| In order to reduce residual oil rate and residual protein rate of solid-phase in the aqueous extraction of peanut oil, the main peanut cultivars (Yuhua 37, Yuhua 9326, and Yuanza 6) in Henan Province were used as the objects of the aqueous extraction, and the structural characteristics of peanut proteins in the solid-and aqueous-phases were characterized through determination of the subunit compositions, endogenous fluorescence spectra, surface hydrophobicity, particle sizes, Zeta potentials, three-phase contact angles and aggregation forces, etc. The results showed that at pH 10, the unpeeled Yuhua 37 had the lowest solid-phase residual oil rate (5.73%), while the residual protein rate (15.37%) was not significantly different from that of the other 2 cultivars. The solid-phase obtained by the aqueous extraction contained more soluble proteins with similar subunit compositions to the aqueous-phase proteins, but the endogenous fluorescence intensity, surface hydrophobicity and three-phase contact angles of solid-phase soluble proteins were significantly higher than those of aqueous-phase proteins, implying that the solid-phase soluble proteins had a stronger ability to bind peanut oil. Solid-phase soluble proteins had lower mean particle sizes and absolute Zeta potentials than aqueous-phase proteins. To address the structural characteristics of solid-phase soluble proteins, which had a strong ability to bind oil and carried less charges, the pH of the extraction system was increased, and it was found that the residual oil rate and residual protein rate of the solid-phase of the peeled Yuhua 37 were reduced to 3.44% and 11.86%, respectively, when the pH was 11. In summary, increasing the pH of the extraction system can reduce the solid-phase residual oil rate and residual protein rate in the aqueous extraction process of peanut oil. |
