Comparative analysis of twin-screw pressing and blending methods for walnut oleosome extraction: Yield, physical stability, and functionalities

Abstract

Walnuts are renowned for their rich oil content and nutritional value, imparting significant health benefits. Walnut oleosomes, naturally present in a pre-emulsified state, can be effectively extracted through aqueous methods. Mechanical processes, such as twin-crew pressing or blending, are commonly employed to disrupt cell walls and extract oleosomes. Our study focused on investigating these two methods under varying soaking pH for walnut oleosomes extraction to develop an efficient extraction process for large-scale production or specific applications. Results showed that the oil content of extracted oleosomes ranged from 84.5% to 89.5%, with no substantial differences noted. Twin-screw pressing significantly achieved higher extraction yields (53.3–57.8%) compared to blending (35.7–36.4%), while blending produced walnut oleosomes with higher zeta potential, viscosity, storage modulus, and smaller particle size, improving physical stability compared to blended samples. The soaking pH levels minimally impacted extraction efficiency and physicochemical attributes of the oleosomes. Overall, blending offered oleosomes with relatively better physical stability, while twin-screw pressing was more advantageous for higher yields, making it more commercially viable for large-scale production. This study underscored the efficiency of sustainable approach in harnessing walnut oleosomes for various industrial applications.