| Human milk contains abundant nutrients for infants’ growth and development. The fat provides main energy and essential nutrients for infants, playing a crucial role in infant nutrition. At present, infant formula on the market emerge in endlessly, but most raw material from cow or goat milk. Its nutritional value can not be equivalent to that of human milk. Thus, breast milk bank arises, solving the problem of infant feeding and playing a key role in the treatment of critically ill neonates and low birth weight premature. However, the quality of human milk in domestic bank can not be guaranteed owing to lack of standards. Except for preservation condition, many factors affect the composition of human milk fat. Therefore, the study on composition of lipids in human milk and its influential factors has significance, not just for determining the proper preservation condition and establishing database of domestic human milk fat, but for providing a reference for the infant formula industry and lactating women’s diet.Firstly, the chemical composition of human milk fat was analyzed by GC and HPLC. The results showed that:(1) Fat content in human milk ranged from 29.72 g/L to 43.57 g/L, and the fat contained more than 98% of triglycerides, about 1% of phospholipids and a small amount of tocopherol.(2) By reverse phase evaporation light liquid chromatography(RP-HPLC-ELSD) and super high conjunction chromatography equipped with quadrupole-time of flight tandem mass spectrometry(ACQUITY UPC2-MSE), 33 different triglycerides were isolated from human milk. The highest content of POL, accounted for about 25% triglycerides, and POO about 16%. The relative abundance of triglycerides fragment ions analysis showed that the POO in human milk mainly existed in the form of sn-OPO.(3) Total fatty acids and sn-2 fatty acids composition of human milk were detected by GC. Saturated fatty acids(SFA) accounted for only 37.48% of the total fatty acids, unsaturated fatty acid(UFA) content was higher than SFA; SFA content in sn-2 fatty acids was as high as 70%, significantly higher than UFA. Palm acid accounted for about 80% of SFA.(4) Polar lipids and fatty acids of them were detected by ultra high performance liquid chromatography(Waters ACQUITY UPLC) and GC. PI, PS, PE, PC and SM were isolated from human milk. SM accounted for about 35% of the phospholipids, PC 28%, the content of PI was the lowest. The content of SFA of phospholipids was around 58%, higher than that of total lipids, and the content of stearic acid and palmitic acid of SFA were high.(5) Four kinds of tocopherol from human milk fat were isolated by HPLC. The content of tocopherol was about 4.8 mg/L. Among them, alpha tocopherol content was the highest, gamma tocopherol content was second-highest, and beta tocopherol and delta tocopherol content were lowest.Secondly, the dynamic changes of the chemical composition of human milk fat in different lactation periods were studied by the significance analysis. The results showed that:(1) Fat content gradually increased with the extension of lactation time and remained stable in mature stage.(2) In different lactating stages, the types of triglycerides were consistent, but the content changed. For example, the content of POL in colostrum stage was significantly higher than transitional and mature stage. The content of POO in colostrum milk decreased significantly, and no significant correlation between transitional and mature stage.(3) The content of SFA increased significantly from colostrum to transitional stage, while declined significantly to the mature stage. The content of MUFA declined significantly with the extension of lactation time, and keeped stable in transitional and mature milk. The content of PUFA in three lactation was no significant difference. The content of SFA of sn-2 fatty acids with the extension of lactation period increased significantly. And MUFA and PUFA contents both were the highest in colostrum stage, and dropped significantly during the transitional and mature stage.(4) The content of PC in colostrum and transitional milk was significantly higher than that of mature milk, but the content of SM was no significant difference. The content of PS and PE was the highest in the mature milk. However, the content of PI in three lactation stages was no significant change. The content of SFA, MUFA and PUFA of phospholipid fatty acids in three lactation stages was no significant difference.(5) The content of total tocopherol decreased significantly during the lactation periods. Among them, the alpha tocopherol and gamma tocopherol contents showed a trend of decline, but no obvious change in beta-tocopherol and delta-tocopherol.Finally, the effects of storage conditions and dietary patterns on the composition of human milk fat were studied. Results showed that:(1) The proper storage condition was at-20 ℃ and-80 ℃ for 3 months and 6 months respectively based on the fat content, acidity and tocopherol content.(2) The dietary patterns of lactation mother in Wuxi was researched through the food frequency questionnaire and the balanced diet recommended by dietary guidelines. Rice was the staple food, and soybean oil was the main edible oil. The intake frequency of rice, vegetables, nuts and dairy was low. And lactating women eat too much fat, leading to unreasonable three major nutrients.(3) The relevance between lactation mothers’ dietary and chemical composition of human milk fat was analyzed. Statistical significance was found in human milk fat content, tocopherol content and fatty acid composition of human milk. Fat and tocopherol content in high fat diet of maternal milk was significantly higher than in high protein and high carbohydrate diet of maternal milk. EPA and DHA content of human milk was positively correlated with intake of seafood. Compared fatty acids in human milk from Wuxi with literature evidence at home and abroad, found that types of cooking oil influenced the composition of fatty acid as well. Keywords: Human milk fat, Chemical composition, Fatty Acids, Triglycerides, Influence... |
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