The protective role of shell, packaging technique and storage temperature in lipid oxidation in walnuts of different varieties

Abstract

In this study, the effects of different packaging techniques (normal and nitrogen atmosphere, and vacuum packaging) and different storage temperatures (4 and 20 °C) on lipid oxidation in in-shell and kernel walnuts of ‘Chandler’ and ‘Sebin’ varieties stored for 12 months were investigated. Free fatty acid, peroxide, p-anisidine, conjugated diene and triene values, hexanal contents, and fatty acid compositions of the walnuts were periodically determined during storage. Free fatty acid values of the samples stored at 20 °C were higher than those stored at 4 °C. Peroxide values of all samples fluctuated during storage but the values determined at the end were higher than their initial values. The highest hexanal and p-anisidine values were observed in the kernels packaged under normal atmosphere and stored at 20 °C. No significant changes were observed in conjugated triene values of the samples. Fatty acid composition was most stable in in-shell walnuts stored at 4 °C. Hexanal contents of the samples stored at 4 °C and the ones packaged under nitrogen and vacuum were remarkably lower than those of the samples packaged under air and stored at 20 °C. As a result, the oxidation reactions were strongly limited in in-shell walnuts of both varieties when stored at 4 °C for 12 months. It was determined that the factors affecting the oxidation reactions in walnuts were in a sequence of storage temperature > presence of the shell > variety > packaging technique. © 2023 Elsevier B.V.