Antioxidant hydrocolloid coating with caffeic acid enhances fruit quality and regulates ascorbic acid and fatty acid metabolism in Rosa roxburghii

• CA enhances quality of R. roxburghii fruit during cold storage. • CA enhances antioxidant enzyme activity and promotes AsA-GSH cycle regulation. • CA increases unsaturated fatty acids while reducing lipid peroxidation. • CA promotes H3K4me3 levels of APX, GR, and DHAR . Rosa roxburghii fruit are rich in bioactive compounds but suffer from a short shelf life due to concentrated harvesting periods, high perishability, and limited postharvest storage technologies. The antioxidant hydrocolloid coating with caffeic acid (CA) significantly reduced fruit decay and respiration rate while preserving higher levels of soluble solids, ascorbic acid (AsA), malic acid, and citric acid, thereby enhancing overall fruit quality. The treatment also upregulated the activity and gene expression of key enzymes involved in AsA metabolism, including glutathione reductase (GR), ascorbate peroxidase (APX), and dehydroascorbate reductase (DHAR). These enzymatic changes lowered hydrogen peroxide accumulation and increased GSH/GSSG and AsA/DHA ratios, thereby improving antioxidant capacity. Furthermore, CA-induced H3K4me3 histone modifications at the loci of APX, GR , and DHAR promote their transcription. The treatment also enhanced fatty acid composition by increasing unsaturated fatty acids (oleic, linoleic, and linolenic acids) and reducing saturated fatty acids (stearic and palmitic acids). This shift was associated with increased fatty acid synthase activity and suppression of enzymes involved in lipid degradation, including lipoxygenase, alcohol acyltransferase, phospholipase D, hydroperoxide lyase, and alcohol dehydrogenase. Collectively, this antioxidant-enhanced hydrocolloid treatment system improves the postharvest quality of R. roxburghii fruit by modulating AsA and fatty acid metabolism, presenting a viable strategy to mitigate postharvest quality deterioration in horticultural fruit.