Amino acids serve as the fundamental building blocks of proteins which play crucial roles in various biological processes. However, there is a relative scarcity of comprehensive analysis regarding the variation of amino acids in donkey milk during different lactation periods and within different domains. Hence, we thoroughly examine the composition of both free and insoluble-proteome amino acids in donkey colostrum (DC) and donkey mature milk (DM). Our investigation includes an assessment of their nutritional significance, flavor analysis, metabolic pathways, and interactions across various lactation stages . Through nutritional assessment , we found that DC and DM exhibit excellent nutritional value . Both kinds of milk possess a delightful taste profile, with the majority of flavors concentrated in the realm of “savory umami” and “sweet-savory”. The most significant pathway of differentially expressed amino acids for both free and insoluble-proteome amino acids groups was “valine, leucine , and isoleucine biosynthesis”. These findings deepen our comprehension of the varying amino acid compositions within donkey milk across different lactation stages, paving the way for future research directions in developing functional foods utilizing donkey milk as a source.
Sialylated N-glycans are an integral component of whey proteins in human milk and play an irreplaceable role in infant growth and development. Currently, there are few studies on quantitative comparison of sialylated N -glycans in milk obtained at different lactation stages. Here, a preliminary isomer-specific quantification of whey sialylated N -glycans of human colostrum milk (CM) and mature milk (MM) was performed by using our recently developed glycoqueuing strategy. Such a preliminary comparison revealed that the whey sialylated N -glycan content was 86.4% lower in MM than in CM. Twenty-three α2,6-linked sialylated N -glycan isomers were detected with no α2,3-linked isomer observed. For the first time, three mono-sialylated and four bi-sialylated glycan isomers were reported. With the prolongation of lactation, the relative abundance of mono-sialylated glycans increased, whilst the relative abundance of bi-sialylated glycans decreased significantly. These findings contribute to the understanding of the structure–function relationship of sialylated N -glycans in the human whey fraction.
Xinyue Dai,Tinglan Yuan,Xinghe Zhang,Qin Zhou,Huiya Bi,Renqiang Yu,Wei Wei,Xingguo Wang
This study aimed to quantify the short-chain fatty acids (SCFAs) and medium-chain fatty acids (MCFAs) in human milk triacylglycerols (TAGs) and investigate their concentrations in human milk consumed during lactation by infants born at different gestational ages. One hundred and eighty milk samples from the mothers of 30 full-term, 10 early-preterm (≤32 weeks), 10 mild-preterm (32–34 weeks), and 10 near-term (34–37 weeks) infants were collected from the colostrum, transitional, and mature milk. The human milk TAGs were transferred into fatty-acid methyl esters via potassium methoxide in methanol and determined using gas chromatography (GC). The total SCFA (4:0) and MCFA concentrations (6:0 and 8:0) were highest in the mature milk (1.47 ± 0.66 mg g−1 fat from full-term infant milk), approximately 42.18% higher than those in transitional milk. Significantly higher SCFA and MCFA concentrations were found in full-term milk than in preterm milk (p = 0.001). The milk TAGs were analyzed using ultra-high-performance supercritical fluid chromatography with quadrupole-time-of-flight mass spectrometry (UHPSFC-Q-TOF-MS), which showed that the SCFAs and MCFAs were mainly esterified with long-chain fatty-acid groups (16:0, 18:1 n-9, and 18:2 n-6) at the glycerol backbone. The infants’ daily SCFA intake from human milk was estimated; this was highest from mature milk for full-term infants (∼14 mg d−1) which was significantly different from that of preterm infants from colostrum and transitional milk (p < 0.001). The correlation between dietary SCFAs and MCFAs in human milk and nutrition in newborns, especially in the gut microbiotas of preterm infants, requires further study.
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