Development and mechanical properties of soy protein fibrils-chitin nanowhiskers complex gel

Abstract

To enrich the use of protein-polysaccharide complex gel as texture assistance, we introduced a soy protein fibrils-chitin nanowhiskers complex gel system. Firstly, a stable positively charged chitin nanowhiskers (CNW) suspension and amyloid-like soy protein fibrils (SPF) were fabricated. We found that the self-assembled SPF and CNW formed complex with each other at pH 5.0–8.0 due to attractive interactions caused by their carrying opposite electrical charges. Then, the MTGase-induced SPF-CNW complex gel were formed and investigated by instrumental analysis. The results showed that the presence of CNW significantly increased the β-Sheet structure in complex gel and the rheological modules of complex gel were pH-dependent and showing G' > G" at all pHs. The SPF-CNW complex gel showed a strong and elastic textural property during compression test at pH 6.0. Meanwhile, the frequency scan showed that the SPF-CNW system is less dependent on the frequency and belonged to the typical physical gel. According to the results of SEM and CLSM images, the SPF, CNW and complex gel presented spherical shape, rod shape and linear alignment microstructure, respectively. We inferred that the CNW provided a framework for gel formation and introduced rigidity to the SPF gel. Thanks to the attractive interactions, the SPF molecules were attached to the growth of CNW to form a longer fiber structure. After the gelation process, the aggregates further interacted with each other and finally form complex gel with linear, ordered and compact microstructure.