Effect of cold plasma treatment time on walnut protein isolate: Revealing structural changes and improving functional...

Cold plasma (CP) was used to modify walnut protein isolate (WalPI), and the effects of different CP treatment times (30 s, 60 s, 90 s, 120 s, and 150 s) on structural and functional properties, along with the modification mechanism, were investigated. The results showed that CP treatment altered the structure of WalPI, primarily by unfolding the tertiary structure and modifying the secondary structure. These modifications included an increase in fluorescence intensity, a decrease in α-helix content, and an increase in β-sheet and random coil content. The three-dimensional network structure exhibited crystalline characteristics, and the microstructure displayed irregular spherical particles. These structural changes led to an improvement in the functional properties, as evidenced by a reduction in average particle size, an increase in solubility to 11.42 %, and improvements in emulsification activity index and emulsification stability index, which increased from 0.50 m²/g and 1.22 min to 2.75 m²/g and 30.50 min. Additionally, water and oil holding capacity increased from 0.45 g/g and 2.54 g/g to 1.21 g/g and 7.46 g/g. Notably, the optimal comprehensive properties of WalPI were achieved after 90 s of CP treatment. This study provides a theoretical foundation for modifying WalPI and enhances its potential for resource utilization.