Heat-induced inulin-gluten gel: Insights into the influences of inulin molecular weight on the rheological and structural properties of gluten gel to molecular and physicochemical characteristics

Abstract

This study evaluates the influences of inulin molecular weight (Mw) on the rheological, textural, and structural properties of heat-induced inulin-gluten gel. L-inulin (420 Da), M-inulin (1020 Da), and H-inulin (3360 Da) were each investigated for their effects on the physicochemical properties and structure of gluten gel. It was found that inulin caused the gels to exhibit a smaller G′ at initial heating, however, gluten gels prepared from M-inulin and H-inulin featured increased G′, G″, and tanδ during cooling. Compared to gluten gel, inulin-gluten gels exhibited lower hardness, cohesiveness, chewiness, recovery, and water holding capacity. All inulin, regardless of Mw, reduced the hydrophobic interaction and hydrophobicity index H0 of the gels. M-inulin and H-inulin reduced ionic bonding but increased hydrogen bonding. In gels comprised of 40% L-inulin, M-inulin, or H-inulin, gluten disulfide bonding was reduced by 31.8%, 68.1%, and 78.2%, respectively. Regardless of Mw, inulin also reduced β-sheets and increased random coils of gluten, and provoked disulfide bond conformation to change from g-g-g to t-g-t and t-g-g, rendering the inulin-gluten gel structure more disordered and less stable. H-inulin mainly influenced the cross-linking of 30–35 kDa gluten molecules. In short, the impact of inulin on heat-induced inulin-gluten gel properties was Mw-dependent, following H-inulin > M-inulin > L-Inulin. H-inulin strongly inhibited the aggregation of gluten, thereby reducing hydrophobic interactions and disulfide bonding to result in a soft inulin-gluten gel.