Search

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. • The shell is a natural protective barrier of walnut against oxidation. • Oil oxidation in walnut was effectively limited when stored in-shell at 4 °C. • Packaging technique did not have significant effect on oxidative stability. • Oxidation progress in walnut varied depending on the variety. [ABSTRACT FROM AUTHOR]