Peleg Micha, Normand Mark D
Department of Food Science, University of Massachusetts, Amherst MA 01003, United States.
Department of Food Science, University of Massachusetts, Amherst MA 01003, United States.
Food Res Int. 2015 Sep;75:174-181. doi: 10.1016/j.foodres.2015.06.005. Epub 2015 Jun 5.
When a vitamin's, pigment's or other food component's chemical degradation follows a known fixed order kinetics, and its rate constant's temperature-dependence follows a two parameter model, then, at least theoretically, it is possible to extract these two parameters from two successive experimental concentration ratios determined during the food's non-isothermal storage. This requires numerical solution of two simultaneous equations, themselves the numerical solutions of two differential rate equations, with a program especially developed for the purpose. Once calculated, these parameters can be used to reconstruct the entire degradation curve for the particular temperature history and predict the degradation curves for other temperature histories. The concept and computation method were tested with simulated degradation under rising and/or falling oscillating temperature conditions, employing the exponential model to characterize the rate constant's temperature-dependence. In computer simulations, the method's predictions were robust against minor errors in the two concentration ratios. The program to do the calculations was posted as freeware on the Internet. The temperature profile can be entered as an algebraic expression that can include 'If' statements, or as an imported digitized time-temperature data file, to be converted into an Interpolating Function by the program. The numerical solution of the two simultaneous equations requires close initial guesses of the exponential model's parameters. Programs were devised to obtain these initial values by matching the two experimental concentration ratios with a generated degradation curve whose parameters can be varied manually with sliders on the screen. These programs too were made available as freeware on the Internet and were tested with published data on vitamin A.
当一种维生素、色素或其他食物成分的化学降解遵循已知的固定顺序动力学，且其速率常数的温度依赖性遵循双参数模型时，那么至少在理论上，有可能从食品非等温储存期间确定的两个连续实验浓度比中提取这两个参数。这需要求解两个联立方程的数值解，这两个联立方程本身又是两个微分速率方程的数值解，需要为此专门开发一个程序。一旦计算出来，这些参数可用于重建特定温度历程下的整个降解曲线，并预测其他温度历程下的降解曲线。采用指数模型来描述速率常数的温度依赖性，在升温和/或降温振荡温度条件下，用模拟降解对该概念和计算方法进行了测试。在计算机模拟中，该方法的预测对于两个浓度比中的微小误差具有鲁棒性。进行计算的程序已作为免费软件发布在互联网上。温度曲线可以作为一个代数表达式输入，该表达式可以包含 “If” 语句，也可以作为一个导入的数字化时间-温度数据文件输入，由程序将其转换为一个插值函数。求解这两个联立方程的数值解需要对指数模型的参数进行接近的初始猜测。设计了一些程序，通过将两个实验浓度比与一条生成的降解曲线进行匹配来获得这些初始值，该降解曲线的参数可以通过屏幕上的滑块手动改变。这些程序也作为免费软件发布在互联网上，并已用关于维生素A的已发表数据进行了测试。
