Effects of Different Gluten Proteins on Starch's Structural and Physicochemical Properties during Heating and Their Molecular Interactions

Abstract

Starch-gluten interactions are affected by biopolymer type and processing. However, the differentiation mechanisms for gluten-starch interactions during heating have not been illuminated. The effects of glutens from two different wheat flours (a weak-gluten (Yangmai 22, Y22) and a medium-strong gluten (Yangmai 16, Y16)) on starch's (S) structural and physicochemical properties during heating and their molecular interactions were investigated in this study. The results showed that gluten hindered the gelatinization and swelling of starch during heating when temperature was below 75 °C, due to competitive hydration and physical barriers of glutens, especially in Y22. Thus, over-heating caused the long-range molecular order and amylopectin branches of starch to be better preserved in the Y22-starch mixture (Y22-S) than in the Y16-starch mixture (Y16-S). Meanwhile, the starch's degradation pattern during heating in turn influenced the polymerization of both glutens. During heating, residual amylopectin branching points restricted the aggregation and cross-linking of gluten proteins due to steric hindrance. More intense interaction between Y16 and starch during heating mitigated the steric hindrance in starch-gluten networks, which was due to more residual short-range ordered starch and hydrogen bonds involved in the formation of starch-gluten networks in Y16-S during heating.

Keywords: gluten; heat; interaction; starch; wheat.

Figure 1

XRD pattern of native starch and different starch–gluten mixtures during heating (RC, relative crystallinity).

Figure 2

The CLSM of native starch and different gluten–starch mixtures during heating. Size bar = 50 μm.

Figure 3

SDS-PAGE patterns and grey-scale measurements in different glutens and gluten–starch mixtures during heating. (A,B) Non-reducing SDS-PAGE patterns of Y22 and Y16, Y22-S and Y16-S mixtures during heating, respectively; (C) reducing SDS-PAGE pattern of Y22-S and Y16-S mixture during heating; (D) relative grey-scale measurements for SDS-soluble protein (130–200 KDa) from (A,B); (E) relative grey-scale measurements for HMW-GS from (C). * and ** indicate significant level of 5% and 1%, respectively.

Figure 4

Molecular docking of HMW-GSs (Y16 and Y22) with starch. (A,D) represent the docking conformations of starch with HMW-GSs from Y16 and Y22, respectively. (B,E) represent the non-bonding interaction of corresponding docking conformations, and (C,F) represent the 2-D interaction of corresponding docking conformations.