GC-MS法测定不同地区生鲜牛乳中的脂肪酸组成及含量

Determination of Fatty Acid Composition and Content in Fresh Dairy Milk from Different Regions by GC-MS

[目的]比较分析不同地区生鲜牛乳中的脂肪酸种类和含量。[方法]于2019年5月—2020年3月,从河南省、河北省、山西省各选取1个规模化奶牛养殖场,按照四个季节分别采集健康奶牛生鲜乳样,每个地区采集12份,3个地区共36份。使用GC-MS法进行脂肪酸的提取和甲酯化,利用CP-WAX 52 CB毛细管色谱柱和质谱联用分析仪进行脂肪酸种类和含量分析。通过与37种脂肪酸甲酯混合标准品的保留时间比对和NIST05谱库检索对脂肪酸进行定性分析,脂肪酸含量通过面积归一化法进行计算。[结果]从河南省采集的生鲜牛乳中共检出28种脂肪酸,其中,饱和脂肪酸15种,癸酸甲酯、月桂酸甲酯、肉豆蔻酸甲酯、硬脂酸甲酯、棕榈酸甲酯5种饱和脂肪酸的含量较高,占检出脂肪酸总含量的57.03%;检测到不饱和脂肪酸13种,多数含量较低,只有油酸/反油酸甲酯含量较高,占检出脂肪酸总含量的32.26%。从河北省以及山西省采集的生鲜牛乳中均检出30种脂肪酸,但其组成略有不同;2个省份生鲜牛乳的脂肪酸含量检测结果与河南省生鲜牛乳的检测结果相似,饱和脂肪酸含量占检出脂肪酸总含量的比例均在60%左右。河北省生鲜牛乳中的油酸/反油酸含量为39.80%,在3个地区中最高。3个地区的生鲜牛乳中均未检测到反亚油酸甲酯、γ-亚麻酸甲酯、顺-15-碳烯酸甲酯、芥酸甲酯、顺-4,7,10,13,16,19-二十二碳六烯酸甲酯。[结论]3个地区生鲜牛乳中的脂肪酸含量都比较丰富,以饱和脂肪酸为主,所有脂肪酸中以油酸/反油酸含量最高,但脂肪酸组成及含量也存在一定的地区差异。

[Objective]This study was conducted to compare and analyze the fatty acid composition and content in fresh dairy milk from different regions.[Method]From May 2019 to March 2020,one large-scale dairy farm each from Henan Province,Hebei Province,and Shanxi Province was selected.A total of 36 fresh milk samples from healthy dairy cows were collected over the four seasons,with 12 samples coming from each of the three regions.Fatty acids were extracted and methylated using GC-MS method.The fatty acid composition and content were analyzed using CP-WAX 52 CB capillary chromatography column and gas chromatography-mass spectrometry analyzer.By comparing the retention time of 37 mixed standard substances of fatty acid methyl esters and searching in the NIST05 spectrum library,the fatty acid composition was qualitatively analyzed.The fatty acid content was calculated using area normalization method.[Result]A total of 28 fatty acids were detected in the fresh milk collected from Henan Province,among which 15 were saturated fatty acids.The contents of 5 saturated fatty acid methyl ester,including methyl decanoate,methyl laurate,methyl myristate,methyl stearate,and methyl palmitate,were relatively high,accounting for 57.03%of the total detected fatty acid content.Thirteen unsaturated fatty acid were detected,among which most had low levels,with only oleic acid/elaidic acid methyl ester having higher levels,accounting for 32.26%of the total detected fatty acid content.Thirty fatty acids were detected in the fresh milk collected from both Hebei Province and Shanxi Province,while the compositions were slightly different.The characterization of fatty acid content in the fresh milk collected from the two provinces were similar to that collected from Henan Province,with saturated fatty acid content accounting for around 60%of the total detected fatty acid content.The content of oleic acid/elaidic acid in the fresh milk collected from Hebei Province was 39.80%,which was the highest among the three regions.No linolelaidic acid methyl ester,γ-linolenic acid methyl ester,cis-15-carboenoic acid methyl ester,erucic acid methyl ester,and cis-4,7,10,13,16,19-docosahexaenoic acid methyl ester were detected in the fresh milk from all three regions.[Conclusion]The fatty acid content in the fresh dairy milk collected from the three regions were relatively rich,with saturated fatty acid as the main component.Oleic acid/elaidic acid had the highest contentsamong all the detected fatty acids,while there were also some regional variations in fatty acid composition and content.