PHYSIOLOGICAL-RESPONSES OF TOMATO FRUIT TO CYCLIC INTERMITTENT TEMPERATURE REGIMES

Long life tomatoes (Lycopersicon esculentum Mill. cultivar 'Durinta') at breaker stage, treated with 0.5 g 1(-1) iprodione or washed in wate r, were stored at 9, 12 or 20 degrees C for up to 28 days. Fruit store d at 9 degrees C were warmed to 20 degrees C for 1 day every week, whe reas fruit stored at 12 degrees C were cooled to 2 degrees C for 1 day every week. Fungicide treatment reduced decay and pitting on fruit st ored more than 3 weeks. At 9 degrees C, a slight synergistic effect on fruit pitting was observed from fungicide alone or fungicide plus int ermittent warming. Compared with fruit stored at a constant 9 degrees C, intermittently warmed tomatoes had better surface colour and flavou r, were slightly less firm with less severe pitting, and were in bette r condition both at the end of the storage period and after a 3-day sh elf-life. In fruit held at constant 20 degrees C, 9 degrees C or inter mittently warmed, increased pectolytic enzyme activity accompanied a f all in respiration rate and ethylene production. In fruit held at a co ntinuous 9 degrees C, polygalacturonase activity was reduced slightly during the third week of storage. Intermittently cooled fruit showed e nhanced taste and appearance compared with fruit held at a constant 12 degrees C, but had more decay and pitting after the second cooling tr eatment. After cooling, slight reductions in La*b* Colour Space light ness were detected. During the shelf-life period, tomatoes previously stored continuously for 2 or 3 weeks at 9 or 12 degrees C produced mor e ethylene and had higher respiration rates. By the third week, ethyle ne production was severely reduced by cooling at 2 degrees C, but a po ssible relationship between pitting and non-ripening-dependent ethylen e production was indicated. The respiration rate was not affected by t he disorder incidence. We conclude that intermittent warming is more b eneficial than intermittent cooling because of pitting development at 2 degrees C in intermittently cooled fruit. (C) 1998 Elsevier Science B.V. All rights reserved.