How G4-amylase and hexose oxidase synergistically improve the qualities and inhibit the retrogradation of steamed breads: A comprehensive study on molecular mechanisms and quality characteristics

The process of starch retrogradation is responsible for the deterioration of the quality of steamed breads. Wheat flour was modified using G4-amylase or/and hexose oxidase. A molecular model and a retrogradation model were established to study the effect of single/compound enzyme-modified flour on the texture of steamed breads stored for different periods. The results showed that G4-amylase could effectively bind with starch chains (−6.9 kcal/mol) and starch molecules with low polymerization degree produced to inhibit the self-assembly of starch, thus inhibiting the retrogradation of steamed breads. Hexose oxidase effectively oxidized the hydrolysate produced by G4-amylase (−7.4 kcal/mol) and H₂O₂ released to increase the disulfide bond content. With the increase of G4-amylase (4–10 U/g) or hexose oxidase (10–40 U/g), the quality of steamed breads improved. Compared to the control sample (native steamed breads), G4-amylase of 8 U/g significantly reduced retrogradation rate (0.20) and hardening rate (0.42) of steamed breads, but the elasticity of steamed breads decreased by 5 %. The content of disulfide bonds increased by 24 % after hexose oxidase (30 U/g) treatment and the elasticity increased by 23.4 %. The qualities of steamed breads modified by the combination of G4 amylase (8 U/g) and hexose oxidase (30 U/g) were superior to that of G4-amylase or hexose oxidase alone under laboratory conditions.