Soybean peptide enhances postharvest apple quality by modulating cell wall integrity, ethylene biosynthesis, and antioxidant systems

Postharvest challenges including dehydration, flavor loss, and excessive softeninglimit economic returns and sustainable development in the apple industry. With growing public awareness of food safety and environmental protection, traditional chemical preservatives face scrutiny due to potential health risks and environmental pollution. Therefore, developing new green, safe, and efficient plant-based preservatives has become critically important. Soybean peptide (SBP), a polypeptide derived from enzymatic hydrolysis of soybean protein, has documented anticancer, antioxidant, and immunomodulatory activities. However, its functions in plants, especially in postharvest preservation, remain unexplored. Here, we determined 0.1 g/L as the optimal SBP concentration for postharvest apple preservation. Further results showed that the 0.1 g/L SBP treatment significantly inhibited ethylene release, cell wall-decomposing enzyme activity, and starch metabolism compared with the control group. The treatment also enhanced antioxidant enzyme activity alongside the levels of VC, phenolics, and flavonoids, contributing to improved antioxidant defense and the preservation of freshness and quality. Transcriptome analysis identified 10 key preservation-related genes regulated by SBP, and their expression was validated through Reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) assays. SBP can be directly sprayed onto fruit surfaces without leaving color or odor and is easy to clean, making it an ideal green antioxidant. This offers a promising solution for non-destructive fruit preservation. Future studies should explore its mechanisms and applications across diverse fruit species.