热烫温度与pH值对香椿维生素C稳定性的影响
Effects of Blanching Temperature and pH on the Stability of Vitamin C of Toona sinensis

为了研究香椿热烫过程中维生素C的变化规律，分析了不同热烫温度(90、95℃与100℃)和pH值(5.5、6.0与6.5)对香椿维生素C保存率的影响。结果表明，香椿维生素C的稳定性易受温度和pH值的影响，且热烫温度对其的影响程度大于pH值的影响程度。升高热烫温度或增大pH值，均使香椿维生素C保存率降低，其热降解遵循一级动力学模型，其降解的活化能分别为62.022、58.489、54.741 kJ？moL-1。相同pH值条件下，升高热烫温度，维生素C热降解速率常数增大，其半衰期缩短。增加pH值，维生素C热降解速率常数增大，其半衰期缩短。香椿加工中适当降低热烫温度及pH值有助于减少维生素C损失和延长维生素C保存时间，尤以降低烫漂温度效果更佳。
To investigate thermal degradation kinetics of vitamin C in tender leaves of Toona sinensis during blanching, the effects of temperature on vitamin C degradation were measured at 90, 95 and 100℃with pH values of 5.5, 6.0 and 6.5, respectively. The results indicated that temperature and pH are important factors for the stability of vitamin C in the tender leaves of T. sinensis, and the influence of blanching temperatures was stronger pH. With the increase of blanching temperature and pH, the retention rate of vitamin C declined. Moreover, the degradation of vitamin C followed a first-order reaction with the activation energy (Ea) of 62.022, 58.489, and 54.741 kJ？moL-1. Increasing blanching temperature at the same pH value, or raising pH value at the same blanching temperature would increase the degradation rate constant and reduce half-life value of vitamin C. Moderately decreasing blanching temperature and pH value, especially reducing blanching temperature were favorable for protecting vitamin C