EFFICACY OF HEAT TREATMENT IN CONTROLLING DECAY BY Fusarium nivale Fries. ON TOMATO AND ITS EFFECT ON FRUIT QUALITY.

Abstract

Investigation was carried out on the efficacy of heat treatment in controlling Fusarium nivale on tomato cv UTC and its effect on fruit quality. Healthy mature green, breaker, turning, pink, light-red and red-ripe tomatoes cv UTC were wound inoculated and heat treated in hot water at 42oC for 25 minutes or 48oC for 10 minutes and hot air at 46oC for 1hr or 70oC for 4 or 6 minutes. The fruits were stored in sterilized desiccators at 28o+2oC and 100% relative humidity after the titratable acidity, total soluble solids, and weight were determined at the beginning of storage. Severity of decay was observed daily for 11 days as well as ripening index. Results obtained showed that heat treatment reduced the severity of decay caused by F. nivale on tomatoes. All forms of heat treatment reduced severity within the 11 days of storage. Hot air at 70oC for 4 min inhibited decay for the 11 days of storage in mature green, breaker and turning fruits. Hot water at 48oC for 10 min inhibited decay for 11 days of storage in mature green and breaker fruits. The treatment also inhibited the growth of both spores and mycelium of the fungi. Spore germination was reduced by 96% at 70oC for 6 minutes. The same treatment also completely inhibited the growth of F. nivale on agar. The quality of the fruit was also improved with heat treatment. Fruit ripening was enhanced in heated fruits than non heated fruits. Fruits heated in hot air at 46oC for 1 hour gave the best colour development. Generally, titratable acidity was lowered and total soluble solid increased in matured-green, breaker and turning fruits after storage; weight loss in the fruits was between 2.51% and 3.43%.