I1 M l lHHlH NIH“ 137 092 HTHS E’RE‘FMATMENT CF 9REPARED APPLES $LICES rm! BAKERS' USE 271352: for We Mgr-as: sf mi. 3. Mifll'flémfil STJRTE {SGMLGE éaé'm Farm“ Veg? “(@565 ‘ i Hm“. ,__‘ N _ .{ This is to certify that the thesis entitled J r . I“ r‘ ‘ t”'(‘:-"I " 19 '5. """ ’ “ m =7‘ ' has been accepted towards fulfillment of the requirements for 7v 4'" I? ,‘ 71‘} ‘ ".\-“r ' ,. - degree in____~i 0‘" ‘ Majofirofessor ’d‘fl‘ . I . e- 1"" in ':|.." ‘I-‘ I . ' I ‘L " ‘W‘CP.’ I...E)‘Q .‘. , ‘ '35 "5 . “~36”??? '. .‘ "" 1-. “- ' "I. ' W .‘EJ'wm'oK' T. "r a ‘ I ’ I y ‘N‘: :‘L‘% 8:13 i..‘ a, , ‘ . :a. . '_-..z, MI . '. ”’in ‘5“ s, .u J ‘v - . . _ 7‘1; “v «I . . . .. . .. -J I . . . . ‘. . I ~ 3” I .. . _ ' igk‘tkfiw‘.‘sq 514%.}? ”§§;"..a; pr i—x-fifvgvgyéwfifie ,3- «(w . .. I “f. -“ Lew’lJyljgt‘I.’_!.II‘4~.“I .. I, . /--‘ ', - I (1 ‘ is I ' ‘V-"I‘ '.‘ 4-. ‘ 0 If? ...¥r “ . . Int") 4 "y “- Winger. "'1 :u -4 "'-’-‘%’7 «ENE ‘ - - ‘ -c . 4 r ‘ 7”: . 95’, In “_ ‘.#\#Q( \I_ 5 'HI‘ - .’ v- _ fi ' 'r («I ' , L» \ ‘3‘] . I . '.""l‘ a '. ' ' 7 z. w ‘4 II V I r h Xi» W ‘40 . .. V‘J_ .; fire 3 JR A’AKI b I ? ‘3)!!! " i u n a I: n. a. v ' ‘ _ ‘ - - ._ ‘u .' ,. ' .1 -- 33’ .. . . ~ _ ‘ - ..‘ ‘ ‘ l ‘ ’ a «_ - a '. ' I . ‘ \ . - 'L j ‘ , , '\.- . .II‘ I W. , . .I l‘ u. _ . - . > -. ... > ' V . l‘ .‘- . II I V. I- r, I ‘ - r’ V r'v '.' -'.'. ', -. .- .; ‘5! f4: -' ' . "I . ‘. '- ' F: ' ‘3‘ " -- '. 5" ' . ‘1‘" _ , - - ‘ ' I - o _ I " ' ' r ' _', y‘ I. F -" ~ 'I' N V! ‘ .‘ ‘ k' - ‘y ‘ ‘ ‘. ‘v '. _ ' ’ _ , '. , ' ' - q . -_ . I v 4 , II . i‘ ' .0 I -.- n 4- ~~t.~- -. -‘- e . A. -. V- - ”U . , ‘V _. L 'A "In.- ' ‘ ' u- - .. If ‘ ' ' ‘ ’ . V o a ' - - . . . 2' . , . I. - . .4 - - J .. .r ,4 , .— . t. . ., .v 4...“: .. . _ ‘. . . .- .. . . . I. A . ‘ .~'- . _ . -. tr ...‘- '-- 5” ;_ _ .;- - .. ' 1 . ,4 .-. - . . n .. I aI-I [74 . t I I. 4 ' . I . _ I I ~. I. . . I“. . __I c 7.. ‘h V" If, D t \ W“ 't.‘ ' c. '5 '\. (- f; 2 ’7! . t" .I _ 339i . A 'A 9 ‘~ A 'r A,- . . '\. ‘ t V ..' 4 y i' r ' " . u: r as" - '. (r . .J ‘. ' .a - 7'4... J ' '0' "", -«;I.- ‘. Hr” ,. ‘. -,,,_ : Kr. J ’Sfiié’s .I’I‘x“'I'I J‘. ,. v I'. V‘ H- ’ A I I . "‘ q ' I - " ,.‘ o ‘ ‘ 'r "- '5 . ‘ '1 x: .... . . t ' ' ‘ « v -. - . ‘ QN‘ u.’"“ 9‘. .- ' 5% t‘ " D ‘ K . .o, "A ‘1 F" . ‘ . t l ’ _'. -6 . » 4. ‘V ‘ '4 r I I \u 9 PRWTREATMENT OF PREPARWD APPLE SLICWS FOR BAKERS' USE By JOHN PARSONS VOGT A THESIS Submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIVWCE Department of Food Technology 1950 Gmalrr pair. T 4 6. *1?» 8‘ V W (a ACKNOWLEDGEMFNT I wish to thank Dr. C. L. Bedford for his help and guidance in this problem and in the preparation of this manuscript. ID '1 :3 $3 w: «2 -1- TABLE OF CONTENTS Introduction Review of Literature General Discussion of The Mechanism of Browning in Apples Experimental Procedure Ascorbic Acid and Sodium Chloride Treatments at Atmospheric Pressure Table I Ascorbic Acid and Sodium Chloride Treatments at Reduced Pressure Table II Sulfur Dioxide Treatments at AtmOSpheric and at Reduced Pressure Table III Conclusions and Graphs Literature Cited PAGE 14 21 24 32 34 4O 42 52 84 55 -2— INTRODUCTION The object of this thesis is to find out what has been done in the past to prevent brown- ing of apple slices, to evaluate the past treat- ments and to experiment and present new data. J :53: ~ I!) filth» . V: l r ’u". -3- PRRTRWATMRNT OF PRVPARRD APPLW SLICRS FOR BAKERS' US? RWIWW OF‘ LITVTRATU‘RE Many treatments have been proposed for the treating of apple slices to prevent darkening during storage, both cold and frozen. These include treatment with $02, sugars, sat, and other antioxidants. SULFUR: Sulfur treatment to date has been the standard of the industry; although an early government publication condemned its use as harmful to digestion and health. In 1906 H. W. Wiley (1) wrote: "The verdict whiCh must be pronounced in this case is decidedly unfavorable to the use of this preservative in any ouantity for any period of time, and shows the desirability of avoiding the addition of any form of sulfurous acid to products intended for human food". Further studies (50) have not shown 803 in the quantities reauired to be harmful to health; however, and considerable work has been done using it. Thatcher (6) in 1915 found that browning was retarded when apples were sealed in an atmosphere of $02 under as nearly sterile conditions as possible. A year later V. Valvassori (7) successfully subjected peeled and halved apples to the action of 802 before steaming and drying them. In 1925 boiling 802 was used successfully -4- by NaVarre (13) to bleach browned slices. Although flowers of sulfur was used effectively by Nichols and Christie (16) in 1950 to retard brown- ing by subjecting a ton of fruit to the fumes from two to three pounds of burning sulfur, by far most of the experimental work has been done using compounds which release $02 when in a water solution. Cruess and Overholser (10) in 1923 reported the immersion of slices ofapple tissue in a 5% N22305 solution for five minutes to be effective. In 1952Nichols and Cruess (18) showed that sulfured dried apples required only a few hundred parts of $02 per million to prevent browning, and in 1933 Joslyn and Mrak (20) showed that immersion for a few minutes in NazSOg solutions re- quired only 3000-4000 ppm 302 to prevent browning. Joslyn and Marsh (22) also reported that ten minutes in 500 ppm 802 preserved the color of Gravenstein apples. In 1952 Murri, et al’(23), believing that the retention of Vitamin 0 (usually destroyed by freezing) would prevent apple browning, reported that 302 effec- tively preserved Vitamin C in apples which were frozen and stored at.0°F. Very satisfactory results from the use of a two minute dip in a 2800-3000 ppm 602 solution, preferably as K28205, at 70°F were reported in 1945 by McArthur (47). H2303 and Na2303 treatments (48) gave partial to complete elimination of browning. If the apples are to be reprocessed later, 1500-2000 ppm 302 -5- was claimed to be effective by Woodroof and Cecil (49). In 1946 Smith (54) showed that a dip of only a few seconds in Na2303 or 302 solutions was preferable to the several minute dips used by earlier experimenters. Further work on H2305 by Schrader and Thompson (57) in 1947 showed that an initially high H2305 content and low moisture content in the dehydrated apples were necessary to lengthen the storage life to practical limits under conditions of high temperature. In 1949 Western Regional Research Laboratories recommended (60) using 200-300 ppm 302 for vacuum treated, filled apple slices. Other solutions which have been used effec- tively are dilute (1-s%) metabisulfite and bisulfite solutions. Mrak (59) found that simply dipping apple slices in these solutions was more effective than sulfuring, and Western Regional Research Laboratories (44) in 1944 reported that dipping in NaH303 was superior to solutions of sulfurous acid or sodium acid sulfite. Thiourea has also been used successfully. In 1935 Denny (25) found a 0.1% solution of thiourea pre- vented or retarded browning of cut surfaces during drying,and in 1943 he developed (42) a drying process using that solution. The apples do not brown when later soaked in water. Denny (43) also patented a process for the substantiallycomplete inactivation of the browning systentnot only in apples but also in other freshly cut surfaces of plant tissue. An -5- aqueous solution of thioamide (0.1-0.2% strength) was used, although thiourea can by substituted. However the Food and Drug Administration in a recently announced policy does not approve its use because of possible injury to humans. SUGAR: Sugars have received considerable attention as preservatives, but their usefulness to the apple in- dustry does not seem to compare to that of 802 in the prevention of br0wning. As long as the slices remain in the sugar solution, oxygen within the slices is used up in respiration and atmOSpheric oxygen is pre- vented from reaching the slice and initiating browning. It is to be noted that most of the sugar solutions described contain an antioxidant. Lodge (3) in 1911 found that dipping fruit in a boiling sugar solution containing a small amount of citric acid, prevented browning during drying. A 5% solution of sucrose was used to prevent darkening even after removal from the solution by Overholser and Cruess (10) in 1923. In 1925 Navarre (13) found that after treating his apples with $02, subjecting them to the action of a sugar syrup helped preserve the color. Experimenters were beginning to use partial vacuums in 1932 to gain a better permeation of the syrups. Todd(19) received a patent on this process in that year, and in 1935 -7- Tierney (27) received a patent for a partial vacuum process in which the solution contained a major por- tion of sugar and citric acid and a manor prOportion of salt. The International Sugar and Alcohol Company (28) also received a French patent to use dextrose or xylose as a preservative for foods containing much water, such as apples. The following year Wiegand (31) stated that fruits packed in syrup retained their quality better than without the syrup. In 1940 Greene (38) published that in spray freezing an invert sugar solution gave the most satisfactory performance in preventing browning and spotting. Tressler and DUBois (45) in 1944 found that a sugar syrup containing 0.2% l-ascorbic acid prevented the develOpment of oxidized flavor and discoloration in apples. McArthur (47) in 1945 found that the addition of pure, dried sugar to apple sections gave little protection. In 1949 the Western Regional Research Laboratory (60) described a method of sugar impregnation of filled apple slices for the prevention of browning. SODIUM CHLORIDE: Salt has been used by man for many years more than most preservatives. It is common knowledge that a weak brine solution (135%) has been used by housewives and the apple baking industry for years to prevent browning. In 1923 Overholser and Cruess (10) found that apple -3- slices immersed in a 5% NaCl solution for three days did not brown even after removal from the solution. By allowing peeled and cut fruit to stand under a 2% NaCl solution before canning, Kohman, Eddy, and Carlson (12) in 1924 and again in 1937 (33) showed that the effect of subsequent heat on the Vitamin C in the fruit was almost negligible. The addition of 2% NaCl . to a $02 solution was found by Joslyn and Mrak (20) in 1933 to aid in the prevention of browning. In 1935 Johnson and.Wallstr5m (29) received a British patent for treating food products prior to storage with a vacuum, allowing Na01 to be forced into the materials by pressure. McArthur (4) in 1945 stated that if the sectioned apples are not used immediately, they should be held in a 1.0-1.5% brine to prevent browning. In 1948 Noyes (58) specified that they should be put in a 3-5% NaCl solution immediately upon cutting and then subjected to a vacuum treatment to get permeation of the brine solution. Cruess (59) in 1948 recommended the same 3-5% NaCl solution to shorten the period of sulfuring. PRESERVATIVE COATING: The function of a preservative coating is to hold the antioxidant directly upon the slice. As long as the antioxidant is effective, the coating will prevent browning. A patent doing this was issued to the 1.0. Farben Industries (British patent, 1927) for coating the fruit with a compound formed from a condensation -9- product of urea and formaldehyde to which various preservatives might be added. Two French patents have also been granted. The Stabavite Syndicate, Limited, (15) patent in 1928 was for the covering of food with a gum to which antiseptics or preservatives such as 802 had been added. The other patent was issued to N.V.Industrieele (35) in 1938 for foods and other mixtures coated with a nonhygroscOpic substance to which ascorbic acid was added. VACUUM: Treatment under reduced pressure has been gaining in pOpularity in recent years. Its beneficial effects were first observed by Kohman (9) in 1923 while study- ing the stability of Vitamin 0 towards heat. He found that insufficient account had been taken of the role of oxygen in its destruction, and that when solid foods were subjected to a high vacuum and the vacuum then released with nitrOgen, oxygen could be removed with- out heat, thus preventing browning. In 1926 a German patent was granted to Hessel (13a) for a fruit drying process in which the comminuting was done under reduced pressure. Other patents using a vacuum process to draw a solution into apple slices have been issued for the following solutions: The United States granted a patent to Tierney (27) in 1935 for a solution containing a major portion of sugar and citric acid and a minor -10- prOportion of salt. Johansson and Wallstrbm (29) received a British patent in 1935 using a NaCl solution. Webb (40) in 1942 was issued a patent by the United States for a pore filling for dried apples of such edible material as fat or milk solids. In 1948 Noyes (58) received a patent for a 3-5% Na01 solution and special vacuum process for freezing apples. Vacuum pack storage of dehydrated apples was also recommended by Schrader and Thompson (57) in 1947. As mentioned before, the Western Regional Research Laboratory (60) in 1949 was using a vacuum process on apple slices prepared for freezing in which the solution used con- tainsd 40% sucrose and 200-300 ppm 302 or 0.2-o.s% ascorbic acid. CALCIUM: Kertesz (34) reported in 1938 that calcium added to certain plant tissues unites with the pectic acid present, giving a firmer tissue. This treatment of sliced apples before freezing not only caused a better preservation of the natural structure, but, he believed, also prevented the browning upon defrosting. That the calcium salts cause the firming of the apple slices through the formation of calcium pectates or pectinates was also shown by Baker (55) in 1947. That same year, Esselen, Hart and Fellers (56) used a solution contain- ing 0.05-0.1% calcium chloride in an investigation of -11- forty-eight varieties of apples prior to freezing or storage, finding that it maintained a desirable firm- 11838. ASCORBIC ACID: In the belief that the presence of ascorbic acid inspples prevented their browning, several investiga- tors have tried various techniques of rehining the Vit- amin C. As early as 1923 Kohman (9) used a partial vacuum process and an atmosphere of nitrogen eflectively before heating the apples. Immersion in a 2% NaCl solu- tion was used successfully by Kohman, Eddy, and Carlson (12) in 1924 before they heat sterilized the apples. Several investigators have found 302 helps retain the Vitamin C. These include Murri, et a1 (23) who in 1924 found 302, and to a lesser degree sodium benzoate, effective in retaining Vitamin C in frozen apples. In 1930 Nichols and Christie (15) also reported 302 effec- tive in the retention of ascorbic acid. Much of this work followed directly from the observations on 1920 of Johnson and Zilva (32) who stated that no enzyme cap- able of oxidizing l-ascorbic directly is present in apples. Some men have tried the use of additions of as- corbic acid to prevent browning. A French patent issued in 1928 to N.V.Industrieele (35) covered the preservation of foods and other mixtures by adding -12- ascorbic acid together with a nonhygroscOpic substance. In 1922 Tressler and DuBois (45) published that a syrup containing 02% l-ascorbic acid prevented the development of an oxidized flavor and the discolora- tion of apples during 0°F storage. McArthur (47) in 1945, however, reported that the addition of 0.098% ascorbic acid on the weight of the apples gave only slightly better results than dry sugar alone. McArthur further believed that ascorbic acid preservation would not be popularly used in industry because of its rela- tively high cost (l.82¢ per pound of apples in 1945). CITRIC ACID: While citric acid is frequently used by house- wives to prevent the browning of apples and other fruits, investigators have reported mainly on its use in solution combined with other antioxidants. Lodge (3) in 1911 received a patent for the preservation of fruit, i.e. apples, by immersing them in a boiling solution of sugar in water to which a small amount of citric acid was added. Another patent was issued to Tierney in 1935 (27) in which he immersed apple pieces in a solution containing sugar, citric acid, and some salt in a partial vacuum process for frozen apples. LACTIC ACID: Lactic acid has been found to be cheaper and more effective than citric acid in decreasing browning by Schoonens (37) in 1940. -13- HYDROGEN, NITROGEN, OXYGEN, AND CARBON DIOXIDE: Atmospheres of various gases have been used to prevent apple browning. Thatcher (6) in 1915 tried sealing the apples under as nearly sterile conditions as possible in air, hydrogen, nitrogen, oxygen, carbon dioxide, and sulfur dioxide. Only the latter two seemed to retard ripening. Later work by Overholser and Cruess (10) in 1923 showed that apples could be stored for one month in nitrogen without changing in appearance even after removal of the gas, but that browning developed rapidly in the presence of hydrogen, oxygen, and carbon dioxide. That same year, Kohman (9) successfully used nitrogen in a partial vacuum process. In 1936 Elwell (30) received a patent in which apple slices are immersed in aqueous carbon dioxide solution. GENERAL DISCUSSION OF THE MECHANISM OF BROWNING IN APPLES Basset and Thompson (2) in 1910 suggested that there is generally present in apples an oxidizing enzyme capable of producing a tannin-like substance having the power to precipitate protein nitrogen. This enzyme is active only in slightly acid solutions, and when the concentration is above a certain minimum. This tannin-like substance, or substances, does not exist in the normal fruit on the tree but is rapidly formed on injury or removal of the fruit from the tree. Its function is to inhibit fungus and bacterial growth on injury of the fruit, in part, probably, by the conversion of the protein into an insoluble form and, in part, by the germicidal action of the substance it- self. In 1915 loker (4) reported that catalase and peroxidase undergo similar changes when submitted to increasing temperatures. At first a new substance which has no peroxidizing effect in the presence of hydrogen peroxide is produced; but, if the temperature is further increased, another new substance is formed which caused both changes to take place. This enzyme, which is stable to heat, is different from the enzymes from which it was formed, and it is the presence of this which enables one to speak of the reactivation of a dead ferment by means of heat. These changes were -15- further clarified in 1920 when Onslow (8) published that three components are present in the oxidase systems: A "catechol" compound, which may give rise to a peroxide, and two enzymes: an oxygenase, which helps the formation of the peroxide, and the peroxi- dase, which decomposes the peroxide forming “active” oxygen. the peroxidase may be partially separated from the oxygenase by fractional precipitation with alcohol. Such substances as organic acids, tannins, etc. may interfere with the reactions. In 1923 Overholser and Cruess (10) reported that on the basis of experiments with Yellow Newton apples, the oxidising system con- cerned in the browning of apple tissue is considered as consisting of a peroxidase and an organic peroxide. The chromogen is a tannin which has been shown by qualitative tests to belong to the catechol group and to be distributed evenly throughout the fruit with a slightly greater concentration in the epidermis. Color reactions indicating a peroxidase were given by fresh apple tissue and juice in the presence of suit- able indicators of which benzidine (1% aqueous solution) was found to be the best. With boiled tissue, benzi- dine showed no evidence of reaction even after 72 hours. Since these reactions occurred without the addition of hydrogen peroxide, the presence of an organic peroxide is suggested; furthermore positive tests for peroxides were obtained with potassium chromate in the juice and -15- with starch iodide in the tissue. Treatment of the apple juice with two volumes of 95% ethyl alcohol precipitated the peroxidase and organic peroxide, leaving the tannin in the solution. The filtrate, con- taining the tannin freed from alcohol, darkened only on the addition of an aqueous solution of the enzyme precipitate, indicatingthat the tannin and organic peroxide are separate entities. Boiled juice did not darken in the presence of various oxidizing agents until the acidity was reduced to nearly the neutral point and manganese dioxide or platinizing solution and hydrogen peroxide were added. That the organic per- oxide is much more sensitive to heat than the peroxi- dase is demonstrated by the inactivation of the former on heating at 73.5 to 78°C; while the latter was ren- dered inactive only at 90 to 100°C. Reformation of the peroxide did not occur in heated tissue or juice within 48 hours. Apples stored in nitrogen for one month remained unaltered in appearance and continued so after removal from the gas, giving positive reac- tions for peroxidase and organic peroxide. In the presence of carbon dioxide, hydrogen, or oxygen, and the vapors of carbon disulfide, formaldehyde, carbon- tetrachloride, ether, gasoline, or ethyl alcohol, browning develOped rapidly and tests for organic per- oxide were negative. The effect of these substances is apparently due to increases in the permeability of the -17- cells, permitting the oxidation reaction to take place. Immersion of slices of apple tissue in 5% solutions of sodium.chloride, hydrochloric acid, sodium sulfite, or sucrose for three days prevented darkening, even after . removal. With tap water and 5% solutions of sodium nitrite, sodium nitrate, or sodium carbonate, darkening, occurred. With hydrochloric acid and sodium.sulfite, five minute immersion was as effective as three days; but under the same conditions, sodium chloride, su- crose, and sodium nitrate reduced but did not prevent browning. The action of hydrochloric acid and sodium sulfite appears to be due to the destruction of organic peroxide in a manner comparable to the action of free sulfur dioxide in practisegwhile destroying neither the organic peroxide nor the peroxidase, sodium chloride appears to inhibit their activity. 'With sodium nitrite and sodium carbonate, the tissue became alkaline in reaction, a condition favoring rapid darkening of the tannin. Laboratory experiments indicated that three to five percent sodium chloride gives a satisfactory dried apple product, although slightly darker in color than when treated with sulfur dioxide; but fruit thus treated required much shorter exposure to sulfur dioxide. Nitrates of 0.01 and 0.1 normal concentrations increased the rate of browning; this was probably due to their oxidizing action. -18-* Drain (11) in 1923 found that the oxidase acti- vity is rather closely localized in the fruit of many apple varieties. Here the cut surfaces of many vari- eties were treated with reagents, including violamin, guiacum gum, and benzidine. Of the three reagents tried, the last named proved most satisfactory in point of cost, ease of handling, and in furnishing satis- factory photOgraphic material. Tests made at various seasons (during the time of fruit develOpment, at harvest, and late in the storage season) enabled Drain to divide varieties into three groups according to the location of oxidase activity. The majority of the varieties fell in that class where the greatest acti- vity was noted in the vicinity of the core and core line. The effect of allowing, previous to canning, the peeled and cut fruit to stand under 2% sodium chloride was studied by Kohman, Eddy, and Carlson (12) in 1924. During this period, the oxygen in the fruit is used up by respiration. It was found that after the prelimi- nary treatment the effect of the sterilizing heat on Vitamin C was almost negligible. In 1933 Joslyn and Marsh (21) gave a preliminary report of data tending to show that peroxidase acti- vity is not responsible for all of the undesirable changes in certain materials preserved by freezing. -19- In some cases blanching at a lower temperature than will inactivate the peroxidase is sufficient to pre- serve satisfactory flavor and color. The work of Johnson and Zilva (32) in 1937 showed that in the presence of léascorbic acid and catechol, the oxidation of catechol does not start until all the l-ascorbic acid has been oxidized. No enzyme capable of oxidizing l-ascorbic acid directly is present in the apple. The phenolase present in this plant can oxidize l-ascorbic acid, however, when the Juice or catechol is present. The importance of this enzyme action has gained increasing recOgnition; Balls (41) in 1941 defined food preservation as a matter of stOpping enzyme ac- tion, whether the enzymes come from microorganisms or are inherent in the food itself. In 1944 Ponting (46) published that pretreatment to decrease the activity of oxidizing enzymes controls darkening of the fruit before freezing, during frozen storage, and after defrosting. The extent of inacti- vation can be detected by spreading on an approximately 1% aqueous solution of pyrocatechol on the cut surface of the fruit. After a few minutes, the portion of the fruit still containing active enzymes will turn black. The test is negative if no dark color appears in twenty minutes. -20- Contrary to Johnson, et a1 (52), Hackney's (52) experiments in 1946 on the respiration of slices of apples indicated that in Granny Smith apples, ascorbic acid might be directly oxidized by an enzyme. The presence of this enzyme was confirmed by cutting Granny Smith apples into small pieces, freezing them, and expressing the Juice by squeezing the tissue through muslin. The filtered Juice oxidized ascorbic acid but showed no phenolase activity. Juice boiled for a few seconds showed very little activity towards ascor- bic acid. _21- PRETREATMENT OF PREPARED APPLE SLICES FOR BAKER'S USE In processing for canning, freezing, or drying, apple slices are commonly immersed in various aqueous solutions aimed at enzyme inactivation for the retar- ding or prevention of browning of the slices for a reasonable length-of time, or until these slicescnn be used in various baked goods. VARIETIES USED IN THIS EXPERIMENT McIntosh, Northern Spy, Grimes Golden, and Delicious apple varieties were used in this experiment. SOLUTIONS USED: Ascorbic acid, sodium chloride, and combinations of these solutions were used at atmospheric pressure and at reduced pressure. All four apple varieties were treated in the following mixed solutions at atmos- pheric and reduced pressure: 0.1% ascorbic acid and 2% sodium chloride 0.2% ascorbic acid and 2% sodium chloride 0.1% ascorbic acid and 4% sodium chloride 0.2% ascorbic acid and 4% sodium chloride In the second series of treatments, five lots (I, II, III, Iv, V) of Delicious apples were dipped. in $02 solutions of the following concentrations: 274 ppm, 445 ppm, 664 ppm, 817 ppm, and 1252 ppm. -22- McIntosh apples were treated with the following solutions at reduced pressures: LOT VI: 2% sodium chloride LOT VII: 296 ppm 302 LOT VIII: 2% sodium chloride and 254 ppm 302 LOT IX: 2% sodium chloride, 1% calcium lactate, and 290 ppm 302 LOT x: 1% calcium lactate and 265 ppm 302 LOT XI: 2% sodium chloride and 1% calcium lactate LOT XII: 2% sodium chloride and 570 ppm 302 LOT XIII: 2% sodium chloride, 549 ppm 802, and 1% calcium lactate LOT XIV: 1% calcium lactate and 528 ppm 302 LOT XV: 40% sucrose, 275 ppm 302, and 1% calcium lactate LOT XVI: 40% sucrose, 549 ppm 302, and 1% calcium lactate PREPARATION OF SOLUTIONS: The solutions were prepared for equal weight of apples, 1.6.: six pounds of apples to six pounds of solution. Distilled water was used in all solutions. The solutions containing 802 were prepared from sodium bisulfite (anhydrous). These solutions were roughly prepared on the assumption of 48% available 302 in sodium bisulfite. They were then analyzed by the Ponting-Johnson titration method(51) for accurate determination of $02 content of the solutions before and after soaking. The apple slices were similarly analyzed. -25- The calcium lactate and sucrose syrups were made up on the percentage by weight basis. PROCEEDURE: The solutions for each sample or lot were pre- pared immediately before use. The apples were washed, peeled, and sliced in twelve slices parallel to the longitudinal axis of the apple. These slices were dropped directly into the solution and allowed to soak for one hour. It required about ten minutes to peel and slice each batch. These slices were then removed, drained, and one pound each held at room temperature (70°F) and at 32°F. Four pounds were frozen at 00F. The vacuum treatments were standardized at a reduced pressure of 26 inches of mercury for twenty minutes and, following removal of the air from the slices, thirty minutes in solution. The system used required ten minutes of pressure come-down time; so that the apple slices were in solution for one hour. -24- THE RESULTS OF THE SOAKING TREATMENTS AT ATMOSPHERIC PRESSURE, USING ASCORBIC ACID AND SODIUM CHLORIDE McIntosh Variety' The untreated McIntosh apple slices browned in 12 minutes. They reSponded to the soaking treatments at atmospheric pressure as follows (summarized in Table I ): ' At room temperature, after soaking one hour in the solution and draining: the 2% NaCl with 0.1 and 0.2% ascorbic acid held for 48 hours before browning; at around 18 hours the surface had become yellow and slightly dry. The interior of the slice was white and firm. The slices at room temperature in the 4% NaCl, and 0.1% ascorbic acid held for only 22 hours before browning, while those in 0.2% ascorbic acid were brown at 48 hours. The slices in the 4% NaCl were very salty to the taste. The slices held at 32°F after draining from one hour in the solution, gave the following results: The 2% NaCl and 0.1% ascorbic acid gave the longest time in this group before browning, 240 hours. The 2% NaCl and 0.2% ascorbic acid treated slices browned at 168 hours. The 4% NaCl and 0.1% ascorbic acid treated slices were brown at 96 hours, while those with 4% NaCl and 0.2% ascorbic acid held for 120 hours. Including the thawing time as part of the browning -25- time, the McIntosh slices which were frozen and held at O°F until used, responded to treatment as follows: All‘slices were thawed under refrigeration, re- quiring 18 to 24 hours to thaw in all cases. Two ob- servations were made on the slices; the first observa- tion was on slices stored for one month at 00F, and the second observation was made after other slices had been stored for six months. I The slices stored one month at 00F, thawed, and placed at room temperature (70°F), showed: 2% NaCl and 0.1% ascorbic acid browned after 42 hOurs; 2% NaCl and 0.2% ascorbic acid browned after 28 hours; 4% NaCl and 0.1% ascorbic acid browned after 46 hours; 4% NaCl and 0.2% ascorbic acid browned after 56 hours. The slices stored six months at 00F, thawed, and observed at room temperature, showed: 2% NaCl and 0.1% ascorbic acid browned after 78 hours; 2% NaCl and 0.2% ascorbic acid browned after 44 hours; 4% NaCl and 0.1% ascorbic acid browned after 54 hours; 4% NaCl and 0.2% ascorbic acid browned after 90 hours. Another group of McIntosh apple slices stored for one month at 00F, thawed, and observed at 32°F, showed: 2% NaCl and 0.1% ascorbic acid browned after 42 hours; 2% NaCl and 0.2% ascorbic acid browned after 32 hours; 4% NaCl and 0.1% ascorbic acid browned after 50 hours; 4% NaCl and 0.2% ascorbic acid browned after so hours. -25- The slices which were stored for six months at 0°F, thawed, and observed at 52°F, showed; 2% NaCl and 0.1% ascorbic acid browned after 258 hours, 2% NaCl and 0.2% ascorbic acid browned after 530 hours; 4% NaCl and 0.1% ascorbic acid browned after 306 hours; 4% NaCl and 0.2% ascorbic acid browned after 462 hours. Northern Spy Variety The normal browning time for the fresh, untreated slices of Northern Spy apples was ten minutes. This time was extended by soaking slices at atmospheric pressure for one hour in various solutions containing sodium chloride and ascorbic acid, as follows (sum- marized in Table I): 0f the slices which were drained and observed at room temperature (70°F), the 2% NaCl and 0.1% ascorbic acid had a browning time of.5 hours; the 2% NaCl and 0.2% ascorbic acid browned after 17 hours; the 4% NaCl and 0.1% ascorbic acid had a browning time of 18 hours; and the 4% NaCl and 0.2% ascorbic acid had a browning time of 40 hours. Drained and observed at 52°F, the slices treated with 2% NaCl and 0.1% ascorbic acid browned in 24 hours, while the slices treated with 2% NaCl and 0.2% ascorbic acid didn't brown for 198 hours. The slices treated with 4% NaCl and 0.1% ascorbic acid held for 168 hours before browning, and the slices given 4% NaCl and 0.2% ascorbic acid lasted for 192 hours. -27- The Northern Spy apple slices which were frozen and stored at 0°F for one month, thawed, and at room temperature (70°F), showed: 2% NaCl and 0.1% ascorbic acid browned after 2% NaCl and 0.2% ascorbic acid browned after 4% NaCl and 0.1% ascorbic acid browned after 4% NaCl and 0.2% ascorbic acid brOwned after Slices frozen and stored at 0°F for six placed 28 hours; 52 hours; 42 hours; 52 hours. months, thawed, and placed at room temperature, showed: 2% NaCl and 0.1% ascorbic acid browned after 2% NaCl and 0.2% ascorbic acid brawned after 4% NaCl and 0.1% ascorbic acid browned after 4% NaCl and 0.2% ascorbic acid browned after The slices which were frozen and stored for one month, thawed, and observed at 52°F, 2% NaCl and 0.1% ascorbic acid browned after 2% NaCl and 0.2% ascorbic acid Drowned after 4% NaCl and 0.1% ascorbic acid browned after 4% NaCl and 0.2% ascorbic acid browned after The frozen slices which were stored for thawed, and observed at 52°F, showed: 2% NaCl and 0.1% ascorbic acid browned after 2% NaCl and 0.2% ascorbic acid browned after 4% NaCl and 0.1% ascorbic acid browned after 4% NaCl and 0.2% ascorbic acid browned after 27 hours; 27 hours; 78 hours; 66 hours. at 0°F showed: 28 hours; 25 hours; 122 hours ‘0 58 hours. six months, 55 hours; 44 hours; 78 hours; 162 hours. -28- Grimes Golden Variety The untreated slices of Grimes Golden apples browned in 12 minutes. The dices soaked for one hour and drained, the soaking being done at atmOSpheric pressure, gave these results at room temperature (70°F) (summarized in Table I): 2% NaCl and 0.1% ascorbic acid browned after 48 hours; 2% NaCl and 0.2% ascorbic acid browned after 48 hours; 4% NaCl and 0.1% ascorbic acid browned after 120 hours; 4% NaCl and 0.2% ascorbic acid browned after 72 hours. The slices of apples placed at 52°F after drain- ing, Slowed: _ 2% NaCl and 0.1% ascorbic acid held for 254 hours; 2% NaCl and 0.2% ascorbic acid browned after 556 hours; 4% NaCl and 0.1% ascorbic acid browned after 288 hours; 4% NaCl and 0.2% ascorbic acid browned after 288 hours. The apple slices which were frozen and stored for one month at 0°F, thawed, and observed at room tempera- ture, showed: 2% NaCl and 0.1% ascorbic acid browned after 28 hours; 2% NaCl and 0.2% ascorbic acid browned after 46 hours; and the 4% NaCl solutions with 0.1% and 0.2% ascorbic acid,molded in 158 hours. The slices which were stored for six months at 0°F, thawed, and observed at room temperature, showed: -29- 2% NaCl and 0.1% ascorbic acid browned after 54 hours; 2% NaCl and 0.2% ascorbic acid browned after 78 hours; 4% NaCl and 0.1% ascorbic acid browned after 90 hours; 4% NaCl and 0.2% ascorbic acid browned after 78 hours; The slices frozen and stored at 0°F for one month, thawed, and placed at 52°F for observation, showed: 2% NaCl and 0.1% ascorbic acid browned after 46 hours; 2% NaCl and 0.2% ascorbic acid molded in 288 hours; Both 4% NaCl solutions with 0.1% and 0.2% ascorbic acid were moldy after 288 hours. The Grimes Golden slices frozen and stored at 0°F for six months, thawed, and observed at 52°F, gave the following results: 2% NaCl and 0.1% ascorbic acid browned after 78 hours; 2% NaCl and 0.2% ascorbic acid molded in 578 hours; 4% NaCl and 0.1% ascorbic acid molded in 426 hours; 4% NaCl and 0.2% ascorbic acid molded in 462 hours. Delicious Variety The Delicious apples had a fresh slice browning time of approximately 10 minutes. The slices, after being treated at atmOSpheric pressure in the soaking solutions, responded as follows: The slices placed at room temperature (70°F) following soaking for one hour and draining, showed: (Summarized in Table I). 2% NaCl and 0.1% ascorbic acid browned after 90 hours; -30- 2% NaCl and 0.2% ascorbic acid and the 4% NaCl with 0.1% and 0.2% ascorbic acid all molded in 84 hours. The slices which were placed at 52°F immediately after draining all molded. The 2% NaCl and 0.1% as- corbic acid molded in 556 hours; while the rest of the samples, 2% NaCl with 0.2% ascorbic acid and 4% NaCl with 0.1% and 0.2% ascorbic acid, all molded in 288 hours. The slices which were frozen and stored at 0°F for one month, thawed, and observed at room tempera- ture, showed: 2% NaCl with 0.1% and 0.2% ascorbic acid browned after 22 Hours; while the 4% NaCl and 0.1% ascorbic acid slices browned after 25 hours, and the 4% NaCl and 0.2% ascorbic acid browned in 52 hours. The slices observed at room temperature (70°F) after six months storage at 0°F, showed: 2% NaCl with 0.1% and 0.2% ascorbic acid browned after 27 hours; while the 4% NaCl with 0.1% and 0.2% ascorbic acid browned after 55 hours. The slices of Delicious apples observed at 52°F after one month's storage at 0°F, showed: 2% NaCl and 0.1% ascorbic acid browned in 25 hours; 2% NaCl and 0.2% ascorbic acid browned after 25 hours; 4% NaCl and 0.1% ascorbic acid browned after 28 hours; 4% NaCl and 0.2% ascorbic acid browned after 58 hours. -31- The slices of Delicious apples observed after six month's storage 2% NaCl and 0.1% ascorbic 2% NaCl and 0.2% ascorbic 4% NaCl and 0.1% ascorbic 4% NaCl and 0.2% ascorbic at 0°F, showed: acid browned after acid browned after acid browned after acid browned after at 52°F 25 hours; 44 hours; 54 hours; 54 hours. -32- TABLE I Browning Time of Apple Slices after Soaking Treatment at AtmOSpheric Pressure, Using Sodium Chloride and Ascorbic Acid Solutions 2% NaCl 4% NaCl Storage Obs. 0.1% 0.2% 0.1% 0.2% Temp.Time Temp. Ascorbic Acid Ascorbic Acid OF months 0F hrs. hrs. ‘hrs. hrs. McIntosh Variety 70 48 48 22 48 52 240 168 95 120 O l 70 42 28 45 55 O 5 70 78 44 54 90 0 1 52 42 52 50 50 O 5 52 258 550 505 452 Northern Spy Variety 70 . 5 17 18 40 52 24 198 168 192 0 1 70 28 52 42 52 0 5 7O 27 27 A 78 55 0 l 52 28 25 122 58 O 5 52 55 44 . 78 152 Grimes Golden Variety 70 48 48 120 72 52 254 555 288 288 0 l 70 28 45 1581 1581 O 5 70 54 78 90 78 0 1 52 45 2881 2881 2881 0 5 52 78 5781 4251 4521 Delicious Variety 70 90 841 841 841 52 5551 2881 2881 2881 0 -1 70 22 22 25 - 52 0 5 70 27 27 55 55 O 1 52 25 25 28 58 0 5 52 55 44 54 54 1molded -33- GENERAL OBSERVATIONS OF THE SOAKING TREATMENTS AT ATMOSPHERIC PRESSURE In the soaking treatments at atmospheric pressure, using ascorbic acid and sodium chloride, we find the 4% sodium chloride kills the tart of the apple slices and, therefore, loss of flavor appeal. The 2% sodium chloride solutions gave an accep- table flavor. In most cases the 4% sodium chloride treated apples stood up the longest without browning or mold- ing. But the gain in time was counteracted by less in apple flavor. The 0.1% ascorbic acid solution appears to retard browning as effectively as the 0.2% ascorbic acid in the 2% sodium chloride, unfrozen slices. In the frozen slices, the 0.2% ascorbic acid treatment prevents browning for a longer period of time, as shown in the case of the Northern Spy and Grimes Golden varieties (Table I). 0f the four varieties used, Grimes Golden and McIntosh were the most acceptable as to flavOr and color of slices(before molding or fermenting). Among the unfrozen apples, the Delicious held up as well as the Grimes Golden apples. The Northern Spy appears to brown or mold the quickest of the varieties tested. -34- PREPARATION OF THE APPLES AND RESULTS OF THE REDUCED PRESSURE TREATMENTS USING ASCORBIC ACID AND SODIUM CHLORIDE The apples were washed, peeled, and sliced into twelve sections which were drOpped directly into the treating solution. It required approximately ten minutes to peel and slice each treatment group. The slices were submerged in the solution and placed in the vacuum chamber. The pump was started, and about ten minutes were required to reduce the pressure to 26' of Hg. This was held for twenty minutes and then released. The slices were held submerged for thirty minutes following removal of the air from the slices. The atmospheric pressure forced the solution.into the exhausted tissue. The apple slices were in the solu- tion for one hour, drained, and gave the following results (summarized in Table II): McIntosh Variety The McIntosh apple slices treated at reduced pressure showed; at room temperature(70°F) the 2% NaCl for both the 0.1% and 0.2% ascorbic acid fer- mented in 56 hours; the 4% NaCl and 0.1% ascorbic acid fermented in 40 hours; and the 4% NaCl with 0.2% as- corbic acid fermented in 56 hours. The slices placed at 52°F immediately following draining from the solution,sh0wed: 2% NaCl with both -35- the 0.1% and 0.2% ascorbic acid browned after 120 hours; the 4% NaCl with both the 0.1% and 0.2% ascor- bic acid browned after 144 hours. The McIntosh apple slices which were frozen and stored at 0°F for one month, thawed, and placed at room temperature (70°F), showed: 2% NaCl and 0.1% ascorbic acid browned after 58 hours; 2% NaCl and 0.2% ascorbic acid browned after 50 hours; 4% NaCl and 0.1% ascorbic acid. molded after 158 hours; 4% NaCl and 0.2% ascorbic acid molded after 158 hours. The slices which were frozen and stored at 0°F for six months, thawed, and placed at room temperature, ahowed: 2% NaCl and 0.1% ascorbic acid browned in 44 hours; 2% NaCl and 0.2% ascorbic acid browned after 90 hours; 4% NaCl with 0.1% and with 0.2% ascorbic acid molded after 90 hours. The McIntosh apple slices frozen and stored at 0°F for one month, thawed, and held at 52°F, gave: 2% NaCl and 0.1% ascorbic acid browned after 46 hours; 2% NaCl and 0.2% ascorbic acid browned in 78 hours; 4% NaCl with 0.1% and with 0.2% ascorbic acid molded in 288 hours. The slices which were frozen and stored at 0°F for six mOnths, thawed, and held at 52°F, gave: 2% NaCl and 0.1% ascorbic acid browned after 54 hours; -36... 2% NaCl and 0.2% ascorbic acid molded in 510 hours; 4% NaCl with 0.1% and with 0.2% ascorbic acid molded in 462 hours. Northern Spy Variety The Northern Spy apple slices treated at reduced pressure and placed at room temperature (70°F) imme- diately following draining from the solution, showed: 2% NaCl and 0.1% ascorbic acid fermented in 24 hours; 2% NaCl and 0.2% ascorbic acid fermented in 56 hours; 4% NaCl and 0.1% and 0.2% ascorbic acid fermented in 56 hours. The slices placed at 52°F after draining, showed: 2% NaCl and 0.1% ascorbic acid browned after 48 hours; 2% NaCl and 0.2% ascorbic acid browned after 96 hours; 4% NaCl with 0.1% and with 0.2% ascorbic acid browned after 120 hours. Slices which were frozen and stored at 0°F for one month, thawed, and placed at room temperature for observation, showed: 2% NaCl and 0.2% ascorbic acid browned after 50 hours; 2% NaCl and 0.1% ascorbic acid browned after 58 hours; 4% NaCl and 0.1% ascorbic_acid browned after 78 hours; . 4% NaCl and 0.2% ascorbic acid browned after 46 hours. (The apple slices which were frozen and stored at 0°F for one month, thawed, and held at 52°F , showed: 2% NaCl and 0.1% ascorbic acid browned after 42 hours; -57- 2% NaCl and 0.2% ascorbic acid browned after 78 hours; 4% NaCl and 0.1% ascOrbic acid browned after 108 hours; ,4%'Na01 and 0.2% ascorbic acid molded in 258 hours. Grimes Golden Variety Treated at reduced pressure, the Grimes Golden apple slices gave the fOllowing results (summariZed in Table II): The slices held at room temperature (70°F) after draining were all fermented in 40 hours. The slices placed in the 52°F room, showed: 2% NaCl and 0.1% ascorbic acid browned after 144 hours; 2% NaCl and 0.2% ascorbic acid browned after 168 hours; 4% NaCl and 0.1% ascorbic acid browned after 144 hours; 4% NaCl and 0.2% ascorbic acid browned after 176 hours. Apple slices frozen and stored at 0°F for one month, thawed, and observed at room temperature, showed; 2% NaCl and 0.1% ascorbic acid browned after 78 hours; 2% NaCl and 0.2% ascorbic acid browned after 60 hours; 4% NaCl with 0.1% and with 0.2% ascorbic acid browned after 158 hours. The slices frozen and held for six months at 0°F, thawed, and observed at room temperature, showed: 2% NaCl with both 0.1% and 0.2% ascorbic acid browned after 78 hours; while 4% NaCl with 0.1% ascorbic acid browned after 90 hours. ' a; -58- The Grimes Golden slices frozen and stored at 0°F for one month, thawed, and held at 52°F, showed: 2% NaCl and 0.1% ascorbic acid browned after 84 hours; 2% NaCl and 0.1% ascorbic acid racided in 288 hours as did the 4% NaCl with both the 0.1% and 0.2% ascorbic acid. The slices held for six months at 0°F, thawed, and observed at 52°F, showed: 2% NaCl and 0.1% ascorbic acid molded in 578 hours; 2% NaCl and 0.2% ascorbic acid molded in 426 hours; 4% NaCl and 0.1% ascorbic acid molded in 452 hours. Delicious Variety The Delicious apple slices treated at reduced. pressure responded as follows: All the slices treated, drained, and left at room temperature fermented in 56 hours. (The slices which were placed at 52°F after draining, showed: 2% NaCl and 0.1% ascorbic acid browned after 96 hours; 2% NaCl and 0.2% ascorbic acid browned after 120 hours; 4% NaCl with both 0.1% and 0.2% ascorbic acid browned, after 96 hours. The slices which were frozen and stored at 0°F for one month, thawed, and observed at room temperature (70°F) showed: 2% NaCl and 0.1% ascorbic acid browned after 38 hours; 2% NaCl and 0.2% ascorbic acid browned after 5) hours; -39- 4% NaCl and 0.1% ascorbic acid browned after 58 hours; 4% NaCl and 0.2% ascorbic acid browned after 58 hours. The Delicious apple slices observed after six . month's storage at 0°F, showed browning when held at room temperature as follows: 2% NaCl and 0.1% ascorbic acid browned in 55 hours. The slices which were frozen and stored at 0°F for one month, thawed, and observed at 52°F, showed: 2% NaCl and 0.1% ascOrbic acid browned after 54 hours; 2% NaCl and 0.2% ascorbic acid browned after 46 hours; 4% NaCl and 0.1% ascorbic acid browned after 58 hours; 4% NaCl and 0.2% ascorbic acid browned after 42 hours. Slices frozen and stored at 0°F for six months, thawed, and observed at 52°F, showed: ' 2% NaCl and 0.1% ascorbic acid browned after 58 hours. TABLE II Browning Time of Apple Slices after Soaking Treatment at Reduced Pressure, Using Sodium Chloride and Ascorbic Acid Solutions 2% NaCl 4% NaCl Storage Obs. 0.1% 0.2% 0.1% 0.2% Temp. Time Temp. Ascorbic Acid Ascorbic Acid °F months °F hrs. hrs. hrs. hrs. McIntosh Variety 70 552 552 402 552 52 120 120 144 144 0 1 70 58 5O 15 1 1581 O 5 7O 44 90 90 901 0 1 52 45 78 2881 2881 0 5 52 54. 5101 4521 4521 Northern Spy Variety 70 242 552 552 55'2 52 48 95 120 120 0 1 70 58 50 78 45 1 O I 52 42 78 108 258 Grimes Golden Variety 70 4O2 402 402 402 52 144 168 144 175 0 1 70 78 50 158 158 0 6 7O 78 78 90 0 1 52 84 2881 2881 2881 0 5 52 5781 4251 4521 Delicious Variety 70 552 552 552 552 52 95 120 95 95 O 1 70 58 50 58 58 0 5 70 55 » 0 l 52 54 45 58 42 0 5 52 58 2fermented lmolded -41- GENERAL OBSERVATIONS ON THE SOAKING TREATMENTS AT REDUCED PRESSURES, USING SODIUM CHLORIDE AND ASCORBIC ACID SOLUTIONS In the soaking treatments at reduced pressures, using ascorbic acid and sodium chloride, the results follow about the same pattern 25 the soaking treatments at atmOspheric pressure. The solutions containing 4% NaCl were too salty to the taste. The 2% NaCl is more noticable to the taste in the slices at reduced pressure than in those treated at atmospheric pressure. There is very little difference in browning time between the 0.1% and the 0.2% ascorbic acid except in the frozen slices. There is very little difference in the browning rate of the slices which were soaked at atmospheric pressure and those which were vacuum treated. The slices which are processed at reduced pressure are more desirable than those processed at atmospheric pressure for pies, because these slices retain their shape in baking, making for a thicker, fuller pie. -42- SULFUR DIOXIDE TREATMENTS Sulfur dioxide ($02) was used in the second series of treatments. The solutions containing 302 were prepared from sodium bisulfite (anhydrous). The first five lots of Delicious apples were soaked for one hour in distilled water solutions containing varying concentrations of $02 (summarized in Table III). I. This 802 solution initially contained 274 ppm 802. The solution, after the slices had soaked for one hour, contained 171 ppm 802, the slices showing 41 ppm 302 had been taken up by the fruit. The slices placed at room temperature (70°F), browned after 24 hours. The slices placed at 52°F, browned after 56 hours. Slices which were frozen and stored at 0°F for one month, thawed, and placed at room temperature, browned after 25 hours. Other slices after being stored for one month at 0°F, browned after 28 hours when held at 52°F. The slices which were frozen and stored for six months at 0°F, thawed, and placed at room temperature, browned after 27 hours; while those held at 52°F browned after 55 hours. II. These apple slices were soaked for one hour in a solution containing 445 ppm 802. At the end of the soaking period, the slices showed 75 ppm 802, while the solution had 569 ppm 302 left. The slices thus treated gave the following results: Left standing at room temperature, the slices browned in 45 hours; -43- Held at 52°F, other slices browned after 96 hours. Slices frozen and stored at 0°F for one month, browned after 50 hours after being thawed and held at room temperature (70°F); while those stored at 0°F for six months, browned in 66 hours after being placed at room temperature. Slices frozen and stored at 0°F for one month, browned after 65 hours when held at 52°F; while the slices stored for six months at 0°F, browned after 126 hours when placed at 52°F. III. Lot III was put in a solution containing 664 ppm 802 for one hour. After the one hour soak, the slices were drained and found to contain 116 ppm 802, while the solution tested 588 ppm 802 left. The slices given such treatment reacted as follows: at room temperature, they browned after 60 hours; while at 52°F, they browned after 208 hours. Slices frozen and stored at 0°F for one month and then placed at room temperature, molded in 182 hours; while those placed at 52°F, molded in 288 hours. The slices frozen and stored at 0°F for six months, molded in 102 hours when placed at room temperature and in 426 hours when placed at 52°F. IV. The solution into which the lot IV slices were dipped contained 817 ppm 802. After the one hour soaking period, the solution retained 722 ppm 802, while the fruit had 157 ppm 302. Drained and placed at room temperature, the slices browned in 68 hours; -44- while those held at 52°F browned after 260 hours. Slices frozen and stored at 0°F for one month molded in 182 hours when placed at room temperature (70°F); while those placed at 52°F, molded in 288 hours. The slices frozen and stored at 0°F for six months, molded in 102 hours when placed at room temperature; while those placed at 52°F, molded in 425 hours. V. In the original solution for lot V there were 1252 ppm 302. After the One hour soaking peflod, the drained slices were found to contain 252 ppm 302; while the used solution retained 1060 ppm S02. These slices gave the following results: those placed at room tem- perature, browned in 80 hours; the ones held at 52°F, molded in 510 hours; slices which were frozen and stored at 0°F for one month and then placed at room temperature, molded in 182 hours; while those placed at 52°F, molded in 288 hours. The frozen slices which were held for six.months at 0°F and then placed at room temperature, molded in 114 hours; while those held at 52°F, molded in 462 hours. McIntosh apples were given the following treat- ments at reduced pressures:- VI. This lot was the first of the vacuum treatments and was used as a control, containing no 302. The solution used contained 2% NaCl. The slices were drOpped directly into the solution and placed in the -45- Vacuum chamber. The come-down time was approximately ten minutes to reach 26" of Hg vacuum. The vacuum was held for twenty minutes and then released, allowing the solution to be forced into the slices by atmos- pheric pressure. The slices were taken from the solu- tion following thirty minutes submersion at atmospheric pressure. They were then drained. The slices placed at room temperature browned dter 52 hours. Slices placed at 52°F browned after 96 hours. The apples frozen and stored at 0°F didn't fare so well; the refrigeration broke down during the storage period, and the slices were thawed for about thirty hours. This lot was brown when refnzen, The same pressure reducing procedure was followed for all lots. VII. For this vacuum treatment, the original solution contained 296 ppm 302. After being treated and drained, the slices contained 65 ppm 302; while the used solution tested 169 ppm 302. The slices thus treated molded at room temperature in 58 hours. Slices placed at 52°F, molded in 288 hours. The slices which were frozen and stored at 00F were thawed for about thirty hours when the refrigeration system broke down. They were then refrozen. These abused slices after storage for one month,were placed at room temperature and some at 52°F and molded in 72 and 264 hours, respectively. Other refrozen slices kept in storage for six months, molded in 114 hours -45- when placed at room temperature and in 462 hours when placed at 52°F. These slices were not too firm and quite slippery. VIII. 2% NaCl was added to lot VIII, the soz-eolution containing 254 ppm 302. After the vacuum treatment, the slices were drained and found to contain 65 ppm 602. The used solution contained 169 ppm 302. These slices molded in 58 hours when placed at room temperature (70°F) and in 560 hours at 52°F. The slices which were frozen and stored at 0°F were also thawed for thirty hours when the refrigeration system broke down. They were refrozen and, after one month's storage at 0°F, they molded at room temperature in 72 hours and in 264 hours at 52°F. After six month's storage at 0°F, other slices molded in 90 hours at room temperature and in 426 hours at 52°F. The sodium chloride had a ten- dency to shroud the taste of the $02 in these slices. It also seemed to decrease the surface slime. IX. The original solution for this lot contained 290 ppm.SO2, 2% NaCl, and 1% calcium lactate. After being put through the vacuum treatment, the slices were drained and found to contain 42 ppm 802; while the solution retained 169 ppm 302. At room temperature, these slices molded in "60? hours. At 52°F they browned and molded in 144 hours. The slices which were frozen and stored at 0°F were unfortunately thawed for thirty hours when the refrigeration system broke down. -47- Thesa were refrozen. Those slices which were then stored for one month at 0°F, molded in 72 hours on being placed at room temperature, while those placed at 52°F, molded in 254 hours. The slices stored for six months at 0°F, browned in 54 hours when placed at room temperature (70°F), and those held at 52°F, molded in 554 hours. These slices remained quite firm with Very little gooeyness on the surface. The taste of 302 was diminished. These slices were crunchy after cooking. X. The McIntosh slices of this lot were vacuum treated in a solution containing 1% calcium.lactate and 265 ppm 302 originally. After draining, the slices contained 42 ppm 802, while the treating solu- tion dill had 190 ppm 302. Slices placed at room temperature molded in 72 hours, whie the slices placed at 52°F, molded in 556 hours. The slices which were frozen and stored at 0°F were also thawed for thirty hours while the refrigeration system was repaired. Following such treatment, the slices which were stored at 0°F for one month, molded in 72 hours when placed at room temperature and in 584 hours when held at 52°F. Slices which were stored for six months at 0°F, molded in 114 hours at room temperature; while the slices held at 52°F were discarded after they had lasted 462 hours without molding or browning. These slices were nice, although the surface was more slimy -48- than those with sodium chloride added to the solution. The $02 taste was much more predominant than in lot IX, and the slices were not quite as crisp after cooking, but still quite firm. XI. This lot was another control group because it cnntained no 802, but did contain 2% NaCl and 1% cal- cium lactate. Slices held at room temperature (70°F) browned in 40 hours, while those placed at 52°F browned after 96 hours. The slices which were frozen and stored at 00F and which thawed for the thirty hour period while the refrigeration system was broken down, browned before the thirty hour period was complete and were discarded. XII. 2% NaCl and 570 ppm 302 were in the solution used in the vacuum treatment of these apples. After being drained, the slices contained 106 ppm 802, while the soaking solution retained 422 ppm 502. The slices which were placed at room temperature, molded in 70 hours, while those placed at 52°F, molded in 560 hours. Once again those slices which were frozen and stored and thawed for about thirty hours during the refrigera- tion system break down, were refrozen and stored for one month at 0°F. These slices molded in 72 hOurs at room temperature and in 584 hours at 52°F. Slices stored for six months, molded in 114 hours at room temperature, but in 462 hours those held at 52°F had neither molded -49- nor browned. These slices were quite limp and broke down very easily and completely in cooking. Their 802 t aste was very strong, almost covering the apple flavor. XIII.The vacuum treatment solution used on these McIntosh slices,originally contained 549 ppm 302 and 1% calcium lactate. The drained slices contained 127 ppm 803, and the soaking solution retained 420 ppm 802. Slices placed at room temperature molded in 72 hours, while those observed at 52°F molded in 244 hours. The frozen and stored at 0°F slices were thawed for thirty hours during a refrigeration break-down. But the slices which were then refrozen and stored for one month, molded after 72 hours when held at room tem- perature and after 584 hours when held at 52°F. The slices which were stored for six months, molded in 114 hours when placed at room temperature and in 426 hours at 52°F. These slices had a very high sulfur taste. The slices were very firm.with only some slip on the surface. XIV. The Original solution contained 1% calcium lactate and 528 ppm 802. After the vacuum treatment and drain - ing, the slices contained 106 ppm 802, while the solu- tion showed 580 ppm 802. These slices molded in 72 hours at room temperature and in 192 hours at 52°F. The slices which were frozen and stored at 0°F, also were thawed for thirty hours while refrigeration re- pairs were made. Refrozen and stored for one month, -50- the slices placed at room temperature molded in 72 hours, while those placed at 52°F, molded in 584 hours. The frozen slices thawed after six month's storage at 0°F, molded after 114 hours when placed at room temper- ature and after 554 hours when placed at 52°F. These slices were quite firm and had little slime on the surface, but had a very strong $02 flavor. XV. The vacuum treatment solution for this lot of McIntosh apples contained 40% sucrose, 1% calcium lac- tate, and 275 ppm 502. After being drained, the slices contained 42 ppm 802, and thetsed solution had 211 ppm 802. These slices browned in 60 hours at room temperature and molded in 216 hours at 52°F. The slices which were frozen and stored at 0°F, thawed for thirty hours due to a refrigeration break-down, and were then refrozen. After one month's storage, some of these slices were placed at room temperature and molded in 72 hours, and some were placed at 52°F and browned after 96 hours. The slices which were held at 0°F for six months, browned in 78 hours at room temperature and molded in 252 hours at 52°F. These slices were firm, sweet, and had only a slight taste of 302. When these slices were cooked, they remained firm, medium sweet, and the 302 was still detectable. XVI. The original solution contained 549 ppm 302, 40% sucrose, and 1% calcium lactate. After being vacuum treated, the McIntosh slices were drained and found -51- to contain 85 ppm 802, while the solution after aaking the slices, contained 422 ppm 802. These slices at room temperature molded in 72 hours, at 52°F they molded in 244 hours. The slices which were frozen and stored at 0°F were accidently thawed for thirty hours during the refrigeration system break down. They were refrozen and observed at the end of one month at 0°F. At room temperature, they molded in 72 hours, and at 52°F, they molded in 586 hours. The frozen slices observed after six month's storage at 0°F and then placed at room temperature, molded in 114 hours;and at 52°F, they molded in 462 hours. These slices were firm, but were still slightly slimy on the surface. The sulfur taste was very strong. eoeHouH mm: HaHH H :s Hma Harm Hue mm mm: mam on H Ham Haas ma .m Hm. HmHm om ms HHm men or H as Hamm HaHH Hamm Hma HmmH Hmm mCH 0mm mmm H aHa Hmmn HeHH Hams Hm. Has Hms HmH om: mam H m HHHa mm: HeHH Hamm Hm» Homm Hoe moH mm: cam m HHM o 5 mm or H m Hm mwu HaHH Hamm Hm» Hmmm HmH m: omH mam H 2 Hear am Hamm Hma new How mu mmH 0mm H m 2H Hmmn Hoo Hamm Hm» Home Has \sm mmH 2mm m HHHe Ham: HmHH Hmmm Hme Hmmm Hmm so mmH mmm HH> o O we mu m H> Hmms HaHH Hmmm Hme HOHm cm mmm omOH mmm > Hews HaoH Hmmm HmmH 0mm mm HMH mm NHm aH Hams HmoH Hm_m Hum mom om mHH amm um HHH maH mm mm om mm me me new man HH mm em .m mm mm mm Ha HHH new H memm aeoa mowm mooe momm moo» mom sag mom and wow and oaoaeamu eeceonH mom Hosmv race .upo .mhca .wpo .daen.mno mcoHHm mafipaaom moo .nneaos m 500 .aasea H eHaae seep seaeaHem Hesamaao can as neaeeaoo aeH "mmmaopm Museum perm "m whaom 2H mafia McHuhoam mummspawae owflmowm Hamafim one mo mamaafim d HHH Mgmda Graph A. 400 - Browning time in relation to $02 550 “ 500 F 250 F 200 r 150 ~ 100 r 50 L Hours or ppm 302 7 l I 1 a I l l ' I I l ‘ I l I IX IV X VII VIII XVI XIV XIII V Lot Numbers. II VII III IV (Lot solutions listed on page 52.) 13000 12000 11000 10000 9000 8000 7000 6000 5000 4000 5000 2000 1000 ppm 302 Graph B. Absorption of $02 from solution. + Original solution. L olution following soaking. 802 in slices. L l k I II III IV Lot Numbers. fl -53- GENERAL OBSERVATIONS ON THE 502 TREATMENTS Those slices treated with the highest concentra- tions of 802 retained their color for the longest time, 18., the higher the 302 concentration,the better the color retention. All treatments tended to mold before browning. Table III and graph A show the changes in browning time with changes in $02 content; graph A being arranged according to increases in 802 content. Graph B shows the parts per million in the ori- ginal solution compared to the ppm absorbed by the apple slices and remaining in the solution after soaking. In the first five lots and lot VII, the 302 had a noticeable effect on softening and the production of a surface slime on the slices. The sodium chloride used in lots VI, VIII, and XII, yielded a firmer structure and less surface slime. In lots X, XIV, and XVI in which calcium lactate was used, the structure was firm, but there was still some surface slime. Lots IX, XI, and XIII in which both sodium chloride and calcium lactate were used, the slices were in very good physical condition; very little slip to the sur- face, and the slices held up firmly and presented a full, firm slice after cooking. Lots VI and XI had the best flavor and slice tex- ture, but turned brown on thawing. This showed that '54“. in these lots the $02 was the inhibitor to browning. The inhibiting action was greatly improved by the use of either sodium chloride or calcium lactate or both. CONCLUSIONS Of the treatments used in this experiment, those containing ascorbic acid in 2% sodium chloride and treated at atmospheric pressure were the most pala- table. The slices so treated were inferior in browning time to those treated with $02. 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