Effect of freeze-thaw treatment on the structure and texture of soft and firm tofu

• More than 50% of tofu is used by consumers after a freeze-thaw treatment. This freeze-thaw treatment may lead to changes in the internal structure of tofu.
• Freeze-thaw treatments on tofu may increase hardness, springiness, cohesiveness and gumminess, and may match consumer preferences on the textural properties.

The effects of freeze-thaw treatments on the microstructural and textural properties in two kinds of commercial tofu were studied. Tofu samples obtained from a commercial supplier were placed in a freezer at −16 °C for various times, then removed and thawed at 20 °C for 20 min. Subsequently, the samples were examined by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) to assess the structural changes during the freeze-thaw treatment. Static compression tests and texture profile analysis were conducted on both freeze-thawed and fresh tofu samples. An analysis of the tofu structure based on the Gibson-Ashby model indicated that freeze-thawed tofu exhibits a reduction in water content compared to fresh tofu. The texture profile analysis results indicated that tofu was harder, springer, gummier and more cohesive after the freeze-thaw treatment. This increase in textural properties of tofu may satisfy consumer preferences for a harder and springier tofu.