A known biological role of casein micelles is to transport calcium from mother to young and provide amino acids for growth and development. Previous reports demonstrated that modified casein micelles can be used to transport and deliver hydrophobic probes. In this study, the distribution of lipid-soluble phospholipids, including sphingomyelins (SM) and phosphatidylcholines (PC), was quantified in whole raw milk, skim raw milk, and casein micelles of various sizes during early, mid, and late lactation stages. Low-pressure size exclusion chromatography was used to separate casein micelles by size, followed by hydrophobic extraction and liquid chromatography–mass spectrometry for the quantification of PC and SM. Results showed that the SM d18:1/23:0, d18:1/22:0, d18:1/16:0, d16:1/22:0, d16:1/23:0, and d18:1/24:0 and the PC 16:0/18:1, 18:0/18:2, and 16:0/16:0 were dominating candidates appearing in maximum concentration in whole raw milk obtained from late lactation, with 21 to 50% of total SM and 16 to 35% of total PC appearing in skim milk. Of the total SM and PC found in skim milk, 35 to 46% of SM and 22 to 29% of PC were associated with the casein micelle fraction. The highest concentrations of SM d18:1/22:0 (341 ± 17 μg/g of casein protein) and PC 16:0/18:1 (180 ± 20 μg/g of casein protein) were found to be associated with the largest casein micelles (diameter = 149 nm) isolated in milk from late lactation, followed by a decrease in concentration as the casein micelle size decreased.

酪蛋白胶束的已知生物学作用是将钙从母体转运至幼体，并为生长和发育提供氨基酸。先前的报道表明，修饰的酪蛋白胶束可用于运输和递送疏水探针。在这项研究中，定量分析了泌乳早期，中期和晚期各种大小的全脂原料奶，脱脂原料奶和酪蛋白胶束中脂溶性磷脂（包括鞘磷脂（SM）和磷脂酰胆碱（PC））的分布。低压尺寸排阻色谱法用于按尺寸分离酪蛋白胶束，然后进行疏水萃取和液相色谱-质谱联用用于定量PC和SM。结果显示SM d18：1/23：0，d18：1/22：0，d18：1/16：0，d16：1/22：0，d16：1/23：0和d18：1 / 24：0和PC 16：0/18：1、18：0/18：2和16：0/16：0是从晚期哺乳期获得的全脂原奶中最大浓度出现的主要候选对象，比例为21至50脱脂牛奶中出现的SM总百分比和PC总数的16％至35％。在脱脂牛奶中发现的总SM和PC中，酪蛋白胶束部分占35％至46％的SM和22％至29％的PC。发现SM d18：1/22：0（酪蛋白蛋白质为341±17μg/ g）和PC 16：0/18：1（酪蛋白蛋白质为180±20μg/ g）最高浓度。泌乳后期从牛奶中分离出最大的酪蛋白胶束（直径= 149 nm），然后随着酪蛋白胶束尺寸的减小而浓度降低。