In this study, a low-fat Cheddar cheese was developed using polymerized whey protein (PWP) as a fat replacer and Lactobacillus helveticus as an auxiliary culture, and the effects of PWP on the physicochemical properties of cheese were studied. Results showed that addition of PWP and Lactobacillus helveticus increased the contents of moisture, protein, free amino acids and volatile compounds and lactic acid bacterial population, and markedly improved sensory characteristics and acceptance of cheese. Addition of PWP reduced the fat ripening period, and increased pH 4.6-soluble nitrogen (SN) fraction by 9.45% and 12 g/100 mL trichloracetic acid (TCA)-SN fraction by 11.74% after ripening. Cheese yield was not affected by adding PWP or the auxiliary culture. All the data indicated that polymerized whey protein can be used as a promising fat replacer for developing low-fat Cheddar cheese with good texture and sensory properties.

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.

Yoghurt was made by fermentation of reconstructed milk mixed with Puerariae radix pulp. The optimization of four fermentation conditions (Puerariae radix pulp concentration, inoclum amount, fermentation time and temperature) for the improved sensory quality and flavonoid content of products was carried out using a combination of single factor and orthogonal array designs. The optimal fermentation conditions were 14%, 2.5%, 4.5 h and 41 ℃ for Puerariae radix pulp concentration, inoclum amount, fermentation time and temperature, respectively. The obtained product contained 1.71 mg/mL flavonoids.