Fatty acid composition and regiodistribution in mare’s milk triacylglycerols at different lactation stages

Abstract

The composition and regiodistribution of fatty acids influence the physical and the nutritional properties of milk fat. The aim of this study was to determine the fatty acid composition and the triacylglycerols’ (TAGs) structure of mare’s milk collected on days 20, 40, and 150 postpartum. Differences in the composition of fatty acids occurred between lactation times. A higher proportion of saturated fatty acids, mainly capric (C_10:0) and lauric (C_12:0) acids, were detected on day 20 in lactation milk TAGs and long-chain unsaturated fatty acids detected on days 40 and 150 lactation milk TAGs. Mare’s milk had interesting nutritional properties due to a high content in essential fatty acids (23.72%). Despite variations in the regiodistribution between lactation periods, fatty acids were generally distributed within the TAGs’ molecules of mare’s milk in a highly specific fashion: from 71.84% to 79.50% saturated fatty acids were mainly esterified in the sn-2 position while unsaturated fatty acids were always preferentially esterified in the sn-1 and sn-3 positions. These results suggest some degree of non-randomness in TAG’s biosynthesis. The fatty acid composition, in particular the level of unsaturation and chain length appeared to be important selectivity factors in the distribution of fatty acids in TAGs’ molecules.

不同泌乳期马乳三酰甘油的脂肪酸组成和区域分布

摘要 脂肪酸的组成和区域分布影响乳脂肪的物理和营养特性。本文研究了泌乳期分别是 20 天、40 天和 150 天马乳的脂肪酸组成和三酰甘油的结构。不同泌乳期马乳三酰甘油脂肪酸的组成存在差异。泌乳期 20 天马乳三酰甘油中含有较高含量的饱和脂肪酸, 主要是十碳酸 (C10:0) 和十二碳酸 (C12:0) 。泌乳期 40 天和 150 天马乳三酰甘油中含有高含量的长链不饱和脂肪酸。由于马乳含有较高含量的必需脂肪酸 (23.72%), 因此有较好的营养特性。尽管不同泌乳期马乳脂肪酸的区域分布存在差异, 但一般都分布在三酰甘油分子内部, 而且是以高度立体专一的形式分布。 71.84% 到 79.50% 的饱和脂肪酸主要在 sn-2 位发生酯化, 然而不饱和脂肪酸经常优先选择在 sn-1 和 sn-3 位发生酯化。这些结果表明三酰甘油的合成在一定程度上并不是随意的。脂肪酸组成, 特别是不饱和脂肪酸和长链脂肪酸组成是三酰甘油分子脂肪酸分布的很重要的选择性因素。