Evaluation of physical parameters of walnut and walnut products obtained by cold pressing

The differences in walnut cultivars related to their chemical composition have been widely reported. These chemical differences result in the differences in the physical parameters of the walnut oils and walnut defatted flours (DF) obtained from cold pressing. In this study, the physical parameters of walnut kernels, walnut oils and DF obtained from nine different cultivars are analysed. Additionally, the effect of the genotype, the crop year and the interaction between both on the colour parameters of walnut oil and DF is studied. The obtained results show that oil colour is mainly determined by the crop year, while the colour of DF is determined by the genotype, the crop year and the interaction of between them. L* is the most useful parameter for cultivar discrimination if two crop years are considered. Among the physical parameters of walnut products, oil viscosity can be considered a parameter of oil quality because it shows strong correlations with the oil fatty acid profile and the concentration of specific triglycerides (LLL, OLO and POO). Physical parameters have been reported to be crucial for consumers and for the food industry and should be considered as quality parameters of walnut by-products.