SILVER CLUSTER GRAPEFRUIT DURING MATURATION1

274 FLORIDA STATE HORTICULTURAL SOCIETY, 1964 components (5). Again, it was the yield of pectin, similar to that found in Valencia orange (5), and not the jelly which increased the jelly in the peel above that found for juice sacs. Summary Evaluations were made of pectins extracted from peel, membrane, and juice sacs of Pineapple oranges during maturation of the fruit. The pec tins extracted from membrane were highest in yield, jelly,, purity as AGA, equi valent, and degree of methylation. Pectins extracted from the peel were lowest in jelly, equivalent, and degree of methylation. Pectins extracted from the juice sacs were least in yield and purity as AGA. Seed pectins had no jelly. The order of component parts of Pineapple oranges for jelly, from highest to lowest, was found to be membrane, peel, and juice sacs. Peel was second in order because of the percent yield of pectin and not because of jelly, which was greater in the extracted pectin from juice sacs. LITERATURE CITED 1. Kertesz, Z. I. 1951. The pectic substances. Interscience Publishers, Inc., N. Y. 1, N. Y. 2. Olsen, A. G., R. F. Stuewer, E. R. Fehlberg, and N. M. Beach. 1939. Pectin studies. Relation of combining to the properties of commercial pectins. Ind. Eng. Chem. 31: 1015-1020. 3. Rouse, A. H., C. D. Atkins, and E. L. Moore. 1962. I. Valencia oranges. J. Food Sci. 27: 419-425. 4. Rouse, A. H., C. D. Atkins, and E. L. Moore. 1964. II. Pineapple oranges. J. Food Sci. 29: 34-39. 5. Rouse, A. H., C. D. Atkins, and E. L. Moore. 1962. The occurrence and evaluation of pectin in comnonent parts of Valencia oranges during maturation. Proc. Florida State Hort. Soc. 75: 307-311. 6. Rouse, A. H. and C. D. Atkins. 1955. Pectin ester? se and pectin in commercial citrus juices as determined by methods used at the Citrus Experiment Station. Univ. Florida Agr. Exp. Sta. Tech. Bui. 570. EVALUATION OF PECTIN IN COMPONENT PARTS OF SILVER CLUSTER GRAPEFRUIT DURING MATURATION1 A. H. Rouse Florida Citrus Experiment Station and E. L. Moore and C. D. Atkins Florida Citrus Commission Lake Alfred Grapefruit residue from processing plants is an excellent source of high quality pectin and is one of the best sources of commercial pectin. Poore (3) reported that the peel of Floridagrown grapefruit, on dry basis, yielded 19.1 and the rag 22.8 in total pectic substan ces. Under optimum extraction conditions, Ker tesz (2) stated that the pectin from grapefruit peel could be roughly set between 250 to 300. The scientific literature is limited concerning information on seasonal changes of the quality of pectin in grapefruit. Gaddum (1) reported that the percentage of total pectic compounds in the Florida Agricultural Experiment Stations Journal Series No. 1960. l Cooperative research of the Florida Citrus Experiment Station and Florida Citrus Commission. albedo and pulp of immature and early ripe grapefruit remains constant throughout a con siderable portion of the growth period. Evaluation data on pectins extracted from peel, membrane, and juice sacs of Valencia and Pineapple oranges during maturation have been presented by Rouse, Atkins, and Moore (6, 8). The purpose of this paper is to show the effect of maturity on the characteristics of pectins, such as jelly, yield, methoxyl content, ash con tent, and jelly, extracted from peel, mem brane, and juice sacs of Silver Cluster grape fruit. Also, those characteristics, which are of importance to any potential commercial pro ducers of pectin in Florida, are evaluated. Experimental Procedure Preparation of Samples. Alcohol-insoluble solids (AIS) were prepared from peel, membrane, and juice sacs of Silver Cluster grapefruit as de scribed by Rouse et al. (5, 9). Grapefruit were picked from the same trees each month ( through ) during both the 1961-62 and 1962-63 seasons. The AIS of similar components for each grow ing season were combined according to months

_ - _ - ROUSE, MOORE, ATKINS: GRAPEFRUIT PECTIN 275 and extracted for 1 hr. at 90 C, using a ratio of AIS to distilled water, 1:80, and a ratio of AIS to Zeo-Karb H, 8:10. Details of the extraction, filtration, and isolation of the alcohol precipitate have been described by Rouse et al. (6). Methods of Analysis. of pectin is based upon the amount of alcohol precipitate extracted from the AIS of the component and the purity of the precipitate was determined as percentage of anhydrogalacturonic acid (AGA) (4)., methoxyl content, equivalent, ash, and relative of the pectins were determined as previously described by Rouse et al. (6). Values for methoxyl content were cal culated on AGA basis. unit is the resulting figure when yield of pectin is multiplied by the jelly. Results and Discussion The effects of Silver Cluster grapefruit ma turity, as reflected by the various physical and chemical values of the extracted pectins from peel, membrane, and juice sacs are presented in Tables 1, 2, and 3, respectively. A factor which might have influenced the various pectin values was the sub-freezing temperature effect. This occurred in of 1962 during the second year of the maturity study, but since the AIS of similar components for each growing season were combined according to months, no definite freeze effect could be ascertained from the pectin values. Rouse et al. (7) found that the pectic substances in pulp, which is primarily juice sacs, was the only component of Silver Cluster grapefruit af fected by sub-freezing temperatures, and these changes were in the pectinesterase activity and the ammonium oxalate-soluble pectin fraction. Rouse et al. (9) have shown that the average distribution of the component parts in the Silver Cluster whole grapefruit during the period be tween and was approximately 28 peel, 10 membrane, 20.5 juice sacs, 37.5 juice, and 4.0 seeds. as Alcohol Precipitates. The monthly yield of pectin from the peel, varying from 18.7 to 24.3 (Table 1) and juice sacs, from 18.4 to 22.3 (Table 3) was slightly greater during the last half of the maturation cycle. This was also generally true for yield of pectin from the membrane, 29.2-36.0 (Table 2) except that the greatest yield was during the month of, whereas, the highest yield of pectin from peel and juice sacs was obtained during the months of and, respectively. Pectins extracted from juice sacs were gen erally lowest in purity expressed as AGA, aver aged 84.9 for the two seasons, while that for the peel extracted pectins averaged 86.5, and pectin from the membrane was of greatest purity, averaged 90.8. Pectins extracted from the mem brane AIS from through ranged from 92.6 to 96.0 as AGA. Degree of Methylation and Weight. The degree of methylation was slightly higher for pectins extracted from grapefruit peel and Table 1. Relationship of Silver Cluster grapefruit maturation to pectin values of the peel. JeUy 18.7 202.5 37.8 6.1* 10.1 2.21 19.8 211.7 1*1.9 90.0 6.5 20.3 liju-7 7.1* 1 211.0 1*1.6 5.9 976 21.9 228.0 h9-9 85.6 7.6 931 2.57 January- 21.1 232.1 1*9.0 81*. 8 10.9 10.8 21*.3 227.6 55.3 81*.0 8.1* 953 10.7 23.9 250.9 60.0 85.6 9.1* 852 10.7 2U.0 2l*5-3 58.9 83.1* 8.2 n.5 1.12 23.1 256.9 59.3 11.3 10.3 21.7 228.6 1* 86.5 8.2 9h5 1.97 1. Anhydrogalacturonic acid in alcohol precipitate. Calculated on AGA basis.

276 FLORIDA STATE HORTICULTURAL SOCIETY, 1964 Table 2. Relationship of Silver Cluster grapefruit maturation to pectin values of the membrane. 29.2 309.5 90. k 16.9 111*1* 11.7 0.61+ 32.5 331.6 107.8 16.9 1111 12.0 31.1 3146.7 107.8 92.6 17.9 1000 11.6 33.9 331.6 112. h 874 Ht.7 952 12.0 36.0 330.8 119.1 90.U 1U.2 952 31.6 0.90 January 3U.8 330.8 115.1 il*.5 870 12.2 33.1 312.5 103.U 92.6 13.2 83U 11.0 35.0 311.0 108.8 96.0 800 10.9 3U.9 321.0 112.0 Sh'O 11.3 831+ 11.1 0.99 35.1 306.6 107.6 93.0 12.6 800 10.8 33.6 323.2 108.6 90.8 U*.3 930 11.5 0.8U ' Anhydrogalacturonic acid in alcohol precipitate.! Calculated on AGA. basis. membrane than for those extracted from similar component parts of Valencia and Pineapple or anges (6, 8). The average values of the methoxyl content of the pectins during the ten-month sea son, from peel, membrane, and juice sacs were, 11.5, and 9.8, respectively, indicating high ly methylated pectins. Methoxyl contents varied with the purity of the alcohol precipitates and are reported on an AGA basis (Tables 1, 2, and 3). The pectins extracted from the membrane were higher in methoxyl content than those from the other two components during the maturation period, and ranged from 10.8 to 12.2. Viscosity. Viscosities of 0.5 solu tions of the alcohol precipitates were measured at 26 C. with an Ostwald viscometer and these values merely represent the approximate jelly of the pectin or size of the polygalacturonic acid chain. Most polyvalent cations, such as cal cium and magnesium, will increase the of pectin solutions. However, due to the use of Zeo-Karb most of these cations were removed dur- Table 3. Relationship of Silver Cluster grapefruit maturation to pectin values of the juice sacs. 18.1* 198.5 36.5 80.0 6.$ 1082 9.9 1.21 18.L* 21+0.7 10J.-3 82.0 1112 19.8 227.3 l*5.o 9.6 1 228.1 hh.9 90.0 91*0 8.9 21.7 228.1 U9-5 82.0 931 10.-3 0.89 January 20.2 kh.$ 8.1 83U 21.1 226.1 1*7.7 6.5 770 21.6 213.1 1*6.0 81;. 6 8.0 797 9.8 22.3 1*9.1 83.0 7.8 852 10.5 1.1*7 21.8 219.2 1*7.8 88.0 8.7 791 20.5 222.1 1*5-5 81*.9 8.7 911 9.8 1.19 ' Anhydrogalacturonic acid in alcohol precipitate.! Calculated on AGA. basis.

ROUSE, MOORE, ATKINS: GRAPEFRUIT PECTIN 277 ing the pectin extraction. The average relative viscosities of pectins extracted from the peel and juice sacs were similar, 8.2 and 8.7, respectively. Pectins from the membrane extracts were high est in viscosities, ranging from 10.4 to 17.9 and averaging 14.3. Similarly, the jelly s of the extracted pectins from membrane were highest, as previously mentioned. Content The average percentages of ash in the pectins extracted from each of the three component parts during the months of,, and were 1.97 for peel, 0.84 for membrane, and 1.19 for juice sacs. indicates the inorganic impurity in the pectin that is probably combined with the carboxyl groups to form pectinic acid salts. Units. Since this value is calculated by multiplying yield of pectin by jelly, it represents the quantity of jelly that may be pro duced from a given of peel, membrane, or juice sacs. The term is synonymous to jelly unit yield and indicates to the pectin manufacturer the maximum potential that can be obtained from the raw pectic material. The jelly of the membrane during the growing season ranged from 90 to 119 (Table 2) which is more than twice that obtained for peel (38-60) or juice sacs (37-50). Highest were obtained for the membrane and juice sacs during, and for peel during. The equivalent or combining s of pec tins from the three component parts generally decreased with maturation. This is a reliable means of determining free acid groups and also a means of measuring degree of methylation on a purified sample with proper correction. The average values of the equivalent s of pectins extracted from peel, membrane, and juice sacs were 945, 930, and 911, respectively. In most cases these values were lower than those for pectins extracted from the same component parts of Valencia and Pineapple oranges (6, 8). Grade. The ability of a high-ester pec tin to form jellies containing 65 soluble solids is the most important property of a commercial pectin. The higher the jelly of pectin the greater is the commercial value in return to the pectin processor. The term jelly designates the parts of sugar which one part of pectin is capable of supporting under prescribed conditions. This term also reflects the degree of polymeriza tion of the polygalacturonic acid molecule. Data on pectin s in Tables 1, 2, and 3 were cal culated on the breaking strength of a standard jelly measured at 50 cm. of water pressure. The average values of the pectin s during the growing season were 229, 323, and 222, respec tively for pectin from peel, membrane, and juice sacs. Pectins extracted from the membrane re sulted in the highest s during the season, ranging from 307 to 347. Lowest average jelly was obtained for pectins from the juice sacs, which ranged from 199 to 241. These jelly s were greater for pectins in grapefruit components than most of those pectins from com ponents of Pineapple and Valencia oranges (6, 8). Pectins from seeds had no jellying power when prepared as standard 65 sugar jellies. Purity of the extracted seed pectins ranged from 48 to 63 as AGA. This was similar to that found for orange seed pectins (6, 8). Because the membrane of Valencia and Pine apple oranges (6, 8), as well as the membrane of Silver Cluster grapefruit, showed the great est potential of jelly, a comparison of the relevant values of the pectins extracted from this component are presented in Table 4. These average values represented a two-year maturity study of the prepared AIS from membranes of these citrus fruits. Table ij.. Comparison of relevant values of pectins obtained from the prepared membranes of oranges and grapefruit. Valencia Pineapple Silver Cluster orange orange grapefruit - 33.5 30.2 33.6 313.9 299.9 323.2 105.0 90.5 108.6

278 FLORIDA STATE HORTICULTURAL SOCIETY, 1964 Summary Evaluations were made of pectins extracted from peel, membrane, and juice sacs of Silver Cluster grapefruit during a two-year maturation study of this fruit. The pectins extracted from membrane were highest in yield, jelly, degree of methylation, purity, and relative, while those from juice sacs were lowest in yield, jelly, methoxyl content, purity, and equivalent. Peel extracted pectins were intermediate in most of these physical and chemical characteristics. The order of component parts of Silver Cluster grapefruit for jelly, from highest to lowest, was found to be membrane, peel, and juice sacs. Grapefruit residue was found to be a better source of raw material for the manufacture of pectin than that from oranges. LITERATURE CITED 1. Gaddum, L. W. 1934. The pectic constituents of citrus fruits. Univ. Florida Agr. Exp. Sta. Tech. Bui. 268. 2. Kertesz, Z. I. 1951. The pectic substances. Interscience Publishers, Inc., N. Y. 1, N. Y. 3. Poore, H. D. 1934. Recovery of naringin and pectin from grapefruit residue. Ind. Eng. Chem. 26: 637-639. 4. Rouse, A. H. and C. D. Atkins. 1955. Pectinesterase and pectin in commercial citrus juices as determined by methods used at the Citrus Experiment Station. Univ. Florida Agr. Exp. Sta. Tech. Bui. 570. 5. Rouse, A. H., C. D. Atkins, and E. L. Moore. 1962. I. Valencia oranges. J. Food Sci. 27: 419-425. 6. Rouse, A. H., C. D. Atkins, and E. L. Moore. 1962. The occurrence and evaluation of pectin in component parts of Valencia oranges during maturation. Proc. Florida State Hort. Soc. 75: 307-311. 7. Rouse, A. H., C. D. Atkins, and E. L. Moore. 1963. Effect of sub-freezing temperatures on component parts of citrus fruits with particular reference to the pectic con stituents. Proc. Florida State Hort. Soc. 76: 295-301. 8. Rouse, A. H., C. D. Atkins, and E. L. Moore. 1964. Evaluation of pectin in component parts of Pineapple oranges during maturation. Proc. Florida State Hort. Soc. 77: 271-274. 9. Rouse, A. H., C. D. Atkins, and E. L. Moore. Sea sonal changes occurring in the pectinesterase activity and III. Silver Cluster grapefruit. Presented at the 24th Annual Meeting of the Institute of Food Technologists, Washington, D. C. 27, 1964. THE DEGREES BRIX & BRIX-ACID RATIOS OF ORANGES UTILIZED BY FLORIDA CITRUS PROCESSORS FOR THE SEASONS 1958-59 THROUGH 1963-64 G. F. Westbrook and E. C. Stenstrom Division of Fruit & Vegetable Inspection State Department of Agriculture Winter Haven The authors have from to reported on the Brix and Brix-acid ratios of citrus fruits utilized by processors (1, 2, 3, 4). This new re port, which contains more recent and more exten sive data than the initial publication on oranges presented at the 1957 meeting of the Horticultur al Society, was prepared at the request of the Quality Advisory Committee of the Florida Canners Association, and the brackets which were selected for degrees Brix and Brix-acid ratios were those recommended by that committee. As in earlier reports, all information was ob tained from the inspectors' worksheets, which are standard forms used for recording analyses of loads of fruit received at processing plants. For reasons of simplicity, loads rather than boxes were used as the basic unit in this tabulation, al though the actual number of boxes utilized per tabulated month is listed, also. The analyses of the individual loads are punched on IBM cards, then the desired data were extracted and grouped in respective Brix and ratio brackets as follows: Degrees Brix less than 9.0, 9.0 to 9.99, to 10.99, 11.0 to 11.99, 12.0 to 12.99, 13.0 to 13.99, and 14.0 degrees and higher; and ratios less than to 1, to 10.99 to 1, 11.0 to 11.99 to 1, 12.0 to 12.99 to 1, 13.0 to 13.99 to 1, 14.0 to 14.99 to 1, 15.0 to 15.99 to 1, 16.0 to 16.99 to 1, 17.0 to 17.99 to 1, and 18.0 to 1 and higher. Each month was tabulated individually, and the per centages of loads falling into each of the cate gories for that period were calculated. The tabu lations were drawn up so as to represent fruit received by all except the very small processors, with every alternate day's receipts for the months of and being included, and with every third day's receipts being tabulated for the principal six months of the processing sea son. In all, nearly 340,000 individual loads were tabulated. Since this represents more than onethird of all oranges received by all processing plants during these seasons, statistical sample variation is not considered to be a factor. The results of the tabulation of the 1958-59 through 1963-64 seasons are shown on Tables 1