Quality, physiological, and transcriptomic insights into blueberry preservation by carbon dot-reinforced composite coating

Blueberries are highly susceptible to postharvest softening, oxidative damage, and microbial decay. In this study, gelatin/ Sargassum fusiforme polysaccharide/carbon dots (gelatin/SFP/CDs) composite coating was applied to blueberries, which were then stored at 25 °C and 50–55% relative humidity for 12 days. The preservation mechanism was investigated from quality, physiological, and transcriptional perspectives. During 12-day storage, gelatin/SFP/CDs-coated blueberries exhibited lower decay incidence, darkening, weight loss, pH increase, and bacterial proliferation, while maintaining higher firmness, soluble solids content, titratable acidity, and commercially acceptable rate. Physiological analyses showed that gelatin/SFP/CDs coating delayed cell wall degradation by preserving cell wall polysaccharides and suppressing enzymes involved in cell wall degradation. Meanwhile, it alleviated oxidative stress by reducing reactive oxygen species (ROS) accumulation and enhancing antioxidant capacity. Transcriptomic analysis further revealed that gelatin/SFP/CDs regulated genes involved in cell wall metabolism, ROS generation, antioxidant defense, and the ascorbate–glutathione cycle. These findings suggest that gelatin/SFP/CDs coating delays blueberry senescence through suppressing cell wall degradation and alleviating ROS accumulation.