Effects of Enzyme Addition on the Evolution of Starch Supramolecular Structure and the Quality of Steamed Bread Made with Starch from Frozen Dough

The effect of addition of mixtures of α-amylase and transglutaminase (TGase) on the quality, starch multiscale structure and physicochemical properties of frozen dough and the quality of steamed bread made with starch extracted from frozen dough. The results showed that enzymatic treatment decreased the content of freezable water in the dough system (13.84%-11.56%) and induced the formation of a starch-protein interfacial interlocking structure, inhibiting phase separation caused by freeze-thaw cycles. The double-helix content (36.2%-30.5%) and short-range order (R_{1 045/1 022} = 0.93-0.79) of starch decreased, and the amorphous region content increased (59.5%-60.1%), leading to a decrease in the gelatinization temperature and gelatinization enthalpy (ΔH), an increase in peak viscosity and rheological properties, and higher elasticity and viscosity. In addition, repeated freeze and thaw of starch in dough decreased the specific volume of steamed bread (2.03-1.78 mL/g), and significantly increased the hardness and chewiness. Enzymatic treatment of starch in dough improved the specific volume and texture properties of steamed bread. The specific volume and texture properties of steamed bread made with starch from frozen dough with 900 U/kg of α-amylase were closer to the level of the unfrozen control group, the specific volume increased from 1.78 to 1.95 mL/g, and the hardness decreased from 1281.38 to 920.67 g. In conclusion, enzymatic treatment can improve the processing quality of frozen dough by affecting the structure and physicochemical properties of starch.