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 Dec;78:388-395. doi: 10.1016/j.foodres.2015.09.003. Epub 2015 Sep 11.
The shelf life of food and pharmaceutical products is frequently determined by a marker's concentration or quality index falling below or surpassing an assigned threshold level. Naturally, different chosen markers would indicate different shelf life for the same storage temperature history. We demonstrate that if there are two markers, such as two labile vitamins, the order in which their concentrations cross their respective thresholds may depend not only on their degradation kinetic parameters but also on the particular storage temperature profile, be it isothermal or non-isothermal. Thus, at least theoretically, the order observed in accelerated storage need not be always indicative of the actual order at colder temperatures, except where the two degradation reactions follow the same kinetic order and their temperature-dependence rate parameter is also the same. This is shown with simulated hypothetical degradation reactions that follow first or zero order kinetics and whose rate constant's temperature-dependence obeys the exponential model. It is also demonstrated with simulated hypothetical Maillard reaction's products whose synthesis rather than their degradation follows pseudo zero order kinetics. The software developed to do the simulations and calculate the thresholds crossing points has been posted on the Internet as a freely downloadable interactive Wolfram Demonstration, which can be used as a tool in storage studies and shelf life prediction. In principle, the methodology can be extended from two to any number of markers.
食品和药品的保质期通常由某种标志物的浓度或质量指标降至或超过规定阈值水平来确定。自然地，对于相同的储存温度历程，选择不同的标志物会表明不同的保质期。我们证明，如果存在两种标志物，比如两种不稳定的维生素，它们浓度越过各自阈值的顺序不仅可能取决于其降解动力学参数，还可能取决于特定的储存温度曲线，无论是等温的还是非等温的。因此，至少在理论上，加速储存中观察到的顺序不一定总能表明在较低温度下的实际顺序，除非这两种降解反应遵循相同的动力学级数且它们的温度依赖性速率参数也相同。这通过模拟遵循一级或零级动力学且其速率常数的温度依赖性服从指数模型的假设降解反应得以展示。还通过模拟假设的美拉德反应产物进行了展示，其合成而非降解遵循伪零级动力学。为进行模拟和计算阈值交叉点而开发的软件已作为可免费下载的交互式Wolfram演示发布在互联网上，可作为储存研究和保质期预测的工具。原则上，该方法可从两种标志物扩展到任意数量的标志物。
