Exogenous glycine betaine maintains postharvest blueberry quality by modulating antioxidant capacity and energy metabolism

Blueberries are susceptible to decay and spoilage due to increased respiration rates and metabolism after harvest. The aim of this study was to examine the impact of postharvest application of exogenous glycine betaine (GB) on blueberry storage quality, antioxidant system, and energy metabolism in order to enhance understanding of the regulatory mechanisms of GB on blueberry quality. Fresh blueberries were soaked for 5 min in different concentrations of GB. Preliminary pre-tests revealed that 10 mmol L⁻¹ GB treatment significantly retarded the quality deterioration, decay and dent rate, while increasing the firmness and soluble solid content. Concurrently, exogenous GB treatment resulted in an increase in the content of anthocyanosides, total flavonoids, total phenols, and reduced glutathione, also exhibited higher antioxidant enzyme activities, including superoxide dismutase, catalase, ascorbate peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, glutathione reductase, dehydroascorbate reductase, and monodehydroascorbate reductase. In GB-treated blueberries, endogenous GB content was significantly higher. The hydrogen peroxide value, superoxide anion, and malondialdehyde content, and higher levels of free radical scavenging rate (DPPH), which significantly improved antioxidant capacity. Meanwhile, succinate dehydrogenase, cytochrome C oxidase, H⁺-ATPase, and Ca²⁺-ATPase, decreased and slowed the senescence of blueberries, the ATP content and energy charge were observed to be elevated. In summary, exogenous GB treatment maintained the quality of post-harvest blueberries by increasing their antioxidant capacity and inhibiting the decrease in the activity of energy metabolism-related enzymes. The results indicate that 10 mmol L⁻¹ GB treatment may be an efficacious approach for maintaining the quality and prolonging the shelf life of blueberries, offering novel insights into the preservation of this fruit.