Effects of Ultraviolet-C Pretreatment on Sugar Metabolism in Yellow Peaches during Shelf Life

Abstract

To investigate the influence of ultraviolet-C (UVC) radiation pretreatment on the sugar metabolism of yellow peaches (cv. Beinong2 × 60–24–7) during storage, the concentrations of soluble sugar (sucrose, fructose, glucose, and sorbitol), and related gene expression were determined. During UVC pretreatment, peaches were subjected to a dose of 4 kJ·m−2 when they were placed at 15 cm under a UVC lamp tube for 10 minutes at 25 °C. Then, they remained at 15 ± 2 °C for 10 days. Peaches stored at 15 ± 2 °C immediately after picking were used as the control group (CG). UVC pretreatment reduced the ethylene production rate and resulted in a significant increase in the accumulation of sucrose during days 2 to 8 of the storage period, followed by a lower concentration of fructose and glucose and the upregulation of PpaSS1. The expression levels of PpaSPS2, PpaSS1, and PpaST3 were significantly correlated with fructose concentration, and those of PpaSPS2 and PpaST2 were significantly correlated with glucose concentration. The enzyme activity of sucrose phosphate synthase (SPS) was positively correlated with PpaSPS2, PpaSS2, and PpaST2. The enzyme activities of sucrose synthase (SS), acid invertase (AI), and neutral invertase (NI) were positively correlated with PpaSS1, PpaST1, and Ppani, respectively. Expressions of PpSPS1 and PpSPS2 in UVC-pretreated peaches were upregulated on storage days 8 and 2, and there was a UVC-induced peak in SPS activity on storage days 4 and 8, which resulted in the rapid accumulation of sucrose. UVC pretreatment could upregulate the gene expression of PpaSS1 on day 2, which could improve and maintain the quality of peaches for consumption.