通过Box-Behnken试验设计和响应面分析法，对紫薯皮色素的提取条件进行了优化，并且研究了各种物理及化学因素对紫薯皮色素稳定性的影响。结果，得出最佳提取条件为：酸醇体积比1∶1（0.5%柠檬酸酸化）、料液比1∶60（g/mL）、提取温度50℃、提取时间20 min。在此优化方案条件下，理论吸光度预测值为0.843，实际吸光度为0.838。紫薯皮色素的稳定性研究结果显示：日光暴晒条件下光稳定性比较差，自然光和避光条件下，稳定性良好；4～60℃的温度范围内具有非常好的热稳定性；紫薯皮色素在含有K＋、Ca2＋、Na＋、Zn2＋等金属离子的溶液中表现比较稳定的状态，在含有Mg2＋、Cu2＋、Mn2＋、Fe3＋等金属离子的溶液中产生沉淀；酸性条件有利于紫薯皮色素的稳定性，而碱性条件不利于紫薯皮色素的稳定性；最大安全使用范围内，紫薯皮色素稳定性几乎不会受到苯甲酸、山梨酸等一系列常用食品添加剂溶液的影响，可作为食品着色剂。%Box-Behnken experimental design and response surface methodology were employed to optimize the conditions for extraction of purple sweet potato peel pigment. Also, the effect of various physicochemical factors on the stability of the pigment was addressed. The optimum extraction conditions were obtained as follows:0.5%citric acid:anhydrous ethanol at a volume ratio of 1:1 as extraction solvent;solid-to-solvent ratio, 1:60 (g/mL);temperature, 50℃;and time, 20 min. Under these conditions, the predicted absorbance value of the pigment solution was 0.843 and the experimental value was 0.838. The pigment was unstable under light and strong alkali conditions (pH>7). It was relatively stable at temperatures between 4 and 60℃. Metal ions including K+, Ca2+, Na+, Zn2+, Mg2+, Cu2+, Mn2+, and Fe3+were helpful in the degradation of the pigment. Within the safe dosage range, its stability was hardly affected by benzoic acid, sorbic acid, citric acid, sucrose, soluble starch, glucose, and sodium chloride. Therefore, it can be used as food coloring agent.
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