棉籽油脂肪酸甲酯化的方法及其脂肪酸含量分析

以新陆早39号以及新陆早50号的棉籽为材料,利用索氏提取仪提取其总油脂,分别采用三种常用的脂肪酸甲酯化方法:KOH-甲醇法,H₂SO₄-甲醇,14% BF₃-甲醇法进行甲酯化后,GC-MS上机分析;通过37种脂肪酸甲酯混标制定标准曲线,用外标法进行定量。结果表明:KOH-甲醇法甲酯化的脂肪酸GC-MS上机分析能检测到10种脂肪酸组分;H₂SO₄-甲醇与14% BF₃-甲醇法只能检测到6种。用KOH-甲醇法甲酯化后GC-MS测定表明,棉籽油脂肪酸以多不饱和脂肪酸的亚油酸为主,其次是饱和脂肪酸的棕榈酸以及单不饱和脂肪酸的油酸。在新陆早39号以及新陆早50号中,每克棉籽中亚油酸的含量分别达147.29 mg与163.2 mg,分别占其油脂含量的60.12%与60.83%;棕榈酸含量分别为65.05 mg与62.28 mg,分别占其油脂含量的26.55%与23.24%。油酸含量分别为24.79 mg与22.19 mg,分别占其油脂含量的10.12%和8.28%。结论:三种常用的脂肪酸甲酯化方法中,KOH-甲醇法更方便,快速,检测种类多,适用于棉籽脂肪酸的甲酯化。

Methods of methyl esterification and analysis of fatty acids content in cottonseed oil

The fatty acid composition in cottonseed of "Xinluzao 39" and "Xinluzao 50" methylated by three kinds of catalysts, KOH-methanol method, H₂SO₄-methanol and 14% BF₃-methanol methods, was determined by GC-MS. The quantitative standard curve was established by mixing 37 fatty acid methyl esters determinated by GC-MS, and the external standard method was used for quantitative determination. The results showed that there were 10 kinds of fatty acid composition in cottonseed oils, which could be detected on GC-MS analysis by the esterification of fatty acids with KOH-methanol. Only 6 kinds of fatty acid composition could be detected by H₂SO₄-methanol and 14% BF₃-methanol method. The results of GC-MS analysis after methyl esterification with KOH-methanol showed that the main fatty acids of cottonseed oil was linoleic acid, followed by palmitic acid and monounsaturated fatty acid of polyunsaturated fatty acids. The linoleic acid content per gram cottonseed was 147.29 mg and 163.2 mg in seed oil of Xinluzao 39 and Xinluzao 50, respectively, which accounted for 60.12% and 60.83% of its oil content. The oil also contained high level of palmitic acid, contents of which were 65.05 mg and 62.28 mg, accounting for 26.55% and 23.24% of their oil content respectively. The content of oleic acid was 24.79 mg and 22.19 mg, accounting for 10.12% and 8.28% of their oil content respectively. Among the three commonly used fatty acid methyl esterification methods, the KOH-methanol method was more convenient, rapid and had many kinds of tests. It was suitable for the methyl esterification of cottonseed fatty acids.