This study aimed to investigate the effect of heat moisture treatment (HMT) on the granular morphology, crystalline structure, short-range ordered structure and digestibility of waxy rice flour (WRF), and the potential mechanism by which HMT influences its digestibility was also revealed. Results indicated that HMT induced significant aggregation of WRF particles, with the average particle size increasing from 13.38 to 23.27 μm as the temperature rose to 120 ℃. Additionally, the relative crystallinity (RC) of WRF decreased from 38.9% to 34.4%, accompanied by a reduction in the short-range order index from 0.97 to 0.81. Although HMT disrupted the ordered molecular structures of WRF, the synergistic action of thermal energy and moisture strengthened the interactions between molecular chains, thereby promoting the formation of Ⅴ-type starch-lipid complexes. Moreover, the RC of Ⅴ-type complexes increased from 1.5% to 2.9%, and the gelatinization temperature of WRF also increased. The aggregation of WRF particles, enhanced formation of Ⅴ-type complexes and higher gelatinization temperature, together impeded adsorption and specific binding of enzymes to WRF and consequently inhibited its hydrolysis, thereby slowing down the digestion rate of WRF and increasing the proportion of slowly digestible and resistant starch, which reached a maximum of 39.4% at 110 ℃. In conclusion, HMT could effectively reduce the digestibility of WRF by modulating its multi-scale structural features, which provides a theoretical basis for the development of low glycemic index products.

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.

The objective of this study is to investigate the effect of addition of different levels of hydrocolloids (flaxseed gum or Artemisia sphaerocephala Krasch. gum) on the physicochemical properties of glutinous rice flour and the quality of the resultant sweet dumplings. The results showed that the addition of hydrocolloids except 0.1% of flaxseed gum could improve the peak viscosity, trough viscosity and final viscosity of glutinous rice flour in a concentration-dependent manner. Moreover, the elastic modulus and viscosity modulus of glutinous rice flour were increased, and the loss tangent was decreased, which was conducive to the formation of a highly stable gel structure. In addition, the addition of hydrocolloids significantly reduced the water loss rate and cracking rate of sweet dumplings and increased the transmittance of the soup (except 0.1% of flaxseed gum) and the hardness of sweet dumplings, indicating that hydrocolloids can improve the quality of sweet dumplings. Fuzzy mathematics was used to standardize the sensory evaluation data of sweet dumplings. It was shown that the sensory evaluation score increased with increasing addition level of hydrocolloids. According to the physicochemical properties of glutinous rice flour as well as using principal component analysis (PCA), a comprehensive evaluation model for the quality of sweet dumplings was established, which can provide a basis for the application of hydrocolloids in sweet dumpling.

This study investigated the effects of adding different amounts of flaxseed gum (0%, 0.2%, 0.4%, 0.6% and 0.8%) on the microstructure and physicochemical properties of starch in frozen dough using scanning electron microscopy (SEM), solid-state nuclear magnetic resonance (SSNMR) spectroscopy, X-ray diffraction (XRD), and rapid visco analysis (RVA). The aim was to reveal the potential mechanism underlying the effect of flaxseed gum on the quality improvement of frozen dough from the perspective of changes in starch characteristics of frozen dough. The results showed that after repeated freeze-thaw cycles, the surface of starch particles appeared sunken, the relative crystallinity of starch decreased, the double helix structure of starch molecules was destroyed, and consequently water molecules were more likely to enter starch particles, thus resulting in an increase in peak viscosity and final viscosity. The addition of flaxseed gum inhibited the formation of ice crystals in frozen dough and delayed the unwinding of the double helix structure of starch molecules, and the hydrogen bond interaction between flaxseed gum and starch molecules increased the relative crystallinity of starch (22.2%–23.8%). As a result, the peak viscosity of starch decreased from 2409.5 mPa·s to 2247.2–2288.5 mPa·s, and the gelatinization temperature gradually increased. In conclusion, flaxseed gum delayed the damage of starch in dough caused by repeated freeze-thaw cycles, thereby protecting frozen dough.