Moderately mechanically activated starch in improving protein digestibility: Application in noodles

The aim of this study was to investigate the mechanism of protein digestibility improvement by exploring the changes in structural characteristics of proteins in noodles with varying levels of mechanically activated starch. Therefore, different levels of mechanically activated wheat starch were mixed with refined wheat flour to produce noodles. Results showed that moderately mechanically activated starch could significantly improve protein digestibility and noodles containing 8.76 % damaged starch exhibited the highest protein digestibility of 88.97 %. This enhancement was due to the ability of moderately mechanically activated starch to hinder the cross-linking of γ-gliadin, D-LMS, and B/C-LMS via disulfide bonds and promote the transition from β-sheets to β-turns. Additionally, moderately mechanically activated starch induced protein unfolding by decreasing the α-helix content and facilitating the transformation from g-g-g to t-g-t conformations, thereby increasing the accessibility of enzymatic hydrolysis sites. However, excessively mechanically activated starch induced protein folding, as evidenced by an increase in the g-g-g conformations content and protein width (11.10), thus slightly reducing protein digestibility to 82.39 % in noodles containing 10.62 % damaged starch. Thus, the results of this study may provide new insights for the development of formulated foods with high protein digestibility for consumers in areas with limited economic resources.