Postharvest Heat Treatment For Maintaining Quality And Control Of Main Diseases Of Apple Fruit During Cold Storage

Apple fruits (Malus domestica Borkh., cv. Golden Delicious and Fuji) were treated by postharvest heat treatment, the effects of postharvest heat treatment on quality and controlling main diseases of apple fruits during cold storage were focused on.1. The effect of hot water treatment and hot air treatment on the quality of apple fruit was discussed firstly. Fuji apples were immerged in hot water at 45 ℃ or 50℃ for short time. There had no obvious effect of hot water treatment on the quality of fruits during cold storage. Apples were easily suffered heat damage when air temperature were higher than 42 ℃. Hot air treatment could maintain postharvest quality of apple fruit treated at 38℃ for 72h or 96h.. After shelf life, heated fruits were firmer and had a better apparent quality, compared with unheated fruits.2. Hot air treatment could maintain postharvest quality of Golden Delicious and Fuji apple fruit treated 72h or 96h at 38℃. After 16 weeks of cold storage at 0℃, heated fruits had a yellower pericarp at the end of the 16 weeks storage and a higher solids/acid ratio and juice pH, a lower respiration rate and ethylene production as well, compared with unheated fruits. Firmness of heated fruits were much higher,; soluble pectin content were lower and insoluble pectin content were higher than control. Soluble protein and heat-stable protein descended slowly, and the proportion of heat-stable protein/soluble protein were much higher. Heat treatment could maintain cell membrane stability preferably, and malonaldehyde accumulated less. After shelf life, heated fruits were firmer and had a better apparent quality.3. Mycelial growth and spore germination of Botrytis cinerea and Penicillium expansum were efficiently controlled by hot air treatment. B. cinerea is much sensitive than P. expansum under heat stress. Spore germination of B. cinerea suspension was completely inhibited for 48h at 38℃, and no mycelium grown in PDA plates for 72h at 38℃. Spore germination and mycelial growth of P. expansum were distinctly slowed to length ofexposure time. Heated spores germinated slowly when inoculated into Fuji apple fruit. Fruits inoculated with B. cinerea spores heated for 72h were found no decay, inoculated with P. expansum spores were found controlled decay distinctly, though the decay incidence was high. Heating apple fruit inoculated with fungi for 96h at 38℃ completely inhibited decay development, whether incubated at 0℃ or 20 ℃, compared with unheated inoculated control fruit.