酸催化糖转化为5-羟甲基糠醛的动力学分析

在食品中，磷酸、柠檬酸等酸味物质可催化葡萄糖、果糖等甜味物质转化为5-羟甲基糠醛(5-HMF)。本研究中，将糖酸混合溶液放于安瓿瓶中，采用油浴加热，三种反应温度分别为373 K、393 K、413 K，以HPLC测定了加热时间8 h内的糖酸体系中5-HMF浓度随着时间的变化；利用origin 8.0对数据进行拟合，建立动力学模型。最终发现无机三元酸磷酸的催化效率高于有机三元酸柠檬酸，果糖转化程度高于葡萄糖。在葡萄糖磷酸体系(GP)、葡萄糖柠檬酸体系(GL)、果糖磷酸体系(FP)、果糖柠檬酸体系(FL)中，5-HMF的浓度随着时间的延长呈直线上升，符合零级动力学模型。动力学分析得到四种反应体系的反应活化能(Ea)分别为109.16 kJ/mol、121.09 kJ/mol、102.89 kJ/mol、112.36 kJ/mol，GP体系中Ea最高，FL体系中最低。在糖酸食品热加工过程中，磷酸、果糖的含量对食品中的5-HMF含量影响很大。
Acids such as phosphoric acid and citric acid in food can catalyze the transformation of sweet substances including glucose and fructose, into 5-hydroxymenthylfurfual (5-HMF). In this study, different sugar-acid solutions, namely, glucose-phosphate acid (GP), glucose-citric acid (GL), fructose-phosphate acid (FP), and fructose-citric acid (FL) systems were placed in ampoules and heated using an oil bath at three reaction temperatures: 373 K, 393 K and 413 K. 5-HMF concentration in the sugar-acid systems over time were monitored using high-pressure liquid chromatography (HPLC) during the eight-hour heating period. The formation kinetics model was estabishedby Origin 8.0 software. The catalytic efficiency of inorganic ternary phosphate acid was found to be higher than that of organic ternary citric acid. The conversion rate of fructose was higher than that of glucose. The concentrations of 5-HMF increased linearly with reaction time for all four sugar-acid systems tested, in accordance with the zero-order kinetics model, the reaction activation energy values were 109.16, 121.09, 102.89, and 112.36 kJ/mol, respectively, with highest values in GP and lowest values in FL system. Thus, phosphoric acid and fructose content had a major impact on 5-HMF concentration of sugar-acid food during thermal processing.