| Short-chain fatty acids(SCFAs),generally defined as organic fatty acids with the number of carbon atoms less than 6,are highly enrich in mammalian gastrointestinal systems.The SCFAs in human diet are generally derived from cow and goat milk.SCFAs is naturally contained in human milk.Studies have shown that SCFAs may promote the absorption of water and sodium in infants,increase the secretion of gastrointestinal hormones,improve intestinal flora which play an important role in the growth and development of infants.At present,the research on breast milk fat mainly focuses on medium-chain fatty acids and long-chain polyunsaturated fatty acids in human breast milk,and there are few studies on SCFAs in breast milk.This study established a method for the determination of SCFAs in breast milk triglycerides,analyzed human milk samples of different lactation periods and different gestational ages,and compared the fatty acid composition and content of human milk with infant formula and other animal milk.To provide a solid data for the research of nutritional value of human breast milk and the development of infant formula and lay the foundation for the study of short-chain fatty acid function in infants.First,we used fatty acid triglyceride standards(4:0-TAG,8:0-TAG,12:0-TAG,16:0-TAG,and20:0-TAG)to compare the three most common fatty acid methyl ester preparation method,and the most effective base-catalyzed transesterification method is selected for FAMEs preparation.In this paper,a total of 180 human milk samples of different lactation periods and different gestational ages were tested.Three types of short-chain fatty acids in human milk were identified,butyric acid(4:0),caproic acid(6:0),and caprylic acid(8:0).Among them,the content of 4:0 was the lowest,and the differences between 4:0 and 6:0 in different lactation periods were extremely significant(p<0.0001).The contents of 6:0 and 8:0 in human milk of preterm infants were significantly lower than those in full-term infants(p<0.0001).The content of short-chain fatty acids in mature milk was the highest,and the content of short-chain fatty acids in human milk in term infants was significantly higher than that in preterm infants(p=0.001).The total intake of short-chain fatty acids from mature milk in term infants was 82.07 mg/d,which was 4-7 times higher than that in colostrum and transition milk.Secondly,in this experiment,ultra-high performance supercritical fluid chromatography quadrupole-time of flight-mass spectrometry(UHPSFC-Q-TOF-MS)was used to separate the triglycerides in 180 human milk samples of different lactation periods and different gestational ages and identify the structures of triglycerides containing SCFAs.The results showed that there were 6triglycerides containing SCFAs in 99 triglycerides identified,which are 4:0/16:0/16:0,4:0/16:0/18:1,and 6:0/16:0/18:1,6:0/16:0/18:2,4:0/18:1/18:1,and 8:0/16:0/18:2.Among them,the lower content is 4:0/16:0/16:0 and 4:0/18:1/18:1,and the range is 0.00-0.07% and 0.00-0.08%.The higher content is 4:0/16:0/18:1 and 6:0/16:0/18:2,and the content in mature milk of term infants is 0.00-0.33% and0.00-0.27%.Short-chain fatty acids are mainly esterified with three long-chain fatty acids at the glycerol backbone: palmitic acid(16:0),oleic acid(18:1 n-9)and linoleic acid(18:2 n-6).In addition,the content of short-chain fatty acid triglycerides varies greatly among different samples.Finally,in this experiment,the composition of short-chain fatty acids in cow's milk,goat's milk,donkey's milk,yak's milk,and commercial infant formula was analyzed and compared with that ofhuman milk.The results showed that the composition of short-chain fatty acids in cow's milk,goat's milk,donkey's milk and yak's milk was basically the same as that in human milk,which were 4:0,6:0 and 8:0,respectively.Due to different metabolic pathways,the content of short-chain fatty acids in different animal milks varies.The content of short-chain fatty acids in camel milk is similar to human milk,and the content of short-chain fatty acids in other animal milk is significantly higher than human milk.In addition,the content of short-chain fatty acids in different formula milk powders varies greatly,but the overall content is higher than the content of short-chain fatty acids in human milk.The content of 4:0 and 6:0 in compound plant-based formula milk powder is low,and some brands of milk powder do not contain short-chain fatty acids.The compound plant-based formula and the compound goat's milk / plant-based formula have a high content of 8:0,and the compound goat's milk / plant-based formula have a high content of 4:0. |
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