牡丹花色苷的热稳定性和降解动力学

研究了pH值和温度对牡丹花色苷热稳定性的影响。动力学数据分析表明,牡丹花色苷的热降解符合一级反应动力学模型。在70～90℃条件下,当pH值为2.6、3.0、3.6、4.0和4.6时,牡丹花色苷的半衰期分别为27.0～7.9、32.1～8.5、27.9～8.9、35.9～9.4和27.3～10.7h。提高温度,花色苷降解反应速率增大;降解反应速率常数与温度的关系附合Arrhenius公式,反应活化能为48.4～69.4kJ/mol。牡丹花色苷单体的降解速率依次为矢车菊-3-O-二葡萄糖苷芍药-3-O-葡萄糖苷矢车菊-3,5-O-二葡萄糖苷芍药-3,5-O-二葡萄糖苷。牡丹花色苷降解生成褐色物质,褐变指数随加热时间的延长、加热温度的升高、pH值的增大而增大。

Thermal Stability and Degradation Kinetics of Anthocyanin in Tree Penoy Extract

Anthocyanin stability of tree penoy was evaluated under different pH and temperature conditions during heating. Analysis of kinetic data suggests a first-order reaction for the degradation of tree penoy anthocyanin with the half-lives of 27.0 to 7.9, 32.1 to 8.5, 27.9 to 8.9, 35.9 to 9.4 and 27.3 to 10.7 h for samples at pH 2.6, 3.0, 3.6, 4.0 and 4.6 between 70 and 90 ℃, respectively. Increasing temperature from 70 to 90 ℃, it enhanced the degradation of anthocyanin during heating. The temperature-dependent degradation was adequately modeled on the Arrhenius equation. The activation energy values for the degradation of tree penoy anthocyanin at different pH values(2.6～4.6) ranged from 48.4 to 69.4 kJ/mol. The first order kinetic constants show the following decreased order for individual anthocyanins:cyanidin 3-O-glucoside＞peonidin 3-O-glucoside＞cyanidin 3,5-di-O-glucoside＞peonidin 3,5-di-O-glucoside. Tree penoy anthocyanin degradation involves in brown pigment formation. The browning index increased with increasing heating time, temperature and pH.