Tree nut oils: Chemical profiles, extraction, stability, and quality concerns

Abstract

Tree nuts are globally consumed. Their kernels are calorie-rich, nutrient-dense foods and contain several bioactive and health-promoting components. While some nut crops have expanded through the world since ancient times (almond, hazelnut, walnut), more recently, there has been a parallel development of underexploited promising species (Brazil nut, macadamia, pecan). Nut kernels have high lipid content, ranging from 40% to 80% depending on nut species and varieties. In general, nut oils contain significant proportions of nutritionally and medicinally desirable fatty acids and nutraceutical compounds (sterols, tocopherols, and other phenolics). A considerable genetic variability in oil content and composition is present in nut genetic resources worldwide. This suggests the possibility of different breeding lines focused to enhance oil yields, chemical and quality traits. Regarding extraction, screw-pressing is suitable to achieve high oil recovery and good quality standards, but seed materials should be conditioned appropriately. Seed moisture content and pressing temperature appear as key variables to enhance oil recovery. This article presents an overview on chemical profiles, mechanical extraction, and quality concerns of oils from the most widely produced tree nut crops. The revision is also aimed at identifying areas where knowledge is insufficient and to set priorities for further research. Practical applications: The review updates and increases knowledge about oils from tree nut genetic resources, encompassing genetic variability and environmental effects on oil yield and compositional traits. It also analyzes findings regarding oil extraction and provides useful insights to establish better conditions for achieving sustainable oil yields and good quality standards.