The alteration of composition, conformation, IgE-reactivity and functional attributes in proanthocyanidins-soy protein 7S conjugates formed by alkali-heating treatment: Multi-spectroscopic and proteomic analyses.

This study assessed the alteration of IgE-reactivity and functional attribute in soy protein 7S-proanthocyanidins conjugates (7S-80PC) formed by alkali-heating treatment (pH 9.0, 80 °C, 20 min). SDS-PAGE demonstrated that 7S-80PC exhibited the formation of >180 kDa polymers, although the heated 7S (7S-80) had no changes. Multispectral experiments revealed more protein unfolding in 7S-80PC than in 7S-80. Heatmap analysis showed that 7S-80PC showed more alteration of protein, peptide and epitope profiles than 7S-80. LC/MS-MS demonstrated that the content of total dominant linear epitopes was increased by 11.4 % in 7S-80, but decreased by 47.4 % in 7S-80PC. As a result, Western-blot and ELISA showed that 7S-80PC exhibited lower IgE-reactivity than 7S-80, probably because 7S-80PC exhibited more protein-unfolding to increase the accessibility of proanthocyanidins to mask and destroy the exposed conformational epitopes and dominant linear epitopes induced by heating treatment. Furthermore, the successful attachment of PC to soy 7S protein significantly increased antioxidant activity in 7S-80PC. 7S-80PC also showed higher emulsion activity than 7S-80 owing to its high protein flexibility and protein unfolding. However, 7S-80PC exhibited lower foaming properties than 7S-80. Therefore, the addition of proanthocyanidins could decrease IgE-reactivity and alter the functional attribute of the heated soy 7S protein.

Multi-spectral and proteomic insights into the impact of proanthocyanidins on IgE binding capacity and functionality in soy 11S protein during alkali-heating treatment.

This study evaluated the impact of proanthocyanidins on immunoglobulin E (IgE) binding capacity, antioxidant, foaming and emulsifying properties in soy 11S protein following alkali treatment at 80 °C for 20 min. The formation of >180 kDa polymer was observed in the combined heating and proanthocyanidins-conjugation treatment sample (11S-80PC) rather than in the heating treated sample (11S-80) using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The structural analyzes demonstrated that 11S-80PC exhibited more protein unfolding than 11S-80. Heatmap analysis revealed that 11S-80PC had more alteration of peptide and epitope profiles in 11S than in 11S-80. Molecular docking showed that PC could well react with soy protein 11S. Liquid chromatography tandem MS analysis (LC/MS-MS) demonstrated that there was a 35.6 % increase in 11S-80, but a 14.5 % decrease in 11S-80PC for the abundance of total linear epitopes. As a result, 11S-80PC exhibited more reduction in IgE binding capacities than 11S-80 owing to more obscuring and disruption of linear and conformational epitopes induced by structural changes. Moreover, 11S-80PC exhibited higher antioxidant capacities, foaming properties and emulsifying activity than 11S-80. Therefore, the addition of proanthocyanidins could decrease allergenic activity and enhance the functional properties of the heated soy 11S protein.

Characterization of the milk fat globule membrane proteome in colostrum and mature milk of Xinong Saanen goats.

Xinong Saanen goat milk is a major source of milk in the Chinese dairy industry. Milk fat globule membrane (MFGM) proteomes of goat colostrum and mature milk were analyzed and compared using proteomic technology. A total of 543 and 585 proteins were identified in goat colostrum and mature milk, respectively. Functional category analyses revealed that most of the MFGM proteins in both colostrum and mature milk were related to phosphoprotein and acetylation. The biological process of translation, cellular component of extracellular exosome, and molecular function of poly(A) RNA binding were the main gene ontology annotations of both colostrum and mature milk. Pathways associated with disease and genetic information processing involved large number of proteins in colostrum and mature milk, and more metabolism-related pathways were observed in mature milk. Protein-protein interaction network analyses showed that ribosome was abundant in both colostrum and mature milk. Colostrum showed more functions associated with protein processing in the endoplasmic reticulum, whereas mature milk had more oxidative phosphorylation functions. The results could provide further understanding of the unique biological properties of MFGM proteins of goat colostrum and mature milk.

Proteomic analysis of whey proteins in the colostrum and mature milk of Xinong Saanen goats.

Xinong Saanen goats are among the major dairy goats in China, and their milk is one of the major milk supplies for the Chinese dairy industry. To explore the whey proteome of Xinong Saanen goat milk, we analyzed the whey proteins of goat colostrum and mature milk using proteomic techniques. We identified a total of 314 and 524 proteins in goat colostrum and mature milk, respectively. Our data showed the first 3 functional categories of signal, disulfide bond, and secreted in both milk types. The most abundant Gene Ontology annotations in both milks were the biological process of positive regulation of extracellular regulated protein kinases (ERK)1 and ERK2 cascade; the cellular component of extracellular exosome; and the molecular function of calcium ion binding. Goat colostrum whey proteins showed more disease-related pathways, and mature milk showed more pathways associated with metabolism. Moreover, we observed several pathways involved in intestinal mucosal immunity only in colostrum. Protein-protein interaction network and module analysis revealed that complement and coagulation cascades and Staphylococcus aureus infection were significant in the whey proteins of both milks, and carbon metabolism was more common for mature milk than for colostrum. These findings could provide useful information for the use of goat milk whey proteins in the Chinese dairy industry.

Protein digestion properties of Xinong Saanen goat colostrum and mature milk using in vitro digestion model.

BACKGROUND: Xinong Saanen goat milk is a raw material for goat milk-based infant formula production. This study aims to analyze digestion properties of Xinong Saanen goat colostrum and mature milk by simulating infant gastrointestinal digestion. Zeta potential, particles size, protein profile and peptides composition of these two kinds of milk during the digestion process were studied. RESULTS: Zeta-potential values of the digested colostrum were lower than those of mature milk through the whole digestion. Absolute zeta potential of colostrum duodenal digestion samples showed a decrease from 16.63 ± 2.08 to 11.80 ± 2.03 mV while that of mature milk decreased sharply and then increased (P < 0.05). Colostrum had a larger particle size than mature milk and both milks showed decreased particle size with increasing digestion time but an increase for the last 30 min. Colostrum showed more high molecular weight (MW) proteins which cannot be hydrolyzed completely compared with mature milk. Digested peptides (< 10 kDa) were characterized using liquid chromatography combined with tandem mass spectrometry (LC-MS/MS). The casein-derived peptides identified in digested colostrum and mature milk accounted for 76.67% and 59.53%, respectively. ß-Casein was the most abundant in colostrum while that in mature milk was αs1 -casein. Enterotoxin-binding glycoprotein PP20K, butyrophilin subfamily 1 member A1 (BTN1A1) and perilipin (PLIN) were only detected in digested mature milk. CONCLUSION: Differences in digestion properties between goat colostrum and mature milk were mainly shown in duodenal digestion phase. Data may provide useful information about utilization of goat milk for infant formula formulation. © 2019 Society of Chemical Industry.