Effect of Temperature and Storage Time on Some Biochemical Compounds from the Kernel of Some Walnut Cultivars Grown in Romania

Abstract

Walnut kernels are appreciated not only for their mineral content, vitamins, proteins, and valuable lipids, but also for the presence of polyphenolic compounds and biogenic amines. The temperature and storage time effects on some biochemical compounds from kernels collected from eight walnut genotypes grown at the Fruit Growing Research and Extension Station (SCDP) Valcea, Romania, were studied. In general, the phenolic and carotenoid compounds followed opposite trends during short-term storage and in some cases in medium-term storage. In both cases, there was a reduction in concentration during long-term storage, which was more pronounced for carotenoids. The most efficient method for preserving the walnut kernel’s phenolic content was freezing. Keeping the walnut kernel at room temperature assured the smallest carotenoid content decrease. Depending on the walnut cultivar, the preservation of the walnut kernel can be extended to five months by storage at −20 to −18 °C without loss of phenolic compounds, while a period shorter than five months (but certainly longer than three months) could be recommended for storage at 3–4 °C. Keeping it at room temperature can be an option for a short period (about three months). None of the preservation methods was adequate if the losses recorded for carotenoids were taken into account.