关键词: GC-MS, 生鲜牛乳, 脂肪酸含量

Abstract:

[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 contents among all the detected fatty acids, while there were also some regional variations in fatty acid composition and content.

Key words: GC-MS, fresh dairy milk, fatty acid content