Effects of Vacuum Freezing Drying and Hot-air Drying on the Quality Characteristics and Microstructure of Yuba Stick

To solve the problem of quality deterioration caused by easy browning in drying of yuba stick, yuba stick made from Jiusan yellow soybean, a specialty of northeast Heilongjiang, was used as the research object. Vacuum freeze drying (VFD) and hot air drying (HAD) were used for dry processing of yuba stick, to obtain the effects of the two drying methods on the quality characteristics, microstructure, and other parameters of yuba stick. The goal was to provide theoretical support for selecting appropriate factory drying methods. The results showed that the effect of the two drying processes on the protein content of yuba stick reached the level of significant difference (P<0.05) and the differential effect on the L^*, a^* and b^* values of yuba stick was highly significant (P<0.01). The VFD-dried yuba stick exhibited the lowest hardness, best chewiness, uniform quality, and highest sensory evaluation score compared to the HAD-dried yuba stick. The rehydration ratio of VFD-dried yuba stick reached 1.90 g·g⁻¹ at 1 min. The VFD-dried yuba stick had the lowest hardness, best chewiness, uniform quality and highest sensory evaluation score as compared to HAD-dried yuba stick. In summary, vacuum freeze-drying is suitable for dry processing of yuba stick with high protein content.