Application of α-aminoisobutyric acid and β-aminoisobutyric acid inhibits pericarp browning of harvested longan fruit

Background: Pericarp browning is a critical problem resulting in reduced commercial value and shelf life of longan fruit. Results: Two non-protein amino acids, a-aminoisobutyric acid (AIB) and beta-aminoisobutyric acid (BAIB) at 100 and 1 mM were applied to longan fruit prior to storage for up to 8 days at 25 degrees C respectively. Contents of the major five phenolics (gallic acid, catechin, corilagin, epicatechin and gallocatechin gallate) were assayed by high-performance liquid chromatography (HPLC). Physiological properties related to pericarp browning of longan fruit were investigated during storage. Respiration rate, membrane permeability, malondialdehyde (MDA) content, and activities of polyphenol oxidase (PPO) and peroxidase (POD) were down-regulated by AIB or BAIB treatments, with significantly lower pericarp browning index and higher proportion of edible fruit than the control. Moreover, exogenous application of AIB and BAIB maintained higher contents of catechin, corilagin, epicatechin and gallocatechin gallate, but lower content of gallic acid compared to the control in the pericarp of longan fruit during storage, which was associated with the oxidation of browning substrate. Conclusions: Pericarp browning was inhibited and storage life of longan fruit was extended effectively by AIB and BAIB treatments with AIB treatment being more significant than BAIB. The findings may provide a new strategy for controlling pericarp browning of harvested longan fruit.