304 FLORIDA STATE HORTICULTURAL SOCIETY, 1970
Acknowledgments of compounds for the reduction of acidityin citrus fruit. Proc. Fla. State Hort. Soc. 81: 1-6. 2. Pieninger, A. P., and W. F. Newhall. 1968. Deriva We would like to thank Messrs. Glen Cop- tives of (_|_)limonene. Effect of chain length in n-alkyl- quaternary ammonium derivatives on plant growth retard- pock, Steve Ropicki, and Jack Lightner for ant activity. J. Agr. Food Chem., 16: 523-524. their help with the yield studies and Mr. Jim 3. Reese, R. L., and G.E. Brown. 1969. Legal ma turity of 'Temple' oranges as influenced by lead arsenate Vice for the juicing operations. sprays. HortScience 4: 96-97. 4. Reitz, H. J. 1949. A study of certain factors affect ing the acidity of Florida grapefruit following arsenic sprays. Ph.D. Dissertation, Ohio State University. LITERATURE CITED
1. Attaway, J. A., and B. S. Buslig. 1968. Screening
BIOCHEMICAL CHANGES IN GRAPEFRUIT AND 'MURCOTT' CITRUS FRUITS AS RELATED TO STORAGE TEMPERATURE1
N. Vakis, J. Soule, R. H. Biggs storage. Glucose decreased at 50 °F and 60°F and fructose increased at 50 and 60 °F. Changes Department of Fruit Crops in total reducing sugars were small. Internal University of Florida ethylene content of grapefruit was related to Gainesville fruit deterioration and respiration rates. Ethy AND lene treatments during storage of 'Marsh' grape W. Grierson fruit resulted in higher cellulase activity and Florida Citrus Experiment Station internal ethylene content. Lake Alfred Introduction Abstract Citrus fruits donot undergo rapid chemical Respiratory activity of 'Marsh' grapefruit at or physical changes ("ripening") after harvest 70 °Fwas highest followingstorage at 70 °F and (1,3,6,7,8,9,10). Their storage life, as with other lowest subsequent to storage at 55 °F. Interme fruits, depends among other factors on the diate respiratory rates were obtained after holding conditions, especially temperature. storage at 34 and 40° F. Respiration of 'Mur- Knowledge of the biochemical changes during cotts'2 at 70 °F was highest after storage at storage is essential if research to extend storage 34 °F and lower after cold storage, differences life and improve keeping quality is to be ef among respiration rates after 40, 55 and 70°F fective. Various workers have reported inthis storage being small. Respiratory rates of 'Marsh* field (3,5,6,7,8,9,10,16,19,21,22), but more in grapefruit peel were increased by wounding and formation is needed relating to local conditions were higher than for intact fruit and pulp. and cultivars not included in earlier studies. Cellulase and polygalacturonase activity in grapefruit peel increased during storage while Materials and Methods pectinmethylesterace activity decreased. Adeno- 'Marsh' grapefruit from several harvests sine-triphosphate (ATP) levels in the peel in and 'Murcotts' from a single harvest were ob creased during the first 2 weeks at 40 °F and tained from the Citrus Experiment Station, Lake then declined sharply. Differences in ATP levels Alfred. Ethylene-treated 'Marsh' grapefruit among storage temperatures were negligible at were provided by the USDA, MORD, Horticul the end of 5 weeks storage. Total sugars and tural Field Station, Orlando. sucrose in grapefruit peel decreased during Oxygen uptake at 70 °F subsequent to storage was measured with an automatic sampling sys lFlorida Agricultural Experiment Stations Journal Series tem (5) every 4 hours. Five replications, each No. 3742. Grateful acknowledgement is made to the TJSDA, MORD, Horticultural Field Station, Orlando, for providing of up to 1 kg, were used for both grapefruit and fruit from their experiments, and to Mrs. Sue J. Wells and Mr. Sidney C-T Chen for technical assistance. 'Murcotts'. CO2 evolution at 70°F by grapefruit 2'Murcott* is a presumed tangor (tangerine x orange was measured by infra-red analysis (23). Re- hybrid). VAKIS, ET AL: GRAPEFRUIT - MURCOTT - STORAGE 305
suits were expressed as ml O2 or mg CO9 per to prior storage temperatures but did not exhibit kg/hr. visual symptoms of chilling injury (Fig. 4). Enzyme activity, adenosine triphosphate 'Murcotts' responded differently than did (ATP), adenosine diphosphate(ADP), an in ternal ethylene were determined by methods previously reported (21). Assays for cellulase used methods previously described (13). Sam ples of both cellulase extract and grapefruit peel were frozen and held until assays were made. 55 F Grapefruit peel was extracted twice with alcohol for sugar determinations and diluted 20 i to 30-fold (on a fresh weight basis). Aliquots were taken for colorimetric determinations of total reducing sugar and apparent fructose. Su 3 4 6 7 DAYS crose, glucose, and fructose contents were cal 1258-67-1 culated from these determinations (19). Fig. 2.60, uptake of 'Marsh* grapefruit at 70 P after 4 weeks storage at 4 temperatures. Results and Discussion 70 F Respiration rates of 'Marsh' grapefruit at 70°F were higher after 2 or 4 weeks storage at 70 °F than those of fruit stored at 34, 40 and 55°F (Figs. 1 and 2). Fruit stored at 40°F for 2 weeks had a higher respiration rate than that stored at 34°F, but this difference disappeared after 4 weeks storage (Figs. 1, 2 and 3). Increased respiration rates following storage at 70°F reflect the faster rate of deterioration of the fruit probably stimulated by higher in ternal ethylene content, as has been reported by others (3, 23). High respiratory activity sub sequent to storage at 40°F indicates chilling injury that typically occurs in grapefruit (1, 3, 4). More mature 'Marsh' grapefruit from a later WEEKS STORAGE harvest showed initial increases in respiratory activity after 2 weeks storage inversely related Fig. 3. Effect of 2 and 4 weeks storage at various tem- 5S5illptal" at 70 p of 'Mareh> srapefniit
i 34 F 2 WEEKS STORAGE \*—-* 40 F 14- ~~\ 55 F » 70 F 70 F INITIAL 12
6 10
4- I 8 2-
0 2 3 4 6 4 DAYS WEEKS 1258-67-1 1252-31-I
Fig. 1. 0, uptake of 'Marsh* grapefruit at 70 F after 2 4- InjtiaI rates of COO evolution of fully mature weeks storage at 4 temperatures. £UU!IIsubse 16 ||4 fl2 *IO PEEL DECAY o STARTED 3 4 5 6 12 16 20 24 48 DAYS HOURS 1258-76-1 I258-8M 7. Oxygen uptake at 70 F immediately after wound- Fig. 5. Effect of 2 weeks storage at various tempera Fig. tures on oxygen uptake at 70 F. of 'Murcotf tangors. ing of 'Marsh' grapefruit tissues. 4 WEEKS STORAGE 12 x a- 10- uJ = 6 UJ d PEEL I4 40F 1 "■* CM -•a WHOLE FRUIT o 2 3 4 DAYS 1258-81-1 1258-76-1 Fig. 8. 0o uptake at 70 F of component tissues of Fig. 6. Effect of 4 weeks storage at various tempera •Marsh' grapefruit. (See Fig. 7 for respiration during the tures on oxygen uptake at 70 F, of 'Murcott' tangors. period immediately following disection). VAKIS, ET AL: GRAPEFRUIT - MURCOTT - STORAGE 309 Table 9. Internal ethylene, as Table 10. Internal ethylene, as ppm, in non-waxed and waxed 'Marsh' grapefruit subsequent to storage ppm, in 'Marsh1 grape for 4 weeks at 40 and 50 F in artificially main fruit and 'Murcotts' tained levels of ethylene in the storage atmosphere. subsequent to storage C2H4 in Non-waxed fruit Waxed fruit at 34, 40, 55 and 70 F storage Picked Mar. ' 70 Picked May '70 Picked Mar. '70 for periods of 2 and 4 atmosphere 40 F 50 F 40 F 50 F 40 F 50 F weeks. 0 .022 .001 .036 .070 .040 .075 1 Storage weeks in storage .021 .102 .023 .066 .024 .069 temperature 0 10 .026 .063 .065 .130 .030 .143 200 .028 .157 .069 .100 .041 .219 'Marsh*harvested Jan., 1970 500 .021 .042 34 F .008* .008 .058 1258-79-1 1258-90-1 40 F .008 .009 .024 LITERATURE CITED 55 F .008 .017 .021 1. Biale, J. B. 1961. The post-harvest physiology and chemistry of the orange fruit. In W. B. Sinclair, ed. The Orange: Its biochemistry and physiology, pp. 96-130. Univ. 70 F .008 .033 .350 Calif. Press, Berkeley. 475. pp. 2. Biale, J. B., R. E. Young and A. J. Olmstead. 1954. Fruit respiration and ethylene production. Plant Physiol. 'Marsh'harvested March, 1970 29:168-174. 3. Eaks, I. L. 1970. Respiratory response, ethylene production, and response to ethylene of citrus fruits during 34 F .027 .045 .023 ontogeny. Plant Physiol. 45:334-338. 4. Eaks, I. L. 1965. Effects of chilling injury on the respiration of oranges and lemons. Proc. Amer. Soc. Hort. 40 F .027 .059 .023 Sci. 87:181-186. 5. Green, G. F., E. M. Ahmed and R. A. Dennison. 1969. An automatic sampling system for respiratory gases 55 F .027 .045 .048 and respiratory response of irradiated citrus fruits J. Food Sci. 34:627-629. 6. Harding, P. L., B. A. Friedman, M. B. Sunday, J. 70 F .027 .078 .154 Kaufman and H. W. Hruschka. 1952. The effect of pre- storage treatments and storage temperatures on the keeping quality of Florida grapefruit at Orlando, Fla. and New York 'Murcott' harvested March, 1970 City, N. Y., U. S. Dept. Agr. H. T. & S. Rep. No. 285. 28 pp. 34 F .018 .060 .179 7. Harding, P. L., J. Soule and M. B. Sunday. 1958. Storage studies on 'Marsh' grapefruit, 1955-56 season. Citrus Ind. 39 (2) :8-10, 12-14, 35-36. 40 F .018 .103 .176 8. Harding, P. L., J. Soule and M. B. Sunday. 1957. Storage studies on 'Marsh' grapefruit, 1955-56 season. I. Effect of nitrogen and potash fertilization on keeping qual 55 F .018 .081 .102 ity. II. Effect of different temperature combinations on keeping quality. U.S. Dept. Agr. AMS-202. 16 pp. 9. Harvey, E. M. and G. L. Rygg. 1936. Field and stor 70 F .018 .121 .392 age studies on changes in the composition of 'Marsh' grape fruit in California. J. Agr. Res. 52:747-787. 10. Jones, H. B., W. R. Buford and A. L. Ryall. 1951. Storage tests on Florida and Texas grapefruit U. S. Dept. Agr. H. T. & S. Rep. No. 237. 17 pp. *Average for 7 fruit, 5 of 11. McDonnell, L. R., E. F. Jansen and H. Lineweaver. 1945. The properties of orange pectinesterase. Arch. Bioch which values were zero. 6 :383-401. 12. Miller, E. V. and H. A. Schomer. 1939. Physiologi cal studies of lemons in storage. J. Agr. Res. 59:601-607. 1252-31-1 13. Pollard, J. E. 1969. Enzymological studies of abscis 1258-67-1 sion in 'Valencia' oranges (Citrus sinensis, L.) and cala- mondin (Citrus madurensis, Lour). Ph.D. Dissertation, Univ. 1258-76-1 Fla., Gainesville, 101 pp. 14. Pratt, D. E. and J. J. Powers. 1953. The thermal effect on internal ethylene levels after subsequent destruction of pectic enzymes in grapefruit juice. Food Res. 18:152-161. equilibration at 70°F (Table 10). Residual 15. Rouse, A. H. and C. D. Atkins. 1955. Pectinesterase and pectin in commercial citrus as determined by methods ethylene levels were higher subsequent to storage used at the Citrus Experiment Station. Fla. Agr. Exp. Sta. at 50 °F than at 40 °F. They were increased by Bull. 570. 19 pp. 16. Rygg, G. L. and E. M. Harvey. 1938. Behavior of waxing prior to storage and appeared to be pectic substances and naringin in grapefruit in the field and in storage. Plant Physiol. 13:571-576. related to the degree of senescence of the fruit. 17. Stahl, A. L. and A. F. Camp. 1936. Cold storage Increased internal ethylene levels in citrus fruits studies of Florida citrus fruits. I. Effects of temperature and maturity on the changes in composition and keeping are associated with fruit deterioration and in quality of oranges and grapefruit in cold storage. Fla. Agr. Exp. Sta. Bull. 303. 67 pp. creased respiration, and may exert secondary 18. Steward, J. McD. and G. Guinn. 1969. Chilling in effects on the rate of fruit senescence. jury and changes in adenosine triphosphate of cotton seedl ings. Plant Physiol. 44:605-608. 310 FLORIDA STATE HORTICULTURAL SOCIETY, 1970 19. Ting, S. V. 1956. Fruit juice assay. Rapid color- of COn in suppressing chilling injury of grapefruit and metric method for simultaneous determination of total re avocados. Proc. Amer. Soc. Hort. Sci. (Trop. Region). ducing sugars and fructose in citrus juices. Agr. and Food Submitted. Ghem. 4:263-266. 22. Vines, H. M., W. Grierson and G. J. Edwards. 1968. 20. Trout, S. A., F. E. Huelin and G. B. Tindale. 1960. Respiration, internal atmosphere, and ethylene evolution of The respiration of 'Washington' navel and 'Valencia' citrus fruit. Proc. Amer. Soc. Hort. Sci. 92:227-234. oranges. Aust. Comm. Sci. and Ind. Res. Dir. Tech. Paper 23. Vines, H. M., G. J. Edwards and W. Grierson. 1965. Citrus fruit respiration. Proc. Fla. State Hort. Soc. 78: *21. *Vakis, N. I., W. Grierson and J. Soule. 1970. Chill 198-202. ing injury in tropical and subtropical fruits. III. The role EFFECT OF TEMPERATURE ON CENTRIFUGAL SEPARATION OF COLD-PRESSED ORANGE OIL Robert E. Berry and Pedro Casals1 technique, these residual amounts of oil inter- ferrd with concentration methods. Consequently, U. S. Fruit and Vegetable Products Laboratory2 treatments were sought by which the residual Winter Haven oil content in aqueous effluents might be reduced. Cursory studies had indicated the possibility of Abstract a relationship between temperature of centri fugation and efficiency of oil separation. Centrifugal separation of cold-pressed orange Centrifugal separation of oil from water oil from aqueous media is greatly influenced by would be expected to be greatly influenced by densities and viscosities of the two principal the relative densities of the two phases. This (oil and water) phases. Both densities and is shown by the Stokes Law equation for the viscosities are likewise affected by temperature. theoretical sedimentation of a solid through a Differentials between densities of oil and water liquid in a centrifugal force field (Perry 1963). were calculated for different temperatures and Although an oil-water system, such as referred increased as temperature increased. Viscosities to here, is different from a solid-liquid system, of both phases decreased with increasing tem nevertheless, the general rate of centrifugal sep perature. Based upon measured differentials in aration could probably be expected to follow the density and changes in viscosity, predictions were Stokes Law relationship. Rate of separation of made for temperature at which optimum separa oil would therefore be expected to be influenced tion of oil could be achieved from an aqueous by any change in viscosity in the aqueous phase. phase upon centrifugation. Optimum tempera Density and viscosity of both phases would be ture for separating oil was 125°F. expected to vary with temperature. Introduction Several studies have been made of the specific gravity (density) of cold-pressed orange oil. As Cold-pressed orange oil is an important by early as 1932, Poore reported specific gravities product of the citrus industry and is usually of California cold-pressed orange oil at 25 and obtained by centrifugation of an aqueous emul 15.6°C and these were verified in reports by sion from pressed peel. This yields two streams, Kesterson and McDuff (1948) and Kesterson and one of which is predominantly orange oil and the Hendrickson (1953). In the latter two studies other an aqueous centrifuge effluent which may the specific gravities of orange oils made by dif contain up to 1% residual oil. In studies being ferent processes and at different times of the carried out at our laboratory on methods for con year were compared. All measurements were centrating the solids (mostly sugars) in these made at 25°C, however, and no attempts were centrifuge effluents using the reverse osmosis made to determine changes in specific gravity with changes in temperature. Kesterson in 1949 lForeign Research Associate sponsored by Ministry of reported no significant changes in specific grav Education and Science, Barcelona, Spain. ity of cold-pressed orange oil obtained under con 2 One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research ditions resulting in different oil yields. In 1953, Service, U. S. Department of Agriculture. References to specific products of commercial manufac Valiente et al. reported on physical characteris ture are for illustration only and do not constitute endorse tics of cold-pressed orange oil from several dif- ment by the U. S. Department of Agriculture.