The use of hot water treatment for the control of Alternaria alternata In tomato

摘要

Tomato (Lycopersicon esculentum Mill.) is widely grown in Nigeria with an average yield of 35 t h1 and annual yield of approximately 1.8 million t. Tomato production is an important source of income to small holder farmers, but this crop suffers many postharvest diseases caused by fungal pathogens including Alternaria alternata f.sp. lycopersici. Many studies have focused on the effect of heat treatment on mature green tomato to assist subsequent ripening at 20°C with little information of the effect on red tomato. This study focused on the effect of hot water dipping on the control of black mould disease caused by Alternaria alternata and the quality of red tomato. Hot water treatment was carried out on the breaker to turning red tomato (10-30% red USDA Grade Standards, Tomato ripeness stage 1976) purchased from a arm shop in Writtle, Chelmsford Essex, England. They were of equal size and colour. The fruit were inoculated and treated in hot water for 10 min at 40,45 and 50°C; also at 50 and 55°C for 5 min. The results showed that hot water treatment at 50°C for 10 min and at 55°C for 5 min inhibited disease emergence by 20% in 48 h. Hot water treatment inhibited the pathogen germination and decay development caused by Alternaria alternata. Theresults showed the fungal pathogen can be inhibited at high temperature in few minutes. Dipping tomato fruit in hot water at 50°C for 10 min or 55°C for 5 min would inhibit germination of spores and reduce decay development caused by Alternaria alternata. The effect of hot water treatment at 40 or 50°C for 10, 20 and 30 min was evaluated on tomato fruit quality such as colour, firmness, aroma, taste and water loss after 24 h storage at 29-30°C and humidity 80-90%. Heat treatment had a significant effect on red colour development and water loss in all the time periods tested but had no effect on firmness and taste.