Effect of exogenous melatonin treatment on quality and softening of jujube fruit during storage

The objective of this study was to evaluate the effects of melatonin (100 μM) treatment on fruit quality and softening of Ziziphus jujuba at (0 ± 0.5) °C and relative humidity of (90 ± 5) %. The results showed that compared with the control, Melatonin (MT) treatment maintained a low level of weight loss rate and a high level of titratable acid and ascorbic acid. MT treatment also delayed the decrease in fruit firmness, protopectin, cellulose, and hemicellulose content and the increase in water-soluble pectin content. In addition, MT treatment also inhibited the activities and gene expression of polygalacturonase, cellulase, β-glucosidase, β-galactosidase, and lipoxygenase. These results showed that MT treatment can not only maintain the quality of jujube fruit by delaying the degradation of nutrients in jujube fruit, but also delay the degradation of cell wall by inhibiting the activity and gene expression of cell wall degrading enzymes, which may be the mechanism of MT treatment inhibiting jujube fruit softening. Novelty impact statement Melatonin was a reliable treatment for maintaining quality and delaying softening of the fruit. Melatonin treatment can maintain the quality of jujube fruit by delaying the degradation of nutrients in jujube fruit. Melatonin treatment can delay the degradation of cell wall by inhibiting the activity and gene expression of cell wall degrading enzymes.