ROUSE, ET AL: ORANGE JUICE STUDIES 145 Sweet potatoes of the Georgia Red variety were preferred over the other varieties as a frozen product. However, a good frozen, prod uct was produced with potatoes of the Goldrush, Porto Rico, and Heartogold varieties. Fresh storage up to 105 days did not seem to affect the quality of frozen potatoes when good sound potatoes were used. The method of cooking the potatoes in preparation for freezing had a significant effect upon their carotene content. There was a greater loss of carotene from the potatoes when they were cooked with dry heat than occurred when steam was used. LITERATURE CITED 1. Hoover, Maurice W. and G. J. Stout. 1956. Studies relating to the freezing of sweet potatoes. Food Technol. 10: 250-253. 2. Huffington, Jessie M., E. R. McConnell, and P. B. Gottschall, Jr., 1956. Sweet potato varieties for canning: Influence of storage on quality. Proc. Amer. Hort. Soc. 67: 504-513. 3. Mitchell, H. L. 1949. Determination of carotene in sweet potatoes. Plant Physiol. 24: 323-326. 4. Woodroff, J. G. and Atkinson, Ida S. 1944. Pre serving sweet potatoes by freezing. Ga. Expt. Sta. Bui. No. 232. STORAGE STUDIES ON 42 BRIX CONCEN TRATED PROCESSED FROM JUICES HEATED AT VARYING FOLDS. II. CHEMICAL CHANGES WITH PARTICULAR REFERENCE TO PECTIN A. H. Rouse, C. D. Atkins and E. L. Moore Florida Citrus Experiment Station Lake Alfred The purpose of this investigation was to determine some of the chemical changes, and especially the loss of pectin, that would occur in frozen orange concentrates during storage at 40 F. It was also desirable that similar in formation be obtained on heat-treated con centrates when the thermal treatment is ap plied either prior to concentration or at dif ferent stages of the concentration process. A total of 24 experimental packs of frozen con centrated orange juices, prepared from Pine apple and Valencia oranges, were used in this study. Experimental Procedures Preparation and Storage of Samples. In preparing the 24 packs of concentrates, singlestrength juice was used as the 1-fold product and concentrates were removed from the pilot plant Model A thermocompressor type eva porator (1) at concentrations of 2-, 3-, and 4- fold. Each of these four products was divided VCooperative research by the Florida Citrus Ex periment Station and Florida Citrus Commission. Florida Agricultural Experiment Station Journal Series, No. 552. into three equal s and one of these was used as an unheated control; the other two s were heated in a tubular pasteurizer to and F., respectively, in 6 seconds and cooled in 14 seconds. All products were further concentrated in the pilot plant Model B evaporator (2) to 55 Brix, cut-back to 42U Brix with unheated juice, sealed in 6-oz. cans, and stored at -8 F. until the beginning of the 40 F. storage period. Further detailed infor mation on the preparation of these 42 Brix frozen orange concentrates is described in the first paper in this series (6). At the beginning of the 40 F. storage period, the 24 experimental packs were thawed for 1 hour in a Thermo-Rotor type thawer with rolls submerged in water at 40 F. The speed of rotation of the rolls was 60 r.p.m. The thawed samples were placed directly in stor age at 40 F. and analyzed at periodic inter vals until an extreme degree of clarification de veloped in each sample. Methods of Analyses. Samples of 42 Brix concentrates were examined for gelation (7), both prior to and after 40 F. storage, and then reconstituted with three s of dis tilled water. After three minutes of stirring, the juices were centrifuged for 15 minutes at 1700 r.p.m. in an International Centrifuge,
146 FLORIDA STATE HORTICULTURAL SOCIETY, 1956 Size 1, Type SB and the percentage pulp by noted. Subsequently, centrifuged juice will be referred to as serum. Other analyses were determined on either the reconstituted juices or serums. Pectinesterase activity (8) is expressed by the symbol (PE.u)g. which represents the milliequivalents of ester hydrolyzed per minute per gram of soluble solids ( Brix). This is multiplied by 1000 for easy interpretation. Hesperidin (3), the principal glycoside of orange, was determined initially and after the concentrates showed extreme clarification. These analyses were made on the reconstituted juices. Light transmittance (5), index of cloud, was determined on the serum by using a Lumetron colorimeter, Model No. 402-E; clarifica tion was considered to be extreme when values were 85 percent or greater. Pectin, as anhydrogalacturonic acid, was measured by the rapid colorimetric method of Dische (4) as applied to citrus juices by Rouse and Atkins (8) with the modifications that the samples of recon stituted juices were not comminuted prior to centrifugation and that the sample used for analysis was 15 grams of serum. Previous tests had shown that the amount of pectin, ex pressed as milligrams per 100 grams of serum, was approximately the same as the watersoluble pectic substances in the reconstituted juice and is a major factor that determines the amount of cloud or turbidity in the juice. Experimental Results and Discussion Pectinesterase activities in the 42 Brix Pine apple and Valencia orange concentrates, prior to storage at 40 F., are presented in Tables 1 and 2, respectively. or unheated sam ples varied very little in activity (14.6 to 17.1 units), while the activity of the heat-treated samples fluctuated ( to 11.2 units) accord ing to thermal treatment and quantity of pulp in unheated cut-back juices added. Approxi mately 50 percent of the activity shown for the 42 Brix concentrates, which were stabil ized at F., and 80 percent or more of that in the products stabilized at F. was from the unheated cut-back juices. The total glycosides, expressed as hesperi din, in the Pineapple and Valencia orange con centrates, prior to storage, ranged from 28 to 37 mg./loo ml. of reconstituted- juice. After the development of extreme clarification in the samples at 40 F. storage, the amount of glycosides remained the same. Pulp (Tables 1 and 2), indicative of in soluble solids, varied from to percent and to percent for the Pineapple and Valencia orange concentrates, respectively. After extreme clarification, the corresponding pulp levels increased, varying from 7.5 to percent and from to percent. Although the size of pulp particles influences the per centage of pulp, as determined by the centri fugal method, it is of interest to know that the water-insoluble solids in the products also TABLE 1 Summary of Ghemloal Properties in 42 Brix Pineapple Orange Oonoentrates Stored at 40 F. Cono entration when stabilized Thermal treatment P. Samples prior to storage (PE.u.)g. soluble solids X 1000 mg.a00g. Samples after extreme clarification Time required days mg.aoog. 1-fold 15.8 10.9 7.9 9.4 10.3 10.3 1.5 10.0 4.3 6.3 2-fold 14.6 9.6 8.6 11.3 11.3 1.0 7.5 3.9 5.2 3-fold 15.9 9.4 6.9 8.4 10.7 11.2 0.5 6.5 3.3 4-fold 15.2 11.2 6.1 10.4 11.1 0.5 6.5 3.2 Analyses on reconstituted juioes.
ROUSE, ET AL: ORANGE JUICE STUDIES 147 TABLE 2 Suaaary of Chemical Properties in 42 Briz Valencia Orange Concentrates Stored at 40 F. Samples prior to storage Samples after extreme clarification Concentration vfaen stabilised Theraal treatment op# (PE.u.)g. soluble solids X 1000 mg.aoog. Time required days mg./loog. 1-fold 16.6 10.5 6.3 12.1 12.8 12.3 1 3 5.1 4.8 2-fold 17.1 7.5 12.3 13.5 13.6 2.0 13.5 2 5.2 4.6 3-fold 1 8.3 5.9 12.1 U.2 13.9 2.0 12.0 16.5 4-fold 14.7 6.8 12.6 13.8 U.2 1.5 4.6 Analyses on reconstituted juices. increased as did the apparent pulp content during storage. For example, the average water-insoluble solids1 found in the Pineapple and Valencia orange concentrates prior to storage were 61 to 52 mg./100 g. of recon stituted juices, respectively, whereas, after ex treme clarification had occurred, these average values for the corresponding juices increased to 80 and 74 mg./loo g. Time required for the 24 samples of con centrates to show an extreme degree of clari fication varied from 0.5 to 34 days, depending on the variety of fruit from, which it was pro cessed, thermal treatment, and fold at which it was stabilized (Tables 1 and 2). As ex pected under similar conditions of processing, Valencia orange concentrates were more stable at 40 F. storage than the Pineapple orange products; also the packs heated at 1- and 2- fold were more stable than those heated at 3- and 4-fold. The amount of pectin in the heat-treated packs was greater than in the control packs because of the partial inactivation of pectinesterase, thereby preventing the destruction of pectin during concentration; also the quan tity of pectin was greater in the Valencia orange products (12.1 to 14.2 mg./loo g.) than in the Pineapple orange products ( to 11.2 mg./100 g.). There were not sufficient quantities of pectin in any of the products to cause semi-or solid gels during storage; how ever, all samples developed No. 2 gels, indi cative of slight gelation, when stored at 40 F. Data in Tables 1 and 2 show that during stor age of the concentrates at 40 F., the pectin decreased 50 percent or more with subse quent increase in clarification. The gradual loss of pectin during storage and its relation ship to clarification, index of cloud, for the controls and heat-treated 1-, 2-, 3-, and 4-fold products is presented graphically in Figs. 1, 2, 3, and 4. As the pectin in the serum de creased during storage of the products at 40 F., the apparent pulp content and the waterinsoluble solids increased, as previously men tioned. Formation of degraded pectic com pounds, such as insoluble pectinates and pectates, through the action of pectinesterase on the water-soluble pectin, is the cause of these increases. The longer storage life'at 40 F. of the Valencia packs was probably due to the greater amount of pectin found initially in the serum and to a higher degree of polymeriza tion of the pectin molecule; the latter was in dicated by a slower rate of change in viscosity as previously reported (9). No significant differences in flavor were ob served by the authors between the controls and the heat-treated samples; neither were flavor differences found when juices were heated at these different folds. However, a slight lowering of flavor quality was observed in both the Pineapple and Valencia orange packs after storage at. 40 F. for 10 and 24 days, respectively.
148 FLORIDA STATE HORTICULTURAL SOCIETY, 1956 Nona \ ^ISO' F. 175* F. Extreme 5* o Extreme PINEAPPLE ORANGE JUICES PINEAPPLE \ \ \ \..175*F. J5O*F. I9O#F. ORANGE JUICES 10 19 20 Time- Days 25 30 Fig. 1. Relationship of pectin to clarification dur when juices to evaporator were heat treated at 1- fold. 19 20 Fig. 2. Relationship of pectin to clarification dur when juices to evaporator were heat treated at 2-fold. 30 Eitrtme 9 5 f -.'I5' F. 3 \ \ F. ***' Estrem* 0 5 10 19 20 25 Fig. 3. Relationship of pectin to clarification dur when juices to evaporator were heat treated at 3-fold. 30 0 5 10 15 20 29 30 Fig. 4. Relationship of pectin to clarification dur when juices to evaporator were heat treated at 4-fold.
HENDRICKSON AND KESTERSON: NARINGIN 149 Summary Storage of 42 Brix Pineapple and Valencia orange concentrates at 40 F. resulted in in creased gelation, clarification, and apparent pulp content, whereas pectin decreased. Total glycosides, as hesperidin, remained constant in these products during storage. The experi mental packs heated at 1- and 2-fold were more stable than those heated at 3- and 4- fold; also all of the Valencia concentrates, control and heat-treated, were more stable than the Pineapple packs. LITERATURE CITED 1. Atkins, C. IX, F. W. Wenzel, and E. L. Moore. 1950. Report on new technical strides in design of FCC evaporator. Food Inds. 22: 1353, 1466, 1467. 2. Atkins, C. D., F. W. Wenzel, and E. L. Moore. 1951. An evaporator of improved design for the con centration of citrus juices. Proc. Fla. State Hort. Soc, 64: 188-191. 3. Davis, W. B. 1947. Determination of flavanones in citrus fruits. Anal. Chem. 19: 467-478. 4. Dische, A. 1947. A new specific color reaction of hexuronic acids. Jour. Biol. Chem. 167: 189-198. 5. Huggart, R. L., E. L. Moore, and F. W. Wen zel. 1951. The measurement of clarification in con centrated citrus juices. Proc. Fla. State Hort. Soc. 64: 185-188. 6. Moore, E. L., A. H. Rouse, and C. D. Atkins. 1956. Storage studies on 42 Brix concentrated orange juices processed from juices heated at varying folds. I. Physical changes and retention of cloud. Proc. Fla. State Hort. Soc. 69: 176-181 7. 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 concentrate made from seedy varieties of fruit. Food Technol., 5: 530-533. 8. Rouse, A. H. and C. D. Atkins. 1955. Pectinesterase and pectin in commercial citrus juices as determined by methods used at the Citrus Experi ment Station. Fla. Agr. Exp. Sta. Tech. Bui. 570. 9. Rouse, A. H., C. D. Atkins, and E. L. Moore. 1955. Chemical changes in processed citrus juices and concentrates during storage at 40 F. Univ. of Florida Citrus Exp. Sta. Mimeo Rept. 56-3, October 4. PURIFICATION OF NARINGIN R. Hendrickson and J. W. Kesterson Florida Citrus Experiment Station Lake Alfred The pharmaceutical usefulness and physio logical importance of naringin has long been overlooked, even though its characteristic bit terness is a nostalgic reminder of early medi cines. Prime interest has been centered on the tasteless glucoside of sweet oranges, hes peridin, which has been closely associated with all vitamin P investigations. Circumstantial evidence has pointed to the fact that naringin may have an even greater pharmacological activity as previously shown by Armentano (1) and recent work on antiviral activity (4). Sufficient evidence has been accumulated to encourage' the pharmaceutical industry to ob jectively re-evaluate naringin. An investigation was therefore undertaken to find an improved naringin purification procedure for preparing a high purity product. As with many products, naringin has a much higher solubility in hot water than in cold and is the basis for an extraction and purifica tion technique reported by Poore (7). Ac cording to this method, crude naringin is ex tracted from chopped grapefruit peel by add ing four parts of water and heating to 90 C. The water extract is filtered off after five min- F'lorida Agricultural Experiment Station Journal Series No. 524. utes and the clear extract concentrated to ap proximately one-ninth the original. The concentrated extract is allowed to crystal lize for two days in a cool place and then filtered. The isolated naringin crystals are then purified by the following technique. First dis solved in a small amount of hot water contain ing 20 percent alcohol, impurities are precipi tated by adding an excess of neutral lead ace tate with the excess lead eliminated by passing hydrogen sulfide through the solution. After filtering, naringin is crystallized by concen trating the solution and allowing it to stand in a cool place. The naringin is further purified by dissolving it in small amounts of hot water, from which it will recrystallize upon cooling. The pronounced solubility of naringin in water above 50 C. has been shown by Pulley (8) who plotted its solubility at numerous tem peratures. The simplicity of recrystallizing na ringin from water can readily be seen from his plotted solubility curve which shows narin gin to be more than 10 percent soluble at 75 C. and less than 0.02 percent soluble at 6 C. This decreased solubility of naringin at low temperatures may at times cause the pre cipitation of this substance in canned grape fruit sections and juice. Naringin may also be recrystallized from water by adding an alkali, which greatly in creases its solubility followed by acidification, and is the basis of another extraction technique