Pg. 15-18 Postharvest Hot Water Treatments for Litchi

The South African litchi industry is striving to gain access to more foreign markets with litchi fruit. Since fruit flies and Cryptophlebia species attack litchi in South Africa, it is important to develop a postharvest quarantine treatment to free fruit from the insects. Therefore, in this study preliminary research was done with hot water immersion as a quarantine treatment.

“HLH Mauritius” and “Red Mclean” fruit were submerged in water at 45°C, 47°C, 49°C en 51°C for 15, 20, 25, 30 and 35 minutes. After hot water immersion fruit were hydro-cooled for 20 minutes in water at ambient temperature. Fruit were then placed in cold storage at 1°C for 26 to 27 days and evaluated. In some of the experiments fruit were sulphur fumigated prior to immersion and in others afterwards. Cryptophlebia leucotreta larvae in “HLH Mauritius” fruit were treated with hot water at 49° C for 20 minutes and the survival rate determined. 

Results indicated that both “HLH Mauritius” and “Red Mclean” immersed in hot water were not damaged and were suitable for exportation. Therefore, litchi fruit can tolerate high temperatures. Fruit must be sulphur fumigated before immersion for improved appearance. More fungal infections and a slightly higher moisture loss occurred on fruit treated with sulphur before immersion. No C. leucotreta larvae survived immersion. These experiments were conducted on a small scale and need to be expanded before final conclusions can be made.

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