核磁共振碳谱测定天然鱼油和加工鱼油中 多不饱和脂肪酸的位置分布Determination of positional distribution of polyunsaturated fatty acids in natural and processed fish oil by 13C-NMR

Abstract

鱼油是n-3多不饱和脂肪酸的重要来源，为明确鱼油中多不饱和脂肪酸的位置分布，采用气相色谱法测定了4种天然鱼油和3种加工鱼油的总脂肪酸组成，并采用核磁共振碳谱（13C-NMR）分析其多不饱和脂肪酸的位置分布，同时运用Novozym 435醇解结合气相色谱分析了4种天然鱼油中甘油三酯上饱和脂肪酸（SFA）和单不饱和脂肪酸（MUFA）的位置分布。结果表明：加工鱼油中二十二碳六烯酸（DHA）含量为28.43%~76.63%，二十碳五烯酸（EPA）含量为12.72%~5637%，总体含量均高于天然鱼油；天然鱼油中DHA主要分布在sn-2位，sn-2 DHA相对含量为50.39%~63.71%，而加工鱼油中DHA则处于随机分布状态，sn-2 DHA相对含量为28.78%~36.76%；不同天然鱼油中SFA和MUFA没有明确分布规律。综上，鱼油的加工工艺可以提高DHA的含量但是改变了其在甘油三酯碳骨架的分布。Fish oil is a rich source of n-3 polyunsaturated fatty acids (PUFA). In order to clarify the positional distribution of PUFA in fish oil, gas chromatography (GC) was used to determine the total fatty acid composition of 4 kinds of natural fish oil and 3 kinds of processed fish oil, and 13C-nuclear magnetic resonance (13C-NMR) was used to analyze the positional distribution of PUFA. At the same time, the positional distribution of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) on triacylglycerol (TAG) in 4 natural fish oils were analyzed using the alcoholysis of Novozym 435 combined with GC. The results showed that the contents of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in processed fish oil generally higher than that in natural fish oil, with DHA content of 28.43%-76.63% and EPA content of 12.72%-5637%. DHA in natural fish oils was mainly esterified at the sn-2 position (relative content of sn-2 DHA 50.39%-63.71%), while that in processed fish oils was in a random distribution state (relative content of sn-2 DHA 28.78%-36.76%). There was no clear distribution pattern of SFA and MUFA in different natural fish oils. In conclusion, the processing technology of fish oil can increase the content of total DHA, but change the positional distribution of DHA on the TAG glycerol backbone.

Keywords

• 鱼油；加工工艺；sn-2位脂肪酸；核磁共振碳谱；二十二碳六烯酸
• fish oil；processing technology；sn-2 fatty acid；13c-nmr；dha