Effects of glutenin/gliadin ratio and calcium ion on the structure and gelatinity of wheat gluten protein under heat induction

In this study, the effects and mechanisms of different ratios of glutenin/gliadin (Glu/Gli) and calcium ions (Ca2+) on the gel properties of wheat gluten under heat induction were investigated. It was revealed that a high ratio of Glu (6:4∼10:0) improved the elasticity of wheat gluten gel and reinforced the gluten network skeleton, but the gel strength was reduced. A high ratio of Gli (0:10∼5:5) increased gel strength and water-holding capacity (WHC) of the wheat gluten gel, enhancing the gel properties and network structure. The gluten strength, WHC and gel strength responses revealed that a Glu/Gli ratio of 4:6 resulted in the best gel properties of wheat gluten and the strongest water binding ability. Incorporation of 0.004 g/mL Ca2+ significantly promoted the cross-linking between Glu and Glu-Gli, enhanced the binding ability of Gli with water, and strengthened the gel network structure and reaching its peak effect. Intermolecular forces and secondary structure analysis revealed that Ca2+ increased the disulfide bonds in Glu, hydrogen bonds in Gli, and β-sheet content. This indicated that an appropriate amount of Ca2+ formed a Ca2+-gluten protein barrier network through electrostatic shielding, which improved the continuity and compactness of the wheat gluten gel network. Excessive Ca2+ retarded wheat protein cross-linking and hydration capacity, leading to decrease in gel properties. Therefore, by adjusting the Glu/Gli ratio and adding an appropriate amount of Ca2+, the structure and gel properties of wheat gluten can be better controlled, thereby improving the quality of wheat-based products.