Effect of genotype and crop year on the nutritional value of walnut virgin oil and defatted flour.

The present study analyses the health-promoting compounds of walnut oil and walnut defatted flour obtained using hydraulic pressing. To identify the cultivar effect, nine walnut varieties were harvested in the same plot for two years to control environmental and agricultural management effects on kernel chemical traits. Beyond the variability reported in the products obtained from the different cultivars analysed, the crop year showed a crucial effect in the nutritional value of walnut products. Specifically, the variability caused for the crop year in the concentration of oleic and linoleic acids, phytosterols, polyphenols, tocopherols, proteins and essential minerals (K, Mg, P, S, Cu, Fe, Mn, Mo, Ni) was greater that the reported for the genotype. These findings suggest that the nutritional value of walnut oil and walnut flour depends on the crop season largely than expected, even when average annual weather conditions are similar. As a result, focus must change in the study of cultivar effect on walnut products to a wider analysis of specific variables related to crop year conditions.