STABILITY OF CONCENTRATED ORANGE JUICES'

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1 186 FLORIDA STATE HORTICULTURAL SOCIETY, 1958 developing fertilizer programs in groves having different potash requirements. Potassium levels of 0.8% and less were found associated with fruit drop and probably losses in yields. There is evidence that levels of 0.8% leaf potassium are not always associated with reduced yields. However, considering the pre cision of the sampling procedure and the year to year variability in potash utilization, it is recommended that the potassium level of five to seven month old spring flush leaves should not be permitted to drop below 1.0% for ferti lizer control purposes. REFERENCES 1. Chapman, H. D. & Brown, S. M. Analysis of Orange Leaves for Diagnosing Nutrient Status With Reference to Potassium. Hilgardia 19: Harding, P. L. & Lewis, W. E. The Relation of Size of Fruit to Solids, Acid and Volume of Juice in the Principle Varieties of Florida Oranges, Proc. Florida State Hort. Soc. 5: Koo, R. C. J., Reitz, H. J. & Sites, J. W. A Survey of the Mineral Nutrition Status of Valencia Oranges in Florida. University of Florida Agricultural Experiment Station Bulletin (in press) Reitz, H. J. & Long, W. T. Mineral Composition of Citrus Leaves From the Indian River Area of Florida, Proc. Florida State Hort. Soc. 65: Reither, W., Smith, Paul F. & Specht, A. W. A Com parison of the Mineral Composition of Valencia Orange Leaves from the Major Producing Areas of the United States, Proc. Florida State Hort. Soc. 6: Reither, W. & Smith, P. F. Relation of Fertilizer Treat ment to Fruit Quality of Valencia Oranges, Proc. Florida State Hort. Soc. 6: Sites, J. W. & Deszyck, E. J. Effect of Varying Amounts of Potash on Yield and Quality of Valencia and Hamlin Oranges, Proc. Florida State Hort. Soc. 65: Willson, A. E., Arey, W. J. & Bistline, F. W. Errors in Citrus Soil and Leaf Sampling Procedures, Proc. Florida State Hort. Soc. 68: <Lpfio<i ±ilnq u faction EFFECT OF STABILIZATION TEMPERATURE ON THE VISCOSITY AND STABILITY OF CONCENTRATED ORANGE JUICES' George H. Ezell and Robert W. Olsen Florida Citrus Experiment Station Lake Alfred The occurrence of clarification and gelatin in frozen orange concentrate, during improper storage at temperatures above 0 F., has been a problem to citrus processors for many years. Although clarification and gelatin in citrus concentrates have been the subject of many investigations and methods for measuring these changes have been devised, there still is no satisfactory, rapid method for predict ing the possible instability of citrus concen trates prior to the packing and freezing of these products in cans. Since the amount of pulp and pectin in citrus concentrates are factors that influence both physical stability and viscosity, it seems reasonable that there may be some relation ship between clarification and viscosity. A 'Cooperative research by the Florida Citrus Commission and Florida Citrus Experiment Station, aided by a grant from the Continental Can Company. Florida Agricultural Experiment Station Journal Series, No. 8. further consideration in attempting to corre late clarification with viscosity is that a vis cosity measurement is rapid and simple to make, although very specific conditions must be used. A previous report () presented some data indicating that such a relationship did exist concerning changes in viscosity and clarification which occurred when Valencia orange concentrate was stored This study was undertaken to obtain further con firmation of this relationship between viscosity and physical stability of these products, as well as to determine the effect of stabilization temperature on these characteristics. Experimental Procedure Preparation of Samples. Valencia oranges were obtained from Station plots at Lake Al fred and on the Florida east coast. Fruit was washed, graded, thoroughly mixed, and then divided into a number of equal lots, depending upon the number of stabilization temperatures to be used. All fruit was held at 0 F. until processed. Juices were extracted using a Food Machinery In-Line extractor, finished through a Model Food Machinery finisher, and

2 EZELL AND OLSEN: STABILIZATION TEMPERATURE STABILITY NO HEAT X 65* F. O 175' F. A 185* F. TEMPERATURE CONCENTRATION- * BRIX Figure 1. The effect of stabilization temperature on the initial viscosity of concentrates. concentrated in the pilot plant evaporator (1). Stabilization of the juices was accomplished using a Walker Wallace heat exchanger prior to concentration. During the evaporation pro cess samples were withdrawn at various de grees of concentration for immediate analysis and samples for storage at F. were packed and closed in 6 oz. cans. Analytical Methods. A Brookfield Model LVT synchrolectric rotational viscometer was used for all viscosity measurements. It was used with either the No. or spindle, with the guard attached, and with the concentrate in a 6 oz. can. A spindle speed of 1 r.p.m. was used, and readings were taken 1 minute after turning on the instrument. For the initial viscosity determination samples were with drawn from the evaporator at different de grees of concentration, usually Thirty seconds after withdrawing the sample the viscosity was measured. The samples for storage at F. were withdrawn along with the initial sample, closed in 6 oz. cans, and immediately placed in a F. water bath. They were then examined at 1,,, and hours after being placed in the bath. The pulp or centrifuged material in the orange concentrates was determined after reconstituting the products to 1 Brix by a centrifugal method (9). A Photovolt Lumetron colorimeter, Model 0-E with a mu filter and a 10 mm. rectangular 1 ml. cell, was used to determine the cloud or turbidity of the centrifuged re constituted juices. Results and Discussion Effect of Stabilization Temperature on In itial Viscosities. The effect of stabilization Table 1. Changes in viscosity, light transmittance, and centrifuged material of Valencia orange concentrates after storage Approx. fold Not heated 165 F. Stabilization tenroerati ure 175 F. 185 F. 195 F. hr hr. hr. hr. 0 hr Viscosity of hr. hr. hr. concentrate - centipoises hr hr. hr U U U U U Light transmittance of reconstituted juice5 -% , U Centrifuged material in reconstituted, juice - % by vol, a.o U. 0 1 Based on 1 Brix juice. Measured, Brookfield LVT viscometer using No. spindle after 1 minute at 1 r.p.m. No. spindle used. * Measured at 7 F. 5 Measured with Lumetron 0-E colorimeter, mu filter, and a 10 mm. rectangular U ml. cell. O-59& = no clarification; = slight; -86 = definite; 85-1OQ56 = extreme. 1. 5

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4 EZELL AND OLSEN: STABILIZATION TEMPERATURE 189 given in Table. After hours storage, much larger percentage increases in viscosity were noted in the -, -, and 5-fold concen trates than in the -, 6-, and 7-fold products. Also, the increases were larger for the unstabilized concentrates than for those made from juices heated to 175 F. Thus it is evident that the changes, which occurred during stor age at F., in concentrates processed from fruit obtained from two different citrus areas in Florida were the same. However, it is im portant to note the differences in the magni tude of these changes, i.e., range for percent age increase in viscosity for concentrates from juices stabilized at 175 F., was 100 to 189 percent (Table ) using fruit from the Lake Alfred area, while the range for products processed from fruit from the east coast was 10 to 18 percent (Table ). Effect of Stabilization Temperature on De gree of Clarification in Concentrates. Re sults reported in Tables 1,, and show the effect of stabilization temperatures on the de gree of clarification in Valencia orange con centrates after storage at F. There was essentially no change in the cloud of any sample, regardless of stabilization temperature, when examined after hours; also, only a very slight change in cloud was noted in the unstabilized products. However, after storage for hours the effect of the stabilization temperature became evident. Definite or ex treme clarification occurred in all of the con centrates made from unheated juices. On the basis of reports by various investigators (,, 5, 6, 7, 10), it was expected and found that the degree of clarification decreased and separation was eventually prevented as the temperature was increased. When clarifica tion occurred, it was greatest in the - and -fold products. Gelation was not evident in any of the concentrates, either initially or after storage at F. Of the stabilized concentrates that changed in cloud, those (Table 1 and ) made from juices heated at 165 and 175 F. showed the most cloud loss, and it was ident ical for each temperature. Clarification did not occur during storage in the products when higher stabilization temperatures were used. Rouse, Atkins, and Moore (8) have shown that there is an increase in the centrifuged material in a reconstituted juice when clarifi cation occurs because of the precipitation and separation of insoluble pectinates and pectates. Similar data, included in Tables 1,, and show such increases in centrifuged material upon clarification of the juices. Relationship Between Changes in Viscosity after Storage and Degree of Clarification. As mentioned earlier, the changes that occur in the viscosity of orange concentrates, during storage, are due to two factors, i.e., thixotropic increase and stability of the products. Since there was no clarification in any of the prod ucts stabilized at 195 F., it is'believed that the viscosity increases found were due only to Approx.1 fold Table. Relationship between degree of clarification and viscosity changes in Valencia orange concentrates during storage Concentrat e Viscosity - centipoises Reconstituted juice Light transmittance - % Reconstituted juice Centrifuged material - % by vol. After hr. $ < lifference After hr. % difference After hr. % difference Hot heated 5, U a Heat stabilized at 175 F Based on 1 Brlx juice. Measured, Brookfield LVT viscometer using No. spindle after 1 minute at 1 r.p.m. Measured with Lumetron 0-E colorimeter, mu filter, and a 10 mm. rectangular U ml# cell 0-59 = no clarification; 60-69* = slight; -8$ = definite; * = extreme, 1 No. spindle used. a.5 a

5 1 FLORIDA STATE HORTICULTURAL SOCIETY, 1958 thixotropy, and any greater changes in the concentrates, produced when other tempera tures were used, were due to instability of the products. Comparison of changes in viscosity in concentrates in which clarification occurred showed that as the temperature of sabilization was increased, the percentage increases in both viscosity and light transmittance were decreased. The data in Tables 1,, and also indicate that the largest increases in both viscosity and light transmittance after hours storage were in the - and -fold products, showing these levels of concentration were the least stable. It should be noted again that the changes in viscosity were much larger in the concentrates made from the fruit from the east coast area. Also instability was evident in all of these unheated packs and in the 5-fold, as well as the - and -fold, for the heated packs. In the light of these results it seems possible that viscosity determinations might be developed into a useful tool for rapidly meas uring the stability of orange concentrates. Summary A relationship was found between viscosity changes and the degree of clarification which occurred when Valencia orange concentrates were stored at F. Large increases in vis cosity of the concentrates resulted as the sta bility of the products decreased, as was indi cated by increase in light transmittance in the reconstituted juices. Generally the most un stable concentrates were - and -fold. Stabilization temperature had no significant effect on the initial viscosity, cloud, or pulp content. However, upon storage at F., vis cosity, light transmittance, and amount of centrifuged material differed, depending upon the stabilization temperature. Data indicated that as the temperature of stabilization was increased, the changes in viscosity and centrifuged material became smaller and the de gree of stability increased. LITERATURE CITED 1. Atkins, C. D., F. W. Wenzel, and E. L. Moore Report new technical strides in design of FCC evaporator. Food Industries : Atkins, C. D., R. L. Huggart, and F. W. Wenzel Clarification in heat-treated Pineapple orange concentrates. Proc. Fla. State Hort. Soc. 65: Ezell, G. H. Viscosity of concentrated orange and grapefruit juices. Presented at the Eighteenth Annual meeting of the Institute of Food Technologists, Chicago, III., May 7, In press.. Duois, C. W. and D. I. Murdock The effect of concentration on quality of frozen orange juice with particular refrence to 58.5 and Brix products. Chemical and physiological aspects. Food Technol. 9: Guyer, R. B., W. M. Miller, O. W. Bissett, and M. K. Veldhuis I. The effect of heat treatment on enzyme inactivation and cloud stability of frozen orange concen trate made from Pineapple and Valencia oranges. Food Technol. 10: Huggart, R. I Effect of concentration on clarification in concentrated citrus jiuices. Proc. Fla. State Hort. Soc. 65: Keller, G. J., R. G. Rice, R. J. McColloch, and E. A. Beavens Stabilization of frozen concentrates by heat treatment. Food Technol. 8: Rouse, A. H., C. D. Atkins, and E. L. Moore Storage studies on Brix concentrated orange juices processed from juices heated at varying folds. II. Chemical changes with particular reference to pectin. Proc. Fla. State Hort. Soc. 69: United States Department of Agriculture, Agricultural Marketing Service, Washington, D. C. U. S. Standards for grades of frozen concentrated grapefruit juice. December 8, Wenzel, F. W., E. L. Moore, A. H. Rouse, and C. D. Atkins Gelation and clarification in concentrated citrus juices. I. Introduction and present status. Food Tech nol. 5: -7. EFFECT OF PROCESSING VARIABLES ON UV ABSORPTION OF GRAPEFRUIT JUICE R. Hendrickson, J. W. Kesterson, and G. J. Edwards Florida Citrus Experiment Station Lake Alfred In a prior investigation (I) of a more specific method for analyzing naringin, a very significant development occurred. A procedure was found that appeared capable of measuring Florida Agricultural Experiment Station Journal Series, No. 81. quantity of peel extractives, as well as the ef fect of other abusive processing conditions. This procedure involves the measurement of a juice sample's ultraviolet absorption in the wavelength range of 60 to 0 millimicrons. Useful application is very conceivable in light of the ultraviolet absorption variations caused by extractor pressure, finisher variations, heat stabilization, etc. In view of the many processing changes that have occurred in the citrus industry in