Oxidative Stability of Walnut Kernel and Oil: Chemical Compositions and Sensory Aroma Compounds

The impact of storage temperature and time on quality of two walnut cultivars (Juglans regia Chandler and Howard) were evaluated. Free fatty acids, peroxides, and oxidative stabilities exhibited significant changes. After the storage period, gamma-, delta-, and alpha-tocopherols in Howard oil significantly reduced by 42, 56, and 100% at 5 degrees C, while 23 degrees C showed 48, 42, and 100% losses, respectively. For Chandler oil, storage at 5 degrees C reduced gamma-, delta-, and alpha-tocopherols by 19, 24, and 100%, while 23 degrees C caused 42, 45, and 100% losses, respectively. Storage of Howard kernels, up to month four, significantly reduced total phenolics by 9 and 18%, at 23 and 5 degrees C, respectively, whereas Chandler also reduced by 9 and 27%, at 23 and 5 degrees C, respectively. Additionally, 14 phenolic compounds were profiled in kernels, where flavonoids were dominant than phenolic acids. At the end of month four, the dominant phenolic compound was gallic acid at 23 degrees C (981.68 and 703 mg/kg for Chandler and Howard, respectively). Additionally, positive correlations were observed between rancid sensory perceptions and oxidative volatiles. Storage conditions are crucial for maintaining the sensory and nutritional attributes of walnuts during postharvest management.