Martins Sara I F S, Van Boekel Martinus A J S
Department of Agrotechnology and Food Sciences, Product Design and Quality Management Group, Wageningen University, P.O. Box 8129, 6700 EV, Wageningen, The Netherlands.
Carbohydr Res. 2003 Jul 29;338(16):1665-78. doi: 10.1016/s0008-6215(03)00174-5.
A kinetic model for N-(1-deoxy-D-fructos-1-yl)-glycine (DFG) thermal decomposition was proposed. Two temperatures (100 and 120 degrees C) and two pHs (5.5 and 6.8) were studied. The measured responses were DFG, 3-deoxyosone, 1-deoxyosone, methylglyoxal, acetic acid, formic acid, glucose, fructose, mannose and melanoidins. For each system the model parameters, the rate constants, were estimated by non-linear regression, via multiresponse modelling. The determinant criterion was used as the statistical fit criterion. Model discrimination was performed by both chemical insight and statistical tests (Posterior Probability and Akaike criterion). Kinetic analysis showed that at lower pH DFG 1,2-enolization is favoured whereas with increasing pH 2,3-enolization becomes a more relevant degradation pathway. The lower amount observed of 1-DG is related with its high reactivity. It was shown that acetic acid, a main degradation product from DFG, was mainly formed through 1-DG degradation. Also from the estimated parameters 3-DG was found to be the main precursor in carbohydrate fragments formation, responsible for colour formation. Some indication was given that as the reaction proceeded other compounds besides DFG become reactants themselves with the formation among others of methylglyoxal. The multiresponse kinetic analysis was shown to be both helpful in deriving relevant kinetic parameters as well as in obtaining insight into the reaction mechanism.
提出了N-(1-脱氧-D-果糖-1-基)-甘氨酸(DFG)热分解的动力学模型。研究了两个温度(100和120℃)和两个pH值(5.5和6.8)。测量的响应包括DFG、3-脱氧邻酮糖、1-脱氧邻酮糖、甲基乙二醛、乙酸、甲酸、葡萄糖、果糖、甘露糖和类黑素。对于每个系统，通过多响应建模，采用非线性回归估计模型参数即速率常数。将行列式准则用作统计拟合准则。通过化学洞察和统计检验(后验概率和赤池准则)进行模型判别。动力学分析表明，在较低pH值下，DFG的1,2-烯醇化更有利，而随着pH值升高，2,3-烯醇化成为更相关的降解途径。观察到的较低量的1-DG与其高反应活性有关。结果表明，DFG的主要降解产物乙酸主要通过1-DG降解形成。从估计参数还发现，3-DG是碳水化合物片段形成的主要前体，负责颜色形成。有迹象表明，随着反应进行，除DFG外的其他化合物自身也成为反应物，其中包括甲基乙二醛的形成。多响应动力学分析表明，它既有助于推导相关动力学参数，也有助于深入了解反应机理。
