Insights Into the Mechanism of Water Migration During Freeze-Thaw Cycles on the Quality Deterioration of Frozen Dough Steamed Buns.

To elucidate the mechanism of water migration in frozen dough steamed buns under varying numbers of freeze-thaw cycles (FTCs) (0, 2, 4, 6, and 8), this study explored the correlation between water migration and quality deterioration. With increasing FTCs, the ordered protein structure was disrupted, and the gelatinization enthalpy of the frozen dough steamed buns decreased. Meanwhile, depolymerization of the protein intact structure occurred. The proportion of α-helices decreased significantly from 22.95% to 12.14% (p < 0.05). The proportion of β-turns decreased significantly from 34.83% to 33.74% (p < 0.05), whereas the proportion of random coils increased significantly from 13.79% to 25.60% (p < 0.05). Additionally, the internal microstructure and gluten network structure were disrupted. These weakened the water-binding capacity of the frozen dough steamed buns. The migration of bound water to free water led to significant increases in the proportion of freezable water, fusion enthalpy, and water activity (p < 0.05), whereas the total moisture content decreased significantly by 14.07% (p < 0.05). Ultimately, these variations resulted in a decline in the gas-holding capacity, accompanied by a significant reduction in specific volume, cohesiveness, and resilience (p < 0.05). In contrast, hardness, gumminess, and chewiness increased significantly (p < 0.05). This study clarified the mechanisms underlying the quality deterioration of frozen dough steamed buns during FTC treatment, providing a theoretical basis for improving the quality and freeze-thaw stability of such flour-based frozen products. PRACTICAL APPLICATIONS: This work offers valuable insights for improving the freeze-thaw stability, overall quality, and industrial development of frozen dough steamed buns.