pickles on commercial lines following a blanching treatment. After 18 months of storage it became increasingly evident that the control slices and spears were becoming more translucent than the blanched treatments. At two years of storage the slice and spear controls showed about 80 per cent translucency in the fleshy parenchyma excluding the seed cavity area, as compared with about 20 per cent fleshy parenchyma translucency excluding the seed cavity area in most of the blanched treatments. Figures 5.1 and 5.2 show typical effects of blanching on preservation of whiteness in fresh cut pickles. A sidelight was the expected observation of a truer green skin in the blanched fruit as compared with the olive green color of the controls. Blanching served to fix the green color of the skin. 44 y NEW “Twist-Off: “w "Twist . off; up Figure 5.1. Typical beneficial effect of blanch treatment on retaining whiteness of fresh sweet slices stored 2 years; unblanched (left), 5 min blanch at 160°F (right). "llmyfifiy' ~um1wubnuu Figure 5.2. Typical beneficial effect of blanch treatment on retaining whiteness of fresh sweet spears stored 2 years; unblanched (left), 5 min blanch at 160°F (right). 45 The effect of the heat from blanching on enzymatic activity in the cucumber may be related to the beneficial effect of blanching on whiteness retention in the final product. Blanching for any time at 160°F would affect pectinolytic systems known to be present in ripe cucumbers (Bell, 1951) and which could act on the pickle tissue at a later time. With enzyme action on cellular structures at a reduced rate because of blanching, diffusion of gas from the tissue would progress at a slower rate in storage. Thus, loss of whiteness from the tissue would be retarded to a certain degree. Another idea of lesser apparent merit as to why blanching reduces flesh translucency concerns the effect of heat on tissues per se. If heat from the blanch treatment were able to modify tissue composition or structure (such as occurs in coagulation or denaturation of proteins) in a direction that made for less tissue permeability then dif- fusion would proceed at a slower rate, and whiteness would be retained to a greater degree than if there were no blanch treatment. A further observation made during this experiment concerned changes in flesh translucency upon opening of the jars. It was noted without exception, that no matter how much whiteness remained in the pickle flesh, opening of the jar caused a rapid onset of total translucency, an 46 observation also noted by Etchells and Jones (1944). Vacuums varied from 10 to 15 in of mercury. 47 VI. Effect of Blanching Cut Cucumbers on Loss of Tissue Whiteness Experimental Procedure Fresh cucumber slices were prepared to fill 12, 16- oz jars. Equal lots of slices were blanched as follows: 0, 2 and 6 min in 180°F water and 6 min in 160°F water. Cooling was effected rapidly by immersing the blanched slices in cold running water. Slices were packed into the jars by weight (265 9.: 2 g) and filled with room temperature 5 per cent salt r 1.4 per cent acetic acid brine. Three replicate jars were prepared per treatment. Jars were pasteurized for 30 min in a 180°F water bath, cooled to about 90°F and stored at about 80°F. One subjective evaluation for degree of translucency was made approximately 5 months after packing. Results and Discussion As a result of blanching cucumber slices prior to packing, translucency became a significant problem (Table 6.1 and Figure 6.1). All blanch treatments showed signifi— cantly more flesh translucency than did the controls; the more severe the blanch the greater the degree of trans- lucency. Both blanches of 6 min at 180 and 160°F resulted in translucency three to four times greater than the controls (no blanch). It would be reasonable to assume that blanching of the cut product would have a far greater effect on cut, H a. 48 exposed tissue than if the cucumber were whole. The relatively tough, closely joined epidermal cells offer a great deal of physical protection to the succulent tissue beneath as well as acting somewhat as a gas barrier. The rapidly expanding tissue gas would be able to leave the un- protected tissue with a minimum of difficulty facilitating the early development of translucency. Table 6.1. Effect of blanching cut cucumber stock on loss of tissue whiteness in fresh pickle slices made from the blanched stock. Estimated degree of translucency (% Blanch Treatment of the fleshy parenchyma tissue ex- 0 cluding the seed cavity area) after Temperature (_F) Min 5 months storage at about 80°F 180 O 25 2 50 6 90 160 . ._ 6 80 49 Figure 6.1. Unblanched (left) versus blanched for 2 min at 180°F in cut condition (right) packed in stgndard brine and stored 3 months at about 80 F. ‘14. or: . n‘v Ib- ‘ U rev. ul~ ‘ q .'q~ N.‘ l ._ r LN” A ~ ‘I u l... “‘ 1' I ~ ~ I l‘ ‘4' 4 “ 50 VII.. Effect of Processinq,Temperature and Time and Storage Conditions on Whiteness of Sweet Fresh Cucumber Spears Experimental Procedure Commercially line-packed 23-oz jars of sweet spears were made using heat processing temperatures and times of 180°F for 25 and 100 min, 189°F for 20 and 50 min, and 198°F for 16 and 35 min. Six replicates were made per treatment so that two duplicate jars per treatment could be placed at each of 40, 72, and 99°F constant temperature rooms for storage. In addition to the above, three jars were purposely underprocessed at 180°F for 13 min, and six jars each for 14, 15, and 16 min. Two 13 min underprocessed jars were placed in 72°F storage, the third at 99°F. Two each of the 14, 15, and 16 min underprocessed jars were placed at 40, 72 and 99°F storage. Subjective whiteness or degree of translucency evalu— ations were made every 30 storage days for a period covering 8 months, with a final evaluation being made at 14 months. Quality evaluations were made using an arbitrarily set up eightflpoint degree of flesh translucency scale based on the ap- Proximate percentage of flesh appearing translucent. 51 Results andfipiscussion Use of pasteurization temperatures of 180, 189, and 198°F indicated no difference in the amount of tissue whiteness in the final product either initially or after 14 months of storage (Table 7.1). However, there existed distinct differences in the amount of whiteness retained by the fresh pickle flesh as a result of varying the length of heat processes at 180, 189, or 198°F. At 99°F, a storage temperature which drastically accelerates all types of pickle deterioration, after only 2 months, 60 to 90 per cent of the spear flesh was observed to be translucent for the shorter of the two heat processes at any of the three processing temperatures. The longer heat processes after 2 months showed only a trace to 10 per cent translucency. After 3 months, however, total trans- lucency had been effected in all cases. And for the under- processed spears held at 99°F, total translucency resulted in all cases at 2 months. Clearly, the longer the heat process the greater the whiteness retention of the flesh. At 72°F the effect of process time on flesh whiteness appeared but was somewhat delayed. Underprocessed spears registered 90 to 100 per cent translucency after about 5 months; the shorter heat process spears registering 90 to 100 per cent translucency at the three different processing temperatures after about 14 months; with the longer heat process spears at the three different processing temperatures 52 .oonmUmHo ocm oouoc How owHHommo .ucoEummuu Hmm.coxmu,mumfl Normm 03o mo ommuo>o mmmcmuH£3 mo coHumHHomon m 8 UN m m m m m m e H H a m m H H H H H H 6H omH m om N m m m m m N e H 0H s m m H H H H H H mH omH m m N m m m m m N m 0H H a m m H H H OH H H 4H omH I o N m m m m m N s 0H H I I I I I I I I I NH omH -m ......... m ........ m ..... m-m--....--m-m-m-a.:m --H.----m--1. H H -HJ. ..1. HM Imm ........ mm--- m N N m m a e a H H H H a H H H H H H H H 8H mmH m e N o m e e e H H H H e H H H H H H H H om mmH m N N m m e e a H H H H e H H H H H H H H ON mmH m a N a m a e e H H H H e H H H H H H H H ooH omH m N N m m e a e H H H H a H H H H H H H H mN omH m N H 4H m N m m a m N H «H m N o m e m N H CH: .Hmoc .msws wmmuoum homo CH mgucoz wmmuoum moNh CH mzucoz ommuoum moog cH mnucoz Qmmwooum HMEHoSB mwucmeumouu Human meon cmwum ummBm HHm mo GOHumus>o mmmcouH£3 .H.h anma 53 registering only 30 to 60 per cent translucency after 14 months. Figure 7.1 pictures typical spear condition as the result of different processing times at a particular pro- cessing temperature under 72°F storage conditions. Figure 7.2 illustrates curves for spears given 15, 25, and 100 min heat processes at 180°F, then held at 72°F up to 14 months in the jar. At 40°F,whiteness was retained in the flesh to a marked degree thus necessarily limiting studies on the progression of translucency. After 7 months the first signs of translucency appeared in the underprocessed spears, a condition noted in the other processes to appear somewhat between 8 and 14 months after packing. This data could be expected from results already discussed for 72 and 99°F storage. At 99°F the flesh first appeared dull looking before attaining any degree of translucency. Such was not the case at 40 and 72°F. Apparently at the elevated temperature other forms of deterioration manifested themselves before translucency. It is not certain as to why an excessively long heat process rather than a more or less normal or underprocess would result in more whiteness retention in fresh pickle flesh. However, a possibility might lie in the incomplete destruction of various enzymes at the lower thermal processes. Nebesky, Esselen, and Fellers (1950) and Nicholas and Pflug Figure 7.1. 54 Class 0 cm I Typical results for nearly normal pasteuri- zation (left) versus overpasterurization (right) on flesh translucency after 16 months of 72°F storage. £693 on Sun gHuwNHuaou—ume we gHuoasu a an. Noun no caucus undone onoHu uooan noon—m 5 honouaHnawuu mo ugHg Sago HE. 88$ 3 NH 2 a a e N I- .. w. - II - -. _-.---,I, I.- I... I- II-.. 878 I ., . .. i .1 . . . l . . . l . .I g _ . I. I _ . . . m .1 a i I w I a o . . 1. 88.8 m l Hz 8H .3. mu .8. 3 , a .3 H 5 s _ . .. , _ 8-3 m m o m 4 4 s I OH acumen. u _ \I z m . ; .25 m _ m , o 31.8 ON.“ 03h « 4 56 (1961) demonstrated enzymatic (peroxidase) activity in various fresh pickles given commercial heat processes. Of more significance, however, is the report by Esselen and Anderson (1952). They worked with pectin polygalacturonase, a known pickle softening enzyme, and showed high activity in quart jars of genuine dill pickles pasteurized for 15 min or less at 180°F, low levels of activity at 20 to 25 min, and zero activity at 30 min. After 9 months of storage, pickles processed for less than 20 min generally exhibited soft texture, 20 to 25 min--firm texture, and 30 min--slightly soft texture again (the latter due presumably to overcooking). It may be reasoned that if polygalacturonase (and perhaps other similar pectin and cellulose degrading en- zymes)affects pickle texture in genuine dill pickles pasteurized for less than 20 min at 180°F, then it could al- so affect texture in fresh—pack pickles. (However, we may assume that polygalacturonase concentration would be higher in genuine dill pickles than in a fresh-pack product since there could be enzyme from both the fermenting microorganisms and from the fruit itself in the genuine dills.) Since texture is intimately associated with intercellular pectins (Kertesz, 1951) the degrading of these pectinaceous sub- stances, say by certain pectinolytic enzymes, would lead to cell separation in fresh pickles, thus allowing the escape of tissue gas and causing the translucent condition to manifest 57 itself. The more severe heat process would destroy the en- zymes and thus preserve the tissue whiteness. Another speculation as to why a severe thermal process of fresh pickles results in whiter flesh concerns the effect of heat on cellular constituents. It is possible that the great amount of heat in some way coagulates or stabilizes some of the intercellular constituents causing a "tougher" or more difficult barrier for the entrapped tissue gas to escape from the tissue. The effect of the storage temperature on rate of whiteness lost from the flesh was striking (Table 7.1 and Figure 7.3). At 40°F, translucency in the spears not under— processed was first evidenced after 8 months but before 14 months; at 72° between 4 and 5 months; and at 99° between 1 and 2 months. After only 2 to 3 months at 99°, total trans— lucency envelOped the spears of all treatments. The effect of storage temperature on loss of whiteness from pickle flesh is discussed in detail in the experiment dealing with storage of sweet slices. It was observed in the underprocessed pickle spears ‘which had spoiled that nearly complete translucency was characteristic of the flesh. Apparently, translucency de- veloPed rapidly once microbial populations and their pectin and cellulose, etc. degrading enzymes reached any degree of magnitude. Thus conditions of salt stock preparation were 58 .33 on... 3 3.393 3 :3 some noun: a a.“ 58 3 uou mom H no .53 ON you Fe: .53 AN you Pom: .423? no «333....— ueo: 633598» a noun we canon—Hm u an undone 3332— neg «Hanna 5 Face—Hung.» mo annex—3025 Snug se.... 3% 3 «H S w o e N Slum on to.— S 525 .. 002 (115211 to 2) msamsuvu 1) ma 0 HHHBV .mH .wHNH 59 effected with the result-translucency. Figure 7.4 pictures normal unspoiled fresh dill spears compared with micro- biologically spoiled fresh spears. 6O "Twist-Off” Figure 7.4. Normal fresh dill spears (left) compared with typical microbiologically spoiled fresh dill spears (right). 61 VII. Effect of Pasteurization on Loss of Gas from Pickle Tissue Experimental Procedure One dozen 28—oz jars of slices were made from number 3 size, SMR 58 cucumbers held under 5 per cent carbon dioxide and 5 per cent oxygen controlled atmosphere storage at 32°F for 4 weeks (the only pickling cucumbers available at the time); six other jars of pickles were packed from SMR 15 cucumbers having the same conditions except for a storage temperature of 34°F. The slices were made using standard procedure except that a 1.4 per cent acetic acid covering solution was used; no blanch treatment was given. Approximate percentage of gas or air by volume in the flesh was determined by calculating the increase in weight in water recorded in the weighed sample as a result of 15 min of vacuum infiltration at 28 in. of mercury vacuum. Three replications were made per treatment on the contents of two jars using approximate lSO-g samples. Results and Discussion The data from Table 8.1 indicate 76 and 71 per cent loss of total air or gas from SMR 58 and SMR 15 cucumber flesh, respectively, as a result of pasteurization (30 min in a 180°F water bath). Storage for 24 days showed insignificant further loss of gas from SMR 58 flesh. 62 Table 8.1. Effect of pasteurization and subsequent storage on loss of gas from raw and pasteurized pickle flesh Approx. % of gas by volume ° a Condition in Product of Product SMR 58 SMR 15 Raw cucumber 6.7 5.9 Immediately after pasteuri- zation and cooling 1.6 1.7 24 days after pasteurization and cooling 1,3 __- aAverage of 3 replications used in developing the data. The conditions in the jar from the time following packing and sealing to the time until the jar was cooled after pasteurization may be described as follows: The contents were at atmospheric pressure after sealing, but as soon as heat was applied the gases in the headspace expanded along with the product and the covering liquid. Pressure was exerted on the tissue cells resulting from the expanding jar contents (osmotic and turgor pressures were also present). As the intercellular gases heated they expanded more rapidly than the surrounding liquid and solid material thus causing the cell walls to push apart somewhat, allowing the trapped gases to eventually work their way to the outside and leaving many intercellular spaces filled with liquid. Then as the pasteurization period ended and cooling began, the 63 closed system passed from a pressure situation to that of a vacuum causing more gas to be pulled from the tissue to the headspace. Figure 8.1 graphically illustrates the changes in pressure that might occur in a jar of commercial fresh pickles (estimates based on an initial vacuum sealing oper- ation which is commonly used in the industry). 64 .25Du<> mmnmmmmm QMAOOU \II/ .moHHUHA neoum ulxuum SHHuHuuen-Bu no nun—smack.— uunuoautcH 5 398:0 05 mo Sawfly 5. 2.6 .3m auddwm ZEDD¢> 7 UHmmmmeZH< .Am HMDmmmmN 4 music nmzmmo nqummZD QMNHMbflHm1 2 tit-{#1: . . 12-2.4» .. .--- 2 2 . 2. 2 A , . . .vn- H .v. . at. o. o . . ... . ,. . -._ 2 2 . .2 . 2. .222. . .2 2 .. , _ .. . .A .M. . 2.4.. u . . - .7 ~ .. - 2 rm .v42. ... . .....2..¢.‘. .- .o.~- . ,a 2 . , 2 2 n 1 . 2 2 o. _ .2 . . 1 F 2 r 20.0112. It- . 4 . < .2 2 . . . . . . . 2. . H w. w 2 . 2 v . 2‘ 2 , v . _ . o 2g. H. 2 . 2 . . . . ,2 2 . . _ 2 . . . . w . ~ -. 2 . ...-4 :2 . VA .2. ‘tv ' ..-IOc.9IbI!. {2"}.-. .Yor’t. .O,2.“|I..¢-o. \{ . . v 2 2 . . . 2 _ MI. - . . 2 2 2 . o . . . 2 2 _ . . 2 2 . .. 2 2 . .v, o l...;v..~. 2 . . . , . 2. . . . . 2 , . 2 ¢ .. . 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The Chemicalfigggineer§:Hand- .2993 (1950) lists diffusion coefficients in water at 20°C of 1.35, 0.88, and 0.45 cmz/sec for dilute solutions of sodium chloride, acetic acid and sucrose,respectively. Apparently salt and acid followed the diffusivity laws in regard to a closed system of pickles in brine. Further, we might expect pickles packed in sweet liquor to assimilate sugars from that liquor even more slowly than salt or acid. The effect of acid-salt brine penetration into the pickle and the flow of water out of the pickle upon white— ness or loss of gas from the tissue is clarified somewhat by the results obtained in this study. Since whiteness in fresh pickles was not lost after maximum uptake of brine by the pickles (between 1 and 4 days after pasteurization) it was obvious that the presence of brine per se was not responsible. The data did indicate significantly more acid and salt in the pickle tissue than in the brine on a percentage by weight basis at only 1 day after pasteurization. Ap- parently the semipermeable membranes of the tissue allowed osmosis to progress at a rapid rate. Presumably, as the salt and acid content of the tissue decreased from 4 days to 94 days after pasteurization, the permeability of the tissue cells was being changed gradually as occurs in salt stock curing (Jones and Etchells, 1943). It may be theorized that 75 as the intercellular and cellular tissue (cell membranes especially) deteriorated through chemical, physical and physiochemical action, true equilibrium conditions between salt, acid, and water in pickles and brine was being estab— lished. Even after 94 days, equilibrium was far from being established. Extrapolation of data using the per cent salt in the pickles lost between 4 and 94 days and 1.55 per cent salt in the brine as base point showed about 210 days as the time in which total equilibrium would have theoretically been reached. It appears from the data that as the intercellular constituents and semipermeability of the membranes were gradually destroyed, the overall permeability of the tissue increased; gas which was present in the tissue was gradually diffused out and replaced by liquid. At one particular low critical point in the gaseous content of the tissue, the ' amount of reflectance to the eye was reduced enough to per- mit the condition known as translucency to emerge. ‘ MU. \ 76 XI. Effect of Several Chemicals on Preservation of Whiteness of Fresh Pickle Flesh Introduction Since many chemicals are utilized in the manufacture of fresh pickle products, it seemed desirable to determine whether these chemicals had any effect on flesh whiteness. A few other compounds were incorporated into the study in order to determine the effect of a larger variety of chemicals on flesh whiteness. Experimental Procedure Jars were packed and processed as described in the general experimental procedure section. Standard brine was used in all treatments. Storage temperatures varied. The various chemicals were added to the contents of each jar prior to sealing and pasteurization. The jars were shaken to insure proper mixing of the chemical with the contents. Results and Discussion Neither alum (aluminum sulfate) in concentrations of 2 or 3 pounds per 100 gallons of brine, nor calcium chloride in concentrations of l, 2, or 3 pounds per 100 gallons of brine exhibited any significant effect on flesh whiteness in fresh pickles which had been in storage up to the time of nearly total flesh translucency (Table 11.1). 77 Table 11.1. Effect of alum and calcium chloride on reten- tion of flesh whiteness in fresh dill pickle slices stored at room temperature (75—850F) Concentration Estimated Flesh Translucency (%)a Additive (pounds/100 Used gal.) 0 Days 192 Days 154 Days 222 Days Alum O O 85 -- 99+ 2 O 85 -- 99+ 3 O 85 —- 99+ Calcium Chloride O O 85 90 99+ 1 O 80 85 99 2 O 85 9O 99 3 O 85 9O 99 aAverage of 3 replicate jars used per estimation. Calcium chloride in the concentration of 1 pound per 100 gallons of brine appeared to produce slightly whiter overall flesh than any of the other treatments, but not significantly so. Calcium chelate of the disodium salt of ethylene- diaminetetraacetic acid (EDTA) has been used in processed pickles in commercial practice. Its effect on retaining whiteness of flesh pickles stored for up to 8 months was found to be slightly beneficial in 10 or 100 ppm concen- tration (Table 11.2). C (C' Sedi: .‘Vun \:A“A he e 1 pa ~M 2i. ac. d- ~l C'M \Ih. q ‘ 78 Table 11.2. Effect of several chemicals on retention of flesh whiteness in fresh cucumber dill spears stored at 75—850F Estimated Flesh Translucency (%)a Concen- Additive tration 0 19 81 111 173 243 Used (Ppm) Days Days Days Days Days Days None (control) --- 0 0 trace 5 10 95 Ascorbic acid 1,000 O 0 trace 5 10 95 EDTA 10 0 0 trace 5 7 85 100 0 0 trace 5 7 85 Sodium bi- sulfite 100 O O 10 50 99+ 100 500 0 trace 97 99+ 100 -- 2,000 0 20 99 99+ 100 —- Tween 80 25 0 0 trace 5 10 90 Zinc acetate 10 O 0 trace 5 10 95 100 0 0 trace 5 10 95 aAverage of duplicate jars used per estimation. Ascorbic acid, tween 80 (a polyoxyethylene type emulsifier) and zinc acetate additives all produced results similar to the controls (Table 11.2). However, sodium bi— sulfite accelerated the translucency condition markedly (Table 11.2). In only 81 days time at room temperature, both the 500 and 2,000 ppm sodium bisulfite treated pickles possessed nearly total translucency. Figure 11.1 is an 79 illustration which compares the control (having a trace of translucent flesh) with 100 ppm of sodium bisulfite (having about 10 per cent translucent flesh) and 500 ppm sodium bi- sulfite (having about 97 per cent translucent flesh) after 81 days of storage at 75—850F. It might be theorized that the extremely radical ef— fect of the sodium bisulfite on flesh whiteness was due to the chemical dissociating into sodium and sulfurous acid, the former replacing calcium of the calcium pectate complex of the middle lamella (Kertesz, 1951) and the latter acting to break down the middle lamellar and intercellular pectins (and perhaps other tissue as well) as has been shown to oc— cur in hydrochloric acid treated pickles (Fabian and Johnson, 1938). The combination of the two factors would render the cell cementing substances soluble and useless. The gaseous matter could then easily diffuse out of the tissue with the help of the small vacuum in the jar, the gas being replaced by liquid to cause the translucent condition. Microscopic examination of the sodium bisulfite treated tissue revealed intact cell walls with some plas- molysis of cellular constituents (due to the 5 per cent salt in the original brine). However, the tissue was found com- pletely devoid of any intercellular gas. This observation was expected because the tissue appeared translucent. The flesh texture was still somewhat crisp, in the sodium bisulfite treated pickles even after 10 months of room temperature storage, and after 8 80 months existing in a translucent condition. This suggested that the cell wall material which lends primary support to the tissue and is mainly responsible for the firm texture (Meyer and Anderson, 1952) was not affected drastically by the sodium bisulfite. This is another indication that inter- cellular and not intracellular material was being broken down to allow escape of tissue gas. The value of adding pectinolytic enzyme inhibitor (extracted from scuppernong grape leaves) to fresh pickle covering brines to inhibit possible residual pectinolytic enzyme and thereby control loss of whiteness from the product following pasteurization was found to be nil. No significant differences could be judged between enzyme inhibitor treated (5 and 10 ppm concentration in the jar contents) and control pickles. It was observed in several cases of the sodium bi- sulfite treated pickles that translucency developed unevenly; that is, the lower flesh turned translucent prior to the upper flesh. Since it has been shown that development of flesh translucency is a function of concentration of sodium bisulfite in the brine and that stratification of brines does occur (Mulvaney, Nicholas, and Pflug, 1960) the uneven translucency is explainable. Figure 11.2 illustrates the result of stratification on translucency in sodium bisulfite treated and regular sweet spears. 81 Table 11.3. Effect of adding pectinolytic enzyme inhibitor to covering brines to control translucency in fresh cucumber dill slices Estimated Flesh Translucency (%)a Storage Inhibitor Jar Temperature Concentration 0 53 156 225 Size (OF) (ppm) Days Days Days Days 32-oz 75—85 0 O trace 50 75 10 0 trace 50 75 99 O 0 10 -- 99+ 10 0 10 —— 99+ 23-02 40 0 0 0 -- 20 5 0 0 -- 20 75-85 0 0 -- 40 99+ 5 0 —- 40 99+ 10 0 -- 40 99+ 99 0 0 10 -- 99+ 5 0 10 -- 99+ aAverage of duplicate jars used per estimation. 82 Figure 11.1. Effect of adding 0, 100, and 500 ppm (left to right) sodium bisulfite to standard covering brine on development of translucency after 81 days storage at about 80°F. Figure 11.2. More severe bottom translucency than the top as a result of brine stratification; sodium bisulfite treated pickles (left), regular fresh sweet spears (right). 83 XII. Estimation of Gaseous Volume in Cucumber Tissue .Experimental Procedure Number 2 and 3 size of SMR 18 variety of pickling cucumber harvested 14 August 1963 were used in this investi- gation. Cucumbers were held for one day in 400F storage before being tested. For each sample, six cucumbers were used and one slice approximately 1/4 in. in diameter was cut from each cucumber to make up the sample. Each sample was weighed and placed in a quart jar with 150 m1 of distilled water. A cap rigged for aspiration work was screwed on and a vacuum of about 28 in. of mercury was pulled. After 15 min the vacuum was released; slices were allowed to remain in the water for l min before being removed to a beaker where they were allowed to drain for 1 min. The slices were then weighed. Percent of gaseous volume in the tissue was taken as the amount of water (9) absorbed by the tissue. In two cases, chunks of tissue about 3/4 in. on a side were taken from number 3 size cucumbers and treated as above for slices. Results and Discussion The differences between localities of a cucumber and their gas holding capacity were great (Table 12.1). Extremes in gas holding capacity of tissue were parenchyma tissue in the blOssom end--highest; and center seed area--lowest. 84 Table 12.1. An indication of the percentage of gas to be found in several localities of the cucumber Estimated % Gaseous Volume of Tissuea Section of Cucumber Number 2 size Number 3 size Center slices 8.6 10.1 Stem-end slices 10.8 14.4 Blossom-end slices 12.1 16.5 Seed-area chunks —- 7.0 Fleshy-parenchyatmous chunksb -— 13.7 aAverage of duplicate determinations taken. bChunks taken from flesh equidistant from the ends of the cucumber, but no skin or seed area used. This is in agreement with observations made on fresh pickles in storage by the author: the last flesh of the cucumber to become translucent in any treatment often was noted to be the interior blossom-end flesh, while the first flesh to show translucency was center seed area. Thus, it is obvious that the gas holding capacity of cucumber tissue is directly related to development of translucency of that tissue. It also can be seen in Table 12.1 that the larger the cucumber, the more the percentage of gas could be found in the tissue. The number 3 size was found to possess an average 22.2 per cent more gas volume than number 2's. 85 It should be observed that all values of gaseous volume are estimations only and that such factors as water taken up by osmosis with no dispelling of gas in the process leads to final values on the high side. 86 XIII. Actual Measurement of the Amount of Gas in Cucumber Flesh Experimental Procedure Estimation of gaseous space in raw cucumber flesh as outlined in previous vacuum infiltration work (weight method) was compared with actual measurement of the gas present in cucumber flesh (volume method). Two center slices about 1/4 in. in diameter from an eating or slicing cucumber variety were cut in half. Two half slices (one-half from each fruit slice) were used per treatment. The two half slices were squeezed by hand until translucent and their gas volumes determined by both of the two gas volume methods. Actual measurement of gas was taken by placing the two half slices under a water-filled glass thimble open end down. The thimble was previously filled with water and placed in a quart jar rigged for aspiration work, the quart jar being about 3/4 full of water. A vacuum of about 28 in. was applied to the quart jar and its contents for 15 min. The vacuum was then released and the gas that had been drawn from the tissue and had ascended to the roof of the inverted glass thimble could be seen. The quart jar was placed in a full bucket of water. The thimble was drawn out of the water by means of an attached wire, making certain that the thimble did not tip and lose any gas. The thimble was then gradually turned upright allowing the gas to enter a water 87 immersed, water filled, shortened, graduated 10 ml pipet fitted with a stOpper on the opposite end. (The end in which the gas entered was fitted with a small funnel at- tached by a short rubber hose). Ml of gas could be read directly as the gas replaced the water in the graduated pipet. Calculation of volume of the cucumber tissue occupied by the gas was as follows: the two half slices were immersed in a 100 ml graduated cylinder and the ml displaced by the slices calculated. This volume was then compared with the volume of gas retrieved from the tissue for the final esti- mation of gas present in the tissue. Results and Discussion Table 13.1 indicates the estimated amount of gas present in cucumber tissue. Table 13.1. A comparison of two methods for estimating ’ gaseous percent of cucumber tissue.a volume (%) of Tissue Occupied by Gas Vacuum Infiltration Raw Raw Tissue Squeezed Until Method Used Tissue Translucency Deve10ped Weight 16.8 16.1 volume 12.6 9.8 aAverage of duplicate determinations taken per treatment. 88 The vacuum infiltration volume method resulted in a significantly lower value for per cent of gaseous space in a cucumber than did the vacuum infiltration weighing method. This data is in agreement with expected results since the weighing method does not take into account the water ab- sorbed beyond normal tissue capacity without replacing any of the intercellular gas. Previous work on the weighing method showed an increase in weight of cucumber tissue of 2.8 per cent after 15 min in water under normal atmospheric pressure. The increase was the result of osmotic action. However, it is also likely that some gas was lost from the tissue during those 15 min. With these considerations in mind, the weight method could be said to give somewhat higher estimations of gaseous volume. The result of squeezing the raw cucumber tissue un- til translucency developed showed up as a significant loss of gas from the squeezed tissue as measured by the direct determination of gas content method. The weighing method would not be expected to indicate a significant loss of gas from the squeezed tissue and although the data does indicate some loss of gas (0.7 per cent) a great amount was not lost. 89 XIV. Studies on the Effect of Vacuum Infiltration on Loss of Whiteness of Cucumber Tissue Experimental Procedure Wedges about 3/4 in. per side were cut from slices taken near the center of slicing type cucumbers. The wedges were vacuum infiltrated in distilled water on other liquids for given time intervals and translucency and/or firmness noted after the vacuum was broken. In arriving at a reasonable estimation of the degree of translucency, the most helpful aid was found to be cutting the chord (mathematically speaking) of the cucumber wedge. Results andipiscussion The data presented in Table 14.1 clearly show onset of translucency in cucumber tissue as a function of the de- gree of vacuum applied. At 25 in. of mercury vacuum, the only white tissue remaining after 1 min was located about 1/8 in. under the skin in a line parallel to the skin. This observation shows the relative impermeability of the skin to gas passage. It can be seen that a vacuum above 7 in. of mercury forl.min results in significant development of translucency, and that 50 per cent translucency is obtained after 1 min at 12 in. of vacuum. ray” ‘MA. 90 Table 14.1. Estimated translucency in wedgesa of a slicing variety of cucumber exposed to one minute of vacuum infiltration with water, the vacuums progressing from 0 to 28 inches of mercury Vacuum Applied Estimation of Translucency (in. of mercury) (% of flesh) 0 0 5 0 7 5 8 15 9 30 10 40 12 50 15 60 20 75 25 98 28 99 aWedges were cut from 3/4 in. wide slices which in turn were taken'from near the center of the cucumber. bData represent the average of three replicates. The effect of different vacuum infiltrating solutions on the degree of translucency obtained in the cucumber tissue did not vary, all assuming total translucency after 2 min at 28 in. of vacuum (Table 14.2). Apparently at high vacuums, little or no protection is offered by common pickle covering brine ingredients in reducing translucency as a result of vacuum infiltration. The effect of different vacuum infiltration mediums on texture, however, was striking (Table 14.2). Distilled water and 2 per cent solutions of alum and calcium chloride produced extremely firm and turgid flesh compared with soft (fi- 4 ...‘u 0" . 20' i ‘. n-d ~«1 ... ... ‘v ‘A In H» N 5 91 and rubbery flesh obtained with 50 per cent sucrose and 10 per cent salt solutions. A 4 per cent acetic acid solution produced a tissue texture somewhere between the preceding two extremes. There exists a strong correlation between the gain or loss in weight of the infiltrated tissue and the re— sultant texture. For example, those solutions exhibiting about a 16 per cent increase in weight were very firm or turgid whereas those solutions exhibiting a loss in weight of about 3 per cent were found soft and pliable exhibiting no turgor at all. Obviously, the osmotic pressure effect exerted by the sugar and salt solutions on the tissue cells was the main factor in this discrepancy. In the case of water and solutions relatively low in alum and calcium chloride the process was reversed from the high sugar or salt case: solution diffused into the tissue replacing intercellular space resulting in turgid cells. Table 14.3 indicates the effect of decreasing vacuum from a maximum of 28 in. of mercury to 0 in. at l min inter- vals on loss of whiteness from cucumber tissue. The initial drop in vacuum from 28 to 20 in. produced no visible change. However, further reduction in vacuum to 15 in., depending on the covering solution, resulted in significant translucency. Tissue in sucrose solution showed the least translucency (about 25 per cent), followed by salt solution (about 50 per cent) with water showing about 75 per cent of translucent tissue. v». “7‘ 92 Table 14.2. Effect of 2 min of 28 in. of mercury vacuum using different infiltration mediums on loss of whiteness, texture, and weight of raw cu- cumber tissuea' Gain or Loss of Tissue Degree of Infiltration Weight Translu— Medium (%) cency Texture Distilled water +16.4 total firm and turgid 10% sodium chloride brine - 3.1 total rubbery 50% sucrose liquor - 3.5 total rubbery 4% acetic acid + 9.3 total slightly firm 2% alum solution +16.l total firm and turgid 2% calcium chloride solution +16.0 total firm and turgid aRefer to Table 14.1 subscript "a" for tissue description. bData represent the average of three replications. The data gathered from this study conclusively point out the beneficial effect of sucrose in preserving tissue whiteness in fresh pickles. In agreement with this finding was the observation made in various fresh pickle storage tests that the sweet packs invariably showed significantly less translucency as compared with dill—type brine packs stored under the same conditions. 93 Table 14.3. Development of translucency in cucumber tissuea as a result of decreasing vacuum in a vacuum infiltration system at one min intervals from a maximum of 28 in. of mercury Li Infiltration Vacuum Applied Estimated Flesh Medium (in. of mercury) Translucencyb Water 28 none 20 none 15 75% 10 nearly totalC 5 total 0 total 50% sucrose solution 28 none 20 none 15 25% 10 75% 0 nearly total 5% sodium chloride 28 none solution 20 none 15 50% 10 80% 5 95% 0 nearly total aRefer to Table 14.1 subscript "a" for description of the tissue used. bData represent the average of three replications. CTransparency was total except for a thin line of white parallel to the skin. 94 XV. A Study_of the Relationship between Vacuum and Loss of Cucumber Tissue Gas Experimental Procedure Essentially the same vacuum infiltration procedure was used in this study as was used in the study on esti— mation of gaseous space in cucumber tissue. In this case, however, Spartan Dawn variety, number 3 size fruit in 40°F storage about 1 week was used. Vacuums at intervals ranging from 0 to 28 in. of mercury were applied to a sample comprising six slices, each slice being about l/4 in. thick and cut from near the center of six different cucumbers. Each treatment or sample, then, contained one slice from each of six different fruit. The average of two runs were used to develop the final data. Results and DisCussion Table 15.1 indicates data for all of the treatments. Table 15.1. Loss of gas from raw cucumber tissue as a function of the degree of vacuum applied Vacuum Applied Gas in Tissue (in. of mercury) (weight increase, %) 0 2.75 5 2.73 10 3.80' 15 4.24 20 4.76 25 6.80 28.5 7.65 95 Regression analysis of the data in Table 15.1 showed the relationship: §X = 4.68 + 0.174 (x - 14.8) as shown in Figure 15.1. The relationship shows loss of gas as a straight line function of applied vacuum, the greater the vacuum the more the loss of gas. No difference in water uptake of the tissue was noted between zero and 5 in. of vacuum, but between 5 and 10 in. of vacuum approximately 1 per cent increase in weight was recorded indicating loss of gas at a vacuum exceeding 5 in. (Table 15.1). The 2.75 per cent increase in weight of the tissue at atmospheric pressure was due to osmosis, the water travelling across the differentially permeable cell mem- branes into the cells. The osmotic effect caused distention of the cells and squeezing of the intercellular spaces. This in combination with the "sucking action" exerted by the vacuum on any movable material such as intercellular gas and soluble substances such as some of the pectins can be as- sumed the cause of the ever increasing losses of gas with in- creasing vacuum. Of course, as the gas leaves the tissue, infiltrating liquid replaces the intercellular spaces left by the gas causing the increase in tissue weight. 96 30 l I T 10'— _ APPLIED VACUUM (means (r m) C? I J l J 1 2 4 6 8 GAIN IN TISSUE WEIGHT (2) Fig. 15.1. Gain in weight of cucumber tissue (an indication of tissue volume occupied by gas) as a function of increasing vacuum infiltration values. 97 XVI. Effect of In—the—Jar Vacuum on Loss of Flesh Whiteness from Fresh Pickle Products Introduction Since the industry most generally employs an initial vacuum treatment of about 10 in. of mercury (Valentine, 1963), the effect of ingoing and final vacuums on flesh whiteness was investigated. Experimental Procedure Three separate packs of slices were made from number 3 size pickling cucumbers. The slices were packed into jars and room temperature covering liquid added: cucumbers were not blanched. In the first pack l6-oz jars were packed by weight (240 g) and standard brine (5 per cent salt - 1.4 per cent acetic acid) added (3 replications per treatment): for the second pack, 28-oz jars were packed by weight (475 g), and covered with standard brine (done in duplicate); the last pack was the same as the first except that a 50 per cent sucrose - 1.4 per cent acetic acid - 5 per cent salt covering liquor was used (done in duplicate). The jars were rigged for the vacuum study as follows: a 1/4 in. hole was drilled in each twist—off cover: the out- side enamel was sanded off in the area surrounding the hole; a 2 in. long piece of l/4 in. copper tubing was placed in the hole so that only about 1/8 in. extended beyond the 98 underside of the cover; solder was used to firmly attach the tubing to the cover with an airtight seal. The covers were twisted firmly onto the filled jars: a vacuum hose was at- tached to the copper tubing and a vacuum drawn. An aspiration' bottle fitted with a vacuum guage was placed between the vacuum source and the jar of fresh pickles in order that the degree of vacuum desired could be readily obtained. Preliminary studies had indicated that a vacuum of about 6 in. of mercury was lost from the initial in—the-jar reading to after pasteurization and cooling. For example, 21 in. of vacuum initially would result in about 15 in. in the final pasteurized product. After the desired vacuum was obtained in a particular jar, the copper tubing was cold-welded shut using a special copper tubing cold welding tool. Jars were then pasteurized for 30 min at 180°F. Flesh whiteness evaluations were made periodically on the jars in storage at about 80°F. Results and Discussion Table 16.1 gives results for the three packs. In general the greater the initial in—the-jar vacuum the greater the degree of translucency. The degrees of translucency are pictured in Figure 16.1. The severe translucency in the jar having 26 in. of vacuum initially can be seen clearly. Fresh pickle slices packed in standard brine in 16- or 28-oz jars under 26 and 21 in. of vacuum produced flesh (excluding seed cavity area) having more than 70 per cent 99 translucency after 20 to 26 weeks at about 80°F storage; this is to be compared with 55 per cent or less translucency for 5 and 10 in. of vacuum for like storage conditions. Table 16.1. Estimated per cent of tissue translucencya in fresh pickles as a function of in—the-jar vacuum and type of covering liquid Initial In-the-jar Storage Time Vacuum (Weeks) Jar Covering (in. of Type Liquid mercury 20 26 30 36 l6—ozb 5% salt - 26 95 95 1.4% acetic 21 70 95 acid 16 60 98 10 55 99 5 30 96 28-ozc 5% salt - 26 95 99 1.4% acetic 21 85 97 acid 16 50 94 10 50 94 5 35 90 16-ozC 50% sucrose 26 80 98 - 5% salt - 21 25 95 1.4% acetic 16 10 75 acid 10 5 80 lucency. aOnly fleshy parenchymatous tissue excluding seed cavity area was used in the estimation of per cent trans- b Three jars used per treatment. cTwo jars used per treatment. 101 The variation in results between different covering liquids was expected. The slices in the sweet liquor re- tained more whiteness on an equal vacuum basis than did the slices packed in standard brine. Sucrose has been observed in other studies to exert a protective effect on the desirable opaque whiteness of fresh pickles. The range of translucency values for the different vacuums of the sweet pack was marked--80 per cent translucency for 26 in. of vacuum down to only 5 per cent translucency at 10in., both after 20 weeks at about 80°F storage. However, even the presence of sucrose in the covering liquid failed to halt the progression of translucency for long, for after 30 weeks even 10 or 16 in. of vacuum produced 75~80 per cent flesh translucency. It should be noted here that perhaps the main reason for quality to deteriorate so rapidly in this series of experiments was the rather high storage temperature (about 80°F) used. The effect of in—the—jar vacuum on flesh whiteness involves gas exchange relationships with intercellular and intracellular liquids plus the covering liquids. Expansion of gas and the setting up of pressure gradients by applied vacuum, expansion of gases and ingredients from heating, and osmotic action of the cellular differentially permeable membranes--all cause the exchange or diffusion between the gases and the liquids. Thus the gas—liquid exchange is 101 The variation in results between different covering liquids was expected. The slices in the sweet liquor re- tained more whiteness on an equal vacuum basis than did the slices packed in standard brine. Sucrose has been observed in other studies to exert a protective effect on the desirable opaque whiteness of fresh pickles. The range of translucency values for the different vacuums of the sweet pack was marked--80 per cent translucency for 26 in. of vacuum down to only 5 per cent translucency at 10in., both after 20 weeks at about 80°F storage. However, even the presence of sucrose in the covering liquid failed to halt the progression of translucency for long, for after 30 weeks even 10 or 16 in. of vacuum produced 75-80 per cent flesh translucency. It should be noted here that perhaps the main reason for quality to deteriorate so rapidly in this series of experiments was the rather high storage temperature (about 80°F) used. The effect of in—the-jar vacuum on flesh whiteness involves gas exchange relationships with intercellular and intracellular liquids plus the covering liquids. Expansion of gas and the setting up of pressure gradients by applied vacuum, expansion of gases and ingredients from heating, and osmotic action of the cellular differentially permeable membranes——all cause the exchange or diffusion between the gases and the liquids. Thus the gas-liquid exchange is 102 dependent partially upon the degree of vacuum applied. In detail, it may be theorized that as the vacuum is increased the greater is the removal of gas from the tissue because of expansion of tissue gases caused by the reduced pressure: there is greater removal of soluble intercellular substances caused by the larger pressure gradients set up between the tissue and the covering liquid and head-space, and greater physical distention of the cells caused by the pressure gra- dients: and finally there is more rapid influx of covering brine into the pickle flesh allowing salt in the brine to act adversely on intercellular constituents such as calcium pectate, a cell cementing compound. Release of vacuum in the jars having initial vacuums of 16 in. or more after only a few hours of storage resulted in totally translucent pickles almost immediately, whereas vacuums below 16 in. initially produced partially translucent pickles after opening. These results are in general agree— ment with those presented by Etchells and Ohmer (1941). It may be surmised that as the vacuum is broken (opening the jar) the gas remaining in the tissue decreases in volume. Liquid is pulled into the vacated gaseous space causing translucency to appear, making for easier conditions for the gas to slip out of the tissue, and,of course, gas being naturally buoyant, it would rise to the surface. 103 XVII. Effect of Pressure in Excess of Atmospheric on Whiteness of Cucumber Flesh Experimental Procedure A slicing variety of cucumber was used in all tests. An ordinary retort fitted with a raised flat platform inside served as the pressure chamber. Air pressure could be easily controlled in the system to i.O-2 p.s.i. Cucumber tissue in all cases but one was placed in beakers containing liquid (one treatment was in air), and the beakers in turn placed on the raised platform inside the retort. Trans- lucency was estimated in all cases (the seed area being ex- cluded from the estimation). Safranin dye was placed in some of the covering liquids to observe penetration of these liquids into the flesh. Results and_Discussion Table 17.1 indicates severe translucency in all cases of cucumber flesh being covered with any of several liquids and subjected to a pressure of 15 p.s.i. for 5 min. The data show a "protective" effect on preservation of flesh whiteness for any solution containing sucrose. For example, the amount of translucency observed in a 5 per cent salt brine, a 1.4 per cent acetic acid solution, and water were approximately 2, 3 and 3-1/2 times, respectively, more than the trans— lucency observed in a 50 per cent sucrose liquor. 104 Table 17.1. The effect of 15 pounds of air pressure for 5 and 15 minutes on loss of whiteness and texture of the flesh of a slicing variety of cucumber immersed in different covering liquids and air Time Estimated Under Degree of Covering Pressure Translucency Flesh Medium (min) (% of flesh)a'b Texture Air 5 0 firm 15 0 firm Water (6OOF) 5 80 very firm 15 90 very firm Water (32°F) 5 90 very firm 15 95 very firm Water (l3OOF) 5 90 firm 15 95 firm 5% salt brine 5 50 soft and rubbery 1.4% acetic acid 5 80 slightly firm 50% sucrose liquor 5 25 soft and rubbery 5% salt—1.4% 5 50 soft and acetic acid brine rubbery 15 75 soft and rubbery 50% sucrose-1.4% 5 25 soft and acetic acid rubbery liquor 15 50 soft and rubbery 50% sucrose-1.4% 5 50 soft and acetic acid-5% rubbery salt liquid aFlesh refers to all flesh excluding the seed cavity area. bAverages of three replications of both 1/4 in. thick Slices and wedges 3/4 in. on all sides cut from slices 3/4 in. thick (as from a pie) were used in all treatments. 105 In all cases when the time was increased from 5 to 15 min at 15 p.s.i., translucency also increased slightly. It may be theorized that the flesh-in-water treat- ments received the greatest amount of translucency because of the ease of the molecules to travel into and out of the tissue as compared with much larger sugar molecules which move slowly (Chemical Engineer's Handbook, 1950). Gas was forced out of the tissue in the case of the water treatments due to the extreme turgidity taken on by the cells as the result of osmotic and retort air pressure. In the case of the sugar solution, osmosis worked in reverse and the cells contracted (water moved out of the tissue) allowing the intercellular gas to remain in the tissue to a certain degree. The same holds true for the salt and acid solutions, only to a lesser extent. The parenchymatous tissue between each of the three placental regions and the skin showed translucency in all treatments save air. This situation most likely was due to the loose tissue structure and abundance of vascular tissue within the placenta allowing for rapid diffusion of gases and liquids through them. With "open" areas on both sides of the band of parenchymatous tissue, the band would be expected to react to the accelerated diffusion phenomena surrounding it in a manner leading to premature translucency. 106 XVIII. Storage of Pickling7Cucumbers: Effect on Flesh Whiteness Introduction Storage tests of pickling cucumbers were conducted during two seasons. Extension of the relatively short fresh cucumber season for several weeks through refrigerated regular or controlled atmosphere (CA) storage was the ulti— mate goal of these studies. In carrying through some of the tests, observations were taken on flesh conditions also. Experimental Procedure Michigan pickling cucumbers were trucked to East Lansing where they were then placed into storage. In the regular refrigerated storage tests, two varieties, three sizes, three storage temperatures, and several sampling periods were used. Fruit was evaluated for quality initially and at each sampling period. Quart jars of whole dills were made from samples taken during each sampling period. Pickles were evaluated one year after packing. For the CA storage tests two atmospheres produced by a Tectrol generator (Tectrol Division, Whirlpool Corporation, St. Joseph, Michigan), SMR 15 variety, number 2 and 3 sizes, and 34 and 40°F storage temperatures, were used. Storages were opened after 2, 3 and/or 4 weeks for fruit examination and taking of samples for packing. Number 2 size were made into whole dills, while number 3's were made into dill spears. 107 Results and Discussion Storage of pickling cucumbers at 34 or 400E for several days prior to packing had negligible effect on flesh whiteness. In fact, even after 18 months of in—the—jar storage at room temperature, number 2, SMR 15 and 58 whole dills which had undergone at least 9 days of 34 or 40°F storage before packing, showed as much white flesh as did the pickles which were not stored at all before packing. The only abnormality noted in the refrigerated fruit was small pockets of translucent flesh beneath the spine spots (areas numbering about 100 spread over the cucumber surface resulting from the severing of spines during harvesting, grading, etc.). The condition was observed to worsen if the fruit were not used within a few hours after removal from the storage. Presumably, condensate which formed on the fruit as a result of moving chilled fruit into a warm atmos- phere acted to favor microbial growth and enzyme production. Growth was concentrated at the spine spots where nutrients were readily available from the cucumber for the rot and other microorganisms to utilize. The situation was similar in the CA storage fruit, only quite often more pronounced. Even though translucent areas beneath the skin often did not show up in the raw product, the areas were very evident in the processed pickles, especially in cut products such as spears. 108 Figure 18.1 pictures a cucumber with severely deteriorated spine spots as the result of microbiological action. Figures 18.2 and 18.3 illustrate the result of spine spot deterioration—-translucent areas beneath the spine spots. As in the case of regular refrigerated fruit, any long delay in packing following removal of fruit resulted in highly inferior product (Figure 18.2). All indices of quality were lower including texture, flavor, odor, color and appearance. Table 18.1 indicates the effect of CA stor- age on degree of flesh translucency developed in fresh spears after six months of storage at room temperature. Table 18.1. Degree of flesh translucency in fresh dill spears stored at room temperature for about six months after packing. Spears were pre- pared from SMR 15, number 3 size cucumbers taken out of CA storage Storage Time in Time elapsed after Degree of Atmosphere Temper— Storage Removal from Trans- (%C02-%02) ature Storage to Packing lucency ' (OF) (weeks) (hours) (%of flesh)3 5 — 5 34 2 2 trace 2 24 50 4 2 10 5 — 5 40 2 2 20 24 9O 10 - 3 40 2 24 90 5 - 5 34 4 4 50 10 - 3 34 4 4 50 aAn observation common to all of the CA treatments was the presence of translucent pockets in the flesh beneath each wart or spine spot. 109 Figure 18.1. Severe spine spot deterioration as the result of microbiological action during excessively long refrigerated storage. Figure 18.2. Fresh dill spears made from cucumbers in re— frigerated storage too long showing deep translucent areas beneath spine spots. 110 Since spears were not made from every treatment, some information gaps exist. However, it may be seen that the 34°F storage temperature preserved flesh whiteness better than 40°F (Table 18.1). The effect of delaying packing one day after removing the fruit from storage was dramatic (Table 18.1 and Figure 18.4). Translucency increased in the delay pack spears markedly. As the storage time of the raw fruit increased, only the 34oF fruit were fit to pack after 4 weeks. In the one case where translucency was recorded at 34°F, both at 2 and 4 weeks storage, the spears showed a 10 per cent increase in the amount of translucency as the result of longer storage. Of course, translucency would have been severe in the 40°F stored fruit after 4 weeks had the fruit been fit to pack. No conclusion could be reached as to the effect of atmosphere on flesh translucency. Not enough treatments were evaluated. The reasons for translucent areas developing beneath the spine spots appear to be both physical and chemical in nature. First of all, when the spine is severed from the skin, an area results which is unprotected by normal epider- mal tissue. Consequently an opening exists where gaseous diffusion and microbiological growth can proceed at a maximum. As the microbial populations increase at the spine spots, enzymes produced by these organisms increase also. The combination of accelerated diffusion rates and enzymatic Figure 18.3. Figure 18.4. 111 um "Tum-0m: Twin - Off" Six month old fresh dill spears made from CA fruit, 10% C03 - 3% 02 (left), 5% C02 - 5% 02 (right) at 34 F for 4 weeks showing trans- lucent areas beneath the spine spots. Test-9.9" Six month old fresh dill spears made from CA fruit (5% C02 - 5% 02) stored 2 weeks at 40°F showing translucency resulting from not using cucumbers soon enough after removing from storage (right) compared with immediately used fruit (left). 112 degradation of the cellular structure allow gas leakage from the parenchymatous tissue causing local translucent areas to appear.‘ 113 XIX. Effect of Storage Temperature and Time on Loss of Whiteness from Commercially Processed Fresh Sweet Cucumber Crosscuts Experimental Procedures Five cases (12 jars per case) of line-packed 23-oz jars of fresh sweet cucumber crosscuts were used. One case was placed in each of constant temperature rooms of 40, 60, 72, 86 and 99°F for 14 months. The entire pack had been given a heat process of 25 minutes at 1800F. After 2 months, then every 30 days thereafter up to 8 months, treatments were evaluated subjectively for degree of translucency. A final evaluation was made after 14 months. For ease in evaluating the different treatments, an eight-point translucency scale was set up and used. Results and Discussion Initial translucency appeared after 7 months at 400E, 6 months at 60°F, 5 months at 72°F, 5 months at 86°F, and 4 months at 99°F (Table 19.1). Maximum or total translucency of the slices occurred only at storage temperatures of 86 and 99°F taking 8 to 14 and 5 to 6 months respectively. Figure 19.1 pictures in color the condition of the sweet slices stored at 40, 60, 72 and 99°F for 19 months. Figure 19.2 pictures in color the condition of spears from another study packed in commercial salt—acid brine after 19 months storage at 40, 72 and 99oF. 114 Table 19.1. Effect of storage temperature and time on the loss of whiteness from commercially line- packed fresh sweet cucumber crosscutsa' Months in Storage Storage Temperature (OF) 2 3 4 5 6 7 8 14 4o 1 1 1 1 1 3 3 4 60 1 1 1 1 3 4 4 5 72 1 1 2 3 5 5 6 6 86 1 2 2 3 7 7 7 8 99 2 2 3 4 8 8 8 8 aDescription of degree-of-translucency values: 1 = Normal bright white flesh 2 = Flesh dull looking but not translucent 3 2 Trace of either or both seed area or peripheral translucency 4 = Trace to 10% of flesh translucent 5 = 10 to 30% of flesh translucent 6 = 30 to 60% of flesh translucent 7 = 60 to 90% of flesh translucent 8 = 90 to 100% of flesh translucent bAverage of 12, 23-02 jars taken for evaluation per treatment. At the lower temperatures, translucency appeared to increase rather gradually or uniformly. At 86 and 99°F, however, the rate of deterioration was very rapid once trans- lucency was initially detected. Figure 19.3, showing plots of translucency values, indicates a plateau or part of each curve leveling off after a certain period of time in storage. Apparently after about 6 Or 7 months of storage at a particular temperature, a 115 Figure 19.1. Quality of line—packed fresh sweet pickle slices stored at several temperatures for 19 months. Figure 19.2. Quality of line—packed fresh dill pickle spears stored at several temperatures for 19 months. 116 level of whiteness is retained in the flesh which changes slowly from then on. The level attained depends on the storage temperature; the lower the temperature the less the degree of translucency in the flesh. Figure 19.4 illustrates a graphic method whereby permissible storage temperature and time can be predicted for three levels or degrees of translucency exhibited by the slices. (Data from the curves of Figure 19.3 were used in developing the data for Figure 19.4) For example, if one wishes to determine the storage time at 50°F allowable be- fore a trace to 10 per cent of the slice will become trans— lucent, one may read over on the 50°F line until it inter- sects with the trace to 10 per cent translucency curve, then read down until slightly less than 10 months is noted on the storage time axis. It should also be mentioned that, in general, as the degree of translucency increased, texture became less crisp, flavor deteriorated, and overall color worsened. Color of the 86 and 99°F slices after 14 months of storage changed to a dark reddish-brown indicating severe degradation reactions at these elevated temperatures. At the elevated storage temperatures the product could be observed to take on an overall dull caste within a few weeks of processing preceding the onset of any trans- lucency. When translucency appeared initially the areas thus affected included the entire seed cavity and/or occasionally 117 39332—53 in. «a: owuuoua «a canon—ow a on 33.3 30.03 :26 such—m 60301.65.“ mafiauuflflau 5 33am. 8303.95... no 09.38 .m.m~ .3» Ago age. 86.8 3 S o." m o a» N .- - - - -..- M 6.3.3.3133 . H --.-3-343311233313131. ooanoa ..-. .- .- . . . ., . -. . . . . . .. . . . l . . 1 . u . . u a n .. . . . . _ ....3. 03.173.3133 .f. .. ..-. 0 ° 3 . 3.. .. .- .. .- I . . .omé .. . . . . .. _ . . . . . . _ . . . . . . . . . . . , . . . . . . . .. .. . .. . . . . . -- __‘_.~_- U W 1 w ,- . .w I _ . w W H .0) Pas. ”8.8 H . 1 i... - . :lv- -.. .vv-... . .34 --.-....v-IJ. .113. .03-- 3...?! -33.. - .-. .ii. .--)- o4 _ . ‘Wom-o~ . 3 -625. ”r3 -- - . 339 (13331.1 80 z) momsum .10 ma o 333 STORAGE rmm (‘13) 118 100 *I I I I ’T7 I I I 90 — - 80 t' A 70 r“ .\\ — 10-3OZ TRANSLUCENCY 6O *- TRACE-101 TRANSwCl-ZNCY 50 r- _. A TRACE OF TRANSEDCENCY 40 t- 30 1 l l 1 1 1 1 .1 1 4 5 6 7 8 9 10 ll 12 13 14 STORAGE TIME (MONTHS) Fig. 19.4. A graphic method of predicting the permissible storage temperature and time to produce fresh sweet pickle slices of three levels or degrees of translucency. (Date from curves of Fig. 19.3 were used in developing these data). 119 small areas directly beneath the epidermal cells. The latter case can most likely be attributable to bruising prior to packing. The cell structure in the seed area is somewhat loose; the cells are in general, large and possess very thin cell walls, and there appears to exist a minimum of solid cellular material within the tissue (other than the seeds, of course) (Figure 3.6). It is thus understandable as to why the seed cavity would be the first area to show signs of translucency. After the seed cavity had become translucent, then the fleshy parenchymatous tissue evidenced loss of whiteness or translucency to varying degrees. The last fortress of tissue to give up its whiteness was generally located near the cen- ter of the fleshy parenchymatous tissue. One may form the conjecture from these observations that the loss of whiteness experienced in pickle flesh is a gradual, progressive phenomenon in which gas barriers are uniformly and systematically destroyed from both the outside and inside toward the center of the fleshy parenchymatous tissue, eventually allowing the escape of all entrapped tissue gas. Furthermore, since temperature is of prime importance in controlling the rate at which the loss of whiteness phe- nomenon progresses, the actual mechanisms involved in the breaking down of the gas barriers and for transporting gas out of the tissue must be of a type possessing activity as a 120 function of temperature. It is difficult to assess exactly the rate of reaction, but as an estimate from the available data this function appears arithmetic in nature possessing a QlB°F(lIan: of about 1. For example, the amount of trans- lucency to be expected at 96°F would be roughly two times that expected at 600E. TheolaoF of gaseous diffusion in biological systems is nearly arithmetic, having a QlBOF of about 1.2 to 1.3 according to Meyer and Anderson (1952). Gaseous diffusion phenomena could conceiveably play the major role in the mechanics involved in the loss of whiteness from cucumber flesh. n1 Irv! ( ‘1) lru n.) I). 121 XX. Effect of Freezing on Raw Cucumber Tissue Introduction The author on three occasions had noted translucent or "watery-looking" skin areas and some translucency in the flesh beneath these areas in cucumbers stored at tempera- tures near freezing. It was thought that freezing injury was to blame rather than chilling injury since fruit stored at 34 or 40°F never showed the condition just described. Thus, a study was set up to observe the effects of freezing temperatures on cucumber tissue. Experimental Procedure Both pickling and slicing cucumber varieties in whole and cut condition were subjected to freezing tempera- tures for various lengths of time. The effects on both external and internal flesh were recorded. Results_apdt9iscussion Freezing of raw cucumbers resulted in a translucent or "water-logged looking" skin area wherever the skin was actually frozen. For example if a cucumber was placed directly onto the freezer surface of a refrigerator's freezer and allowed to remain there for about 15 min, the area of the cucumber making contact with the freezer surface would turn translucent, and this was the only area of the fruit to actually freeze under these conditions. As the severity of 122 freezing increased the greater the amount of translucency was noted both in the skin and in the subepidermal tissue. According to Meyer and Anderson (1952) ". . . living plant cells are usually killed when water freezes within them" due to the lacerating effect of the ice crystals formed. Presumably as the protoplasmic and cellular structure of the cucumber tissue was disorganized by inter- and intracellular freezing, the tissue liquids leaked out of the cells replacing intercellular gas which (1) was forced out of the tissue by ice crystal formation and (2) was able to escape more easily through the highly permeable tissue. Dead, translucent tissue was the final result. 123 XXI. Effect of Light on Whiteness of Fresh Pickle Flesh Experimental Fresh pickle spears and slices were prepared in the usual way in l6-oz jars. Variables included blanch versus no blanch: standard brine versus sweet liquid: slices versus spears: sunshine versus dark. Duplicate jars were prepared for each treatment. The jars exposed to sunshine were placed on a window- sill having, more or less, a western exposure. Duplicate jars were placed in a heavy brown paper sack and left under the windowsill. The jars exposed to fluorescent light were placed approximately one yard from two cool white, 40 watt fluo- rescent lights. This light was on for about 15 hours per day. Replications of these jars were placed in a cardboard case in the same area. Visual observations were made after about 1, 3 and 9 months. Resultsgand:piscussion No observable color affects or differences in trans- lucency were noted in pickle flesh after 9 months as a result of subjecting fresh pack pickle slices and spears to fluo- rescent light. However, for the jars exposed to sunlight through windows, after 1 month the flesh had lost its slight 124 greenish tinge and showed up whiter than duplicate jars kept in the dark. Apparently the sunlight bleached the green chlorophyllous pigments naturally present in pickling cu- cumber flesh. The slices and spears near the center of the jars, however, still possessed the greenish tinge. The slices and spears exposed to sunlight were compared with those exposed to fluorescent light. The latter possessed a greenish tinge even after 9 months. GENERAL DISCUSSION The data obtained in this thesis indicated that many factors have a bearing on the undesirable translucent con— dition found in certain fresh pickle flesh. Major factors include: refrigerated storage of the raw product, blanching of the cucumbers (whole and cut), pasteurization, pasteuri- zation time at a particular temperature, covering liquids used, pressure attained in the jar, vacuum attained in the jar, temperature and time of in—the—jar storage. There appears to be one overriding reason for the chalky, opaque white condition found in normal raw cucumber and fresh pickle tissue to change to an irreversible, under- sirable, translucent condition--that is loss of gas from the tissue. Careful microscopic studies of white opaque tissue, partially opaque white tissue, and totally trans- lucent tissue clearly indicate the relationship of degree of whiteness with degree of gas present in the tissue. Vacuum infiltration studies were also of great help in establishing the relationship. The presence of undissolved gas in the tissue causes reflectance of light perceived by the eye as an opaque, white, desirable condition (in the case of fresh pickles), but as the gas escapes the tissue by one means or another, translucency develops when a certain low critical 125 126 level of gas is reached, the intercellular spaces formerly occupied by the gas being filled with liquid. Some of the physical characteristics of gases are very important in regard to the present problem. For ex- ample, the fact that gas possesses, first, natural buoyancy within a liquid suggests that any time in-the—jar tissue is in some way changed to allow gaseous movement the natural buoyant force exerted by the gas will tend to carry it out of the tissue in an upward direction, the spaces left by the gas being replaced by liquid: and the more the gas joins to- gether in pockets the greater this buoyant force will be. A second physical factor would be the effect of expansion and contraction of gases within the tissue on loss of the tissue gas. Heating and application of vacuum to in-the-jar tissue act to expand tissue gas, whereas cooling and exerting pressures in excess of atmospheric result in contraction of gas. Expansion of gas in tissue could push cells apart physically and open intercellular spaces and/or force gas to move from gas pocket to gas pocket: while contraction of gas in tissue would result in displacement of gaseous space by liquid. Third, the solubility of gases in water changes but slightly with pressure, but with temperature the change is great. According to the Chemical Engineers Handbook (1950) the solubility of air in water at 32°F (0°C) is roughly one and one-half times that at 68°F (20°C) and two times that at 104°F (400C). Fourth, the effect of gaseous 127 diffusion phenomena in pickle tissue and liquid is an im- portant factor. The Chemical Engineers Handbook (1950) re- ports an increase in the diffusion coefficient of air in water of about 3 per cent per OC temperature rise near 20°C (68°F) and an increase of about 2 per cent per 0C for other liquids. Applied to the problem of loss of gas from pickle tissue in the jar, this information suggests a serious problem at high temperatures and a beneficial effect in the form of reduced gaseous diffusion rates at low temperature. Many of the whys and hows of loss of cucumber tissue gas are answered by the data'and results reported in this thesis, and also by the tying together of seemingly unrelated facts gleaned both from the present studies and from the Literature. To be considered first is the curing process en- countered in the manufacture of genuine dill and salt stock pickles. What factors affect this curing process? To name the key factors would be to include: temperature (the cooler the temperature the less the curing), low-salt curing (ap- proximately 300 salometer brine initially results in highly cured pickles), size of the pickles (the larger the cucumber the slower the cure), rate of fermentation (the more rapid the rate the faster the cure), type of fermentative micro- organism used in pure culture inoculation techniques(hetero— fermenters produce more fully cured pickles than do homo- fermenters), and blanching (blanching of cucumbers prior to fermenting results in poor cures). NOW we may ask, do some 128 of these factors have anything in common? The answer is yes. Apparently factors which are favorable to fermentation, or increased numbers and/or activity of microorganisms in the brine produce more fully cured pickles than those factors which act to suppress the fermentation; thus number and activity of microorganisms have a direct pertinent relation- ship to curing. It is a known fact that many of the micro- organisms present in pickle fermenting brines are able to and do produce quantities of pectinaCeous substance degrading enzymes. Polygalacturonases are a group of such enzymes commonly occurring in fermenting brines. Since curing is a loss of tissue gas phenomenon, the pectin degrading enzymes hold great significance. Middle lamellar and intercellular pectinaceous cementing substances in general are prone to enzyme degradation, thus rendering them soluble and useless in their role as cementing substances for adjoining cells. With the close intercellular network broken down through the action of pectinolytic enzymes, "avenues of escape" open be- tween the cells to allow the heretofore trapped gas to diffuse or migrate to the outside, eventually creating the desirable (in the case of fermented pickles) translucent condition. Actually the same reason exists for the translucent condition so often observed in low heat processed or under— pasteurized fresh pickles as exists for salt stock. If the jar undergoes microbial spoilage as the result of 129 underpasteurization, translucency of the flesh manifests it— self once again as the indirect result of pectin degrading enzymes produced by the spoilage microorganisms. Of course, all microorganisms do not produce pectinolytic enzymes and in line with this fact is the observation that all under- processed fresh pickles which undergo microbial spoilage do not become translucent. For the underprocessed fresh pickles which do not undergo microbial spoilage, pectin degrading and other en— zymes naturally occurring in the cucumber and on the fruit surface, not destroyed or inactivated by the heat process, act slowly but surely in bringing about the terminal trans- lucent condition of the flesh long before properly processed fresh pickles do. Probably the prime factor contributing to the problem of translucency in fresh pickles was found to be that of pasteurization. This one process accounted for roughly 75 per cent of the tissue gas loss, thus leaving the level just short of that required to produce a translucent flesh condition. It is not difficult to comprehend why so much gas is lost during the pasteurization treatment. The combination of heat (acting to degrade tissue constituents, expanding the gas and contents, and increasing diffusion rates and other reactions), pressure (increased enormously by expansion of jar contents due to heating), vacuum (caused by contraction is: . 130 of jar contents in the cooling process), and the rather rapid change of these conditions literally "tortures" the tissue into giving up most of its gas. Heat, pressure, vacuum, and rapid change of conditions have all been shown to have a derogatory effect on tissue-gas retention. As concerns heating of tissue, one of the chief reasons for blanching or exhausting many food products is to remove tissue gas, especially the oxygen in the gas, in order to avoid oxidative reactions in the container as much as possible during storage. Another consideration of heat should be restated here and that is "heat alone changes water-insoluble pectic constituents of plants (protopectin, etc.) into soluble ones," (Kertesz, 1953). With the cell cementing substances affected (solubilized to some extent) intercellular gas can move more freely through the tissue. Pressures of 15 p.s.i. applied to cucumber tissue immersed in various covering liquids for 5 to 15 min resulted in highly significant translucency. Least affected by the pressure was that tissue immersed in 50 per cent sucrose solution. Sucrose is a large molecule and diffuses slowly, slower than water, salt, or acetic acid. In addition, sucrose does not affect pectin greatly. The combination of these two factors were attributed to preventing the gas in the tissue from moving out easily. The studies on the effect of vacuum on loss of tissue gas clearly demonstrated a linear relationship between amount 131 of vacuum and extent of tissue gas lost; the greater the vacuum the greater the loss. The recommendation of main- taining less than 10 inches of mercury vacuum in-the-jar (Etchells and Ohmer, 1941; Etchells and Jones, 1948: and Valentine, 1963) was substantiated by the data presented in this thesis. Vacuum creates a pressure gradient in the tissue when applied causing anything that is soluble and/or loose to be prone to relocation. Some pectinaceous and proteina- ceous substances are literally pulled out of the tissue be- tween the cells along with intercellular gas to be replaced by cell sap and infiltrating liquid, whatever the latter may be. In the case of 5 per cent salt — 1.4 per cent acetic acid covering brine, diffusion of the salt and acid into pasteurized fresh whole pickles was found to be extremely rapid as was the exit of a great deal of water and gas. Osmosis and other diffusion phenomena progress very rapidly under pasteurization conditions. Apparently an equilibrium between the jar contents (including gas) and the internal vacuum is assumed some time after pasteurization. Even in jars of cut fresh pickles given initial in-the-jar vacuums of 26 and 21 in. prior to pasteurization,flesh whiteness was maintained to a large de- gree in the closed system. When a jar of fresh pickles was opened, thus allowing the vacuum (more or less equalized throughout the jar) to give way to atmospheric pressure, the 132 white opaque pickle flesh assumed a translucent condition, the degree of which generally depending on the amount of vacuum present in the jar. If the vacuum was generally greater than 10 in., then total translucency would result almost immediately; with less than 10 in., partial trans- lucency would result. Perhaps the key to controlling loss of whiteness from fresh pickle flesh is storage temperature. Shelf life of fresh pickles can be increased markedly by the appli- cation of cool storage temperatures, the cooler toward freezing the better. The illustrations shown in this thesis relating to this aspect of the overall study demonstrate better than words the highly beneficial effect of cool stor- age temperatures on fresh pickle quality. One example will be taken from the data, however, to show the extreme desirability of low storage temperatures for preserving fresh pickle quality. In the case of purposely underprocessed sweet spears (l3, 14, 15, or 16 min in 180°F water), for those that did not undergo microbial spoilage "initial translucency (trace only) was first observed after 7 months storage at 40°F, after 3 months at 72 and after only a little over a month at 99. Total translucency was not effected in the 400F pack after 14 months, but was recorded after 5 months at 72 and after only 2 months at 99. The observation by Nicholas and Pflug (1960) of high warehouse temperatures used for holding pickle products led 133 to research from which these workers recommended storing pickles at temperatures of 72°F or less to preserve quality. Data gathered in this thesis essentially substantiate the findings of Nicholas and Pflug. The recommendation might be reworded to include advising usage of the coolest storage temperature (above freezing) that is practical, and not only in the warehouse but also in the retail stores. The extremely beneficial effect of cool storage tem— peratures on fresh pickle quality should be expected. It is true that refrigerated storage has been applied to mostly perishable goods in the raw state, but it is also a fact that just because a foodstuff has a wrapper or covering of some description around it, the foodstuff will not undergo serious deterioration also. The importance of applying refrigeration to certain processed products in storage has been too long underrated. A classic study dealing with the problem of deterioration of a packed product in storage was that made by Livingston, Esselen, and Fellers (1954) on processed applesauce. Here again refrigerated storage was the "governing" answer to the problem. The role of cool temperatures is to reduce or in— hibit the rate of chemical, physical, and biological reac- tions and/or combinations of these reactions. For fresh pickles, decrease in rate of reactions leading to breakdown of intercellular constituents such as pectins and proteins, and decrease in diffusion rates of gases and other substances 134 could probably account for most of the beneficial effect of cool storage temperatures in retaining the desirable white, opaque condition of the tissue. Studies on the effect of common salt, acetic acid, and sucrose, the three most common ingredients used com- mercially in covering liquids for fresh pickles, on loss of opaque whiteness of the flesh revealed major differences be— tween sucrose or acetic acid and salt. Sucrose and acetic acid generally acted in a positive manner relative to salt in preserving the opaque white flesh. In one of the studies, 5 per cent salt-only covering brine (an experimental brine, and a brine not used commercially for fresh pickles) proved to have an extremely deleterious effect on flesh whiteness as compared with 1.4 per cent acetic acid-only covering liquid (also a liquid not used commercially). The various roles of salt, acid, and sucrose in the covering liquids on loss of gas from fresh pickle tissue might be clarified if the action of each ingredient on pectinaceous substances were considered. Sucrose and acid are two of the four ingredients (pectin and water are the other two) required for forming the pectin gel complex (Kertesz, 1951: Preservers Handbook, 1956), therefore, neither of these substances would be expected to drastically affect the pectinaceous substances and apparently they do not in this case. But in the case of sodium chloride (sodium bisulfite also) the literature does not state any clear 135 relation of either of these two sodium compounds in solution to pectinaceous substances (protopectin, pectin, etc.). How— ever, since calcium salts of the pectic compounds of the middle lamella have been shown to exist in quantity (Kertesz, 1951: Meyer and Anderson, 1952), replacement of calcium with sodium would act to seriously impair the so called calcium pectate insoluble complex (Kertesz, 1951). Permeability of the tissue would increase markedly allowing gases to diffuse more readily out of the tissue between the cells. Explanations as to why a blanch treatment of whole cucumbers prior to pasteurization resulted in somewhat more opaque white tissue are not forthcoming. However, the answer might lie in greater destruction or inactivation of pectin degrading tissue enzymes, such as the polygalacturo- nases, by the extra heat afforded the tissue through blanching. Blanching of cucumbers often led to a condition of flesh translucency associated with the periphery under the skin to depths of up to a quarter of an inch. This situation was thought to be intimately associated with rough handling techniques which resulted in bruised fruit. Although the bruised areas often did not show up as translucent in the raw state, after blanching these areas showed translucency, the result of gas being given up by the damaged tissue with the application of heat. 136 The effect of blanching cut cucumbers on loss of flesh whiteness was undesirable. Blanching slices at 160 or 180°F up to 6 min resulted in significantly more translucency in the-jar after a storage period. The blanch was thought to be too severe (excessive heat) for the exposed flesh, literally cooking the tissue and causing rapid expansion of tissue gases and solid tissue both. At the 180°F blanch temperature it was found that translucency increased with in- creasing blanch times. This would be expected once it was established that blanching of cut fruit resulted in inferior product compared with unblanched cut fruit. Obviously the more severe the blanch the more the tissue was broken down and gas driven off finally resulting in more flesh translucency. In the case of cucumbers stored under refrigerated regular or controlled atmosphere (CA) storage conditions, the translucent condition appearing in the flesh beneath the spine spots was attributed to a combination of: (l) enzy— matic activity originating from microorganisms concentrated at the spine spots and (2) increased diffusion at the spine spots as the direct result of the severing of the spines allowing unprotected openings in the skin. Fresh pickles made from cucumbers stored under CA conditions up to 4 weeks and allowed to stand at room tem- perature beyond a few hours after removal from storage were poor in quality. Grayish color, soft texture, and off-flavors 137 were evidenced. Most of these problems could be attributed to high pectinolytic and other enzyme activity in the fruit and on the surface, the latter originating from high yeast, mold and bacterial counts. Pickles that were made from cucumbers shortly after being removed from CA storage were of much higher quality than the aforementioned fruit. The study in which diffusion rates of salt-acetic acid covering brine into fresh pickles was determined showed diffusion to be more rapid than had been anticipated. In fact,on a percent by weight basis only 1 to 4 days after pasteurization there was significantly more acid and salt in the pickle tissue than in the brine: the semipermeable membranes of the tissue cells allowed. osmosis to occur. Thus it may be observed that since the opaque whiteness of pickle tissue requires a considerable length of time to degenerate to a translucent condition, the presence of acid or salt per se in the tissue in relatively large amounts re- sults in at least a very slow effect on tissue constituents. That is to say, pickle tissue does not lose its whiteness or gas shortly after coming in contact with salt or acid and actually not even after relatively long periods of time. The use of alum and calcium chloride (two commonly used pickle firming agents) in concentrations in covering brines of 0, 2 and 3 and 0, l, 2 and 3 pounds per 100 gallons of brine for each chemical respectively showed no significant effect on opaque whiteness of fresh pickle flesh. It was 138 thought that calcium chloride might exert a beneficial effect on maintaining flesh whiteness by stabilizing some pectic substances such as calcium pectate, thus aiding in the blocking of gas escaping from the tissue. This was not the case, perhaps because of the abundance of sodium present in the sodium chloride brine. Ascorbic acid, tween 80, and zinc acetate added to fresh pickle covering brines in low concentrations did not affect flesh whiteness significantly. The use of EDTA in 10 or 100 p.p.m. concentration in the covering brine of fresh pickles was found to have a slightly beneficial effect in retaining desirable whiteness of flesh. However, the use of sodium bisulfite was found to exert a marked deleterious effect, accelerating development of translucency dramatically. After only 2 to 3 months at about 800F storage temperature, pickle flesh in covering brines containing 500 or 2000 p.p.m. of sodium bisulfite was nearly translucent 100 per cent com- pared with normal whiteness for the controls with no added chemical. The dissociation of sodium bisulfite into sodium and sulfurous acid was deemed responsible for sodium being able to replace calcium of the intercellular calcium pectate complex, thus solubilizing it, and allowing the acid to seriously affect the tissue structure. With the combination of these two undesirable reactions, the tissue gas was better able to move through the permeable tissue ultimately result- ing in translucency. 139 Application of pectinolytic enzyme inhibitor to fresh pickle covering brines in concentrations of 5 and 10 ppm proved of no value in controlling loss of whiteness from the flesh. Lactic acid used as a total or partial replacement for acetic acid in covering brines exerted no different effect on fresh pickle whiteness than that of acetic acid. There was judged to exist a positive correlation between loss of whiteness or gas from fresh pickle tissue and loss of texture (softening). It was observed upon several occasions that as translucency became progressively more severe, loss of texture or firmness paralleled the phenomenon. This relation seems quite plausible since both loss of gas and loss of texture appear to depend to a great extent on the amount of nondegraded or nonsolubilized inter- cellular cementing substances such as middle lamellar pectins. There appeared numerous instances of uneven develop— ment of flesh translucency in jars of fresh pickle products in several of the studies. The condition was characterized by a greater degree of translucency of flesh located in the lower part of the jar than in the upper part. Stratification of ingredients used in fresh pickle manufacture has been shown to occur by Mulvaney, Nicholas, and Pflug (1960), thus accounting for the stratification of translucency. The most clear cut examples of stratification translucency was in the sodium bisulfite treated covering brine study. It was shown 140 that flesh translucency was a function of the concentration of the chemical in the brine, thus with stratification of the chemical being effected within the jar, the flesh ex- posed to the greater concentration of chemical would turn translucent first. Stratification of ingredients occurs when water of the pickles moves out of the pickle into the brine by osmosis and other diffusion phenomena, the water assuming an upper position thereby promoting the stratifi- cation. Other factors which may be involved in the uneven development of flesh translucency include greater hydro- static pressure and greater molecular density in the lower part of the jar. Fresh pickle slices and spears exposed to sunlight through a window or to fluorescent lighting for several months showed no observable effect on loss of tissue white- ness as compared with replicate jars held in the dark under the same temperature conditions. However, a bleaching of the greenish chlorophyllous pigments in the exposed flesh of the sunshine treatments was noted. A study from the chemical standpoint might be of considerable value in clarifying many of the relationships discussed in this thesis. For example, if pectic substances (type and amount) were closely followed through the entire fresh pickle manufacturing procedure and during storage, gas exchange relationships within the tissue would probably be greatly clarified. Also the role of enzymes in fresh pickles 141 might be clarified if their type, amount, and activity were followed through the manufacture and storage procedures. Although some histochemical and histological work was attempted in this thesis a good method was not found to study the tissue changes (especially intercellular tissue changes) using histochemical techniques. The author is in agreement with Kertesz (1951) who has also realized the great need for a stain that would be specific for pectic substances only: ruthenium red being the best there is at the time of this writing. There is also a great need for histochemical methods for the identification, amount, and activity of the pectinolytic type of enzymes, there being no good methods of this nature existing today. SUMMARY AND CONCLUS ION S l. Opaque whiteness of fresh pickle internal tissue is desirable. 2. Loss of opaque whiteness from fresh pickle flesh results in degrees of undesirable translucency. 3. Opaque whiteness of raw cucumber or fresh pickle tissue is due to the reflectance of light by intercellular gas (plainly visible under the microscope in freshly pree pared seetions). 4. Any factor causing a disruption, a degradation or solubilization of the intercellular matrix of cementing substances was suggested as aiding in the escape of the trapped intercellular gas, thus promoting the development of tissue translucency. 5. Development of translucency in fermented pickles was attributed to action of cucumber and microbial enzyme activity on intercellular and intracellular pickle tissue making the tissue more permeable to gaseous diffusion. Blanching of cucumbers prior to making salt stock resulted in incompletely cured pickles; the blanch treatment is thought tOhave inactivated much of the cucumber pectinolytic enzyme PQPulation, thus accounting for the poor cure. 142 143 6. The beneficial effect of blanching whole fruit on preservation of fresh pickle whiteness was attributed to significant inactivation of tissue enzymes such as poly— galacturonases, thus saving the intercellular pectinaceous substances from degradation to a certain extent. However, blanching of the cut.product resulted in excessive trans- lucency in fresh pickles made from the blanched fruit. The open condition of the flesh allowed too much heat into the flesh and allowed the expanded gas to move easily out of the tissue to create premature translucency conditions to develop later on in storage. 7. For underprocessed fresh pickles, development of flesh translucency was attributed to either of two following possibilities: (l) in the case of microbially spoiled pickles, enzyme action produced by the spoilage microorganisms and/or by cucumber enzymes not destroyed in the pasteurization treatmentacting on tissue structures (as in the case of salt stock fermentations) to cause more tissue permeability allow— ing escape of gas and (2) in the case of unspoiled (micro- biologically speaking) pickles, the action of residual tissue degrading enzymes not destroyed by pasteurization resulting in more tissue permeability allowing for more escape of tissue gas. 8. Pasteurization of fresh pickles was found to re- SUIt in about a 75 per cent loss of tissue gas. This loss was attributed to the increased diffusion coefficients of gas 144 and liquids as a result of the heat applied to the system, to expansion of gas and other contents creating pressures able to disrupt the close interwoven cellular network, to action of heat per se on tissue constituents such as pectin- aceous substances making them soluble, and to final con- traction of gas and other contents in the jar creating a vacuum thus setting up further pressure gradients between the tissue and the covering liquid and headspace in a direction favoring flow of tissue gas to the outside. 9. The temperature used for pasteurization of fresh pickles in the range of 180 to 1980F was found insignificant in regard to having any effect on tissue whiteness; but it was found that as the length of pasteurization at a par— ticular temperature increased the greater the tissue white- ness was during subsequent storage. It was thought the severe heat treatment completely (or nearly so) inactivated all enzymes present in the tissue that could otherwise play a role in breaking down intercellular cementing substances allowing for greater tissue permeability. 10. The preserving effect of sucrose and to some extent acetic acid on fresh pickle flesh whiteness was at— tributed to the nondetrimental effect each of these compounds has on pectinaceous substances such as are found in the intercellular tissue. Another effect of sucrose on the tissue was to dehydrate causing a toughening of the tissue WhiLe making it flaccid at the same time. 145 11. The marked deleterious effect which salt in covering brines was found to have on fresh pickle flesh whiteness was attributed primarily to the replacement of calcium of the important cell cementing substance calcium pectate with sodium causing solubilization of the intercel- lular matrix to a large extent, thus allowing escape of tissue gas. 12. The marked deleterious effect which sodium bi- SLilfite in concentrations as low as 100 ppm in covering txrines was found to have on fresh pickle flesh whiteness was arttributed to the combination of (a) replacement of calcium (pf calcium pectate by sodium and (b) chemical action of the ciissociated sulfurous acid on tissue components, both of tinese factors causing high tissue permeability thus allowing :for extreme loss of tissue gas. 13. The addition of alum or calcium chloride to the «:ovexxing brines of fresh pickles in concentrations that might be used commercially produced no change in the rate of trans- lucency development. Addition of low concentrations of zinc acetate, ascorbic acid, tween 80, or pectinolytic enzyme inhibitor to fresh pickle covering brines was found to un— EiffeCtl tissue whiteness when compared with controls having no additives. The use of EDTA in 10 or 100 ppm concentration ‘1“ the covering brine was found to have a slightly beneficial effect on preserving flesh whiteness. 146 14. The extremely beneficial effect of cool storage temperatures on preserving opaque whiteness of fresh cucumbers was attributed to a reduction in rate and number of chemical, physical, and biological reactions and/or combinations of these reactions. The cooler the storage temperature toward freezing the better the quality. Both cool warehousing and .retail areas are recommended for holding fresh pickles. (3301 holding temperatures would also contribute to the gxreservation of pickle firmness or crispness. In cucumbers which had been stored in either the unsightly 15. reafrigerated regular or controlled atmospheres, Izranslucent areas observed beneath the spine spots were at- izributed to the combination of: (a) increased diffusion rates and activity at these areas and (b) action of certain ‘tissue degrading enzymes produced by microorganisms concen- trated at the spine spots. Both factors would act to en- liance 'tissue permeability allowing escape of tissue gas. In the storage tests it was also found advisable to utilize SEIuit.,as soon as possible after being removed from storage. If fruit were allowed to remain at room temperature too long the microbial populations were thought to produce enzymes that resulted in inferior fresh pickles made from these firuit, The fresh pickles assumed a great amount of trans- lucency, took on a grayish caste, and became soft and mushy. 16. The translucent flesh area sometimes observed irlt: . . lus jperlphery of cucumbers and more severely in some 147 blanched fruit can be attributed primarily to bruising of the tissue during the harvesting, grading, etc. operations. The gas can escape easily from damaged tissue. 17. Vacuum infiltration studies clearly showed a linear relationship between the amount of vacuum applied to the tissue and the resultant degree of translucency or loss of gas. Vacuum infiltration of cucumber tissue was ac- cxmnpanied by a firming of the tissue and an increase in “weight in the cases of water and low concentrations of cxalcium chloride or alum brines: but in the case of high sucrose or salt concentrations a softening of the tissue and a decrease in weight was evidenced. Osmotic action was re— sponsible in both instances, the cellular membranes acting as semipermeable membranes. 18. The estimated amount of gaseous volume of the i:issue of a slicing cucumber variety was found to lie between 13 anti 17 per cent determined by two methods. The amount of 12issue: gas was found to vary considerably with different aJi‘eas of the fruit. Center slices of number 3 size, SMR 18 ((Dr SEER 58) variety registered approximately 10 per cent gaseous volume, 14 per cent for stem-end slices, and 16 per <=eent chr blossom—end slices. Seed cavity tissue registered a low 7 per cent gaseous volume accounting for the relatively low 9aSeous volume of center slices; fleshy parenchymatous t:‘ . lssue alone registered 14 per cent gaseous volume. Smaller lilyllr fin! . ,IKJ 148 size number 2's of the same variety registered significantly less gaseous volume for any given area of the cucumber. 19. Development of flesh translucency was found to be gradual and systematic. The first tissue to show indi— cations of translucency in fresh pickles was generally located in the seed cavity area, the area of least amount of tissue gas per unit volume of cucumber tissue, the area possessing the most diverse tissue types, and the area where parenchyma tissue showed the least wall thickness. The last tissue to show signs of translucency in cut products was generally located near the geographical center of the fleshy parenchymatous tissue, the lines of translucency moving both from the inside out and from the skin side in. 20. The translucent condition inflicted upon previous- ly opaque white cucumber tissue as the result of freezing was attributed to pressure created by ice crystal formation and increased tissue permeability, thus resulting in the re— lease of tissue gas and subsequent filling of the intercel— lular spaces by tissue liquid. 21. Diffusion of salt and acid into fresh whole dill Pickles was found to occur rapidly reaching a maximum between 1 and 4 days after pasteurization. At that time the concen— tration of salt and acid in the pickles far exceeded that in the brine, this situation being due presumably to the osmotic effect of the cell membranes. Equilibrium between brine and Pickles was estimated to occur about 7 months after 149 pasteurization, a time when the tissue would be very permeable. It can be concluded that the presence of covering liquid ingredients per se in the fresh pickle tissue did not cause loss of whiteness in any short period of time. 22. Stratification of liquids within the jars of fresh pickles was found to lead often to uneven development of translucency in the flesh, the reason being that some of the ingredients present in the stratified brine (such as sodium chloride) affect loss of whiteness from the tissue. LITERATURE CITED Anderson, E. E., L. F. Ruder, W. B. Esselen, Jr., E. A. 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