Effects of nitric oxide fumigation on phenolic metabolism of postharvest Chinese winter jujube (Zizyphus jujuba Mill. cv. Dongzao) in relation to fruit quality

The effect of nitric oxide fumigation on phenolic metabolism of harvested Chinese winter jujube in relation to the fruit quality was investigated. The fruits were fumigated for 3 h with NO (0, 10, 20 and 30 μl/l) then stored at 22 °C and RH 95%. Changes in color, phenol and anthocyanin levels in pericarp, activities of the related enzymes, and total soluble solids and vitamin C from mesocarp were measured. The results showed that treatment with 20 μl/l NO significantly slowed the increase in red index, inhibited changes of polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) activities, maintained a low total anthocyanin content and a high total phenol content, and delayed the increase of soluble solids and decrease of vitamin C. Treatment with NO solution at less than 1 μmol/l exhibited inhibitory effects on in vitro PPO and PAL activities in a dose-dependent manner.