Problems in the Dehydration of Orange Juice

26 FLORIDA STATE HORTICULTURAL SOCIETY, 1946 is prohibited at the present time because its is known, the results reported here seem very toxic effect on humans is not yet known. hopeful that such a compound can be dis A few proprietary materials that have been covered. supplied by their distributors have been given very thorough tests for their ability to con Literature Cited trol rots. Paper mats containing some am 1. CHILDS, J. F. C. and E. A. SlEGLER. Con monium compound were found to give no con trolling orange decay. Ind. and Eng. Chem. trol over stem-end rot or molds when 8 to 24 38: 82, 1946. 2. CHILDS, J. F. C. and E. A. SlEGLER. Experi wafers were placed in a packed box of oranges. mental control of orange decays with thiourea. Various green paper wraps were extensively Phytopath. 34: 983-985, 1944. tested on oranges and grapefruit for their 3. HOPKINS, E. F. and K. W. LOUCKS. Keeping quality of oranges. Rept. to Fla. Citrus ability to control storage diseases in lighted Com/77. June 30, 1943 (Mimeographed). and darkened storage rooms. They were found 4. HOPKINS, E. F. and K. W. LOUCKS, and to have no effect on the diseases and shrink CHARLES" R. STEARNS, Jr. A study of cer age was just as great in the green wraps as tain methods for the control of stem-end rot it was in the light orange colored paper wraps and blue mold in oranges. Proc, Fla. State Hort. Soc. 57: 87-98, 1944. that are commonly used for wrapping citrus. 5. HOPKINS, E. F. and K. W. LOUCKS. Pulling Two epoxides, ethylene oxide and propylene versus clipping of oranges in respect to loss oxide, which were tried as fumigants proved from stem-end rot and blue mold. Proc. Fla. ineffective at any concentration that was low State Hort. Soc. 57: 80-86, 1944. 6. HOPKINS, E. F. and K. W. LOUCKS. Investi enough to be harmless to the fruit rind. gation of the fungicidal action of various Although at the present time no usable chemicals in respect to their effect on stem- chemical has been found that is highly effective end rot and mold fungi of citrus fruit. Fla. against citrus storage rots by any of the Exp. Sta. Ann. Rept. pp 174-175, 1945. 7. SNEDECOR, G. W. Statistical methods. Iowa methods so far. used, that is cheap enough to State College Press, Ames, Iowa. pp. 179- be profitable, and whose toxicity to humans 248, 1940.

PROBLEMS IN THE DEHYDRATION OF ORANGE JUICE -

Norman V. Hayes, Robert H. Cotton and now deprived of this valuable food. The de Wallace R. Roy : hydration can be stopped short of the powder National Research Corporation state to make a concentrate which can be sold as a frozen food. This frozen concentrate when Plymouth reconstituted with three times its volume of water closely approximates fresh juice. \ process has been developed employing The purpose of the present paper is to dis vacuum diffusion for the dehydration of or cuss the process and describe some of the ange juice to a virtually anhydrous powder. problems involved, as well as to present data The powder is extremely palatable and should in the hope that some duplication of effort go far in increasing the distribution of orange by other workers may be avoided. juice to segments of the world's population Orange juice is screened and circulated at a temperature of 55 °F. through concentrators 1 Presented before the American Society • of where the water is evaporated under vacuum Horticultural Science meeting, St. Louis, March 1946. until the concentration reaches 50 to 60% HAYS, COTTON AND ROY: ORANGE JUICE DEHYDRATION 27

solids. At this point some of the concentrate (9) has made blends of orange concentrate is further dried to powder, some is stored at containing, for example, 25% Valencia and 0° F. and the remainder is blended with fresh 75% Parson Brown or Hamlin juice. The juice to approximately 42% solids. This latter taste is superior to the Parson Brown or Ham operation restores volatiles lost by vacuum lin alone and,, therefore, these early season concentration. The addition of fresh juice to juices of very high ascorbic acid content, obtain optimum quality was developed by Dr. which are rather thin in taste, can be advan L. G. MacDowell of the Florida Citrus Com tageously used with late Valencia, which is mission. A public service patent for this pro full-bodied but rather low in ascorbic acid. cedure has been requested by the Commission. Harding's taste studies show that a ratio of The concentrate is introduced into large total soluble solids to anyhydrous citric acid vacuum driers where it is dried to a powder of at least 10 or 10.5 to 1 is necessary in order containing not more than 1.5% moisture at to have maximum palatability. Here again is temperatures in the order of magnitude of a useful tool in intelligent blending and room temperature. Pressures obtained in this scheduling. J step go as low as a few microns, with 100 Concentrate made in this laboratory of a microns typical of the end of the cycle. mixture of Hamlin arid Parson Brown juice In the drying of the concentrate to powder, was of higher palatability than the initial the driving force for movement of water vapor juice, probably because it was reconstituted in the vacuum is a trap in series with the to 12% soluble solids as compared to an initial pumping line. This is held below -50° F. and value of 9.5%. It had more "body." its surface is continually renewed by rotating Studies will have to be made over several scraping blades. In this way maximum ef seasons before precise recommendations on fectiveness is obtained from the refrigeration, blending can be made, however. since ice, which is a heat insulator, is never Orange juice is recognized as a rich carrier allowed to accumulate on the condensing sur of vitamin C. Table 1 summarizes changes in face. ascorbic acid in production of orange concen The powder and concentrate are readily re- trate having 50 to 60% solids. The mean hydrated to a drink containing 11.3% solids. retention was 96.6%. Data for six dehydra This serves to introduce the horticultural tions of juice to powder gave the following aspects of the problem. The processor buys recoveries in percentage, 97.3, 98.8, 92.3, 95.4, juice having from 9 to 15% solids but sells 96.6, 99.0. The mean retention was also 96.6%. on a fixed solids basis. Orange varieties hav It should be emphasized that these are pilot ing high solids content and capable of high plant data representing in some cases pur yields would be of great interest. Perhaps the posely drastic treatments for experimental time will come when oranges are sold on a reasons. The temperatures employed were solids basis. This would certainly encourage often greatly in excess of, and the times of further genetic research. treatment as much as several hundred percent Extremely thorough work by Paul L. Hard higher than, the current technique used in the ing (3, 4) and coworkers on seasonal changes pilot plant and the procedure used in the newly in Florida oranges forms a basis for planning constructed production unit, Vacuum Foods operational schedules of a dehydrating plant. Inc., formerly Florida Foods, Inc. Two values It gives data on solids, acid, ascorbic acid, pH, of 102% recovery were obtained. It is felt and ratio of total soluble solids to acidity as that they arise from sampling error. a function of time and rootstock. The work The stability of flavor and ascorbic acid in is a .guide to intelligent blending of orange any processed orange juice product is of tre juice which should go far in making for uni mendous significance. The vitamin C level formity in taste and in 'maintenance of a when the purchaser consumes canned, con relatively high level of ascorbic acid. Stahl centrated or powdered juice is important fromj 28 FLORIDA STATE HORTICULTURAL SOCIETY, 1946 the human nutrition viewpoint. Moore, Wie- Dowell and Heid (6) in a review of proposed derhold and Atkins (7) report for canned methods of making powder and concentrate orange juice retentions of 81.7 and 95.1% of quote Stevens (11) as saying that orange the initial ascorbic acid after six months stor- juice concentrate stored at' -5° F. for six age at 80 °F. and 40° F. respectively. The years retained over 90 percent of its ascorbic method of analysis used was the standard acid. Tests in this laboratory (Plymouth) for indophenol procedure. (2) Four batches of shorter periods confirm the above finding.

TABLE 1—Changes in Ascorbic Acid Manufacture of Orange Concentrate Hav ing 50% Solids

Ascorbic Acid mg/gm Percentage Run No. dry basis Recovery

Fresh juice Concentrate

Al 4.11 3.94 95.8 A2 4.53 4.38 96.6 A4 5.02 4.74 94.5 A6 4.84 4.76 98.4 A7 4.75 4.72 99.4 A8 4.29 4.22 98.4 A9 4.48 4.29 95.8 A10 4.37 4.05 94.8 All 4.39 4.13 94.1 A12 4.26 3.86 90.6 A14 3.91 4.01 102.0 A15 4.12 4.10 99.3 A16 4.65 4.65 100.0 A17 4.12 4.03 97.8 A18 4.25 4.11 96.7 A19 4.23 4.19 99.1 A21 3.99 3.77 94.5 A22 4.33 4.14 95.7 A23 3.99 3.92 98.2 A24 ,4.18 3.64 • 87.0 A25 4'.16 4.07 97.8 A26 4.24 3.96 93.4 A27 3.71 3.79 102.0

Mean percentage retention of ascorbic acid in concentrate 96.6% orange powder made by the vacuum diffusion Where a great many determinations of as- process were stored six months at about 80° F. corbie acid are being made a rapid method of The average retention of ascorbic acid was analysis is highly desirable. Stevens (10) has 99.2%. The powders were loose and fluffy, shown that for citrus juices iodate titration val- rehydrated easily, and had a good taste when ties closely check indophenol titrations. Ballen- opened. Moore, Atkins, Wiederhold, Mac- tine (1) has also reported this and gives a HAYS, COTTON AND ROY: ORANGE JUICE DEHYDRATION 29 slightly simpler technic. Table 2 gives a com in orange powder is good. Of course, a pro parison of values obtained in this laboratory duct containing high amounts of fructose does by the Ballentine procedure and by the widely not retain excellent flavor at 100° F. for many used indophenol titration. weeks, especially if amino acids are also pres-

TABLE 2—Ascorbic Acid in Mg/gm

Sample Indophenol Iodate Photometric Titration Titration Analysis

0.469 0.472 0.471 0.474 Fresh juice 0.471 0.474 Average 0.470 0.473 2.04 2.09 Orange 2.06 2.05 Concentrate 2.04 2.05 Average 2.03 2.06 3.89 3.96 Orange 3.94 3.96 Powder 3.92 3.94 Average 3.92 3.95 Orange powder No. 14' stored several months at 100° F. , 2.59* 2.69 2.59* Orange powder No. 33 heated to 100° F. for a week 2.70* 2.87 2.67*

*Data obtained by Bernard L. Oser, Food ent. The use of 100° F. constitutes, therefore, Research Laboratories, Long Island City, N. Y. an accelerated ageing test. The flavor reten tion in the powder at 75° to 85° F. is so It will be seen that the iodate values for good, however, that it constitutes one economic the first three samples are approximately 1% argument for its production in spite of costs higher than the values obtained with indo higher than canned juice. The results of hun phenol. In order1 to determine whether pow dreds ot taste tests of new and aged powder der that had been subjected to very severe are almost universally expressed as "excellent, ageing tests gave a fictitiously high value, not quite so good as fresh juice but far supe careful analyses of two samples of powder rior to canned juice." were made by the elaborate method of Hoch- It may be of interest to list here several berg, Melnick and Oser (5), which minimizes of the technics employed in this laboratory in errors caused by reducing substances other stability and drying rate studies. Water con than ascorbic acid. Powder stored at 100° F. tent changes are important in both the above. for a week or for several months had ascorbic Since some reactions involving sugars are ac acid levels 6 and 4% higher respectively by companied by decrease in water (hydrolysis of the iodate method than by indophenol titra disaccharides) while others release water tion. The photometric method, which includes (amino acid—sugar reactions and degradation dehydroascorbic acid, gave analyses within 1% of monosaccharides) one can obtain clues as of the indophenol titration values. to reactions involved by accurate measurement At room temperature the retention of flavor of changes in water content. Moisture deter- 30 FLORIDA STATE HORTICULTURAL, SOCIETY, 1946

minations dependent upon complete removal of run on a small laboratory scale instead of in water by vacuum drying were found to be in the pilot plant. Two useful tools were at hand adequate because of (1) excessive time re for drying an experimental concentrate and its quired to reach constant weight and (2) control to a powder. One is a cabinet dryer breakdown of the material at the high temper made in the shop, consisting of a vacuum-tight ature needed, 60° C. The measurement of the square box, 24 inches by 16 inches by 10 equilibrium vapor pressure over powder as an inches. It has a self-contained pumping sys index of water content was studied. The pres tem capable of holding 20 microns pressure, a sures are correlated with the amount of water heating system controlled by a variable trans but the manipulations are very delicate and former, thermocouple selector switch for read the time to reach equilibrium was often as ing tempeatures at various places inside the long as an hour. The Fischer method (12) was cabinet, a dry ice-acetone water vapor trap found to give highly reproducible results after and a "thermocouple gauge" panel by which either storing a sample overnight in anhydrous pressures are read directly in microns on a methanol or heating it 20 minutes at 55° C. dial. The gauge consists of a filament with an A simplified titrimeter for this analysis de attached thermocouple. The heat input to the signed by Glenn Mellen of this company was filament is kept constant. Variations iii pres made at cost of less than five dollars and was sure cause variations in the temperature of the completely satisfactory. This is less than 10% thermocouple, the current from which is read of the cost of a commercial titrimeter, primar on a scale calibrated in microns pressure. The ily because only current measurement is in gauge employs the principle that removal of volved instead of potentiometric. Briefly, it heat from a filament varies with the concen consists of a Triplet 0-200 microampere me tration of vapor molecules surrounding it. A ter, a 1.5 volt flashlight battery and resistors McLeod gauge .was used at times but the par which impress a potential of 15 millivolts ticular gauge employed is not accurate in the across two platinum electrodes in the analyti presence of water vapor above pressures of cal solution. When the titration is complete the 100 microns. When total pressures were desired current drops from 75 to 100 microamperes to the themocouple gauge could be calibrated for zero. water vapor or the Alphatron gauge was used. Total and reducing sugars are analyzed by This gauge reads directly in pressure from one a modification of Scales technic (8). Data on micon to 10 millimeters of mercury and from water and sugar changes will be reported else a graph up to one atmosphere. It has a radium where. Preliminary data from five storage source of alpha particles and the ionization runs show that samples having 1.1% water current reaching a grid is directly proportional or less initially experience increases of approx . to the molecules of vapor present since the imately 30% after three weeks at 100° F. These emission of alpha particles is constant. are followed by very slight changes up to nine A second device was made which while ot weeks. Samples held at 80° F. show slight but small capacity, was found to be decidedly val definite increments, 3 to 15 per cent, after uable. It consists of two pyrex desiccators with three weeks, beyond which time the changes standard taper female fittings at the top (also are very much less. After 25 weeks at 80° F. called vacuum distilling apparatus—Central the water content was within 10% of the Scientific catalog No. 12910). Into each was value obtained at 3 weeks. Preliminary data fitted a manifold, one end of which was taper on changes in total and reducing sugars have ed to 1/4 inch and was sealed by pressure tub shown no notable changes. Titratable acidity ing and clamps. Thermocouples could be intro and pH are usually followed in storage studies duced through the tubing. The rest of the man but as yet no significant changes have been ob ifold was 1 1/2 in diameter and led into a served. common copper pipe at right angles to the A great number of experiments have been manifolds, which in turn was in series with a HAYS, COTTON AND ROY: ORANGE JUICE DEHYDRATION 31 dry ice trap and a vacuum pump. The two des 5. HOCHBERG, M. MELNICK, D. and OSER, B. iccators were thus in parallel and were totally L. Photometric determination of reduced and total ascorbic acid. Ind. Eng. Chem. Anal. inclosed in a small thermostatically controlled Ed. 15: 182, 1943. oven. The external temperature could then be 6. Moore, E. L., Atkins, C. D., Wiederhold, adjusted and both vessels reached the same Eunice, MacDowell, L. G. and Heid, temperature at the same time. Any available J. L. The concentrating and drying of cit pressure reading device could be used. In this rus juices. Proc. Inst. Food Tech. for 1945: small dryer differences in drying rates caused 160-168. 7. Moore, Edwin L., Wiederhold, Eunice, by different treatments of the juice could be and ATKINS, C. DONALD. Changes occur observed. Control runs showed that conditions ring in orange and grapefruit juices during could be closely duplicated so that two separate commercial processing and subsequent stor dehydrations of a concentrate had points on a age of the glass- and tin-packed products. drying curve that never deviated by more than Fruit Prod. Jour. 23: 270-275, 285, 1944. 0.1% water from each other. 8. ROY, W. R. and HUGHES, A. E. Application of the Scales method to determination of sugar in plant juices and tissues. Assoc. Off. Literature Cited Agr. Chem. Jour. 21: 636-645, 1938. 9. STAHL, A. L. Personal interview at Univer 1. BALLENTINE, ROBERT. Determination of as sity of Fla. December, 1945. corbic acid in citrus fruit juices. Ind. Eng. 10. STEVENS, J. W. Estimation of ascorbic acid Chem. Anal. Ed. 13: 89, 1941. in citrus juices. An iodine titration method. 2. BESSEY, O. A. The distribution of vitamin C Ind. Eng. Chem. Anal. Ed. 10: 269, 1938. in plant and animal tissues, and its deter mination. J. Biol. Chem. 103: 687-698, 11. STEVENS, J. W., SHIPSTON, G. T., and WlL- SON, C. P. The value and uses of concen 1933. 3. Harding, Paul L.. Winston, J. R. and trated citrus juices. Cal. Fruit Growers Ex FISHER, D. F. Seasonal changes in Florida change Res. Lab. Mimeograph 1-15, 1941. oranges. Tech. Bui. 753 U. S. Dept. Agr. 12. Wernimont, Grant and Hopkinson, F. J. 1940. The dead-stop point, as applied to the Karl 4. HARDING, PAUL L., and WADLEY, F. M. Fischer method for determining moisture. Study of quality in Temple oranges. Food Ind. Eng. Chem. Anal. Ed. 15: 272-274. Research 10: 510-517, 1945. 1943.

CITRUS PRODUCTS TECHNOLOGY

J. L. Heid and C. G. Beisel applied science of processing and distributing Florida Citrus Canners Cooperative food products achieved the maturity of a na tional Institute of Food Technologists. Lake Wales Basic foods may be conveniently classed as grains, fruits, vegetables, spices, nuts, condi Food Technology was one of the earliest ments, meats, fish, poultry and dairy products. arts practiced by primitive man. Capturing or Methods for processing fruits and vegetables finding his foods where and when he could, are generally similar and are ordinarily con this hunter and forager was impelled by lean seasons to develop crude methods of preserva sidered together. Within this field, citrus prod tion by salting, smoking, drying and cool stor uct technologists apply skills in horticulture, age, before he learned to cultivate plant and plant physiology, microbiology, enzymology, animal crops. chemistry, physics, engineering, cooking, nu However, the development o.f Agriculture trition and related arts and sciences to the se outstripped that of Food Technology, and it lection, harvesting, processing, packaging and is only within the last ten years that the handling of citrus fruits and products and the