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.

Potential of mangaba (Hancornia speciosa), mango (Mangifera indica L.), and papaya (Carica papaya L.) seeds as sources of bioactive compounds

“…The bioactive substances in fruit seeds are described in Table 3. The total quantities of phytosterols were 1951.7, 3540.3, and 4565.7 mg kg -1 in mango, papaya, and mangaba seed oils, respectively, similarly to values found in some nuts for example almond, brazil nut, pecan, pistachio and walnut (Maestri et al, 2020). In all samples, β-sitosterol stood out among other phytosterols.…”

“…The amounts of total tocopherols were 14.37, 31.17, and 36.77 mg kg -1 in mango, papaya, and mangaba seed oils, respectively, similarly to macadamia oil (Maestri et al, 2020). These values are lower than what found in traditionally consumed oils such as corn (314-3116 mg kg -1 ), soybean (252-3627 mg kg -1 ), and sunflower (401-1021 mg kg -1 ) (Codex Alimentarius Commission, 2009).…”

“…The fatty acid composition of mangaba and papaya oils is similar to that of olive oil (55-83% of oleic acid, 7.5-20% of palmitic acid, and 0.5-5% of stearic acid) and of peanut oil (35-69% of oleic acid, 8-14% of palmitic acid, and 1-4.5% of stearic acid) (Codex Alimentarius Commission, 2009). The predominance of oleic acid is also observed in nut oils like almond (43-75%), cashew (57-64.2%), hazelnut (76-82%), macadamia (34-75%) pecan (40.6-75%) and pistachio (52-70%) (Maestri et al, 2020).…”

“…In the review by Bodoira and Maestri et al (2020), the authors concluded that innovative extraction techniques such as microwaves, ultrasound and compressed fluids are being used to obtain phenolic compounds because they are ecologically cleaner techniques. In general, phenolic compounds exist naturally in a wide variety of foods of vegetable origin, such as fruits, legumes, seeds, flowers, and leaves, and are part of the human diet.…”

Effect of low pressure cold plasma treatment on microbial decontamination and physicochemical properties of dried walnut kernels (Juglans regia L.)

“…Moisture content is one of the critical factors in nuts because it directly affects color, texture, rancidity, and shelf life. Maestri, Cittadini, Bodoira, and Martínez (2020) have investigated the effect of moisture content on nut tree oils. The study revealed that moisture content to be the most important factor influencing the onset of rancidity and high oil yields in nut kernels (Maestri et al, 2020).…”