Corradini Maria G, Peleg Micha
Department of Food Science, Chenoweth Laboratory, University of Massachusetts, Amherst, 01003, MA, USA.
Crit Rev Food Sci Nutr. 2006;46(6):489-517. doi: 10.1080/10408390600758280.
Isothermal acrylamide formation in foods and asparagine-glucose model systems has ubiquitous features. On a time scale of about 60 min, at temperatures in the approximate range of 120-160 degrees C, the acrylamide concentration-time curve has a characteristic sigmoid shape whose asymptotic level and steepness increases with temperature while the time that corresponds to the inflection point decreases. In the approximate range of 160-200 degrees C, the curve has a clear peak, whose onset, height, width and degree of asymmetry depend on the system's composition and temperature. The synthesis-degradation of acrylamide in model systems has been recently described by traditional kinetic models. They account for the intermediate stages of the process and the fate of reactants involved at different levels of scrutiny. The resulting models have 2-6 rate constants, accounting for both the generation and elimination of the acrylamide. Their temperature dependence has been assumed to obey the Arrhenius equation, i.e., each step in the reaction was considered as having a fixed energy of activation. A proposed alternative is constructing the concentration curve by superimposing a Fermian decay term on a logistic growth function. The resulting model, which is not unique, has five parameters: a hypothetical uninterrupted generation-level, two steepness parameters; of the concentration climbs and fall and two time characteristics; of the acrylamide synthesis and elimination. According to this model, peak concentration is observed only when the two time constants are comparable. The peak's shape and height are determined by the gap between the two time constants and the relative magnitudes of the two "rate" parameters. The concept can be extended to create models of non-isothermal acrylamide formation. The basic assumption, which is yet to be verified experimentally, is that the momentary rate of the acrylamide synthesis or degradation is the isothermal rate at the momentary temperature, at a time that corresponds to its momentary concentration. The theoretical capabilities of a model of this kind are demonstrated with computer simulations. If the described model is correct, then by controlling temperature history, it is possible to reduce the acrylamide while still accomplishing much of the desirable effects of a heat process.
食品及天冬酰胺 - 葡萄糖模型体系中丙烯酰胺的等温形成具有普遍特征。在约60分钟的时间尺度上，温度在大约120 - 160摄氏度范围内时，丙烯酰胺浓度 - 时间曲线呈特征性的S形，其渐近水平和斜率随温度升高而增加，而对应于拐点的时间则减少。在大约160 - 200摄氏度范围内，曲线有一个明显的峰值，其起始、高度、宽度和不对称程度取决于体系组成和温度。模型体系中丙烯酰胺的合成 - 降解最近已由传统动力学模型进行了描述。这些模型考虑了该过程的中间阶段以及不同详细程度下反应物的去向。所得模型有2 - 6个速率常数，兼顾了丙烯酰胺的生成和消除。假定它们的温度依赖性服从阿仑尼乌斯方程，即反应中的每一步都被视为具有固定的活化能。一种提出的替代方法是通过在逻辑斯蒂增长函数上叠加一个费米衰变项来构建浓度曲线。所得模型并非唯一，有五个参数：一个假设的不间断生成水平、两个斜率参数（浓度上升和下降的）以及两个时间特征（丙烯酰胺合成和消除的）。根据该模型，只有当两个时间常数可比时才会观察到峰值浓度。峰值的形状和高度由两个时间常数之间的差距以及两个“速率”参数的相对大小决定。该概念可扩展以创建非等温丙烯酰胺形成的模型。基本假设（尚未经过实验验证）是，在对应于其瞬时浓度的某个时刻，丙烯酰胺合成或降解的瞬时速率是该瞬时温度下的等温速率。通过计算机模拟展示了这种模型的理论能力。如果所描述的模型正确，那么通过控制温度历程，有可能在减少丙烯酰胺的同时仍实现热加工的许多期望效果。
