The Ohio State University, Dept of Food Science and Technology, 2015 Fyffe Ct., Columbus, OH 43210-1007, United States.
Science Group, Mars Wrigley Confectionary Inc., 800 High St, Hackettstown, NJ 07840, United States.
Food Chem. 2019 Jan 15;271:497-504. doi: 10.1016/j.foodchem.2018.07.096. Epub 2018 Jul 17.
Purple sweet potato, a source of acylated cyanidin and peonidin derivatives, is commercially available as a food colorant. Our objectives were to determine molar absorptivities (ε), spectral and colorimetric properties of purple sweet potato anthocyanins. Anthocyanins were isolated by semi-preparative HPLC, weighed, dried, and redissolved in acidic methanol or water. Anthocyanins were diluted in pH 1-9; ε, spectra, and color were measured on the methanolic and aqueous solutions. Higher ε were obtained in 0.1% HCl methanol (10,797-31,257 L/(mol × cm)) than in aqueous solution pH 1 (8861-24,303 L/(mol × cm)). Peonidin-3-sophoroside-5-glucoside had greatest ε in pH 1, but in alkaline pH, ε of acylated Peonidin-3-sophoroside-5-glucoside derivatives were greatest. Generally monoacylation decreased ε while diacylation increased ε. Location of acylation also affected ε of two Peonidin isomers (pH 1: 15,999 and 21,011 L/(mol × cm)). All anthocyanins expressed red-pink hues (330°-13.2°) in acidic pH and blues (230°-262°) in alkaline pH.
紫薯是酰化矢车菊素和芍药素衍生物的来源，可作为食品着色剂在商业上使用。我们的目标是确定紫薯花色苷的摩尔吸光系数 (ε)、光谱和比色特性。花色苷通过半制备高效液相色谱法分离、称重、干燥并重新溶解在酸性甲醇或水中。将花色苷稀释在 pH 1-9 范围内；在甲醇和水溶液中测量 ε、光谱和颜色。在 0.1% HCl 甲醇中（10,797-31,257 L/（mol×cm））获得的 ε 值高于 pH 1 的水溶液（8861-24,303 L/（mol×cm））。矢车菊素-3-槐糖苷-5-葡萄糖苷在 pH 1 时具有最大的 ε 值，但在碱性 pH 下，酰化矢车菊素-3-槐糖苷-5-葡萄糖苷衍生物的 ε 值最大。一般来说，单酰化会降低 ε 值，而二酰化会增加 ε 值。酰化位置也会影响两种芍药素异构体的 ε 值（pH 1：15,999 和 21,011 L/（mol×cm））。所有花色苷在酸性 pH 下呈现红粉色调（330°-13.2°），在碱性 pH 下呈现蓝色调（230°-262°）。
