CONSEQUENCES OF COOL STORAGE OF BROCCOLI ON PHYSIOLOGICAL AND BIOCHEMICAL-CHANGES AND SUBSEQUENT SENESCENCE AT 20-DEGREES-C

In most broccoli (Brassica oleracea L. var. italica) cultivars studied , the loss of chlorophyll was marginal after 5 weeks cool storage (1 d egrees C) + 2 days at 20 degrees C, but there was significant loss of chlorophyll from some poor-storing cultivars, particularly after 10 we eks cool storage (+2 days at 20 degrees C). Soluble sugars were deplet ed rapidly during cool storage (especially sucrose) and were essential ly exhausted after 10 weeks at 1 degrees C. Losses of total proteins w ere only 20% after 10 weeks cool storage. There is preferential catabo lism of carbohydrates (sucrose, glucose, and fructose) at low temperat ures, whereas, at 20 degrees C, protein and carbohydrate levels declin e concomitantly. The patterns of sugar and protein depletion suggest t hat all soluble sugar is potentially accessible for metabolism, but pr otein catabolism is targeted to specific tissues or organs. After 5 we eks at 1 degrees C and placing at 20 degrees C, ethylene production an d respiration increased to steady-state levels. Peak production of wou nd ethylene usually occurs 4 to 6 flours after harvest at 20 degrees C . After 5 or 10 weeks cool storage, this peak of production was not de tected at 20 degrees C. After 10 weeks at 1 degrees C, recovery of eth ylene production was delayed and the respiration rate only partially r ecovered to the steady level. However, chlorophyll loss is the major d eterminant of marketable life without cool storage, and, after 5 weeks at 1 degrees C, postharvest decay is the major determinant of marketa ble life after cool storage, particularly after 10 weeks at 1 degrees C.