Antifreeze Protective Effect of Winter Wheat Ice Structural Proteins on the Quality and Protein Properties of Frozen Tofu
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Abstract:
Frozen tofu is often associated with quality issues, such as coarse texture, inconsistent pore sizes, and even broken sections. Herein, ice balls were combined with phosphate buffer solution (PBS) to extract winter wheat ice structural proteins (WISPs). Based on the analysis, its thermal hysteresis activity (THA) was 0.46 ℃. The ice crystals in the solution were small and numerous, and exhibited a certain anti-freezing activity. When 1.00% of WISP was added to frozen tofu, the water holding capacity, rehydration capacity, cooking resistance, elasticity, and stretchability increased by 114.17%, 57.42%, 56.25%, 21.52%, and 23.71%, respectively, compared with those of the control, while the firmness and shear force decreased by 24.83% and 23.75%, respectively. The content of bound water, semi-bound water, and non-flowing water increased by 133.77%, 131.78%, and 26.41%, respectively. The cross section was smooth and delicate, the honeycomb was uniform, and the pore sizes were moderate. Compared with the control, the free sulfhydryl group content of the frozen tofu protein increased by Frozen tofu is often associated with quality issues, such as coarse texture, inconsistent pore sizes, and even broken sections. Herein, ice balls were combined with phosphate buffer solution (PBS) to extract winter wheat ice structural proteins (WISPs). Based on the analysis, its thermal hysteresis activity (THA) was 0.46 ℃. The ice crystals in the solution were small and numerous, and exhibited a certain anti-freezing activity. When 1.00% of WISP was added to frozen tofu, the water holding capacity, rehydration capacity, cooking resistance, elasticity, and stretchability increased by 114.17%, 57.42%, 56.25%, 21.52%, and 23.71%, respectively, compared with those of the control, while the firmness and shear force decreased by 24.83% and 23.75%, respectively. The content of bound water, semi-bound water, and non-flowing water increased by 133.77%, 131.78%, and 26.41%, respectively. The cross section was smooth and delicate, the honeycomb was uniform, and the pore sizes were moderate. Compared with the control, the free sulfhydryl group content of the frozen tofu protein increased by 37.50% and the content of disulfide bonds decreased by 29.79%. All components above 90 ku in the control group and 0.25% group had degraded. Except for the 0.75% and 1.00% groups, the low molecular weight components of the BS subunits in other groups were degraded. The contents of the AS and BS subunits in each group were lower than those in the 1.00% group, indicating that the protein components in the 1.00% group were the most stable. As an antifreeze protective agent, WISPs improved the quality and characteristics of the protein structure of frozen tofu, and exhibited an antifreeze protective effect. This result provides a theoretical basis for the application of antifreeze protein in frozen food.
