Yogurt was fermented from milk subjected to protein stabilization at 90 ℃ for 0 (T00), 30 (T30), and 60 s (T60) followed by sterilization at 137 ℃ for 4 s and its viscosity, texture, stability and microstructure were analyzed by a rheometer, a texture analyzer, a stability analyzer and a confocal laser scanning microscope (CLSM). The results showed no significant difference in the viscosity, stability and texture between yogurts T00 and T30. The viscosity of yogurt T60 was only 55.23%–58.98% of that of T30 and T00, and the instability index was 0.19, which was significantly higher than that of T30 and T00. In summary, as the protein stabilization time became longer, the density of yogurt proteins decreased, and protein aggregation occurred.

The differences in fermentation characteristics of commercial ultrafiltrated and nanofiltreated milk, ultrafiltrated milk and untreated milk with and without added sugar were compared in terms of fermentation time, and changes in lactose and glucose contents before and after fermentation, viscosity, texture, and water-holding capacity (WHC). The results showed that compared to untreated milk, the higher the protein content of membrane treated milk, the longer the fermentation time. The consumption rate of lactose was increased by ultrafiltration, while nanofiltration led to a significant decrease in the consumption rate of glucose, which could not be significantly increased even with the addition of sugars. The viscosity of membrane treated milk after fermentation was significantly higher than that of the untreated control, but the shear resistance was worse. Texture profile analysis (TPA) showed that the hardness and chewiness of membrane treated milk after fermentation were significantly higher than those of the control. The WHC of membrane treated milk after fermentation was higher.

In order to provide a deep understanding of flavor formation in cheese, this paper reviews the formation and metabolism of flavor compounds in cheese with respect to proteolysis, lipolysis, and lactase and citric acid fermentation. The focus of this review is on protein breakdown into short-chain peptides and amino acids by natural enzymes, chymotrylase, starter cultures, secondary starter cultures and non-starter microorganisms, the formation of lactone and butyric acid as metabolites during the enzymatic hydrolysis of fatty acids, the conversion of lactose into lactic acid by lactic acid bacteria, and the conversion of the intermediate pyruvate into diacetic acid and 3-hydroxy-butanone, acetaldehyde or acetic acid. Conclusively, the flavor substances of cheese mainly include fatty acids, esters, aldehydes, alcohols, ketones, sulfides, phenols and ethers.

The four taste-active compounds in Edam cheese, i.e., lactic acid, sodium chloride, free amino acids and free fatty acids were determined. Changes in the contents of lactic acid, sodium chloride and free amino acids were examined after being treated with human saliva, simulated saliva and deionized water were examined. The contribution of these compounds to cheese taste was identified by taste active value (TAV). The results showed that lactic acid had no contribution to cheese taste after three treatments. Sodium chloride mainly contributed to the salty taste and there was no significant difference of sodium chloride content between human saliva and deionized water treatments. Free fatty acids were primarily responsible for the acid taste with a mellow mouth feeling. The glutamic acid content of cheese was below the threshold value after human saliva treatment and no umami taste was perceived. Sensory evaluation indicated that the salty taste of cheese was strong and retained well.