Changes in the Phenolic Content and Free Radical-scavenging Activity of Vacuum Packed Walnut Kernels during Storage

Abstract

In this study, the effects of storage temperature, O₂ permeability of packaging materials and variety on phenolic content and free radical-scavenging activity of vacuum-packaged walnut kernels were studied over a 12 months storage period. Methyl gallate (23.70 − 93.75 mg/kg), ellagic acid (137.95 − 569.22 mg/kg), and an ellagic acid pentoside (270.59 − 637.17 mg ellagic acid equivalent/kg) were identified in walnut varieties. While a slight decrease in the amount of ellagic acid was observed during 12 months storage, decreases in the amount of ellagic acid pentoside, total phenolic content and free radical-scavenging activity were severe. The present study concluded that it is possible to protect the phenolic content and antiradical activity of walnut kernels by packaging in Polyamide/Polyethylene laminate pouches having an oxygen permeability lower than 63.40 ± 0.40 (mL/m²/24h at 23°C) under vacuum at 20°C up to twelve months.