Jensen S K, Nielsen K N
Department of Nutrition, Danish Institute of Animal Science, Research Centre Foulum, Tjele, Denmark.
J Dairy Res. 1996 Nov;63(4):565-74. doi: 10.1017/s0022029900032106.
Milk fat globule membranes (MFGM) were isolated from milk from cows injected intraperitoneally with dl-alpha-tocopherol acetate. The fatty acid composition and content, and the contents of tocopherols, retinol and beta-carotene were determined and compared with the composition and content in the original cream sample. Intraperitoneal injection of 10 g dl-alpha-tocopherol acetate elevated the alpha-tocopherol content in the milk fat from 13-30 to 50-70 micrograms alpha-tocopherol/g milk fat 2-3 d after injection. The increase depended on the alpha-tocopherol status of the cow prior to injection. The concentrations of retinol and beta-carotene in the milk fat were unchanged after the alpha-tocopherol injections. MFGM fatty acids made up 18-27 g/kg total fatty acids in the milk fat. However, the proportions of monounsaturated and polyunsaturated fatty acids were higher in MFGM than in total milk fat, while the proportion of saturated fatty acids was lower in MFGM (P < 0.001). Thus, the long-chain polyunsaturated fatty acids in MFGM constituted approximately 40-70 g/kg total milk fat. alpha-Tocopherol was the only fat-soluble vitamin detected in MFGM; gamma-tocopherol, retinol and beta-carotene were detected only in the cream. A significant relationship between alpha-tocopherol contents in cream and MFGM was found: (alpha-tocopherol in MFGM fatty acids) = -1652 x (1/ln(alpha-tocopherol in cream fatty acids)3) + 97 (r = 0.857, P < 0.001) when the contents of alpha-tocopherol were expressed as microgram/g fatty acid. According to this equation the upper limit for incorporation of alpha-tocopherol into MFGM is 97 +/- 5 micrograms/g MFGM fatty acids. Thus, under normal farming conditions the alpha-tocopherol content will be highest in MFGM. However, in cream with an alpha-tocopherol concentration < 15 micrograms/g cream fatty acids the concentration in MFGM will be lower and furthermore will decrease rapidly. The possible importance of this relationship in relation to the oxidation of milk fat is discussed.
从腹腔注射dl-α-生育酚醋酸酯的奶牛所产牛奶中分离出乳脂肪球膜（MFGM）。测定了其脂肪酸组成和含量，以及生育酚、视黄醇和β-胡萝卜素的含量，并与原始乳脂样品中的组成和含量进行比较。腹腔注射10 g dl-α-生育酚醋酸酯后2 - 3天，乳脂肪中α-生育酚含量从13 - 30微克α-生育酚/克乳脂肪提高到50 - 70微克α-生育酚/克乳脂肪。这种增加取决于注射前奶牛的α-生育酚状态。α-生育酚注射后，乳脂肪中视黄醇和β-胡萝卜素的浓度没有变化。MFGM脂肪酸占乳脂肪中总脂肪酸的18 - 27克/千克。然而，MFGM中单不饱和脂肪酸和多不饱和脂肪酸的比例高于总乳脂肪中的比例，而MFGM中饱和脂肪酸的比例较低（P < 0.001）。因此，MFGM中的长链多不饱和脂肪酸约占总乳脂肪的40 - 70克/千克。α-生育酚是在MFGM中检测到的唯一脂溶性维生素；γ-生育酚、视黄醇和β-胡萝卜素仅在乳脂中检测到。发现乳脂和MFGM中α-生育酚含量之间存在显著关系：当α-生育酚含量以微克/克脂肪酸表示时，（MFGM脂肪酸中的α-生育酚）= -1652×（1/ln（乳脂脂肪酸中的α-生育酚）³）+ 97（r = 0.857，P < 0.001）。根据该方程，α-生育酚掺入MFGM的上限为97±5微克/克MFGM脂肪酸。因此，在正常养殖条件下，MFGM中的α-生育酚含量将最高。然而，在α-生育酚浓度<15微克/克乳脂脂肪酸的乳脂中，MFGM中的浓度会更低，而且会迅速下降。讨论了这种关系与乳脂肪氧化相关的可能重要性。
