六种果皮原料果胶的理化及凝胶特性比较

为了解不同品种水果的果皮(柚子皮、西番莲皮、脐橙皮、石榴皮、榴莲皮)以及向日葵盘所提取果胶的理化和质构特性,研究了不同原料果胶的得率、色泽、果胶酸含量、甲氧基含量、酯化度、黏度及质构特性,特别是采用高效液相色谱准确测定了各类果胶的分子量。结果表明:柚子皮、向日葵盘和脐橙皮果胶质量分数较高,分别为18.06%、14.61%和14.43%;西番莲皮果胶质量分数为8.76%;而石榴皮及榴莲皮果胶质量分数较低(均<3%)。从分子量看,石榴皮、脐橙皮果胶分子量较大(>1000kDa),向日葵盘果胶分子量最小(483kDa)。此外,几种果胶的溶胶均属低黏度值果胶(<25厘泊),且在pH值为7.0时黏度最大、在pH值为5.0时黏度最小。结合凝胶质构分析表明:石榴皮果胶分子量最大,凝胶强度最大,但为高甲氧基果胶,且得率较低;而向日葵盘果胶分子量最小,但得率较高,且为低甲基果胶,在非糖及含糖体系中均可形成性能优良的凝胶,因此是生产果胶的良好原料。该文为果胶的生产及应用提供参考。

Comparison of physicochemical and gelation properties of pectins extracted from six pericarps

In order to supply useful information to guide the practical production of pectins, the pectins extracted from six pericarps (shaddock peel, passionflower peel, navel orange peel, pomegranate rind, durian shell, sunflower head) were studied for their physicochemical and gelation properties. The recovery, color, viscosity, pectic acid content, methoxy content, the degree of esterification and gelation properties of pectins from the six pericarps were determined. The molecular weights of pectins were exactly analyzed by HPLC. The results showed the pectins of shaddock peel, sunflower head, navel orange peel and passionflower peel were 18.06%, 14.61%, 14.43% and 8.76%, respectively, while those in pomegranate rind and durian shell were low (<3%). The molecular weights of pomegranate rind and navel orange peel pectin were larger than 1000 kDa, and that of the sunflower head was the lowest (483 kDa). Besides, these pectins demonstrated low viscosity (<25 centipoise), which was proved to be the highest at pH value 7.0 and the lowest at pH value 5.0. Pomegranate rind demonstrated the largest molecular weight and the strongest gelatin strength, which was high methoxy pectin, and the recovery was very low. As a comparison, pectins extracted from sunflower head exhibited low molecular weight, high recovery, which was low methoxy pectin, since it could form good gelatin with or without the presence of sugar, which was proved to be a good material for pectin production.