β-lactoglobulin (β-LG) is a major allergen in cow’s milk. In this study, synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, circular dichroism (CD) spectroscopy, molecular docking, and indirect competitive enzyme-linked immunosorbent assay were used to explore the interaction of docosahexaenoic acid (DHA) with β-LG and its influence on the allergenicity of β-LG. The results showed that the binding of DHA to β-LG significantly changed the microenvironment of the aromatic residues of β-LG and increased its polarity. DHA bound to β-LG to form a stable complex through hydrophobic interactions, changing the secondary structure of β-LG and resulting in folding of its backbone. The relative content of β-sheet increased and then decreased with increasing concentration of DHA, while the relative content of α-helix showed an opposite trend. However, the relative contents of β-turn and random coil showed irregular changes. In addition, the antigenicity of β-LG decreased after combination with DHA, and the immunoglobulin E (IgE) binding ability inhibition rate was about 29% by 3 mmol/L DHA.

In this study, the bioinformatics software DNAStar and Geneious and multiple reaction monitoring mass spectrometry (MRM-MS) were used to predict the linear epitope parameters, secondary structure content and epitope regions of bovine whey proteins. Meanwhile, relative quantification of linear allergenic epitopes was carried out. The results indicated that α-lactalbumin (α-LA) and β-lactoglobulin (β-LG) had 7 and 10 linear epitope regions, respectively. The secondary structure of α-LA and β-LG mainly consisted of α-helix, followed by β-turn, β-sheet and random curling, indicating that the structure of α-LA and β-LG made them more likely to become epitopes. Alkaline, protamex and flavourzyme treatment effectively reduced the linear allergenic epitopes of α-LA and β-LG by 50.0%–80.0%, with this effect being more pronounced for β-LG. The relative quantitation results showed that the content of 95.0% of linear epitope peptides was significantly reduced.

The effects of Alcalase (AT), Protamex (PT) or Flavorzyme (FT) treatment on the antigenicity and molecular mass distribution of proteins, flavor and color of skim milk were investigated by using various techniques such as indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and Tricine-sodium dodecyl sulphate polyacrylamide gel electrophoresis (Tricine-SDS-PAGE). The results showed that the effect of AT treatment on reducing the antigenicity of the major milk allergens was significantly better than that of PT and FT treatment (P < 0.05). The antigenicity of α-lactalbumin (α-LA), β-lactoglobulin (β-LG) and casein (CN) was inhibited by 64.01%, 76.00% and 69.10% by AT treatment for 20 min at an enzyme/substrate ratio of 500 U/g, respectively. The amount of low molecular mass peptides in skim milk increased significantly after treatment with each of the three enzymes. The bitterness, astringency, aftertaste of bitterness (aftertaste-B) and aftertaste of astringency (aftertaste-A) increased with increasing enzymatic treatment time and with increasing enzyme/substrate ratio. The taste of FT-treated milk was better than that of AT- or PT-treated milk. The brightness value of milk decreased significantly, while the redness value increased significantly after enzymatic treatment (P < 0.05). The transmittance increased as well. The color of skim milk treated by AT was more similar to that of whole milk.

In order to explore the inhibitory effect of bioactive substances on the degradation of milk fat during simulated gastrointestinal digestion, the impact of bioactive substances on the in vitro digestibility of milk proteins was examined as well as the inhibitory effect on pancreatic lipase activity and the micellar solubility of cholesterol. The results showed that the in vitro digestibility of milk proteins was inversely proportional to the concentration of the tested bioactive compounds, which decreased from 90.94% to 68.37% and 86.00% with increasing concentration of epigallocatechin (EGC) and β-glucan, respectively. The inhibitory effect of EGC on pancreatic lipase activity decreased to different extents with increased amount of added milk proteins, and so did the inhibitory effect of β-glucan and a mixed solution of 2.5 g/L β-glucan, 3.0 g/L epigallocatechin gallate (EGCG) and 2.0 g/L EGC on the micellar solubility of cholesterol. The inhibitory effect of this mixture on the degradation of milk fat was stronger than that of β-glucan.

Dairy products are an important part of the dietary structure of Chinese residents. A wide variety of dairy products are commercially available, which are rich in nutrients and contain high-quality protein, various trace elements and functional ingredients including such active ingredients that are beneficial for lipid metabolism as milk calcium, whey, polar lipids and conjugated linoleic acid. Dairy products have the potential to regulate blood lipids and reduce the risk of cardiovascular disease. In addition, dairy products are high-quality carriers of active ingredients, and the active ingredients in milk can synergize with those added to milk to regulate blood lipids or to protect them. For this reason, milk is often used as an ingredient of functional dairy products. Hyperlipidemia is recognized worldwide as one of the risk factors for cardiovascular and cerebrovascular diseases such as atherosclerosis, coronary heart disease and hypertension. Studies have shown that functional milk can aid in regulating blood lipids. This paper reviews the current status of studies on dairy products and lipid metabolism-related health problems, aiming to provide a theoretical basis for the research of functional dairy products.

In order to understand the influence of interaction between the functional components and milk proteins in lipidlowering milk on the effectiveness of the functional components, we investigated the influence of casein and whey protein on the inhibitory effect of epigallocatechin (EGC) against pancreatic lipase, and we also determined the influence on the antioxidant activity of a mixture of EGC and the functional components as well as the influence on the inhibitory effect of a mixture of β-glucan and the functional components on the solubility of cholesterol-containing micelles. The results showed that milk protein could reduce the inhibitory effect of the functional components on pancreatic lipase activity, and decrease their antioxidant activity and their ability to inhibit the solubility of cholesterol-containing micelles.

Breast milk is the best source of food for infants and young children, and the whey proteins contained in the milk are the base of nutritional and bioactive substances including bioactive peptides, which play an important role in promoting human health. In this research, the antioxidant activities of peptides prepared by enzymatic hydrolysis of breast milk whey proteins with four different proteases, i.e., neutral protease, alkaline protease, papain and trypsin, were assessed and compared. The hydrolysis conditions were optimized using combination of one-factor-at-a-time method and response surface methodology. Neutral protease was found to be the most suitable enzyme for the production of antioxidant peptides from breast milk whey proteins. The optimal hydrolysis conditions were established as follows: pH 7.21, 50.03 ℃, an enzyme/ substrate ratio of 4 486.68 U/g and 5 h. The effect of hydrolysis parameters on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity was in the decreasing order: enzyme/substrate (E/S) ratio > temperature > initial pH. Fraction I with the highest antioxidant activity was separated chromatographically with macroporous resin, Sephadex G-25 and Sephadex G-15, which could scavenge 60.31% of DPPH radical.

Milk protein is the most important nutrient in the initial stage of life, and it is abundant in kind and quantity. The composition of milk proteins has been made more complex and tremendously increased through a large number of genetic variations and sufficient protein translation. Proteomics permits one to systematically and integrally study milk proteins to understand the ways milk proteins constitute and regulate some life activities and further obtain a comprehensive and in-depth understanding of the expression levels of milk proteins. This paper describes the main techniques used in proteomics studies, including two dimensional electrophoresis, high performance liquid chromatography (HPLC), isobaric tags for relative and absolute quantitation (iTRAQ), mass spectrometry and bioinformatics techniques. The applications of proteomics in studies on human and bovine milk in particular differential proteomics analysis are discussed. To conclude, proteomics allows a better understanding of human and bovine milk which can provide a theoretical basis for developing infant foods and dairy products.

In this study, proteins from human and bovine milk fat globule membranes were separated using SDS-PAGE and identified by liquid chromatography-mass spectrometry (LC-MS). It was found that 1 076 proteins from human milk fat globule membrane were identified, and 682 proteins from bovine milk fat globule membrane. Among these proteins, 757 specifically expressed proteins were derived from human milk fat globule membrane, and 363 specifically expressed proteins from bovine fat globule membrane, with 319 of these being common to both. According to gene ontology (GO) annotations analysis, human milk fat globule membrane proteins played a more significant role in biological process than did bovine milk fat globule membrane proteins, especially in cellular component organization. The molecular function of human milk fat globule membrane proteins was exerted mainly through binding. In cellular composition, human milk fat globule membrane proteins were more dominant than bovine milk fat globule membrane proteins, and mostly participated in intracellular components. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that there were 15 human milk fat globule membrane proteins involved in the digestion and absorption related KEGG pathway—enzymatic glycolysis. The study of human milk fat globule membrane proteins can improve the accuracy of milk fat globule membrane protein utilization, and the experimental data obtained may provide theoretical reference for future development of functional foods for infants.

In this study, the whey proteins in human and bovine colostrum were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and identified by liquid chromatography-mass spectrometry (LC-MS). A total of 477 whey proteins were identified in human colostrum and 325 in bovine colostrum. Totally, 343 proteins were specifically expressed in human colostrum and 191 in bovine colostum. Moreover, 134 specifically expressed proteins were common to both. Gene ontology (GO) annotation analysis revealed that human colostrum whey proteins played a more important role in bioprocesses especially stress responses than their bovine counterparts. Human colostrum whey proteins exerted functions by binding to other molecules. Human colostrum whey proteins were more important constituents of cellular structures as compared with their bovine counterparts, and they were the most significant constituents of extracellular structures. According to the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database, 23 whey proteins in human colostrum were involved in the KEGG pathway related to digestion and absorption, enzymatic glycolysis.