Effects of heat treatment on flesh leatheriness and related enzyme activities of loquat fruits during cold storage

The study was conducted to investigate the effects of heat treatment on flesh leatheriness of cold-stored loquat fruits and the possible mechanisms. Freshly harvested loquat fruits were pre-treated with hot air at 38℃ for five hours and then stored at (1±1)℃ for 35 days. Fruits firmness, extractable juice rate, the activities of phenylalanine ammonium-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO) and polygalacturonase (PG) that were related to flesh leatheriness, and contents of lignin and pectin were analyzed at seven-day intervals during storage. The results indicated that heat treatment significantly delayed the increase of fruits firmness and the decrease of extractable juice rate, inhibited the increase of PAL, POD and PPO activities and the decrease of PG activity. Meanwhile, heat treatment reduced the accumulation of lignin and protopectin and maintained higher content of water soluble pectin, thereby prevented the development of flesh leatheriness and maintained the quality of cold-stored loquat fruits. These data suggest that the reduction of flesh leatheriness by heat treatment may be related to the inhibition of lignin synthesis and the enhancement of pectin solubilization.