Modeling and Experimental Analysis of Tofu-Drying Kinetics

Drying critically shapes tofu’s texture, structure, and final appearance, whether it occurs during cooking or is applied intentionally in reprocessing. This study aimed to characterize the drying kinetics of tofu through experimental analysis and through modeling. Tofu samples were dried at temperatures ranging from 40 °C to 90 °C using a convective drying tunnel and an oven. Shrinkage and color changes were analyzed. Empirical models, a shrinking-core model and a newly developed oven-cooking model were tested against experimental data. The drying kinetics exhibited a constant and a decreasing rate phase, which were separated by a water content threshold of 2.56 kgW/kgDS. Tofu undergoes non-enzymatic browning and exhibited total shrinkage of 0.38. These physical changes were more significant at lower drying temperatures when the product was dried below a water content of 1.39 kgW/kgDS. The logarithmic model provided the best fit (R2≥0.9920) to the experimental data. However, the cooking model shows good results as well (R2=0.9678) and offers physical validity. This study provides evidence that the drying mechanisms of tofu are not temperature-dependent within the studied range. It also emphasizes the importance of drying time over drying temperature in the physical changes of the product. The successful fit of the cooking model highlights the link between drying and cooking processes, suggesting potential applications in both areas.