Functionalizing walnut protein via consecutive purification and ultrasound modification: Self-assembled structure and interfacial properties
Jisong Zhou, Jingjing Wang, Wenjie Xia, Ying Peng, Jing Yang, Weiping Jin, Dengfeng Peng
Abstract
The preparation of plant proteins generally involves three independent steps, which is time-consuming. Here, we integrated these three steps into one consecutive process (one-step preparation), which involved alkali extraction, membrane purification, and ultrasound modification. The obtained walnut protein was evaluated in terms of self-assembled structure, interfacial behaviors, and emulsifying properties. Compared with the traditional preparation method, our one-step preparation regulated the aggregation of walnut protein from a dissolved state to a well-organized assembly. When the ultrasound modification was conducted at 10 W/mL for 30 min, the walnut protein (WP-U2) showed the highest surface hydrophobicity ( H 0 = 36704), the smallest particle size (205 nm), and highest solubility (58.70 %) at pH 7.0. These well-assembled proteins rapidly diffused, anchored, and rearranged at the oil–water interface, resulting in an increase of the interfacial pressure to 19 mN/m. The adsorbed proteins formed a dense and stiff solid-like interfacial film with a storage modulus of 64 mN/m at an amplitude of 5 %. These enhanced interfacial properties endow WP-U2 with superior emulsifying properties (EAI ∼ 12 m 2 /g, ESI > 150 min) compared to other groups. This study provides a simple and environmentally friendly way to produce functionalized walnut protein, which shows great potential as an effective food emulsifier.