The lipid profiles of raw, pasteurized and fermented cow milk and goat milk were investigated using lipidomics based on ultra-high performance liquid chromatography (UPLC) coupled with quadrupole tandem electrostatic field orbitrap mass spectrometry. A total of 27 lipid subclasses were detected in all samples, including 1607 lipid molecules. The results proved that pasteurization had no effect on the lipid profiles of cow milk or goat milk, while fermentation had a significant influence on the lipid profiles of cow milk and goat milk; in particular, it greatly reduced the content of hemolytic phospholipids. Totally 27 and 23 lipid molecules which could be used as potential biomarkers for the identification of pasteurized and fermented milk were selected. This study has provided an understanding of the lipid profile and dynamic changes in the fermentation process of milk, which can provide a molecular basis for understanding the effects of heat treatment and fermentation on milk fat during yogurt processing and be helpful to understand the quality and nutritional characteristics of yogurt products.

In order to understand the dynamic changes of complex lipid contents in human milk during infancy, sequential window acquisition of all theoretical mass spectra (SWATH) with high acquisition hit rate assisted ultra-high performance liquid chromatography-triple quadrupole time of flight tandem mass spectrometry (UPLC-Triple-TOF-MS/MS) was used to identify and quantitatively analyze lipids in human milk at different lactation stages. The results showed that a total of 229 lipids were detected in human milk at the three lactation stages. According to the “Lipid Metabolism and Pathways Strategy”, five classes of lipids were identified: 1) glycerolipids (GLs) mainly including 24 diglycerides and 28 triglycerides; 2) glycerophospholipids (GPs) including 33 phosphatidylethanolamines, 21 phosphatidylcholines, 8 phosphatidylserines, 13 phosphatidylglycerols, 10 phosphatidic acids and 7 phosphatidylinositols; 3) 22 sphingolipids (SP); 4) 10 sterol lipids (ST); and 5) 4 fatty acids (FAs) and their derivatives. The relative contents of GL and SP increased gradually with lactation time, while the relative contents of GP, ST and FAs decreased gradually. This study achieved a comprehensive qualitative and relative quantitative analysis of lipids in human milk. The developed method is sensitive, precise and stable. It provides a basis for the development of infant food simulating human milk at different stages of lactation.

In this study, untargeted metabolomics based on ultra-high performance liquid chromatography-quadrupole electrostatic field orbitrap mass spectrometry (UPLC-QE-MS) was used to explore the differences in metabolite profiles between ordinary yogurt and brown yogurt, and the differences between them were evaluated from the perspective of metabolites. The metabolite information of yogurts was collected in both the positive and negative ion modes, and the metabolites were screened by multivariate statistical analysis. A total of 117 differential metabolites were obtained. Compared with ordinary yogurt, the relative contents of 106 metabolites were up-regulated and 11 metabolites were down-regulated in brown yogurt. Compared with ordinary yogurt, the contents of 3 flavor amino acids, 8 peptides, 12 sugars, 2 Maillard reaction products and one quinone in brown yogurt changed significantly. The results of this study can provide some theoretical support for the future research and development of brown yogurt.

This study was conducted in order to explore the influence of different milks on the stability of infant formula milk powder. The physicochemical properties of infant formula milk powders made from goat milk and cow milk such as moisture content, water activity (a_w), glass transition temperature (T_g), lactose crystallinity, solubility, color, protein composition, total fatty acid and the composition of surface free fatty acids were analyzed. The surface components were determined by X-ray photoelectron spectroscopy (XPS), and the surface morphology was observed by scanning electron microscopy (SEM). The results showed that goat milk infant formula powder had good physicochemical properties. Compared with cow milk infant formula powder, goat milk infant formula powder had lower moisture content, a_w, chroma and T_g, but similar crystallinity and solubility. Fatty acid composition analysis by gas chromatography-mass spectrometry (GC-MS) showed that in both infant formula powders, unsaturated fatty acids accounted for a higher percentage of the total fatty acids, while saturated fatty acids accounted for a higher percentage of the surface free fatty acids. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the content of β-casein in goat milk infant formula powder was higher, and the difference in casein content affected the surface components of milk powder. Consistently, the XPS results showed that goat milk infant formula had a relatively low fat content and a relatively high protein content in the surface composition, which could explain the more agglomerated and denser particles of cow milkinfant formula powder observed by SEM. The above results indicated that the physicochemical properties and surface composition of infant formula powders made from different milks are different due to the difference in casein composition, affecting the stability of infant formula powder.