Application of Ferulic Acid to Alleviate Chilling Injury of Banana Fruit by Regulating Redox, Phenylpropanoid, and Energy Metabolism

Banana fruit is susceptible to chilling injury (CI) during low-temperature storage, which results in economic loss. Ferulic acid (FA) is an endogenous phenolic chemical derived from phenylpropanoid pathway and involves in stress response. This study investigated the effect of FA on the cold resistance of banana fruit under 6°C storage for 7 days. Fruits were sampled at Days 0, 1, 3, 5, and 7. Indicators that associated with the occurrence and development of CI were detected. In comparison with control, 3 mM FA treatment significantly alleviated chilling symptoms and reduced CI index, malondialdehyde (MDA) content, and electrolyte leakage by 28.64%, 5.21%, and 9.12% averagely over storage. FA also inhibited the production of hydrogen peroxide (H₂O₂) and superoxide radical (O₂^−.), increased superoxide dismutase (SOD) and catalase (CAT) activities, as well as ascorbic acid (AsA), glutathione (GSH), total phenolic, and flavonoid contents. Phenylpropanoid metabolic pathway was also enhanced in FA-treated fruit, as phenylalanine ammonia lyase (PAL) activity increased and expression levels of genes, including PAL, 4CL, C4H, and chalcone synthase (CHS), were upregulated. Additionally, FA treatment promoted energy supply by increasing contents of ATP and ADP, energy charge (EC), activities of Ca²⁺-ATPase and H⁺-ATPase, as well as expression levels of ATPase, H⁺-ATPase, and Cyt b₆f. These findings suggested that FA might alleviate CI of banana fruit by regulating redox homeostasis, phenylpropanoid metabolism, and energy state.