油脂中总不饱和脂肪酸的紫外光谱测定

利用紫外光谱测定油脂中不饱和成分，以动物油为对照，主要分析检测了常见的7种植物油．本文确定了紫外谱图分析油脂的检测条件，将原始油配制成0．2％的环己烷溶液；以相似度为指标比较光谱曲线，验证该检测方法具有很好的重现性和特异性；用w检验法确定了共有峰，运用紫外谱图检测化合物共轭结构的原理，对各种油脂中总不饱和脂肪酸进行识别并计算相对含量．紫苏油和核桃油中的不饱和脂肪酸种类最丰富，紫苏油中不饱和双键数4的脂肪酸含量为核桃油的1．5倍，橄榄油中包含的不饱和脂肪酸主要为此种脂肪酸．其次，葵花籽油、玉米油、花生油、杏仁油的总不饱和脂肪酸含量依次递减，动物油中的不饱和脂肪酸未检出．经过碱皂化、甲酯化等方法处理后的样品中，不饱和脂肪酸的紫外吸收光谱特性明显减弱，因此该方法可以简单、快速、准确地测定油脂中的不饱和脂肪酸．

Detection of All Unsaturated Fatty Acids in Oil Based on Ultraviolet Spectra

The unsaturated components mainly in 7 kinds of vegetable oil were studied with ultraviolet spectra and analyzed against animal oil. The testing method was thus determined. 0.2% of the original oil with cyclohexane was first of all prepared. Comparisons of ultraviolet curves＇ features with similarity is an indicator showed that the method had excellent reproducibility and differentiae. The common peaks were identified with W testing method, and then all unsaturated fatty acids in different oil were recognized in spectrum and their relative contents were obtained by applying the principles of the conjugate structures of the compounds analyzed with ultraviolet spectra. The analytical results showed that the unsaturated fatty acids were the most abundant in perilla oil and walnut oil, though the content of fatty acid of unsaturated double bond number 4 in perilla oil was 1.5 times as much as in walnut oil, and this kind of fatty acid was the major of all unsaturated fatty acid in olive oil. The content of all unsaturated fatty acids in sunflower seed oil, corn oil, and peanut oil decreased successively, and no unsaturated fatty acids were detected in animal oil. The ultraviolet spectra characteristic of unsaturated fatty acids weak- ened obviously in the oil samples, after being pretreated with alkali, saponification, or transesterification. Therefore, this is an easy, fast, accurate method to determine the unsaturated fatty acids in oil.