高压二氧化碳对桃果胶甲基酯酶活性的钝化效果与动力学研究

Inactivation Kinetics of Pectin Methylesterase from Peach under High Pressure Carbon Dioxide

采用高压二氧化碳技术(High Pressure Carbon Dioxide,HPCD)处理桃果胶甲基酯酶(Pectin Methylesterase,PME)粗酶液,分析了HPCD对粗酶液中PME的钝化效果及动力学,进一步比较了粗酶液和桃汁两种体系中PME对HPCD的敏感性。HPCD对粗酶液中PME具有较好的钝化效果,处理温度和压力的共同作用导致了PME活性降低,钝化动力学遵从一级动力学模型。随着处理压力和温度的提高,钝化速率逐渐增大,而指数递减时间则逐渐减小;在最优的处理条件(22MPa、55℃)下,HPCD钝酶的钝化速率和指数递减时间分别为0.408 8min-1和5.63min。温度为55℃时HPCD钝酶的压力敏感指数为16.40MPa,活化体积为-383.00cm3/mol;压强为15MPa时HPCD钝酶的温度敏感指数为13.30℃,活化能为1 845.86kJ/mol。比较HPCD对桃汁和粗酶液中PME的钝化效果,发现HPCD处理16min后(15MPa、55℃),桃汁中PME残存酶活在80%左右,而粗酶液中PME活性已完全钝化,表明桃汁体系中存在保护PME活性的因素,有关机制需要进一步研究。

The inactivation of pectin methylesterase(PME)from peach in buffer and juice by high pressure carbon dioxide(HPCD)was investigated.PME in buffer is effectively inactivated by HPCD,their residual activity decreases with the increase of pressure and temperature.The residual activity of the PME exhibited a fast decrease after a prolonged treatment time;their inactivation kinetics is adequately modeled by the first order kinetics model.With the increase of pressure and temperature,the kinetic rate constant increases and the decimal reduction time decreases for PME in buffer inactivated by HPCD.The Kinetic rate and the decimal reduction time are 0.408 8min-1 and 5.63 min respectively at the optimal condition(22MPa,55℃).The activation volume and the pressure sensitivity exponent of inactivation PME by HPCD at 55℃are-383.00cm3/mol and 16.40 MPa respectively.In contrst,the activation energy and the pressure sensitivity exponent at 15 MPa are 1 845.86kJ/mol and 13.30℃respectively.The residual activity of PME in peach juice is significantly greater than that in buffer after the same HPCD treatment,indicating that the original PME in the juice is less inactivated by HPCD.