豆浆在凝固过程中的动态流变特性研究

Dynamic Rheological Properties of Soymilk during the Coagulation Process

摘要:

为了研究豆腐的凝固工序，实现豆腐的规格化和标准化生产，本研究对豆浆在凝固过程中的动态流变特性进行了研究，并进行了动力学分析。在凝固温度分别为75 ℃、80 ℃、85 ℃时进行动态时间扫描，得出豆浆的凝固过程由两段一级反应组成且符合连续一级反应模型；第一段反应速率远远大于第二段反应速率；根据弹性模量和黏性模量计算所得活化能分别为19.19×101 kJ/mol和8.67×101 kJ/mol；当温度小于70 ℃时，豆浆不能形成豆腐凝胶；当温度在75 ℃时，弹性模量G'和黏性模量G"相交，豆浆的凝胶温度为75 ℃。通过动态温度扫描得出豆浆的凝固过程可分为三个阶段：诱导阶段（65~70 ℃），弹性模量G'和黏性模量G"缓慢增大，豆浆体系中有絮状沉淀生成；加速阶段（70~92 ℃），弹性模量G'和黏性模量G"急剧增大；稳定阶段（温度大于92 ℃），弹性模量G'和黏性模量G"趋于稳定，凝胶反应结束，豆腐凝胶形成。

Abstract:

To achieve normalization and standardization of tofu production, the dynamic rheological properties of soymilk and related kinetics during the coagulation process were investigated. Dynamic time scanning was performed at 75 ℃, 80 ℃, and 85 ℃; coagulation of soymilk consisted of two first-order reactions and matched a consecutive first-order reaction model. The rate constant in the first stage was much higher than that in the second stage and the calculated activation energy values from elastic modulus and viscous modulus were 19.19 × 101 kJ/mol and 8.67 × 101 kJ/mol, respectively. Tofu gel could not be formed from soymilk at temperatures below 70 ℃. The elastic modulus G'-t and viscous modulus G"-t curves intersected at 75 ℃, which indicated that the coagulation temperature of soymilk was 75°C. Through dynamic temperature scanning, it was found that the coagulation process could be divided into three stages: induction stage (65 ℃~70 ℃), acceleration stage (70 ℃~92 ℃), and stabilization stage (above 92 ℃). The elastic modulus G' and viscous modulus G" increased slowly and a small amount of flocculent precipitate was generated in soymilk during induction; G' and G" increased rapidly during acceleration and tended to be stable during stabilization, indicating that the coagulation process was complete and tofu gel was formed.