Differences in Oils from Nuts Extracted by Means of Two Pressure Systems

Abstract

Nuts are nutrient dense foods especially appreciated for the fatty acids composition of the oil fraction and other bioactive compounds, like polyphenols or sterols. Almond, pistachio, and walnut oils were extracted by two pressure systems (hydraulic press and screw press) in order to obtain virgin oils. A comparison of the fatty acids was performed for oils from different sources. Although the main components of oils (fatty acids and sterols) did not vary according to the system used, some differences among the three types of nut oils were found. Almond and pistachio oil samples showed a similar fatty acid profile with a substantial amount of monounsaturated fatty acids, 70 and 61%, respectively. However, the majority proportion in walnut oils was the polyunsaturated fatty acids (60%). The highest total sterol content was presented by pistachio oils (4476 mg/kg). Screw press oils showed higher values of the regulated quality parameters (acidity, peroxide value, K 232 , and K 270). In the same way, polyphenols and oxidative stability were slightly higher when the nut oils were extracted with a screw press.

Pistachio oil: A review on its chemical composition, extraction systems, and uses

“…They are both considered as cold extraction methods, but when the screw press is used, the oil may reach temperatures near 40À50°C due to the friction of the pistachios during the extraction process, which may lead to changes in the oil characteristics. Oils obtained with the screw press show a slight increase in the acidity, peroxide value, and oxidative stability [53,61] with slight increases in the polyphenols content [61].…”

Kernel oil content and oil composition in walnut (Juglans regia L.) accessions from north‐eastern Italy

“…It is a valuable lipid food source; indeed the oil content, ranging in commercial walnut varieties from 620 to 740 g kg −1 kernel, is the predominant component of this nut crop . Walnut oil is naturally rich in polyunsaturated fatty acids (PUFAs), mainly linoleic (55–70%) and linolenic (10–18%) acids, and is consequently poor in monounsaturated fatty acids (MUFAs), represented by oleic acid (10–20%), and in saturated fatty acids (SFAs) . Walnuts are mainly consumed as fruit, and their nutritional qualities and use depend mainly on their oil fatty acid profile.…”

“…The development of alternative walnut oil feedstocks with improved functionality while maintaining nutritional quality has therefore become a priority for the food industry. The specific goal in walnut breeding could be improving the oxidative stability through reduction of PUFAs and relative increase of MUFAs . The objective of improved stability could be reached by raising the SFA content, but that can have adverse effects on human health due to the increase of low‐density lipoprotein (LDL) in blood caused by high palmitic acid (C16:0) consumption .…”

“…[2][3][4] Walnut oil is naturally rich in polyunsaturated fatty acids (PUFAs), mainly linoleic (55-70%) and linolenic (10-18%) acids, and is consequently poor in monounsaturated fatty acids (MUFAs), represented by oleic acid (10-20%), and in saturated fatty acids (SFAs). 2,[4][5][6] Walnuts are mainly consumed as fruit, and their nutritional qualities and use depend mainly on their oil fatty acid profile. Walnut oil is excellent if used fresh for edible purposes, because it is rich in the so-called -3 and -6 fatty acids that are essential for the human diet.…”

“…The specific goal in walnut breeding could be improving the oxidative stability through reduction of PUFAs and relative increase of MUFAs. 2,5,6 The objective of improved stability could be reached by raising the SFA content, but that can have adverse effects on human health due to the increase of low-density lipoprotein (LDL) in blood caused by high palmitic acid (C16:0) consumption. 8 Genotypes with high oleic acid content are naturally present in walnut.…”