CHILLED CITRUS PRODUCTS1

WENZEL ET AL: CHILLED CITRUS PRODUCTS 161 CHILLED CITRUS PRODUCTS1 F. W. Wenzel, E. L. Moore, C. D. Atkins and Roger Patrick Florida Citrus Experiment Station Lake Alfred Chilled citrus products - - such as chilled orange juice, chilled grapefruit sections or fruit mixtures containing chiefly citrus sec tions - - are providing an outlet for a large volume of citrus fruit. During the 1954-55 season a tremendous increase occurred in! the production, distribution and consumer con sumption of chilled orange juice. Over 3 million boxes of Florida oranges (18) were used in the production of this product.! It has been estimated that about 5& million boxes will be used during the 1955-56 season. Large volumes of frozen orange concentrates also have been and will continue to be used in the production of chilled orange juice. At least 12 citrus processing plants in Florida produced chilled citrus products during the last season and many of these plants have expanded tljieir facilities during the summer months. There is evidence that other companies are interest ed and preparing to enter this field. The purpose of this report is to present in formation that should be of interest to pro ducers/ distributors and consumers of chilled citrus products. Emphasis will be given to available technical data that will indicate the importance of factors, such as fruit quality, processing procedures, plant sanitation and storage temperature, on the quality of chilled citrus products. An extensive bibliography, including some historical references, is pre sented. Included is a brief discussion of (45 references in the literature that are sources of useful information. Chilled Orange Juice. Fresh chilled or ange juice has been served to consumers eyer since the first roadside store in Florida or California sold juice from oranges and stored the product under refrigeration for one or more days. Fresh oranges have been extracted mechanically for a long time on a small or '! 1. Cooperative publication by the Florida Citrus Ex periment Station and the Florida Citrus Commission. Florida Agricultural Experiment Station Journal Series No. 445. I moderate scale in various cities throughout the United States, the juice refrigerated, and then distributed locally to restaurants, hotels or directly to consumers. However, such op erations remained limited in volume chiefly because of either high operating costs or the difficulty of maintaining, even for a few days, the initial good quality of orange juice, since it deteriorates rapidly after extraction unless the juice is protected against microbiological growth, flavor and enzymic changes. Dairies throughout the country have been interested for many years in distributing various types of orange drinks along with milk. A recent report (3) indicated that 76% of the country's dairies are selling today either orange juice or various types of orange beverages on their retail milk routes. In 1946, Foremost Dairies distributed reconstituted processed orange concentrate that was packed in Florida (25). Since freshly extracted orange juice deterior ates rapidly in quality, extensive attempts have been made to pack and distribute frozen orange juice of good quality. Tressler, Joslyn and Marsh (45) and Tressler and Evers (44) discussed the procedures used in Florida and California for the production of frozen orange juice. An interesting discussion of the prob lems involved in the production and distri bution of frozen orange juice is reported by Shrader and Johnson (41). This report is based upon the operation by the National Dairy Products Corporation of a plant in Tampa, Florida, for the freezing of orange juice. Timmons (43) reported that this op eration during the 1930-31 season in Tampa, together with a similar endeavor at the same time and place by the Borden Company, was the first commercial attempt to freeze citrus juices in Florida. These operations were eventually discontinued because of the many and various problems involved as indicated in the published report (41). One of the major difficulties was the long time required for the thawing of the frozen juice before it could be used by the consumer. The distribution of chilled orange juice produced commercially in Florida in large volume began after the end of World War II. The description of a Miami plant for the ex-

162 FLORIDA STATE HORTICULTURAL SOCIETY, 1955 traction and rapid refrigeration of 2,000 gal. per day of orange juice was published (1) in 1948. For a number of years, orange juice from this plant was distributed chiefly in the Miami area; however, expansion of production led to bulk shipments of refrigerated orange juice in 3,750 gallon tank trucks to a dairy in Newark, N. J. There it was packaged in waxed paper containers, similar to milk car tons, and distributed (2). About 1950, a plant in DeLand, Florida, began the produc tion and distribution of refrigerated orange juice; its operations were described in an article (50) published in 1952. A recent re port (3) indicated that this company sold more than one million gallons during July, 1955, in the 36 states in which it was distri buted and that estimated sales by this com pany for this year would exceed 10 million gallons. Since 1953, other companies have produced and sold chilled orange juice. A plant in Bradenton has increased its produc tion and sales of this product during recent years. It has been reported (3) that Kraft Foods, a subsidiary of National Dairy Prod ucts Corporation, is investigating the distribu tion on a national scale of chilled juice, using reconstituted frozen concentrated Characteristics of Chilled Orange Juice. Regulations concerning the production, com position, packaging and labeling of chilled orange juice have been issued by the Florida Citrus Commission, Lakeland, Florida (19). Any company or person concerned with the production and distribution of this product should obtain a copy of these regulations. In part, these regulations indicate that "the juice may be treated to reduce bacteriological or enzymatic action or to remove objectionable peel oil, but shall not contain any additives of any kind. The juice may be admixed with reconstituted frozen concentrated orange juice or reconstituted frozen concentrated orange juice for manufacturing; or the juice may be prepared solely from reconstituted frozen con centrated orange juice." Also, specified for chilled orange juice is a Brix of not less than 10.5 degrees; a ratio of Brix to Acid of not less than 12.0 to 1, nor more than 22.0 to 1; and.not more than 0.035% by volume of re coverable oil. Other characteristics, such as color and flavor, are also designated. Processing Procedures for Chilled Orange Juice. Equipment and procedures for wash ing the fruit and extracting and finishing the juice are the same as those used by the citrus canning and concentrate industry. Incorpora tion of air into the juice should be avoided wherever possible; deaeration of the juice may help to prevent off-flavor development. How ever, the literature contains conflicting data concerning the use of either deaeration or inert gases for the prevention of off-flavors. Plant sanitation is very important for the pro duction of a product of good quality and plant sanitation practices should be as good or pos sibly better than those used in citrus concen trate plants. Brokaw (9) discussed the sani tation procedures used in plants packing frozen concentrated citrus juices. The quality of freshly extracted orange juice deteriorates rapidly and even when refrigerat ed most juices will be of fair or poor quality after one week. Two procedures have been tried as a means of stabilizing orange juice against changes that bring about deterioration in quality, namely (a) sufficient heat treat ment to destroy a large percentage of the microorganisms and enzymes in the juice with out causing any significant change in flavor and (b) irradiation processes. During the last few years producers of frozen citrus concentrates found that enzymic, microbiological and flavor changes in these products could be prevented by heat treatment of juices prior to concentration. The applica tion of this procedure for the stabilization of orange juice, prior to rapid cooling and sub sequent refrigeration, was one of the chief factors that has made possible the large ex pansion in the production and distribution of chilled orange juice. Such stabilization of the juice has made possible the preservation of the initial quality of this product over the period of time necessary for its large scale distribution to consumers throughout the country. Tubular or plate-type heat exchang ers are used for this stabilization process and the time and temperature of heating is care fully controlled so that no significant change in flavor will occur. After stabilization, the juice is rapidly cooled to 32 F. or lower, packaged and then maintained at refrigerated temperatures as close to 32 F. as possible until it is delivered to and used by the consumer.

WENZEL ET AL: CHILLED CITRUS PRODUCTS 163 Various irradiation processes have been used (8, 50) in attempts to stabilize or pro tect orange juice from deterioration. A small amount of bacterial and enzyme destruction may occur when a very thin film of orange juice is exposed to various types of irradiation for long periods of time; however, it is not be lieved that the irradiation of large volumes of juice for short periods of time - - as nec essary in a commercial operation - - will re sult in significant amounts of enzyme inactivation or bacterial destruction. Ellis, Wells and Heyroth (14) are the authors of a book concerning the chemical action of ultraviolet rays and Proctor and Goldblith (34) have re viewed the uses of ultraviolet light in various food industries. The evaluation of ultraviolet or other irradiation processes for the preven tion of deterioration of orange juice is I im possible at this time because of the lack of sufficient experimental or commercial data. Distribution of Chilled Orange Juice: Chilled orange juice produced in Florida is shipped intra- or interstate either in waxed cardboard cartons (usually of one quart capac ity and similar to milk cartons) or in bulk in tanks hojding several thousand gallons. Refrig erated shipments by truck or rail can j be made from Florida to New York in approxi mately 36 hours. When shipped in bulk, the juice is packaged in cartons or bottles at ;the point of distribution. Chilled orange juice is distributed chiefly today to the consumer either by dairies or through chain or other retail stores which have the necessary refriger ation facilities for the storage of this product. Refrigeration of the juice as it travels through these various channels of distribution is ab solutely necessary at all times and the length of time from the production of the product until it is used by the consumer should ibe as short as possible. I Citrus concentrate manufacturers and dis tributors are aware of the difficulties encount ered during the production and distribution of frozen citrus concentrates. The mishandling of these products eventually forced the con centrate industry to the use of heat treatment for the stabilization of frozen concentrates. Thus the chilled orange juice producers should anticipate the mishandling of this product both during distribution to and use by trie consumer. Each producer must select fruit carefully and stabilize the product to such an extent as to take care of anticipated mistreat ment, if consumer complaints and loss of product are to be avoided. Preservation of the Quality of Chilled Orange Juice. As previously indicated, orange juice deteriorates in quality because of vari ous chemical or microbiological changes that may occur. Such changes are retarded at low temperatures but eventually spoilage will oc cur. Yeasts will cause fermentation and the growth of bacteria will produce off-flavors in the juice. Off-flavors may also be produced by chemical changes, such as oxidation. The enzyme, pectinesterase, will demethylate the pectin in the juice causing clarification as a result of the separation or coagulation of sus pended materials. If the consumer is to re ceive chilled orange juice of good quality, all of these changes must be prevented. Technical data concerning these changes and methods for prevention will be discussed briefly. Moore et al. (26) reported that flavor changes and fermentation occurred more rapidly than loss of vitamin C in freshly ex tracted orange and grapefruit juices stored at 40 F. Data obtained in an investigation (46) concerning the use of eight citrus dis pensers showed the wide variations that did occur in the quality of orange juice when it was maintained at temperatures ranging from 33 to 54 F. Results indicated that poor quality was caused chiefly by microbiological and flavor changes; that vitamin C retention was good and that enzymic clarification did not occur. Microbiological counts in juices after three days in the dispensers ranged from 19,000 to 1,500,000 per ml. when plated on dextrose agar, ph 7.0. From the standpoint of keeping quality, both the number and types of microorganisms in a product are important. Faville and Hill (15) pointed out that the maturity of the fruit is the most important factor in the pro duction of a lowcount citrus juice, but also stressed the importance of using efficient fruit washing procedures and clean equipment. Total counts in orange juices, extracted in the Station pilot plant from 112 different lots of Hamlin, Pineapple and Valencia oranges over a period of two canning seasons, ranged from 1,200 to 745,000 per ml., even though the fruit was tree-picked, carefully graded, ef-

164 FLORIDA STATE HORTICULTURAL SOCIETY, 1955 ficiently washed and extracted and handled in equipment which was washed with a hot detergent before each run and all exposed surfaces thoroughly steamed. Faville et al. (17) have discussed the sur vival of some microorganisms in orange juice and concentrate. Faville and Hill (16) also isolated 204 bacterial cultures from fermenting citrus juices and from rotting oranges. They described and studied six species of bacteria, representing 5 genera, which cause spoilage in unpasteurized juice or in mature oranges on the tree. The genera represented were Lactobacittus, Leuconostoc, Aerobacter, Xanthomonas and Achromobacter. The rate of growth oi various microorganisms in orange juice at temperatures of 60 to 80 F. were determined by Barreto (6) and similar studies were reported by Rushing (39) and Rushing et al. (40); however, data concerning the growth rates of bacteria or yeasts in orange juice at 40 F. or lower are very meager. Recca and Mrak (35) reported considerable data concerning yeasts occurring in citrus products, such as fruit, juices and concentrates. During the production of chilled orange juice the initial microbiological contamination in the juice should be kept to a minimum by careful fruit grading, efficient washing and use of good plant sanitation procedures. Furth er reduction of the number of microorganisms in the juice may be accomplished by heat treatment. Patrick and Hill (33) found that Lactobacillus plantarum and Leuconostoc mesenteroides inoculated into pasteurized juices were completely destroyed when the inoculated juices were heated to 165 F. in 12 sec.; also that this same amount of heat treat ment greatly reduced the initial counts in Hamlin, Pineapple and Valencia orange juices from grovekrun fruit, picked late in the sea son and containing some dropped fruit which were soft but not rotten. Coliform organisms that may sometimes be present in orange juice (12) (32) (49) will also be destroyed by heat treatment of the juice to 165 F. in 12 sec; thereby eliminating questions that may be raised as to the significance of these organisms in the product. Murdock et al (27) showed that the regenerative section of a plate-type heat exchanger could be a potential source of bacterial contamination and there fore necessary precautions should be taken if this type of equipment is used. Separation or coagulation of suspended sub stances in orange juice and the subsequent clarification of the juice is caused by the demethylation of the pectin in the juice by the naturally occurring enzyme, pectinesterase. Such changes have been extensively investi gated (5, 30, 42, 48) because of the problem of clarification and gelation in frozen citrus concentrates, which arose when these products were mishandled and stored at temperatures above 0 F. Enzymic changes take place faster in 42 Brix orange concentrate than in reconstituted juices as pointed out by (11, 23, 48). Since clarification occurs slowly in or ange juice maintained at low temperatures, it will be the cause of fewer complaints from consumers than those brought about by flavor or microbiological changes. As previously in dicated, clarification did not occur in recon stituted orange juices held for 4 days at tem peratures ranging from 33 to 54 F. in juice dispensers (46), but spoilage resulted because of flavor changes and growth of microorgan isms. The inactivation of pectinesterase in orange juices by heat treatment has been ex tensively studied (4, 7, 24, 37, 38). Heat treatment of orange juice to 165 F. in 12 sec, as suggested for the destruction of microorgan isms, will also result in sufficient enzyme in activation so that the chilled product will have additional protection against enzyme changes. The initial flavor quality of chilled orange juice will depend upon the quality of the fruit and also upon the quality of any frozen orange concentrate used in its production. It is in teresting to note that in 1934, Camp and Stahl (10) reported that bottled orange juice kept at 32 F. for a week or more without loss of flavor, provided good sanitation procedures were used and that only carefully selected oranges of good quality were extracted. Wenzel and Moore (47) discussed the flavor, color and vitamin C content of concentrates made from different varieties of citrus fruits produc ed in Florida and this information is applicable to the characteristics of chilled orange juice. Oranges susceptible to black rot, caused by a fungus, should not be used because an offflavor and high microbial count will result in the juice. Hill (21) reported on the occur rence of this problem with Jaffa oranges and

WENZEL ET AL: CHILLED CITRUS PRODUCTS 165 pointed out that often internal infection is not detectable by the external appearance of the fruit. Poor flavor quality in chilled orange juice will also result if immature, overmature or stale fruits are used. Since it is most desirable to have chilled orange juice available for distribution through out the year, the use of frozen orange concen trate becomes necessary if large volume pro duction is to be maintained. This is especial ly true when fresh fruit becomes limited in Florida from July through October. Good quality chilled orange juice cannot be made if orange concentrate of poor quality is used. Concentrate quality depends upon fruit quality, processing procedures, storage conditions and other factors as discussed by Wenzel and Moore (47). An off-flavor, usually described as being similar to buttermilk, may occur in orange concentrate because of bacterial growth during processing as reported by Hays and Riester (20) and Murdock et al. (29). This off-flavor results from the bacterial production of diacetyl and Hill et al. (22) suggested a method for the measurement of the amount of this substance in juices or concentrates. Oxi dized flavors, such as cardboard, castor oil or tallowy, sometimes develop in frozen orange concentrates during storage at 0 F. The fac tors involved in this off-flavor problem wpre recently discussed by Olsen et al. (31). Either 42 Brix or 6-fold (58-60 Brix) frozen or ange concentrates may be used in the pro duction of chilled orange juice. Because of the deficiency in aroma and flavor, fresh juice must be added if 6-fold concentrates are us^d. Characteristics of 58-60 Brix concentrates have been discussed by various investigators (13, 23, 28, 36). The addition of some fresh juice, when concentrates are used, will usually result in a better flavored product, except per haps where 42cBrix frozen orange concentrate of excellent flavor and quality is used, j It has been found that flavor changes in orange juice are also somewhat retarded when juice is stabilized by the partial destruction of microorganisms and enzymes. It is believed that heating of orange juice to 165 F. in 12 sec. or its equivalent, followed by very rapid cooling, can be done without the production of flavor changes of any significance to the consumer. However, undesirable heated fla vors will result in orange juice, if the heat treatment is excessive and not carefully con trolled. Considering the information presented, it is evident that chilled orange juice can be ob tained which will remain acceptable to con sumers for a period of approximately two weeks. This is true if the juice produced initially has a good flavor and low microbio logical contamination through the use of good fruit and employing good sanitary procedures; also by stabilizing the product against micro biological, enzymic and flavor changes by carefully controlled heat treatment, followed by rapid cooling; and finally by distribution and storage of the chilled juice at temperatures as close to 32 F. as possible. Other Chilled Citrus Products. - Refriger ated orange or grapefruit sections and fruit mixtures containing large amounts of citrus sections have been produced and distributed for a considerable period of time. Indica tions are that extensive attempts will be made this season to increase the production and sale of these chilled products, especially chilled grapefruit sections. The possibilities of the sale of other chilled citrus products, such as grapefruit juice and limeade are being cur rently investigated. All of the factors affect ing the quality of chilled orange juice, such as fruit quality, plant sanitation, low storage temperatures and rapid distribution, are im portant and must be considered if other chilled citrus products of good quality are to be made available to consumers and meet with their acceptance. Interest in the production, distribution and consumer acceptance of chilled citrus prod ucts, such as chilled orange juice and chilled grapefruit sections, constantly increased dur ing the 1954-55 season. Indications are that interest and further expansion in the produc tion of these products will continue during the coming season. Continued acceptance by con sumers of chilled orange juice at prices suf ficient to justify costs of production and dis tribution will depend upon the quality of these products when used by the consumer. Such quality should be as close as possible to that of freshly extracted orange juice. Technical information available is presented to indicate the importance of various factors on the quality of chilled citrus products, such as fruit quality, concentrate quality, processing procedures,

166 FLORIDA STATE HORTICULTURAL SOCIETY, 1955 plant sanitation and temperature of storage. A list of references containing information pertinent to the quality of citrus juices and concentrates is given. LITERATURE CITED 1. Anonymous. 1948. New refrigeration process be ing applied to orange juice by Miami bottling industry. Industrial Florida 25 (4): 5-7. 2. Anonymous. 1954. Juice in cartons. Food Eng. 26 (12) : 164. 3. Anonymous. 1955. Kraft enters chilled orange juice field; 76% of dairies sell orange beverages. Quick Frozen Foods 18 (2) : 107-108. 4. Atkins, C. D., and A. H. Rouse. 1953. Timetemperature relationships for heat inactivation of pectinesterase in citrus juices. Food Technol. 7: 489-491. 5. Atkins, C. D., A. H. Rouse. R. L. Huggart, E. L. Moore, and F. W. Wenzel. 1953. Gelation and clari fication in concentrated citrus juices. III. Effect of heat treatment of Valencia orange and Duncan grape fruit juices prior to concentration. Food Technol. 7; 62-66. 6. Barreto, A., Jr., 1953. Studies on the rate of growth of potential spoilage bacteria in orange juice. Master's Thesis, University of Florida, Gainesville, Florida. 7. Bissett, O. W., M. K. Veldhuis, and N. B. Rushing. 1953. Effect of heat treatment tempera ture on the storage life of Valencia orange concen trates. Food Technol. 7: 258-260. 8. Blumenkranz, N. M. H. 1944. Method of pre serving fruit ' and vegetable juices. U. S. Patent 2,365,674. December 26. 9. Brokaw, C. H. 1952. The role of sanitation in quality control of frozen citrus concentrates. Food Technol. 6: 344-349. 10. Camp, A. F., and A. L, Stahl. 1934. Cold storage methods of handling orange juice. Fruit Products J. 13: 361-364, 379. 11. Cotton, R. H., W. R. Roy. C. H. Brokaw, O. R. McDuff, and A. L. Schroeder. 1947. Storage studies on frozen citrus concentrates. Proc. Florida State Hort. Soc. 60: 39-50. 12. Dack, G. M. 1955. Significance of enteric bacilli in foods. Am. J. Public Health 45: 1151-1156. 13. DuBois, C. W., and D. I. Murdock. 1955. The effect of concentration on quality of frozen orange juice with particular reference to 58.5 and 42 Brix products. I. Chemical and physiological aspects. Food Technol. 9: 60-63. 14. Ellis, C, A. A. Wells, and F. F. Heyroth. 1941. The chemical action of ultraviolet rays. Reinhold Publishing Corp., New York. 15. Faville, L. W., and E. C. Hill. 1951. Incidence and significance of microorganisms in citrus juices. Food Technol. 5: 423-425. 16. Faville, L. W., and E. C. Hill. 1952. Acidtolerant bacteria in citrus juices. Food Research 17: 281-287. 17. Faville, L. W., E. C. Hill, and E. C. Parish. 1951. Survival of microorganisms in concentrated orange juice. Food Technol. 5: 33-36. 18. Florida Canners.Association, Winter Haven, Florida. Report of August 20, 1955. 19. Florida Citrus Commission, Lakeland, Florida. Regulations pursuant to the Florida Citrus Code of 1949, as amended. Effective September 1, 1955. 20. Hays, G. I*, and D. W. Riester. 1952. The control of "off-odor" spoilage in frozen concentrated orange juice. Food Technol. 6: 386-389. 21. Hill, E. C. 1953. Microbiological examination of Jaffa oranges with stylar end spot. Proc. Florida State Hort. Soc. 66: 240-242. 22. Hill, E. C, F. W. Wenzel, and A Barreto. 1954. Colorimetric method for detection of microbiological spoilage in citrus juices. Food Technol. 8: 168-171. 23. Huggart, R. L. 1952. Effect of Concentration on clarification in concentrated citrus juices. Proc. Florida State Hort. Soc. 65: 237-242. 24. Keller, G. J., R. G. Rice, R. J. McColloch, and E. A. Beavens. 1954. Stabilization of frozen citrus concentrates by heat treatment. F'ood Technol. 8: 195-200. 25. Mauldin, E. 1946. Orange juice delivered by the milk man. Food Inds. 18: 1713. 26. Moore, E. L., C. D. Atkins. E. Wiederhold, and L. G. MacDowell. 1945. Flavor and ascorbic acid retention in fresh Florida citrus juices. J. Home Econ. 37: 290-293. 27. Murdock, D. I., C. H. Brokaw, and W. E. Allen. 1954. Plate type heat exchanger as a source of bacterial contamination in processing frozen concen trated orange juice. Proc. Florida State Hort. Soc. 67: 179-183. (also Food Technol. 9: 187-189 (1955)). 28. Murdock, D. I., and C. W. DuBois. 1955. The effect of concentration on quality of frozen orange juice with particular reference to 58.5 and 42 Brix products. II. Bacteriological aspects. Food Technol. 9: 64-67. 29. Murdock, D. I., V. S. Troy, and J. F. Folinazzo. 1952. Development of off-flavor in 20 Brix orange concentrate inoculated with certain strains of Lactobacilli and Leuconostoc. Food Technol. 6: 127-129. 30. Olsen, R. W., R. L. Huggart, and D. M. Asbell. 1951. Gelation and clarification in concentrated citrus juices. II. Effect of quantity of pulp in con centrate made from seedy varieties of fruit. Food Technol. 5: 530-533. 31. Olsen, R. W., E. L. Moore, F: W. Wenzel, and R. L. Huggart. 1955. Oxidized flavors in frozen citrus concentrates. Sixth Annual Citrus Processors Meeting. Citrus Experiment Station, Lake Alfred, Florida. October 4. 32. Patrick, R. 1953. Coliform bacteria from or ange concentrate and damaged oranges. Food Technol. 7: 157-159. 33. Patrick, R., and E. C. Hill. 1954. Effect of heat treatment on the survival of microorganisms in single-strength and concentrated juices from groverun oranges. Fifth Annual Citrus Processors Meet ing, Citrus Experiment Station, Lake Alfred, Florida. October 12. 34. Proctor, B. E., and S. A. Goldblith. 1951. Elec tromagnetic radiation fundamentals and their applica tions in food technology. Advances in Food Research 3: 119-196. Academic Press Inc., New York. 35. Recca, J., and E. M. Mrak. 1952. Yeasts oc curring in citrus products. Food Technol. 6: 450-454. 36. Rice, R. G., G. J. Keller, R. J. McColloch, and E. A. Beavens. 1954. Fruit concentrates. Flavorfortified high-density frozen citrus concentrates. J. Agr. Food Chem. 2: 196-198. 37. Rouse, A. H., and C. D. Atkins. 1952. Heat inactivation of pectinesterase in citrus juices. Food Technol. 6: 291-294. 38. Rouse, A. H., and C. D. Atkins. 1953. Further results from a study on heat inactivation of pectin esterase in citrus juices. Food Technol. 7: 221-223. 39. Rushing, N. B. 1954. Growth rates of Leuconos toc and Lactobacilli in single-strength orange juice at various ph levels. Citrus Processing Conference, U. S. Citrus Products Station, Winter Haven, Florida. October 7. 40. Rushing, N. B., M. K. Veldhuis, and V. J. Senn. 1955. Growth rates of Lactobacillus and Leu conostoc species in orange concentrates. Citrus Pro cessing Conference, U. S. Citrus Products Station, Winter Haven, Florida. October 11. 41. Shrader, J. H., and A. H. Johnson. 1934. Freez ing orange juice. Ind. Eng. Chem. 26: 869-874. 42. Stevens, J. W., Dl E. Pritchett, and W. E. Baier. 1950. Control of enzymatic flocculation of cloud in citrus juices. Food Technol. 4: 469-473. 43. Timmons, D. E. 1950. Citrus canning in Flor ida. Early history and current statistics. AE Series 50-4. University of Florida, Gainesville. Florida. January 31. 44. Tressler, D. K., and C. F. Evers. 1943. The freezing preservation of foods. The Avi Publishing Co., Inc., New York. 45. Tressler, D. K., M. A. Joslyn, and G. L. Marsh. 1939. Fruit and vegetable juices. The Avi Publish ing Co., Inc., New York. 46. Wenzel, F. W., C. D. Atkins, E. C. Hill, R. L. Huggart, and R. W. Olsen. 1952. Evaluation and use of citrus juice dispensers. Quick Frozen Foods. 14 (12): 49-51, 96, 97. 47. Wenzel. F. W., and E. L. Moore. 1955. Charac teristics of concentrates made from different varieties of citrus fruits. Food Technol. 9: 293-296. 48. Wenzel, F. W., E. L. Moore, A. H. Rouse, and CD. Atkins. 1951. Gelation and clarification in con centrated citrus juices. I. Introduction and present status. Food Technol. 5: 454-457. 49. Wolford, E. R., and J. A. Berry, 1948. Condi tion of oranges as affecting bacterial content of frozen juice with emphasis on coliform organisms. Food Research 13: 172-178. 50. Wright, C. E. 1952. Keeping orange juice fresh. Food Eng. 24 (11) : 93, 162.