巧克力中脂肪酸组成及反式脂肪酸含量的分析

目的建立测定巧克力中脂肪酸组成和反式脂肪酸含量的气相色谱方法。方法采用氢氧化钾-甲醇甲酯化方法,将甘油三酯转化为脂肪酸甲酯,并使用气相色谱-氢火焰离子化检测器进行分析。结果以三油酸甘油三酯为模型化合物,确定甲酯化效率为99.8%。使用面积归一化定量方法,对市面上不同品牌、不同种类的5种巧克力进行分析。巧克力油脂中主要脂肪酸为棕榈酸、硬脂酸和油酸,含量范围分别为:25%~27%、32%~35%及30%~32%;反式脂肪酸含量范围为0.4%~1.1%(以油脂中含量计)。结论该方法简单快速,适合巧克力油脂中脂肪酸组成和反式脂肪酸含量的分析。

Analysis of fatty acids composition and trans-fatty acids content in chocolate

Objective To build testing method for analyzing the fatty acid composition and the trans-fatty acids content in chocolate. Methods Based on the esterification method of potassuim hydroxide-methanol, the triglycerides were transferred to fatty acid methyl esters, which were analyzed by gas chromatography/ flame ionization detector (GC/FID). Results With glycerol trioleate as research model, the esterification efficiency was determined to be about 99.8%. With the quantitation method with area normalization, 5 chocolate samples with different brands and different varieties were tested, it showed that palmitic acid, stearic acid and oleic acid were the 3 main fatty acids in chocolate, and their content were 25%~27%, 32%~35% and 30%~32% respectively. Besides, the amount of tans-fatty acids ranged from 0.4% to 1.1% in chocolate. Conclusion The developed method was easy to implement and could be applied to the fatty acid analysis in chocolate.