REDUCING CHILLING INJURY AND DECAY OF STORED CITRUS-FRUIT BY HOT-WATER DIPS

The effect of hot water dips (53 degrees C, 2-3 min) on chilling injury (CI) and decay of various citrus fruits was compared with the effect of curing (36 degrees C, 72 h). Experiments were conducted with grapefruit (Citrus paradisi Macf., cv. Marsh), lemon (Citrus limon. Burm., cv. Eureka), oroblanco (C. grandis Osb. x C. paradisi, cv. Oroblanco, syn. Sweety) and kumquat (Fortunella margarita Swingle, cv. Nagami). Prestorage hot water dips reduced significantly the sensitivity of all these fruits to CI. Subsequent sealing of hot water-dipped fruit improved the positive effect but was not essential for the success of treatment. In our experiments, addition of fungicides (imazalil or thiabendazole, 1000 ppm) to the hot dip did not increase significantly the CI-reducing effect, but prevented fruit decay. Hot water dip also reduced decay of citrus fruits stored both at low and optimal temperatures, demonstrating an effect comparable to that of curing. An increased level of putrescine was observed in hot water-dipped grapefruit and lemons. Compared with curing, hot water dip was much easier to implement and could be combined with regular packing-house treatment procedures.