Abstract:

The effect of preservative SO2 on oxidation-reduction equilibrium capacity and secondary metabolism in grape
berries of Longan cultivar during storage was explored. The results showed that application of preservative SO2 extended the
shelf life of grape berries. Their intactness was significantly higher than that of the control grapes, and threshing and decay
rate were also lower relatively. During SO2-fumigated storage, antioxidant capacity of grape skins was increased, the activity
of phenylalanine ammonialyase (PAL), a key enzyme involved in secondary metabolic pathways, was enhanced, and total
anthocyanin content was elevated slightly. In addition, the contents of H2O2 and malondialdehyde (MDA) in SO2-fumigated
grape skin tissue were higher than those of the control group. These findings indicated that reactive oxygen species (ROS)
signals were activated in grape skin cells. Antioxidant capacity and the secondary metabolism associated with the synthesis
of phytoalexin were increased by preservative SO2, thereby enhancing defense capabilities and leading to an extended shelf
life of grape berries.

Key words: grape berries, postharvest storage, SO2 storage, defense response, secondary metabolism