Bioactive peptides were prepared from sheep casein by neutral protease hydrolysis. The effect of hydrolysis time on the degree of hydrolysis and angiotensin converting enzyme (ACE) inhibitory activity of hydrolsates was investigated. The peptides were analyzed and identified by liquid chromatography-mass spectrometry (LC-MS) to select the ones with potential ACE inhibitory activity. The results showed that the highest degree of hydrolysis of 9.65% as well as a percentage of ACE inhibition of 84.55% was attained after 300 min, and the concentration of the peptide YYQQRP required for 50% ACE inhibition was 5–10 μmol/L. The sequence analysis of the peptides was performed by ultra-high pressure liquid chromatography-time of flight mass spectrometry (UPLC-TOF-MS). YYQQRP was identified as a new peptide with potential ACE inhibitory activity by comparison with the protein database. It was hypothesized that the structure of YYQQRP might be similar to that of the substrate and could reduce the catalytic activity of ACE by binding to the active site of ACE.

The purpose of this study was to investigate the effects of geographical origin, dairy animal species and fermentation on the contents of mineral elements (calcium, iron and zinc), vitamin A and vitamin E in milk from minor dairy species (horse, camel and yak). In total, 86 samples of fresh and fermented milk were collected in main pastoral areas of Xinjiang, Inner Mongolia, Qinghai and Gansu in western China. The contents of mineral elements and vitamins in these samples were determined and by inductively coupled plasma mass spectrometry (ICP-MS) and high performance liquid chromatography (HPLC), respectively. The results showed that: 1) There was no significant difference in the contents of calcium, iron and zinc in fresh horse milk between Xinjiang and Inner Mongolia (P > 0.05), whereas there was a significant difference in the contents of calcium and iron in fresh camel milk between the two pastoral areas, as well as in the contents of iron and zinc in fresh yak milk between Gansu and Qinghai (P < 0.05); the contents of vitamins A and E were higher in fresh camel milk from Xinjiang than Inner Mongolia, as well as in fresh yak milk from Qinghai than Gansu (P < 0.05). 2) There were significant differences in calcium, iron and zinc contents among dairy animal species with significantly higher levels for each element being observed in yak milk than in camel milk and horse milk (P < 0.05); likewise, significant inter-species differences in the contents of vitamin A and E in milk were found (P < 0.05); the contents of both vitamins were slightly higher in horse milk from Inner Mongolia than Xinjiang (P > 0.05). 3) Fermentation had no significant effect on mineral element contents in milk. The content of vitamin E in fermented horse milk was significantly higher than in fresh horse milk (P < 0.05), and the contents of vitamins A and E in fresh milk from the other species decreased in varying degrees after fermentation.

The purpose of this study was to investigate the factors affecting somatic cell counts (SCC) and milk composition of Chinese Holstein cows in Ningxia. The correlation of 198 855 measurements of the dairy herd improvement (DHI) data of 19 020 Chinese Holstein dairy cows (from 2009 to 2018) from 7 different dairy farms was analyzed using Minitab software. The results showed that 1) SCC was significantly correlated with farm, year and parity (P < 0.05); 2) SCC fluctuated with season and calving month, and decreased first and then increased with increasing lactation length; and 3) there were significant correlations between SCC and milk yield, milk fat percentage, milk protein percentage, milk sugar percentage and dry matter percentage (P < 0.05). Moreover, SSC, milk yield and the major milk components were influenced by environmental factors (farm, year and season) and cow’s own factors (parity, calving season and lactation period). In summary, fine management is an effective avenue to improve milk production and quality.

The aim of this paper is to explore the amino acid composition and nutritional evaluation of mare milk and traditional fermented mare milk in two pasture areas of western China. In this study, 40 samples of mare milk and traditional fermented mare milk were collected in the main pastoral areas of Xinjiang and Inner Mongolia. An amino acid automatic analyzer and high performance liquid chromatography were used to determine the composition and content of free amino acids and hydrolyzed amino acids in the samples. The obtained data were analyzed using analysis of variance (ANOVA) and nutritional evaluation was performed. The results showed that there was no significant difference in the total amino acid of mare milk in both areas (P > 0.05); the free amino acid contents of two fermented mare milk samples were generally significantly increased relative to their unfermented counterparts (P < 0.05), and new amino acids with special physiological activities were produced such as gamma-aminobutyric acid (GABA), beta-aminoisobutyric acid (BAIBA) and gammahydroxylysine; the content of sweet amino acid Xinjiang mare milk was significantly increased after fermentation, and the total amino acid content was higher than in fresh mare milk, indicating that fermentation helped improve the flavor of mare milk; the essential amino acid index values of fresh and fermented mare milk from the two areas were all greater than 95, indicating that both fresh and fermented mare milk were high-quality protein sources. Moreover, the nutritional evaluation of fermented mare milk was higher than fresh mare milk in each area.