This study was undertaken in order to explore the effect of exogenous sucrose treatment on the peel coloration in postharvest peaches. Freshly harvested ‘Chunmei’ peaches were dipped in 200 mmol/L sucrose and then stored at (20 ± 1) ℃. Fruit quality traits, and the contents of anthocyanins and endogenous sugars and enzyme activities related to anthocyanidin metabolism were measured during postharvest storage. The results showed that sucrose treatment had no significant effects on the respiratory intensity, ethylene release rate, total soluble solids content or hardness of peach fruit (P > 0.05), but it increased the contents of anthocyanins and sucrose. In addition, sucrose treatment maintained relatively high activities of the enzymes related to anthocyanin synthesis in postharvest peach peel, such as chalcone synthase (CHS), flavonoid 3-hydroxylase (F3H), dihydroflavonol reductase (DFR) and UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT). Therefore, exogenous sucrose treatment can improve anthocyanin synthesis by regulating anthocyanidin metabolism-related enzyme activities in peach peel. This finding will provide a reference for research on the improvement of color in peach peel after harvest.

In order to explore the effect of postharvest treatment with combined phenylalanine (Phe) and 1-methylcyclopropene (1-MCP) on the appearance quality of peach fruits, bagged peach fruits were treated after harvest with water (control), Phe, 1-MCP or Phe combined with 1-MCP (Phe + 1-MCP). The changes in peach fruit phenotype, peel color difference, anthocyanin content, and the expression of genes associated with anthocyanidin and ethylene metabolism were measured during storage. The results showed that the single treatments with Phe or 1-MCP led to a higher peel anthocyanin content compared with the control group. Furthermore, the combined treatment was more effective in increasing the synthesis of anthocyanin than the single treatments. On the 6th day of storage, the anthocyanin content in the peel in the combined treatment group was 76.71 mg/kg, which was 7.29, 3.36, and 1.33 times higher than that in the control, Phe and 1-MCP groups, respectively. Phe + 1-MCP treatment effectively enhanced the expression of genes related to the synthesis of anthocyanins (PAL, CHS, CHI, F3H, DFR, ANS, UFGT, MYB10.1, bHLH-3 and WD40-1) and reduced the expression of genes related to ethylene synthesis and signal transduction (ACS, EIN4 and EIL) in peach peel. This study not only further confirmed that 1-MCP treatment can effectively promote the synthesis of anthocyanin in peach peel, but also found a synergistic effect between Phe and 1-MCP, which will provide a theoretical basis for the application of Phe + 1-MCP in the regulation of peach color after harvest.

In order to study the effect of 1-methylcyclopropene (1-MCP) combined with konjac glucomannan/κ-carrageenan (KGM/KC) coating treatment on the preservation of pears, ‘Sucui 1’ pears subjected to one of four treatments: water (control), 1-MCP, KGM/KC coating, and 1-MCP + KGM/KC coating was evaluated for quality and reactive oxygen species metabolism during shelf life. The results showed that both 1-MCP and KGM/KC coating treatments delayed the decline in the quality of ‘Sucui 1’ pears. Compared with the single treatments, 1-MCP + KGM/KC coating treatment reduced the postharvest respiration intensity and ethylene release rate, and improved the activities of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT). Furthermore, it significantly inhibited the production rate of superoxide anion radical, reduced the accumulation of H₂O₂ and malondialdehyde (MDA), and delayed the decrease in the hardness and the contents of ascorbic acid, soluble sugar and titrable acid in pear fruits. In conclusion, KGM/KC treatment could maintain the quality of ‘Sucui 1’ pears during shelf life, and 1-MCP + KGM/KC coating treatment could more effectively delay the quality decline and extend the shelf life of ‘Sucui 1’ pears, providing a reference for its application in post-harvest preservation of pears.