紫甘蓝花色苷稳定性及热降解动力学研究

为有效控制紫甘蓝加工过程中花色苷的降解，研究了pH、温度、光照、金属离子及外源添加物对花色苷稳定性的影响。实验表明，紫甘蓝花色苷稳定性受pH、温度和光照影响较大，pH2.0左右的花色苷5 h保存率仍有92.92%±0.69%、40℃下避光5 h花色苷保存率有70.50%±0.52%，花色苷稳定性较强；添加不同浓度的金属离子（K+、Mg2+、Na+）低浓度Fe3+（0.01~0.02 g/mL）及抗坏血酸（0.03 g/mL）、蔗糖和乳糖均可提高花色苷稳定性；氧化剂H₂O₂及还原剂Na₂SO₃、高浓度Fe3＋（0.03~0.04 g/mL）和抗坏血酸（0.09和0.12 g/mL）均加快花色苷降解，且降解速率随浓度增大而增加。花色苷热降解符合一级动力学，降解速率随温度升高而增加，半衰期随之减小，50℃ pH2.0的t_1/2最大为67.28 h，活化能最大为39.16 kJ/mol，为吸热非自发反应。采用紫甘蓝花色苷加工产品时，应尽量使温度低于40℃或者控制pH在2.0左右、选择提升或者不影响花色苷稳定性的辅料，于避光环境下操作及储存。

Stability and Degradation Kinetics of Anthocyanins from Red Cabbage

In order to effectively control the degradation of anthocyanins during deep processing of red cabbage,the effects of pH,temperature,light,metal ions and external additives on the stability of anthocyanins were studied.Experiments showed that the stability of red cabbage anthocyanins could be greatly affected by pH,temperature and light.The 5 h retention rate of anthocyanins at pH2.0 was 92.92%±0.69%,and the 5 h retention rate of anthocyanins at a temperature of 40℃in the dark was 70.50%±0.52%,which showed a strong stability of anthocyanin.The stability of anthocyanins could be improved by adding different concentrations of metal ions including K⁺,Mg²⁺ and Na⁺,low concentrations of Fe^3+(0.01~0.02 g/mL)and ascorbic acid(0.03 g/mL),saccharose and lactose.The oxidizing agent of H₂O₂,the reducing agent of Na₂SO₃,high concentrations of Fe³⁺(0.03~0.04 g/mL),and ascorbic acid(0.09 and 0.12 g/mL)would accelerate the degradation of anthocyanins while the degradation rate would rise as the concentration increased.The thermal degradation reaction of anthocyanins was in accordance the first-order kinetics,the rate of degradation would rise as the temperature rose and the half-time period was reduced.The maximum of t 1/2 was 67.28 h at 50℃pH2.0,and the maximum activation energy was 39.16 kJ/mol.And the thermal degradation reaction was endothermic non-spontaneous reaction.The temperature should be controlled at a degree of no more than 40℃or the pH should be controlled at a value around 2.0 when using red cabbage anthocyanins to process products and excipients that improves or do not affect the stability of anthocyanins should be selected.The product should be processed and stored at a dark environment.