Abstract:The coagulation process is an extremely crucial step during preparation of plaster tofu as the quality and yield of tofu are influenced by the gelling properties during this process. The gelling properties of plaster tofu were characterized by dynamic rheological testing, texture analysis, and scanning electron microscopy, considering changes in coagulation temperature and calcium sulfate concentration. Dynamic viscoelastic testing showed that the highest storage modulus of tofu gel is obtained at 85 ℃ regardless of the calcium sulfate concentration, and the relationship between storage modulus and coagulant temperature followed first-order reaction kinetics. Texture analysis revealed that the hardness of tofu increased with increasing coagulation temperature at a calcium sulfate concentration of 20~50 mM. At the calcium sulfate concentration of 20 mM or 30 mM, the tofu gel was fragile with a loose gel network, which gradually became thicker and more elastic with increased pore size as the coagulation temperature increased, and the highest water holding capacity was reached at 85 ℃. At the calcium sulfate concentration of 40 mM or 50 mM, elasticity of the tofu gel decreased with an increase in coagulation temperature; the tofu gel was thick and dense, and larger pore size and irregular morphology were observed with an increase in coagulation temperature. The highest water holding capacity of tofu gel was obtained at 80 ℃ and 75 ℃.
