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.