核桃外果皮棕色素的提取纯化及其稳定性研究

提取、纯化核桃外果皮棕色素,并研究其稳定性。采用溶剂提取法提取得到棕色素粗品,利用盐酸沉淀法和乙醇沉淀法纯化棕色素粗品,并且研究了pH、氧化剂、还原剂、温度、金属离子、食品添加剂对纯化色素稳定性的影响。结果表明,核桃外果皮棕色素的最佳提取溶剂为水,不溶于非极性溶剂,通过盐酸沉淀法和乙醇沉淀法纯化后分别制得色素Ⅰ和色素Ⅱ,色素Ⅰ提取率为6.2%;色素Ⅱ提取率为5.3%。色素Ⅰ和色素Ⅱ性质相近,最大吸收波长均为570 nm和670 nm,两种色素在酸性条件下均有沉淀产生,碱性条件下颜色加深。双氧水使其褪色,而亚硫酸钠不影响其稳定性;色素Ⅰ耐高温,色素Ⅱ在80℃下较稳定;金属离子Na^＋、Ca^2＋、Cu^2＋、Zn^2＋、Mg^2＋对色素色泽无明显影响,而Fe^3＋、Al^3＋、Pb^2＋对其稳定性影响较大;食品添加剂柠檬酸、维生素C、山梨酸钾、氯化钠、苯甲酸钠对色素无不良影响,而蔗糖会影响两种色素的稳定性。首次提取纯化制得核桃外果皮棕色素,并确定其最大吸收波长,因原料易得,生产工艺简单,并可用于工业化生产,所以核桃外果皮棕色素是一种很有推广价值的天然色素。

Study on the Extraction, Purification and Stability of Brown Pigment in Walnut Outer Peel

To extract, purify and study the stability of the brown pigment in walnut outer peel. The brown pigment could be extracted by solvent extraction, and its purified pigment could be obtained with the method of ethanol-precipitation and hydrochloric acid-precipitation, and the influence to stability of the purified pigment by pH, oxidizing agent, reducing agent, temperature, metal ion, and food additive was studied. The results showed that the pigment dissolved easily in water, but undissolved in noapolar solvent. Pigment I and pigment II could be obtained with the method of ethanol-precipitation and acid-precipitation, the extracting rate of them was 6.2% and 5.3% respectively. The biggest absorption wave length was 570 nm and 670 nm. There were sediment when pH〈6.0, and Under alkaline conditions they became darker in color. Hydrogen peroxide bleached it, and the sodium didn＇ t affect its stability. Pigment I was also at a high temperature stability, pig- ment II in a more stable below 80 ℃. Metalions Na^＋、Ca^2＋、Cu^2＋、Zn^2＋、Mg^2＋ had no significant impact on the pigment color, and Fe^3＋、Al^3＋、Pb^2＋ had a greater impact on its stability. Citric acid, vitamin C, potassium sorbate, sodium chloride, sodium benzoate had no adverse impact on the pigment, and the sugar will affect the stability of the two pigment. The author extracted and purified the brown pigment in walnut outer peel first time, and deftnited its maximum absorption wavelength. Owing to easy to get the raw materials, production technology is simple, can be used for industrial production, so the brown pigment of walnut epicarp is a great generalization value in the natural pigment.