GLYCOSIDASE ACTIVITIES IN GRAPEFRUIT FLAVEDO, ALBEDO AND JUICE VESICLES DURING MATURATION AND SENESCENCE

Glycosidases were extracted from grapefruit (Citrus paradisi Macf. cv. Ruby Red) flavedo, albedo, and juice vesicles harvested at five perio ds throughout the season. Flavedo beta-galactosidase activity was high at the September harvest and then significantly declined by November. Thereafter, no further changes occurred in beta-galactosidase activit y. Flavedo alpha-galactosidase activity was low and unchanged througho ut the study. Alpha-mannosidase, initially low in flavedo, steadily in creased with advanced maturity. Trends in glycosidase activities of al bedo were similar but attenuated. Juice vesicle beta-galactosidase did not change through the study period, whereas alpha-galactosidase acti vity decreased 70% after the initial harvest period. Alpha-mannosidase was initially high and then decreased to 50% of the original activity . A second peak of activity was measured in March, followed by a secon d decline. Extractability differences of the glycosidases suggest diff erences in compartmentation and function. Two isozymes of alpha-mannos idase were separated in flavedo and one in juice vesicles. and charact eristics were determined at an early and late harvest period. The resu lts suggest that changes in the three glycosidases could be used to fu rther define maturity and senescence in grapefruit.