Inhibitory effect of anthocyanin extract from seed coat of black bean on pericarp browning and lipid peroxidation of litchi fruit during storage

Anthocyanins were extracted from seed coats of black beans (Glycine max [L.]) and the inhibitory effects of anthocyanin extract on pericarp browning and lipid peroxidation of litchi fruit were investigated. Litchi firuit were infiltrated for 3 min with 0 (control) or 50 mg/L of anthocyanin extract at a reduced pressure of 53 kPa, then packed in 0.03 mm thick polyethylene bags, and finally stored at 28C for 6 days. Changes in browning index, contents Of anthocyanins and total phenol, peroxidase (POD) activity, levels of relative leakage rate and lipid peroxidation, alpha,alpha-diphenyl-beta-picrylhydrazy (DPPH) radical scavenging activity and reducing power were evaluated. Application of anthocyanin extract from black bean delayed pericarp browning of litchi fruit during storage, which was associated with reduced POD activity and higher contents of anthocyanins and total phenol. Moreover, the anthocyanin extract was found to have a direct inhibition on the POD activity in vitro. Furthermore, application of the anthocyanin extract apparently reduced lipid pet-oxidation and relatively maintained membrane integrity, which may account for browning inhibition to an extent. Finally, higher DPPH radical scavenging activity and reducing power of the fruits treated with the anthocyanin extract than control fruits possibly benefited in scavenging free radicals and reducing lipid peroxidation. It is, therefore, suggested that inhibited POD activity and reduced lipid peroxidation by the anthocyanin extract from seed coats of black beans were responsible for the inhibition of pericarp browning of litchi firuits.