Storage Changes in Frozen Concentrated Citrus Juices-Preliminary Report1 2

MOORE, HUGGART AND HILL: CONCENTRATED CITRUS 165

Since the temperature needed for obtained by setting the prepared sample enzyme inactivation is above that used in the refrigerator overnight. The test to pasteurize citrus juices, it is sug agrees well with the results of other gested that this rapid test for pectines- tests. terase inactivation be used as an indica REFERENCES tion that adequate pasteurization tem 1. Jansen, E. P. Private communication, Septem peratures have been used. ber 14, 1949. 2. Linweaver, H., and Ballou, G. A. "The Effect Summary of Cations on the Activity of Alfalfa Pectine sterase (Pectase)." Arch. Biochem, 6. 373-387. The new procedure has been devised 1945. and described for testing the effective 3. MacDonnell, L. R., Jansen, E. F., and Line- ness of the pasteurization of citrus weaver, H. "The Properties of Orange Pec tinesterase." Arch. Biochem. 6: 389-401. 1945. juices. Evidence of the presence of 4. Stevens, Jesse W. "Method of Testing Fruit pectinesterase is used as the index. The Juices." U. S. Patent No. 2,267,050, December test is rapid in that it canbe completed 23, 1941. in four hours. A color indicator is used 5. Kertesz, Z. I. "Pectic Enzymes III. Heat In activation of Tomato Pectin-Methoxylose (Pec- to detect changes in acidity in the pre tose)." Food Research 4: 113-116. 1939. pared sample. The test is simple, re 6. Johnson, Arnold H., and Green, Jessi R. quiring only two solutions, and can be "Modified Methyl Red andSodium Alizarin easily performed in the control labora Sulfonate Indicators." Analytical Edition of In dustrial and Engineering Chemistry, January, tory. A confirmation of the test can be 1930, p. 2-4, Vol. 2, No. 1.

STORAGE CHANGES IN FROZEN CONCENTRATED CITRUS JUICES-PRELIMINARY REPORT1 2

Edwin L. Moore3, ently low so that any chemical, micro Richard L. Huggart3, and biological, or enzymatic changes that Elmer C. Hill3 may cause deterioration will be prevented Citrus Experiment Station or kept at a minimum. Curl (3) studied the effects of degree Lake Alfred of concentration and of temperature of The purpose of this investigation, storage on various characteristics of started in the 1949-50 season and now in orange juices, that had been pasteurized progress, is to determine what effect prior to concentration and subsequently temperature of storage will have on the benzoated and stored at temperatures of quality of frozen concentrated citrus 40° F. and above. Cotton and associates juices. In order that high quality may (2) made studies on frozen orange and be retained, frozen citrus concentrates tangerine concentrates stored at various should be stored at temperatures suffici- temperatures. They reported excellent retention of aroma, taste, ascorbic acid 1 Cooperative research by the Florida Citrus Com and "cloud during storage at 0° F., but mission and the Florida Citrus Experiment Station. storage at 40° F. resulted in clarification, 2 Paper presented by Richard L. Huggart at the 63rd Annual Meeting of the Florida State Horticultural separation and flavor degradation. Rouse Society, Winter Haven, Florida, November 1, 1950. (4) presented data on gel formation in 3 Research Fellow,Florida Citrus Commission; also frozen citrus concentratesthat had been cooperating were C. D. Atkins, Florida Citrus Com thawed and stored at 40° F. His data mission, and Robert W. Olsen, L. W. Faville, F. W. Wenzel, andDorothy Asbell, Citrus Experiment Station. indicated that the presence of low 166 FLORIDA STATE HORTICULTURAL SOCIETY, 1950 methoxyl pectin, which resulted from the plain tin cans, and (j) frozen by storage activity of the pectic enzyme, pectase, is at —8° F. This processing procedure the cause of gelation in frozen citrus simulated commercial methods during concentrates during storage at 40° F. the 1949-50 season with the probable ex At the beginning of the 1949-50 season ception in these pilot-plant packs of it was evident that there was a need for lower juice yield and possible slower rate more data, than were then available, in of final freezing. After the packs had order to advise processors, transportation been in storage at —8° F. for one day, companies, wholesalers, retailers, and samples for this investigation were consumers concerning the changes that stored at -8°, 10°, 20°, 32°, and 40° F. will take place if frozen citrus concen It was not possible to include 0° F. stor trates are mishandled by storage at age as facilities for this temperature elevated temperatures during any part were not available. of the period from the time the products Periodic chemical and microbiological are processed until they are used by the examinations of these packs are planned consumer. At the time this investiga for at least a period of one year. Fre tion was begun, it was generally believed quency of examination depends upon the that a temperature of 0° F. was suffici storage temperature and other factors. ently low to prevent deterioration, and Examinations include (a) Brix, (b) total that this low temperature should be acid, (c) peel oil, (d) ascorbic acid, (e) maintained at all times during storage, pH, (f) color, (g) pulp, (h) headspace, transportation, and distribution of these (i) vacuum, (j) clarification, (k) pectase products. activity, (1) gelation, (m) viscosity, (n) microbiological counts, and (o) flavor. Experimental Procedure Only the data summarizing the more The six packs of frozen concentrated important changes, especially gelation citrus juices used in this investigation and clarification, that have occurred in were processed in the pilot plant at the the concentrates during storage for six Citrus Experiment Station using an months will be presented in this pre evaporator described by Atkins and as liminary report. sociates (1), and included the following citrus varieties: Hamlin, Pineapple, and Experimental Results and Discussion Valencia oranges, Dancy tangerines, and Some of the initial analyses of the six Duncan and Marsh grapefruit. The pro concentrated citrus juices together with cessing procedure used may be outlined the dates at which the fruit was pro briefly as follows: (a) fruit washed and cessed are presented in Table 1. It will graded, (b) juice extracted by rotary be noted from this table that the tan press, (c) juice for concentration passed gerine concentrate had a low pectase ac through 0.030 inch finisher screen, (d) tivity as compared to the other five con cut-back pulpy juice secured by passing centrates. All varieties of fruit were pulp and seeds from (c) mixed with some held at room temperature from the time juice through 0.125 inch finisher screen, of picking until processing. (e) sugar added to tangerine and grape fruit juices, (f) juice concentrated to Gelation of the Concentrates: approximately 55° Brix, (g) 55° Brix The data for gelation of Hamlin, Pine concentrate cut back to approximately apple, and Valencia orange concentrates 42° Brix with fresh pulpy juice from and Dancy tangerine concentrate are (d), (h) slush frozen in Votator, (i) presented in Table 2. In this table and machine filled and vacuum closed in 6-oz. also in Table 3, the degree of gelation is MOORE, HUGGART AND HILL: CONCENTRATED CITRUS 167 indicated by the numerals 0, 1, 2, 3, and It will be noted from Table 2 that 4, these referring respectively to a de after storage of these four concentrates gree of gelation of none, very slight, at —8° F. for six months, only the Pine slight, semi-gel, and solid-gel. The oc apple orange concentrate showed any in currence of a semi-gel or a solid-gel in a dication of gelation and that was very frozen citrus concentrate would cause slight. Very slight gelation occurred in consumer complaints. Rouse (4) shows all three orange concentrates after three a picture of a semi-gel and a solid-gel in months storage at 10°F., and in the tan frozen concentrated citrus juices. gerine concentrate after six months

TABLE 1. INITIAL ANALYSES OF THE CONCENTRATED CITRUS JUICES.

Hamlin Pineapple Valencia Dancy Duncan Marsh Orange Orange Orange Tangerine Grapefruit Grapefruit

Date fruit processed •26-50 :2-15-50 4-20-50 1-25-50 2-21-50 2-28-50 Brix, 28° C, corrected for acid 42.3 42.1 42.2 42.1 42.1 41.9 Total acid, % as anhydrous citric 2.78 2.98 3.25 2.93 4.64 4.03 Maturity ratio: Brix/acid 15.2 14.1 13.0 14.4 9.1 10.4 pH 3.6 3.7 3.6 3.6 3.1 3.3 Ascorbic acid, Mg./lOO gm. 205.8 211.5 158.5 73.9 136.2 129.4 Pectase activity1 5.65 6.42 6.35 1.85 6.34 6.81 Microbiological count on D.A.2 16,500 57,200 76,200 33,300 3,700 13,200 Microbiological count on P.D.A3 4,480 19,100 28,300 4,200 2,020 3,860

1 Expressed as mg. methoxyl released per hour per gm. of soluble solids. 8 D. A. is Dextrose Agar, pH 7.0. • P. D. A. is Potato Dextrose Agar, pH 3.5. storage at this temperature. Pineapple Marsh grapefruit concentrate showed orange concentrate showed a semi-gel no gelation after six months storage at after two months storage at 20°F., and —8°F., but did show very slight gelation after two weeks storage at 40°F. Even after four months storage at 10 °F., and after six months storage at 40 °F., the after two weeks storage at 20°, 32°, or other two orange- concentrates showed 40°F. Even after six months storage at only a slight gel, and the tangerine con 40°F., the Marsh grapefruit concentrate centrate showed only a very slight gel. showed only a slight gel. The data for gelation of Duncan and On the basis of the results presented Marsh grapefruit concentrates are pre for gelation in these six concentrate sented in Table 3. Duncan grapefruit packs, it is indicated that a degree of concentrate showed the fastest rate of gelation which would be definitely objec gelation of any of the six concentrates. tionable from the consumer standpoint Very slight gelation occurred in this occurred only in the Pineapple orange concentrate after three months storage concentrate and Duncan grapefruit con at —8°F., and after two months storage centrate that were stored for sufficient at 10°F. Semi-gels occurred in the Dun periods of time at temperatures of 20°, can grapefruit concentrate after one 32°, or 40°F. This might be an indica months storage at 20 °F., and after two tion that gelation occurs to a greater weeks storage at 32° or 40°F. extent in concentrated juice from seedy 168 FLORIDA STATE HORTICULTURAL SOCIETY, 1950

TABLE 2.

DEGREE OF GELATION OF CONCENTRATED ORANGE AND TANGERINE JUICES*.

Time and Temperature of Storage

Variety Period -8°F. 10°F. 20°F. 32°F. 40°F.

Initial 0 0 0 0 0 1 week 0 0 0 0 0 2 weeks 0 0 0 0 0 1 month 0 0 0 0 0

Hamlin Orange 2 months 0 0 1 2 2 3 months 0 1 2 2 2 4 months 0 1 2 2 2 6 months 0 1 2 2 2

Initial 0 0 0 0 0 1 week 0 0 0 0 0 2 weeks 0 0 0 2 3 1 month 0 0 1 3 3

Pineapple Orange 2 months 0 0 3 3 3 3 months 0 1 3 4 4 4 months 0 1 3 4 4 6 months 1 1 3 4 4

Initial 0 0 0 0 0 1 week 0 0 0 0 1 2 weeks 0 0 1 1 1 1 month 0 0 1 1 1

Valencia Orange 2 months 0 0 1 2 2 3 months 0 1 2 2 2 4 months 0 1 2 2 2 6 months 0 1 2 2 2

Initial 0 0 0 0 0 1 week 0 0 0 0 0 2 weeks 0 0 0 0 0 1 month 0 0 0 0 0

Dancy Tangerine 2 months 0 0 1 1 1 3 months 0 0 1 1 2 4 months 0 0 1 1 2 6 months 0 1 2 1 1

°Degree of gelation: 0=None; l=Very slight; 2=Slight; 3=Semi-gel; 4=Solid gel. MOORE, HUGGART AND HILL: CONCENTRATED CITRUS 169

TABLE 3. DEGREE OF GELATION OF CONCENTRATED GRAPEFRUIT JUICES0

Time and Temperature of Storage. Variety Period -8°F. 10°F. 20°F. 32°F. 40°F

Initial 0 0 0 0 0 1 week 0 0 0 0 0 2 weeks 0 0 1 3 3 Duncan 1 month 0 0 3 3 4 Grapefruit 2 months 0 1 3 3 4 3 months 1 1 3 3 4 4 months 1 2 3 4 4 6 months 1 2 4 4 4

Initial 0 0 0 0 0 1 week 0 0 0 0 0 2 weeks 0 0 1 1 1 Marsh 1 month 0 0 1 1 1 Grapefruit 2 months 0 0 1 1 1 3 months 0 0 2 2 2 4 months 0 1 2 2 2 6 months 0 1 2 2 2

* Degree of gelation: 0 = None; 1 = Very Slight; 2 = Slight; 3 = Semi-gel; 4 = Solid gel. varieties of citrus fruit, such as Pine using a rectangular absorption cell (juice apple orange and Duncan grapefruit, thickness, 10 mm.) and a filter No. 730, than in the concentrated juice of varieties that was calibrated to read 100 with containing fewer seeds such as Hamlin distilled water. With this filter a com and Valencia orange and Marsh grape pletely clarified juice will read 98 to 100 fruit. percent transmission despite its color, and the presence of turbidity or "cloud" Clarification of the Concentrates in the centrif uged juice reduces the light A citrus concentrate might not be transmission by dispersion and absorp acceptable to a consumer because of tion. clarification or loss of "cloud." Loss of The data for clarification of reconsti "cloud" is a further clarification than tuted juices of Hamlin, Pineapple, and the usual settling of the chromatophores Valencia orange concentrates and Dancy or color bodies of the juice. The pectic tangerine concentrate are presented in enzymes act on the pectin responsible for Table 4. In this table the degree of the "cloud," resulting in precipitation of clarification is indicated by the percent colloidal particles, and finally leaving a age light transmission of the centrif uged clear supernatant liquid. juices, as follows: 50-60 % = none; The turbidity or "cloud" in all concen 60-70% = slight; 70-85% = definite; trates was determined by centrif uging a 85-100% = extreme. sample of the reconstituted juice (25 The data in Table 4 indicate that a gm./lOO ml.) for 15 minutes at 1700 temperature of 20°F. was too high for r.p.m. in an International Centrifuge, the proper storage of the orange and tan Size 1, Type SB, and reading the light gerine concentrates on the basis that transmission of the centrifugate in a definite clarification in these concen Lumetron Colorimeter, Model No. 402-E, trates, which might be noticeable to the 170 FLORIDA STATE HORTICULTURAL SOCIETY, 1950

TABLE 4. CLARIFICATION OF RECONSTITUTED ORANGE AND TANGERINE JUICES.0

Time and Temperature of Storage. Variety — Period -8°F. 10°F. 20°F. 32°F. 40°F

Initial 62 62 62 62 62 1 week 64 66 76 97 98 2 weeks 63 66 85 98 99 Hamlin 1 month 65 74 97 99 100 Orange 2 months 64 73 97 98 98 3 months 67 78 99 99 99 4 months 67 81 98 97 97 6 months 63 75 98 98 97

Initial 58 58 58 58 58 1 week 60 61 63 74 91 2 weeks 62 64 72 96 98 Pineapple 1 month 62 66 85 98 99 Orange 2 months 60 64 97 99 98 3 months 59 60 84 99 99 4 months 61 61 97 98 98 6 months 59 59 98 98 98

Initial 54 54 54 54 54 1 week 57 60 61 66 81 2 weeks 58 64 . 64 89 96 Valencia 1 month 55 60 65 94 95 Orange 2 months 57 59 87 93 92 3 months 54 56 75 89 88 4 months 55 60 91 95 93 6 months 56 59 91 94 91

Initial 55 55 55 55 55 1 week 56 57 60 71 81 2 weeks 57 55 58 85 98 Dancy 1 month 55 58 74 99 100 Tangerine 2 months 56 59 77 99 99 3 months 58 60 84 100 100 4 months 57 58 84 99 99 6 months 54 57 94 99 98

•Reconstituted 25 gm./lOO ml. Clarification measured by light transmission of centrifuged juices. Degree of clarification: 50-60% = None; 60-70% = Slight; 70-85% = Definite; 85-100% = Extreme. consumer, is indicated by a light trans trates or tangerine concentrate after six mission of 70 percent or higher. Definite months storage. clarification occurred after one month in The data for clarification of reconsti the Hamlin orange concentrate stored at tuted juices of Duncan and Marsh grape 10°F. At —8°F. there was no evidence fruit concentrates are presented in of clarification in the orange concen Table 5. In this table the degree of clari- MOORE, HUGGART AND HILL: CONCENTRATED CITRUS 171

TABLE 5. CLARIFICATION OF RECONSTITUTED GRAPEFRUIT JUICES.0

Time and Temperature of Storage. Variety Period -8°F. 10°F. 20°F. 32°F. 40°F

Initial 69 69 69 69 69 1 week 71 68 74 95 96 2 weeks 86 89 95 96 96 Duncan 1 month 88 94 95 97 97 Grapefruit 2 months 83 98 95 96 97 3 months 90 94 96 99 99 4 months 77 93 95 96 96 6 months 92 95 96 96 96

Initial 62 62 62 62 62 1 week 70 68 75 92 94 2 weeks 75 78 92 95 96 Marsh 1 month 87 89 95 97 97 Grapefruit 2 months 70 80 92 98 98 3 months 72 85 94 97 97 4 months 72 79 95 97 97 6 months 75 88 96 96 94

°Reconstituted 25 gm./lOO ml. Clarification measured by light transmission of centrifuged juices. Degree of clarification: 60-70% = None; 70-80% = Slight; 80-90% = Definite; 90-100% = Extreme. fication is indicated by the percentage tion indicate that the temperature of light transmission of the centrifuged storage is an important factor and that juices, as follows: 60-70% = none; as the temperature is increased, the rate 70-80% = slight; 80-90% = definite; of clarification and gelation become 90-100% = extreme. greater. Although both are the result The data in Table 5 indicate that a of enzymatic changes, clarification took temperature of 10°F. was too high for place in these citrus concentrates at a the proper storage of the two grapefruit faster rate than did gelation. Slight concentrates on the basis that definite flavor changes were noted to follow the clarification in these concentrates, which trend of gelation and clarification. might be noticeable to the consumer, is indicated by a light transmission of 80 Retention of Ascorbic Acid in the percent or higher. Even at —8°F., defi Concentrates nite clarification occurred in the Duncan The average retention of ascorbic grapefruit concentrate and slight clarifi acid in all six concentrates stored at cation occurred in the Marsh grapefruit —8°F. for six months was slightly over concentrate. The Marsh grapefruit con 98 percent, decreasing gradually with centrate did not show such an objection an increase in storage temperature to able degree of gelation as the Duncan slightly over 96 percent average reten grapefruit concentrate; however, it tion for six months storage at 40°F. So showed clarification at practically the although the concentrates in some in same rate as Duncan grapefruit concen stances may have gelled, clarified, and trate at storage temperatures of 20°, developed slight flavor changes, there 32°, and 40°F. was no appreciable decrease in the The results on gelation and clarifica ascorbic acid content 172 FLORIDA STATE HORTICULTURAL SOCIETY, 1950

Microbiological Plate Counts on the of frozen concentrate after storage at Concentrates -8°F. for one day (See Table 1). The Microbiological plate counts were packs were examined at intervals of one made initially on the six different packs month for a period of six months after

35.0

31.5

100 2 3 4 MONTHS OF STORAGE Figure 1. Trend in Reduction of Average Total Microbiological Counts of Six Packs of Citrus Concentrates Stored at Different Temperatures. MOORE, HUGGART AND HILL: CONCENTRATED CITRUS 173 being placed at storage temperatures Summary of -8°, 10°, 20°, 32°, and 40°F. A Six packs consisting of Hamlin, Pine total count was obtained by plating with apple, and Valencia orange, Dancy tan Dextrose Agar, pH 7.0, incubated for gerine, and Duncan and Marsh grape 48 hours at 30°C. (86°F.). A yeast and fruit concentrates were prepared dur mold count was determined by plating ing the 1949-50 season. Samples of the on Potato Dextrose Agar, pH 3.5, incu freshly frozen concentrates were stored bated at room temperature for five days. at -8°, 10°. 20°, 32°, and 40°F., tem The concentrate stored at 40°F. peratures that approximate those to showed an immediate sharp reduction which concentrates may be subjected in total count leveling off at about two by processors, wholesalers, retailers, months. The reduction in total count and consumers. Periodic examinations of the concentrate at —8°F. storage was of these samples are being made over a much slower with a gradual decrease period of one year. over the entire six months. After six Results obtained after six months in months, the average reduction in total dicated no appreciable decrease in count of all packs stored at —8°F. was ascorbic acid content in any of the sam 80 percent while 40 °F. storage packs ples. Gelation and clarification were had an average reduction in total count more pronounced in the concentrates of 96 percent. prepared from seedy varieties of fruit. The packs stored at 32°F. closely Clarification and varying degrees of paralleled the 40°F. storage packs in gelation occurred in all samples stored reduction of organisms. Packs stored at 20°, 32°, and 40°F., and the rate of at 20°F., although showing a smaller clarification was greater than that of reduction in the first month, closely ap gelation. Varying degrees of gelation proached in the third month those packs and clarification occurred in some of stored at the two higher temperatures. the samples stored at 10°F. and in the Reduction of microorganism count in Duncan grapefruit concentrate stored packs stored at 10°F. was less rapid at —8°F. Slight flavor changes were than in packs stored at 20 °F . noted to follow the trend of gelation Average values of the total counts for and clarification. all six packs stored at each temperature The concentrate stored at 40°F. were calculated for each examination showed immediate sharp reduction in period in order to determine the trend total microbiological count leveling off in the reduction of total count for a at about two months. The reduction in period of six months. These trends total count of the concentrate at —8°F. are shown in Figure 1. storage was much slower with a gradual The yeast and mold count presented decrease over the entire six months. a somewhat different picture in that the After six months, the average reduction reduction was more gradual. Initial in total count of all packs stored at yeast and mold counts are presented in -8°F. was 80 percent while 40°F. stor Table 1. After the second month the age packs had an average reduction in yeast and mold count was very close to total count of 96 percent. that of the total count in the 20°, 32°, and 40°F. packs, indicating that the LITERATURE CITED total count at these later examinations 1. Atkins, C. D., Wenzel, F. W., and Moore, E. was made up primarily of yeast and that L. Report New Technical Strides in Design of FCC Evaporator. Food Industries 22: 1353, few of the surviving organisms in these 1466, 1467. 1950. packs were bacteria. 2. Cotton, R. H., Roy, W. R., Brokaw, C. H., 174 FLORIDA STATE HORTICULTURAL SOCIETY, 1950

McDuff, O. R., and Schroeder, A. L. Storage Conner 105: (13), 14-16, 38, 40, 42. Septem Studies on Frozen Citrus Concentrates. Pro ber 20, 1947. ceedings of the Florida State Horticultural Society 60: 39-50. 1947. 4. Rouse, A. H. Gel Formation in Frozen Citrus 3. Curl, A. L. Concentrated Orange Juice Stor Concentrates Thawed and Stored at 40° F. age Studies. The Effects of Degree of Concen Proceedings of the Florida State Horticultural tration and of Temperature of Storage. The Society 62: 170-173. 1949.

A METHOD FOR ESTIMATING SOLUBLE SOLIDS IN DRIED CITRUS PULP

Owen W. Bissett relative molasses content in terms of U. S. Citrus Products Station* soluble solids. Official methods of analysis (2) are tedious and time-consuming, and Winter Haven require use of equipment not generally

Introduction available in citrus pulp plants. Proces sors feel that such methods attain a de Inquiries and requests on the part of gree of accuracy not warranted and are processors of dried citrus pulps and so expensive and time-consuming as to be citrus molasses indicate a need for a economically impracticable. *■■' method whereby the soluble solids present A simple and rapid method has been in commercial, dried citrus pulps might developed which is satisfactory for esti be estimated. mating the Processors are adding molasses at varying rates to pressed pulps prior to drying. Few, if any, operators use proportioning equipment to control the process and very little is known concern ing the storage life or keeping qualities of the products as related to the molasses content. The problem facing the indus try is therefore twofold: (1) Develop ment of a method for evaluating the molasses, or soluble solids, content of the finished products; and (2) studying the hygroscopic characteristics as related to storage life of dried citrus pulps contain ing varying amounts of citrus molasses. This latter problem will be the subject of a later report. The method for estimating the soluble solids content of dried citrus pulps should be simple and reasonably accurate, such that it would have practical application in the processing plants, for the purpose of differentiating sweetened and unsweet ened feeds as well as establishing the

1 One of the laboratories of the Bureau of Agricul tural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.