PUHGEEQCY STUEEES Gi‘é C‘NEC‘ 3 PRO-ELECTS "fifiasis its: i'fm Qagraa a? M. S. MECHIGAR $?ATE 5 $353153? ’ 6 ‘3 ‘ o‘- 3 Raiph éxgnafius ‘5": are: £9522. MSU RETURNING MATERIALS: Place in book drop to LJBRAfiJES remove this checkout from w your record. FINES W1” be charged if book is returned after the date stamped below. PUNGENCY STUDIES ON ONION PRODUCTS BY RALPH ALBERTUS WARD AN ABSTRACT Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE DEPARTMENT OF FOOD SCIENCE I962 ABSTRACT PUNGENCY STUDIES ON ONION PRODUCTS by Ralph Albertus Ward A study was made to investigate the possibilities of preparing a concentrated onion juice for greater and more convenient use of onions as a flavoring substance and to determine the effect on the pungency of adding fresh onion to reconstituted dehydrated onion. Onion juice was extracted with a Carver press at 5000 psi and concentrated at 95°F. (35°C.) under 29 inches of vacuum. The results indicated that satisfactory concentrated onion juice could not be prepared because of the development of off color and odor during concentration and storage and the rapid loss of pun- gency during storage. The addition of ground fresh onion to reconstituted dehydrated onion did not increase the pungency over the amount normally developed by the two separately but it did improve the color and flavor of the product. The addition of ground fresh onion to the dehydrated onion, in the proportion of IE to 20 per cent on a fresh weight basis, doubled the pungency of the mixture. Maximum pungency was developed A-6 minutes after macerating fresh onion and after 20 minutes from the beginning of the rehydration of the dehydrated onion. Longer periods of holding neither increased or decreased the pungency. Gas chromatographic procedures available were found not suitable for use as a quantitative measure under the conditions used in this study because of small sample size. PUNGENCY STUDIES ON ONION PRODUCTS BY RALPH ALBERTUS WARD A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE DEPARTMENT OF FOOD SCIENCE I962 .5 .. I"~ 3 1 .’\) I. >\ .> —-(xg [\ t‘Ko _.-_.— ACKNOWLEDGEMENTS The author is deeply indebted to Dr. Clifford L. Bedford for his assistance in conducting this study, his aid and his advice in analyzing the data, and for his counsel in the preparation of the manuscript. The author also wishes to express his sincere apprecia- tion for the assistance given him by Dr. P. Markakis and Mr. Albert Hafner, without which this study would not have been possible. TABLE OF CONTENTS Introduction Review of Literature Materials and Methods Results and Discussion Summary Appendix Literature Cited Page 15 22 24 3A INTRODUCTION Onions, as a flavoring ingredient in food products, have been used for a long time. Their use has been a source of concern to many food proCessors because of the difficulty in controlling the strength of the onion or onion compound flavoring (23). Varia- tions due to the variety of the onion, the harvest time, the type of dehydration encountered, or even the type of fertilizer used in growing the onion can effect the pungency of the final product (22). An onion juice concentrate has been suggested as a possible. means of obtaining and maintaining a natural fresh flavor and a uniform product. In this study an onion juice concentrate was made using the ”add-back process”, and analyses were made to determine its suitability for flavoring. In addition, a study was made to determine if the flavoring constituents of dehydrated onions could be enhanced by the addition of fresh onion juice, blended whole onion or a crude onion enzyme preparation. The formation of pyruvic acid was used to measure the changes occurring in the pungency of the onion and onion mixtures. Gas chroma- tography procedures were also tried. REVIEW OF LITERATURE .The study of the volatile components of the onion, Allium cepa, and the use of these as flavor enhancers has been largely ignored, until recently, in the food industry. The use of the onion has been governed by the taste senses and therefore has caused considerable variation in the flavor of certain products and increased costs in flavoring techniques (23). Volatile Components In 1892, Semmler (32) studied the extracted oil of onion and surmized that the principle component of this crude oil was allyl n-propyl disulfide (CH2:CHCHZS.SCH2CH2CH3), which could be reduced by zinc powder to C6HIZS’ This theory was accepted by many chemists (l4) until the mid l940's when Kohman (20), and Challenger and Greenwood (6) demonstrated that there were other major components such as propionaldehyde and n-propyl mercaptan. Other investigators (S, 6) using the principles of analytical chemistry, paper and gas chromatography, mass Spectrometry, and infrared and ultraviolet photometry, have identified l8 compounds in onion oil (Table I). It is to be noted that the list does not include Semmler's allyl n-propyl disulfide. Table l. The Volatile Components of Onion (5) Hydrogen sulfide Sulfur dioxide Ammonia n-Propyl mercaptan Ethyl alcohol n-Propyl alcohol Isopropyl alcohol Methyl disulfide Methyl n-propyl disulfide Methyl ethyl ketone n-Propyl disulfide Methyl trisulfide Methyl n-propyl trisulfide n-Propyl trisulfide Acetaldehyde Propionaldehyde n-Butyraldehyde Acetone Determination gj,Pungency Since l945, the methods of measuring the pungency of the onion have been as many as the number of investigators. Currier (8) developed a procedure for the measurement of the total volatile sulfur as a means of determining the pungency by using acid hydrolysis, distilling the elemental sulfur and determining it as barium sulfate. Others (I, 26, 3]) have theorized that the pungency is related to the enzymatic degradation (alliinase) of the S- substituted l-cysteine sulfoxide derivatives to pyruvic acid and organic disulfide compounds. (Fig. I). Figure l. The Natural Formation of Pungency in the Onion Aligm cepa. 0 2 RSCH CHNH COOH + H 0 Alliinase_¢ 2 2 2 2 (RSOH) + 2 NH + 2 CH3COCOOH 3 (pyruvic acid) 0 RSSR + H20 heat RSSR The precursor of pyruvic acid in onion was initially considered to be Identical to alliin (S - allyl - l - cysteine sulfoxide) (35), which is similar to the precursor of methylene disulfide in cabbage (9). Recently, however, by the use of gas chromatography, deoxyalliin (S-allyl-cysteine) and dihydroallin (S-propyl-cysteine sulfoxide) have been shown to be the precursors (30). Figure 2. The Precursors of Pyruvic Acid in Onion (34). Alliin Dihydroalliin Deoxyalliin CH CH CH II2 I3 II2 CH CH CH I I2 I CH CH CH I2 I2 I2 $“§ 0 $—-—5() S I I I CH CH CH .2 .2 .2 CH-NHZ CH-NHZ CH-NHZ COOH COOH COOH Schwimmer and Weston (31) developed a colorimetric method for the determination of pyruvic acid with 2,A-dinitrophenylhydrazine to determine the rate of pyruvate formation in onions. The alliinase degradation of these S-cysteine complexes the di- and trisulfides has been studied, (l5, 3], 33), and it has been noted that the components are formed immediately upon cell rupture during the slicing or grinding process.3 During blanching or dehydration the volatiles are driven or carried off and the flavor approaches that of a cooked, or in extreme cases, a badly bruised onion. Also, if a high temperature is used in the dehydration process the enzyme is inactivated and the rehydrated product will not develop the flavor expected (33). Gas chromatography is one of the newer methods which is being used in the food industry for the qualitative and quantitative study of the O‘x volatile flavors and odors of foods and their additives (A, S, 17, 18, 23, 2h, 25). Carson and Wong (A, 5) have developed a model system which seems most promising in the study of onion flavors. Their method (5) involves extraction of the oil of onion by means of steam distillation from an onion alurry and adsorption of the oil on activated carbon with subsequent extraction and purification by anhydrous ethyl ether. The purified oil is then injected into a gas chromatograph containing a Reoplex #00 column at 150°C. with helium gas as the carrier at a flow rate of 45 ml. per minute. By this means, the di and trisulfides are separated cleanly and can be measured. However, the volatiles that are separated here are more nearly representative of the flavor of a cooked onion, because of the steam distillation, and cannot be considered as necessarily representing the fresh product. Another method (5) is the direct extraction with isopentane, but complete extraction cannot be achieved as in the ether- carbon adsorption method. The onion oil has been steam distilled by Kohman (20) and Carson and Wong (5). solvent extracted (two Japanese patents (I6, 21)) and vacuum distilled by Niegisch and Stahl (28) for use as a flavor enhancer. A new method for continuous distillation is described by Dimick and Simone (10). Concentrated Products There has not been any attempt made to produce a concentrated onion juice, although the oil and the dehydrated product have been on the market for some time. The addition of newly developed flavor enzyme concentrates to the rehydrated product has been demonstrated as a possible flavor enhancer in the dehydrated product, providing that the flavor precursor has not been destroyed (13). This has not proved satisfactory in the case of onions (17). The manufacture of frozen citrus fruits concentrates has been considered as the basis for making a concentrated onion juice of natural flavor and of constant strength. In the citrus industry, there are many methods for producing a con- centrated juice such as the ”add-back process”, the "Sperti process", and the"step freeze process” (3). The add-back process is considered . the process which achieves the most natural and uniform product and is used in most commercial industries at the present time (12). A process developed by Potter (29) for concentrating apple juice to be used as a flavoring in jams and jellies, desserts, and pastry products demonstrates the need for a depectinizing substance which will break down the propectins and prevent a high viscosity in the final product. This need also has been demonstrated in peach and other concentrates (ll, 27). The depectinizing rates vary from 1-3 hours at room temperature 75-86OF. (ZS-30°C.). Ascorbic acid 15 added to some fruit juices before concentrating and during depectinization to prevent the enzymatic browning reactions. Flash heating is usually used to stop the polyphenolase reactions, (11, 12). Any contamination by iron, even a few parts per million, will cause a rapid browning in the fresh juice and therefore the fresh juice is pressed and held in an iron-free environment (11). The vacuum process of concentration is usually employed to prevent a cooked flavor or destruction of the natural flavor. The temperature normally is not allowed to rise above 120°F. at 20 psi, or less in 122.126.”)- After the concentration step, the product may be stored at room temperature, if the pH is sufficiently low, or frozen, such as the orange juice concentrates on the market (3h). Dehydrated Prodgcts The use of dehydrated onions became a major flavoring ingredient during World War II, when it was neither feasible nor practical to ship fresh onions to all parts of the world. The onion used in the dehydration process is usually one of high pungency. White onions are preferred for dehydration because they yield the industry desired light colored products. Varieties such as the Southport White Globe, Ebenezer and the Louisiana Creole are used (7). The onions are steam or flame peeled, trimmed of any defects and sliced or chipped by special knives to minimize juice loss. The slices or chips are then placed on trays ( 1 1/4 pounds per square foot) and placed in a continuous dehydrator at a temperature of 165 0F. to 200°F. for the initial hour to hour and a half. The extreme heat has no cooking effect on the onion as the rapid loss in moisture has a cooling effect on the onion slices. After the initial treatment, the onions are dried to 6-7 per cent moisture at i3o-i3s°r., which is high enough to inhibit enzyme activity but not destroy it. The remaining moisture is then removed at llO-IZOOF. ‘untll a final moisture content of approximately 3.5 per cent is reached. The onions are then bagged, boxed, or placed in cans for shipment to the consumer (7, 37, 38). MATERIALS AND METHODS The onions used in this study were obtained from the Food Stores of Michigan State University. They were a common commercial variety (Yellow Globe) grown in Michigan (Lacerne Dixon, Munith, Michigan) and were held in 32°C. storage for a period of up to ten months during the studies. Onion Juice Preparation The onion bulbs were peeled, trimmed, and washed immediately prior to the extraction of the juices. Bruising and defects were removed and only onions which had not begun to sprout were used. The Juice of the onion was extracted by three methods. I. The onions were diced to approximately 1/4” x 1/8“ x l/Z” and placed in nylon press cloths. The juice was then extracted on a Carver laboratory press by placing the filled cloths between stainless steel mesh plates. The cast iron plates of the press were covered with a vinyl plastic (Saran) to prevent any iron contamination of the juice. Pressures of up to 5000 pounds per square inch were used and the juice was collected in a glass container. The juice was tested or concentrated immediately or held at 32°F. (0°C.) for periods of no longer than 24 hours. 2. The onions were ground through a laboratory size meat grinder with a stainless steel plate and placed in a nylon cloth lined Carver cylindrical press. The pulped onion was subjected to 5000 pounds per square inch pressure and the juice collected from an aluminum foil shield on the (press to prevent iron contamination. The juice was held in a glass container at 32°F. (0°C.) as above. 3. The onions were cut and placed in a Waring blendor and blended until a uniform pulp was obtained. The pulped onion was then centrifuged 10. at 2100 r.p.m. (1174 R.C.F.) for 15 minutes and the juice was collected by siphoning from the centrifuge bottle. The Juice was held in a glass container at 32°F. (0°C.) and used within 12 hours. Representative samples of the press extracted juices were also frozen at 00F. (-l7.8°C.) in 3/4” x 6” test tubes. The weights of test samples were taken before and after extraction so that the methods could be compared as to the percentage yields of the juices. Onion Juice Concentration The juice was concentrated with a laboratory rotary flash evaporator at a vacuum of approximately 29 inches of mercury. Several temperatures in the range of 750 to 104°F. (24° to 40°C.) were used to determine the optimum temperature at which evaporation could take place. Several concentrations in the range of 25 to 90 per cent were made in an attempt to determine the highest concentration that could be obtained with the least loss of pungency and the greatest retention of natural flavor. An add-back concentration procedure was also employed by collecting the volatiles in a dry ice trap on the flash evaporator. The effect of using a pectic enzyme (Pektizyme Concentrate, Takamine Laboratory) to destroy the viscosity of the juice during con- centration was studied. One per cent solution by volume of this enzyme was added to the juice at room temperature, mixed well, and allowed to react during concentration. The enzyme's effects on color and appearance was also noted. Dehydrated Onion The dehydrated onions used in these studies were of a commercial brand purchased at retail food stores in East Lansing, Michigan (Quick 11. Instant Onion, the Woolson Spice Company, Toledo, Ohio). The commercialy suggested measure of the strength of the product, one ounCe dehydrated onion equivalent to one-half pound of fresh, peeled, trimmed onion, was used throughout the tests as a basis for quantitative measurement. Representative samples of dehydrated onion equivalent to one half pound of fresh onions were tested as to the time required during rehydration to obtain the maximum amount of pungency expressed as pyruvic acid. Also the effects of an addition of fresh juice, fresh whole ground onion, and crude enzyme preparation on the pungency of dehydrated onion were studied. The percentages of fresh onions added ranged from 5 to 2000 per cent, based on the assumed fresh weight values. For example, to one ounce of dehydrated onion was added 187 inl. of H20 and 10.7 grams of ground fresh onion representing Siper'cent the total amount. Other percentages were derived similarly, as was the addition of onion juice. Onion Enzyme Preparation An onion enzyme preparation was used in an attempt to increase the pungency expressed as pyruvic acid in the fresh onion and in the dehydrated onion. The procedure used was essentially an acetone precipitation method in which 100 grams of onion were blended with 200 ml. of ice cold water for 5 minutes in a Waring blendor. The mixture was allowed to stand for 30 minutes and then centrifuged 20 minutes at 2200 r.p.m. The supernatant was filtered and to it was added 2.5 times its volume of cold (-10°F.) acetone. This acetone-water mixture was allowed to stand for one hour and then centrifuged 15 minutes at 2200 r.p.m. The 12. supernatant was then discarded and the crude enzyme precipitate suspended in 30 ml. of water. Gas chromatography A modified method of Carson and Wong (4, 5) was used, in which the onion's volatile oils were collected from the juice by solvent extrac- tion. A sample of approximately 300 grams of onion juice, or its equivalent in concentrated juice was extracted continuously for 24 hours with 100 ml. of ethyl ether at room temperature. The ethyl ether layer was then separated from the juice in a 500 m1. separatory funnel. The residue juice was then washed again with 50 ml. of ether and the combined ether extracts dried over anhydrous sodium sulfate to insure a completely dry extract. The ether extract was distilled from a small round bottom side arm distilling flash to remove the excess ether and concentrated to as small a volume as possible (near dryness). The ether extract was then held in 32°F. (0°C.) storage until use in the gas chromatography apparatus. The gas chromatography apparatus employed was a Wilkins Aerograph, model A-90, which contained a l/4 inch 0.0. stainless steel column, 5 feet long. The stationery phase was composed of firebrick (c-22, Johns-Manville Co.) ground to 40-60 mesh, acid washed, heated to 400°C., and impregnated with the organic phase in the ratio of firebrick to liquid phase of 4-1 (by weight). The liquid phase was a polyoxyalkylene adipate, Reoplex 400, (Geigy Pharmaceutical Division, Geigy Chemical Corporation). A sample of oil of 5-l0 microliters was injected into the column at temperatures of lIO-ISOOC. and helium flow rate of 45-60 ml. per 13. minute used. The sample size was measured as accurately as possible using a specially made micro syringe. Pyggvic Acid Determination The determination of pungency was made by measuring the formation of pyruvic acid in the onion. The development of pyruvic acid in the onion macerates was done by using a combination of methods (3, 17). The onion juice was allowed to stand for 20 minutes after extraction, so that maximum pyruvic acid could form. A 5 ml. aliquot was taken and 5 ml. of 40% trichloracetic acid was added to deproteinate the sample. After at least one hour, the juice was filtered through Celite (Hi-flo Supercel) on a Buchner funnel and the sediment was washed until 200 ml. of filtrate were collected. A control sample was prepared in the same manner except that the ‘juice was immediately subjected to a boiling water bath for 10 minutes to stop the enzymatic reaction. To 1 ml. of the prepared filtrate was added 1 m1. of 0.0125% 2,4 dinitrophenylhydrazine in 2 hydrochloric acid and 1 ml. of water. After 10 minutes at 37°C. (98.6°F.) 5 m1. of 0.6 sodium hydroxide were added and absorbance was measured with the Evelyn colorimeter at 420 mu. 10 ml. setting reagent blank set at 0 absorbance. A method to compare the readings of the suggested 8 m1. procedure with that of a 10 m1. procedure, which is normally used with the Evelyn calorimeter, was also run. In this procedure 0.5 ml. of distilled water and 7.5 m1. of 0¢4 N sodium hydroxide‘were used instead of l.0 m1. of water and 5 ml. of 0.6 N sodium hydroxide. 14. A calibration curve was obtained by using sodium pyruvate as a standard (Fig. 3). Sodium pyruvate concentrations of 0 to 0.20 micromoles per ml. were used as it has been reported that absorbance is linear with concentrations in this range (31). The average K value was calculated from the data obtained by the formula, K = optical density/concentration of pyruvate, micromoles per milliliter. The formula used for determining the amount of pyruvate in the onion samples was:Sodium pyruvate in micromoles per gram = absorbance x dilution K.weight of sample The pungency of the laboratory concentrate, the commercial dehydrated product, and fresh juice was compared as to the enzymatic development of pyruvic acid. (A modified method for measuring the development of pyruvic acid was also used in order to reduce the time and difficulty involved in the suction filtering and washing which occurred in the deproteinization of the slurry with trichloroacetic acid. In place of the trichloracetic acid, 0.3 N HCl was added in sufficient amounts to decrease the pH of the onion slurry to 1.5 or lower (approximately l0 ml. 0.3 N HCl for each sample diluted to 50 ml.). The slurry was then filtered through a milk filter and used as in the previous method. A control test was made to determine this method's effectiveness and the effect of any colloidal suspension which might be present. The addition of this small amount of acid does not materially affect the alkalinity of the final solution. mcc_c0 c_ v_o< o_>3c>¢ 00 comumcmEcouoo toe mo>c30 co_umcp__mu. .m oc:m_u ._E\v_u< o_>3c>a mo mo_OEoco_z 0N.0 n_.0 0..0 . :_.0 N_.0 0_.0 w0.0 00.0 30.0 No.0 00.0 a a _ a a J m H Id _ \. mom._ u M \ \ oczvoooca _E 0_ IIII~ \\.MH \ ocznoooca _E m wm@.NHM J 00.0 00_.0 00N.0 00m.0 .00:.0 oom.o ”w ozn ‘Aiisuaa neaszdo RESULTS AND DISCUSSION The juice yields for the three methods of extraction used in this study are given in Table 2. The juice yield from both diced and ground onions, using the Carver press were similar with average yields of 43 and 39 per cent respectively. The juice yield from the centrifuged onion was only 27.4 per cent. This was due to rapid reabsorption of juice by the pulp before it could be removed from the centrifuge bottles. Although centrifugation is considered one of the better methods for juice extraction, these results indicated that a basket type centrifuge will have to be used for an efficient operation to eliminate reabsorption. The data on the rate of concentration at 75°, 86°, and 95°F. (25°, 30°, and 35°C.) with 29 1 0.5 inches of vacuum are summarized in Table 3. At temperatures above 95°F. (35°C.) the vigorous boiling and frothing of the juice resulted in carry over of juice into the condensing flask and it could not be controlled sufficiently to make the use of these higher temperatures suitable for concentration. Depectinizing the onion juice during concentration reduced the viscosity of the juice and the color of the juice seemed to remain more nearly like that of the fresh juice. The pectic enzyme did not alter the evaporation rate of the juice. The concentration of pyruvic acid (as sodium pyruvate) in fresh onion juice, onion juice concentrates and reconstituted onion juice is given in Table 4. The freshly pressed onion juice was very low in pyruvic acid, which would indicate a low enzyme activity enzymatic reaction and a mild onion. However, when the fresh onion was frozen and held for 24-48 hours, the pyruvic acid increased to nearly three times that in the fresh l6. juice. This may be explained by either a rapid breakdown of the inhibitors of the enzyme, a rapid chemical reaction or an inactivation of enzymes concerned with the destruction of pyruvic acid occurring during the freezing or thawing period. In the concentrated products, the increase in pungency was due only no the concentration and there was no destruction since the pyruvic acid in the reconstituted samples had the same level as that of the fresh juice. Method Table 2. Onion Juice Extraction 17. Juice Yield % Average Carver press, rack 5000 psi, diced Carver press, cylinder, 500 psi, ground Centrifugation, 2100 r.p.m. (1174 R.C.F.) 15 min. 41.2-47.4 36.2-44.0 22.1733.0 43.5 39.2 27.4 Table 3. Concentration Rates of Onion Juice at Various Temperatures Temperature Time Weight loss Weight Loss OF. hrs. % Per Hour % 75°F. (25°C.) 3 28.6 9.5 86°F. (30°C.) I 33.3 33.3 95°F. (35°C.) I I/z 75.0 50.0 Table 4. Pyruvic Acid in Onion Juice and Its Concentrated Productsl Juice Concentrate Reconstituted (fresh micromoles pyruvate/ basis) micromoles gm. (F.w. 110.051) pyruvate/gm. 2 Fresh Juice 4.45 :_ .43 4.45 :_ .43 Frozen Juice 11.31 :_ .62 11.31 .i .62 Concentrated 28.6% 8.33 ‘i .52 5.96 .i .39 Concentrated 75% 17.0 i_1.17 4.4 i. .29 Concentrated (75%) plus 10% Dry Ice Condensate 14.0 :_ .76 6.5 i, .38 Concentrated (75%) plus 10% Fresh Juice 16.0 i 1.19 5.7 i, .41 Concentrated (75%) plus 20% Fresh Juice 15.0 . :_ .69 6.8 ‘1 .32 1 Average values for 10-40 determinations 2 Standard deviation 19. In the concentrated samples, in which, either condensate or fresh juice had been added, the reconstituted pyruvic acid values were only slightly higher than that of the fresh juice indicated that there was either a loss of pyruvic acid during concentration or low enzyme activity. This higher reconstituted value decreased rapidly upon storage and after one month of frozen storage (0°F.) (-I8OC.) the samples lost approximately 30 per cent of their pungency expressed as pyruvic acid (sodium pyruvate). This did not occur in the single strength frozen juice. During concentration, the increase in pyruvic acid follows very closely that of the increase in soluble solids (oBrix) (Figure 4) and when they are compared to each other, a straight line is obtained (Figure 5). This would be expected since pyruvic acid is not volatile. When the pyruvic acid present in the reconstituted product is plotted against the per cent concentration, it was found that there was no decrease in the amount of pyruvic acid until there was more than a'70 per cent decrease in weight (Figure 6). These results indicated that it would not be practical to attempt to concentrated onion juice beyond 70 per cent weight reduction. The concentrates had a yellowish-brown color before freezing which increased during frozen storage. The thawed reconstituted juice had a much darker and browner color than either the fresh juice or the thawed single strength juice. This was most probably due either to a chemical or enzymatic browning. In the fresh juice, there were a great deal of colloidal size particles that coagulated and rose to the surface after concentration, creating a very undesirably appearance. These particles could not be . _ . CECLU. co_umcucoocoo cc_c:o Coco con oum>3c>a mo_ .: oum>3c>m 00 mo_OE0cu_z 0cm mn__0m o_nnfiom N - mamco> mm__0m o_n:_0m X .m oc:o_u mamco> co_umcucouc00 .3 oc:o_e mt__0m o_nn_0m ucou com co_umcucoocou ucoo com 0: mm 0m mm 0N m~ 0_ m o 00 on 00 cm 0: 0m ON 0_ 0 i4 _ a a . A _ a 0 a. q 0 M m. a fl. 0 i m I m 0. m 3 J i w m. o N S I O_ 1% ON m I A i m. 2 9 d a a J t m e w a L e I mm a a . Emcm con .0 1 ON .\\ oum>ac>m mo_050cu_z .IIIIIo is a _ 3:8 «3:3... .\. ii... i I m: L 3 L om mer Jed ejeAnJAd salowOJoiw - Spglog olqnios % comumcucoUCOU “sputum oz“ 0“ voum_om mm >ocooc3m oo_:fi co_co tou:u_umcooom .o oc:m_u ~ ou_:0 eo cc_umcucouc00 uCMUEom on oe om .. 0: am ON oz 0 a 0 a 0 wer Jad QIQAHJAd salowOJogw 20. completely removed by filtration prior to concentration and filtration after concentration was slow and difficult due to the high viscosity of the concentrate. The juice also developed during concentration had a disagreeable odor of rotting, sulfur compounds which was highly disagreeable to the olfactory system. For this reason the use of a concentrated juice as a flavoring ingredient was considered impractical at the time. Rate 9f Pyruvic Acid Formation Since in the fresh juice it was found that the amount of pyruvic acid was relatively low immediately after extraction and that it tripled after freezing and thawing, the rate of pyruvic acid formation was determined. It was found that in fresh, concentrated or thawed juice, maximum development occurred 4-6 minutes after pressing or reconstituting (Figure 9i). In reconstituted dehydrated onion, the rate of formation was much slower and required 20 minutes rehydration time for maximum formation (Figure 7). Addition 2: Freshiggmgng m _t_g Rehydrated Dehydrated 9.19.; Since the results on concentrated onion juice indicated, at least with the method used in this study, that a desirable product could not be obtained due to the development of off-color and odor, it seemed desirable to determine if the pungency of dehydrated onion could be increased by the addition of freshly'ground onion. It was thought that the addition of an active enzyme system might react with the remaining substrate in dehydrated onions to enhance the pungency. The results obtained, however, showed a simple additive effect (Figure 8, also appendix table 3) indicating that there was enough enzymatic activity in the dehydrated onion to react with the substrate III .III. -.A—.._._. I ri.l ow oc30x_z co_c0 cmocu 0cm voomc0>co0 m c_ >ucovczu E:E_xmx ac ucoan_o>00 och .m ocnm_m mmuac_E i UE.H 00 0m 0: 0m 4 d _ a 0— 00N.0 00m.0 003.0 00m.0 000.0 mm 039 ‘A115ua0 [eogido co_c0 npumc0>coo ou co_c0 .cmocu we co_u_00< 00 6:0 >oco0cnm 00 ummmcuc_ .w oc:o_u co_c0 woumc0>cm0 ou wonv< :o_c0 smocu Lo ucoocom o:_ ON. oo_ em 00 o: ...j w A a . ~ 00. OQN 00m 00: 00m 000 )UODJQd Aouabund I0 9598J3U| oo_30 co_c0 smote 0cm .noumcgcoocou .cowccu c. CO_umEgOu Dmu< U_>:L>m EDE_XGI L00 UQL_JUvm ®E_H .m.menm_u mou:c_E i wE_» . n_ N. 0 _ _ _ 0 10 *— —Ipo ‘—ILT “I“ 00.0 on: 00.: 00.0 H—w-~-—i I..." -m .‘V‘. ~As- v...“ 00.0_ 1.00.9 1w) padolanag piov DIAnJAd (wb/salowOJo 21. present to produce the maximum possible pungency. The addition of 15- 20 per cent of fresh onion to the reconstituted dehydrated onion, however, did increase the pungency by 100 per cent. Therefore, this would seem to be of value to the food industry since a higher level of pungency could be obtained using less dehydrated onion and also because the addition of fresh onion tends to give the mixture a color and flavor similar to that of fresh onion. The dehydrated onion contained an average of 15.0 micromoles of pyruvic acid per gram or 1.5 micromoles on a fresh weight basis. Assuming that the common dehydrating onion, Southport White Globe (15 micromoles per gram, fresh weight basis) was used by the producers, the amount of sbustrate remaining in the dehydrated onion would be 10-15 per cent of that in the fresh onion. This could be the reason why no additional increase in pyruvic acid was obtained when fresh onion was added to reconstituted dehydrated onion. Egg Chromatoqraphy Gas chromatography is considered one of the better methods available for the study and determination of the volatile constituents of various substances, including onion. However for the onion, which is used in minimal quantities for flavoring, the methods available were not adequate to determine on a quantitive basis the effect of various treatments on its volatile constituents. In this experiment, the use of gas chromatography did not give results which could be used as a quantitative measurement, because of the difficulty in duplicating the sample size and the large quantities. of juice needed to extract a sample for study in the laboratory. 22. SUMMARY The possibilities of preparing and using a concentrated onion juice as a means of Increasing the use of onions in industry has been studied. Various methods of extraction and concentration of the juice were used. Also, the possibility of increasing the pungency of the dehydrated onion by the addition of fresh onion was studied. 0n the basis of the data obtained, the following conclusions could be made: I. The Carver press or cylindrical press methods were both more efficient in the extraction of the juice from the onion, than was the centrifuge method. 2. The onion juice, after being frozen was approximately three times as pungent as was the fresh juice. 3. The optimum temperature for concentration at 29 inches of mercury vacuumiwas 95°F. (35°C.). 4. There was an approximately 30 per cent loss of pungency in the frozen concentrate after one month storage at 00F. (‘18OC.). There was little or no loss in frozen single strength juice. 5. The maximum pungency formed was between 4-6 minutes after comminution of the fresh onion. 6. The maximum pungency during rehydration of the dehydrated onion was developed approximately 20 minutes after the addition of the water. 7. The increase of pyruvic acid during concentration followed the increase in soluble solids and there was a straight line relationship between soluble solids and pyruvic acid. 8. The maximum concentration allowable without the loss of pyruvic 23. acid was 70 per cent. 9. The onion juice concentrate was undesirable because of its color and off odor. 10. The addition of fresh onion to the dehydrated product does not product any additional pungency in excess of the summation of the two. The addition of 15 per cent fresh onion to the dehydrated onion gave an approximately 100 per cent increase in the pungency of the final product. 11. The use of gas chromatography as a quantitative measure of the volatiles of onion was limited to the extracts from large quantities of onions. APPENDIX APPENDIX TABLE 1 Sodium Pyruvate Calibration Curve 8 ml. Procedure Absorbance 420 mu. 24. Micromoles Pyruvate per m1. Reaction time-minutes O 15 30 O .000 .000 .000 .010 .021 .021 .021 .020 .058 .056 .056 .030 .086 .085 .086 .040 .102 .102 .102 .050 .137 .131 .134 .060 .155 .152 .155 .070 .187 .184 .184 .080 .216 .215 .215 .090 .244 .244 .244 .110 .300 .301 .301 .120 .321 .319 .321 .130 .354 .354 .352 .140 .374 .372' .374 .150 .398 .398 .398 .160 .426 .423 .426 .170 .465 . .462 .462 .180 .476 .472 .472 .190 .509 .505 .509 .200 .523 .512 .516 Micromoles Pyruvate/ml. APPENDIX TABLE 2 Sodium Pyruvate Calibration Curve 10 m1. Procedure Absorbance 420 mu. Replicate* 25. 1 2 0.00 .000 .000 0.02 .041 .043 0.00 .085 .085 0.06 .122 .120 0.08 .168 .163 0.10 .201 .196 0.12 .222 .200 0.14 .280 .288 0.16 .312 .310 0.18 .307 .344 0.20 .377 .382 * 15 minutes after adding NaOH APPENDIX TABLE 3 Pyruvic Acid Formation in Fresh Onion-Dehydrated Onion Concentration No. Fresh Onion Produced Expected Gain Recovery Added % Micromoles per gram 5% Fresh Onion 70 0% 258 5% 368 328 39 112 10% 432 398 33 108 15% 549 468 81 117 Average 113 i 3.66 5% Fresh Onion 95 0% 231 5% 326 325 1 100 10% 454 420 34 108 15% 500 515 -14 97 20% 596 609 - 13 98 25% 627 704 "77 89 Average 99 :_6.79 5% Fresh Onion 127 0% 106 5% 462 533 '72 87 10% 560 659 '101 85 15% 627 785 -l61 80 20% 756 912 ‘159 83 25% 823 1038 -220 79 Appendix Table 3-cont. Fresh Onion Produced Expected Gain Recovery Added % Micromoles per gram 30% 986 1165 '184 85 35% 1118 1291 '180 87 Average 84': 8.07 5% Fresh Onion 139 0% 326 5% 448 465 -17 96 10% , 593 605 - 12 98 15% 740 744 -44 99 20% 874 833 '9 99 25% 1039 1023 -16 102 30% 1136 1162 -26 98 Average 99 i 4.14 5% Fresh Onion 126 0% 343 5% 405 469 -64 86 10% 504 594 --91 85 15% 657 720 '53 84 20% 773 846 -73 91 25% 907 972 '65 93 30% 1009 1098 - 109 92 35% 1113 1224 -111 91 50% 1457 1349 - 145 108 Average 91,: 7.53 No. Appendix Table 3-cont. 28. Fresh Onion Produced Expected Gain Recovery Added % Micromoles per gram 5% Fresh Onion 119 0% 452 5% 519 569 '51 91 10% 697 686 11 102 15% 834 804 30 104 20% 898 821 '23 98 25% 1039 1038 1 100 30% 1213 1155 58 105 35% 1306 1273 33 103 Average 100 i 4.70 5% Fresh Onion 93 0% 218 5% 274 31 1 '37 88 10% 345 404 -59 85 15% 432 496 '64 87 20% 542 589 '47 92 30% 674 774 -100 87 40% 853 960 '107 89 60% 1198 1331 '133 90 80% 1554 1701 - 148 91 100% 1816 2072 -256 88 Average 80‘: 2.15 No. Appendix Table 3-cont. Fresh Onion Produced Expected Gain Recovery Added . % Micromoles per gram 5% Fresh Onion 102 0% 364 5% 409 465 '56 88 15% 588 668 '79 88 20% 696 769 '73 87 40% 1031 1175 '144 88 60% 1334 1580 -246 84 80% 1701 1985 -284 87 100% .2045 2391 '346 86 120% 2414 279 '382 86 140% 2657 3201 -545 83 Average 86': 1.76 5% Fresh Onion 96 0% 275 10% 410 460 '50 89 15% 516 553 '37 93 30% 801 830 '29 96 50% 1156 1201 -44 96 90% 1809 1941 '132 93 110% 2166 2311 -445 94 130% 2779 2681 98 104 150% 3163 3051 112 104 No. 10 11 Appendix Table 3-cont. 30. Fresh Onion Produced Expected Gain Recovery Added % Micromoles per gram 170%. 3560 3421 139 104 Average 97 i 5.49 5% Fresh Onion 78 0% 315 5% 440 393 47 1 12 10% 515 471 44 109 15% 576 549 27 105 30%. 795 782 12 102 60% 1146 1249 -103 92 90% 1528 1717 '188 89 '1 20% 1947 2184 '243 89 150% 2317 2651 '334 87 180% 2684 3118 '434 86 Average 97,: 10.15 5% Fresh Onion 102 0% 259 5% 329 361 '32 91 10% 420 463 '43 91 15% 526 564 '39 93 50% 1121 1278 '158 88 100% 2062 2297 '235 90 150% 2976 3316 '340 90 200% 4007 4335 '328 92 250% 4807 5354 -649 90 No. 12 13 Appendix Table 3-cont. Fresh Onion Produced Expected Gain Recovery Added % Micromoles per gram 300% 4671 6367 '804 89 Average 90‘: 1.69 5% Fresh Onion 100 0% 299 100% 2105 2287 '182 92 200% 4143 4274 '132 97 300% 5671 6262 '591 91 400% 7102 8250 '1148 86 500% 9939 10238 '299 97 600% 11911 12226 '315 97 700% 13374 14214 '840 94 800% ' 14466 16202 -1736 89 900% 16634 18190 '1556 91 1000% I7756 20178 '2422 88 Average 92 :_3.97 5% Fresh Onion 101 0% 883 200% 5447 4905 542 111 600% 12962 1295 13 100 800% 18177 16972 1206 107 10007. 21725 20994 731 103 1200% 25020 25016 4 100 No. Appendix Table 3-cont. 32. Fresh Onion Produced Expected Gain Recovery Added % Micromoles per gram 1400% 34095 33060 1035 103 Average 104 i 4.11 Total Average % 95 3; 7.86 33. APPENDIX TABLE 4 Increase in Pungency Due to Addition of Fresh Onion to Dehydrated Onion Increase in Total Pungency Replications, % Fresh Onion Added 1 2 3 4 5 6 7 8 9 10 5% 42 41 37 18 14 15 26 13 -- 37 10% 67 96 82 55 38 54 58 -- 49 60 15% 112 116 126 92 54 84 98 62 87 83 20% 158 168 125 86 99 148 91 -- 25% 272 218 164 102 130 -- 30% 248 194 142' 168 208 191 152 35% 298 225 175 188 40% 290 183 50% 325 320 60% 448 267 263 70% I 80% 612 367 90% 557 385 100% 732 462 110% 687 120% 552 517 130% 910 140% 630 150% 1049 635 160% 170% 1194 180% 751 34 LITERATURE CITED Bennett, E. "The Presence of Pyruvic Acid in Ebenezer 0nion”., Plant Physiol. 22, 461-3 (1945). Berdick, M., Land, D.A. and MacKay, D.A.M. ”Measuring and Deodorizing Breath Odor“, Reprinted from the Proceedings of the Scientific Section of the Toilet Goods Association, No. 32, December, 1959. 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