紫甘蓝花色苷的热降解动力学研究

探讨在不同温度和pH条件下紫甘蓝花色苷的热稳定性和降解动力学。以80%乙醇浸提,D-101大孔吸附树脂分离纯化制备紫甘蓝花色苷,在50、60、70、80 ℃温度范围内,于不同pH(2.0~6.0)体系中测定不同时间点的花色苷含量,研究其热降解动力学参数和褐变指数。结果表明,紫甘蓝花色苷热稳定性和褐变反应受温度和pH的影响,且其降解速率与时间呈良好线性关系,符合一级动力学模型。随着温度的升高,不同pH下花色苷的半衰期t_1/2均呈下降趋势,最大值为83.51 h(50 ℃,pH3.0),最小值为4.43 h(80 ℃,pH6.0),且各pH(2.0~6.0)体系的活化能E_a依次为42.30、45.31、38.85、26.83、31.20 kJ/mol。此外,其褐变指数随热处理时间延长、温度升高及pH增大而增大。

Thermal degradation kinetics of anthocyanins from red cabbage

The thermal stability and degradation kinetics of anthocyanins from red cabbage at different temperatures and pH values were investigated. The anthocyanins from red cabbage were extracted by 80% ethanol aqueous solution and then purified with D-101 macroporous adsorption resin. Within the temperatures range of 50,60,70,80 ℃,the anthocyanins contents at different time points were measured at different pH(2.0~6.0)to investigate its thermal degradation kinetic parameters and browning index. Results showed that the thermal stability of anthocyanins from red cabbage was influenced by temperature and pH. The degradation rate was in good linear relation with time and followed first order reaction kinetics. With the increasing of temperature,the half-life(t_1/2)at different pH were declining,in which the maximum value was 83.51 h(50 ℃,pH3.0)and the minimum values was 4.43 h(80 ℃,pH6.0),and the activation energy(E_a)of reaction systems(pH2.0~6.0)were 42.30,45.31,38.85,26.83 and 31.20 kJ/mol,respectively. Besides,the browning index increased with the extension of heat treatment time and the increase of temperature and pH.