The differences in characteristics between stirred and set yogurt produced from A1 or A2 β-casein milk were studied. The water-holding capacity of stirred and set yogurt produced from A1 β-casein milk was greater than 69%, and the water-holding capacity of stirred and set yogurt produced from A2 β-casein milk was greater than 65%. Textural analysis showed that the hardness and consistency of set yogurt produced from A1 β-casein milk were 41.4% and 59.8% higher than those of set yogurt produced from A2 β-casein, respectively. Compared with A2 β-casein yogurt, A1 β-casein yogurt had better viscosity. The results of rheology and microstructure showed that the hysteresis loop area of A1 β-casein yogurt was 14.6% smaller than that of A2 β-casein yogurt indicating that the former’s structure can be more easily damaged and its network structure is sparser. This study provides theoretical support for the application of A2 β-casein milk in yogurt.

In this study, we investigated the changes in the functional properties (meltability and fat precipitation), texture, rheological properties, and microstructure of processed cheese during emulsification (5–30 min) at different temperatures (80 and 85 ℃). The results showed that as the emulsification time increased, the meltability and fat precipitation showed a decreasing trend, and the fat precipitation at 85 ℃ was significantly higher than that at 80 ℃ during the emulsification process (P < 0.05). The gumminess and chewiness increased significantly (P < 0.05) with the increase in emulsification time, and the hardness, gumminess and chewiness at 85 ℃ were greater than those at 80 ℃. The storage modulus (G’) of processed cheese was greater than the loss modulus (G”) at the same degree of emulsification for both temperatures and both G’ and G” showed an upward trend with increasing frequency from 0.1 to 10 Hz. The microstructure of processed cheese showed that the number of fat globules was greatly reduced, the diameter was decreased, the distribution of fat globules became more uniform, the protein matrix became smoother and the cheese structure became denser at 5–15 min of emulsification. However, the microstructure of processed cheese was honeycomb-like at 20–30 min of emulsification, suggesting excessive creaming reaction. Therefore, a short emulsification time during the processing of processed cheese will result in inadequate creaming reaction; too long emulsification time will cause adverse changes in cheese texture. During the emulsification process, the protein-protein and protein-fat interactions were enhanced, thereby improving the functional properties of the product. In conclusion, the emulsification process of processed cheese is closely related to its physicochemical and functional properties and microstructure. This study provides some theoretical guidance for future process development of processed cheese production.

In this study, calcium-chelating casein hydrolytic peptide (CHP-Ca) was prepared by the chelation reaction between CHP, which was prepared from enzymatic hydrolysis of micelle casein, and calcium chloride at a mass ratio of 2:1. Five enzymes (flavourzyme, alcalase, trypsin, papain and neutral protease) were screened based on hydrolysis degree (DH) and calcium-chelating capacity. A mixture of flavourzyme and trypsin was found to be the best enzyme for the enzymatic preparation of CHP. Furthermore, response surface methodology (RSM) was used to optimize the enzyme hydrolysis conditions. The results showed that the optimal conditions were enzyme-to-substrate ratio 6000 U/g, flavourzyme-to-trypsin ratio 1:1, hydrolysis time 90 min, pH 6.9, and temperature 42 ℃. The calcium chelation capacity of the peptide prepared under these conditions was (90.46 ± 0.72) μg/mg. Finally, the structural properties and formation mechanism of CHP-Ca were investigated by X-ray diffraction (XRD), thermogravimetry (TG), zeta potential, particle size analysis and infrared (IR) spectroscopy. The results showed that CHP-Ca bound mainly by the interaction of carboxyl, amino and phosphate groups, and the zeta potential and particle size decreased after chelation, and the structure of CHP-Ca became more compact.

An emulsion gel stabilized by a mixture of whey protein and pectin (WP) and an emulsion gel stabilized by a mixture of whey protein and glucan (WG) were prepared by an acid induction method. The functional properties of WP and WG emulsion gels with dispersed phase volume fractions of 35% and 75% (called WP35, WG35, WP75, and WG75) were evaluated and compared, and the efficiency of high internal phase emulsion gels as a fat replacer in replacing fat in low-fat processed cheese was further investigated. The results showed that WP75 had the smallest mean particle size, uniform fat distribution, and a stable protein network structure. Within the frequency range of 0.1–10 Hz, both the elastic modulus (G’) and viscous modulus (G”) values of the emulsion gel samples tended to increase as the oil phase volume fraction increased. Compared with the other samples, WP75 was superior in terms of deformation resistance, thermal stability, and water-holding capacity. Addition of WP75 into processed cheese with 15% (m/m) fat reduced the oil syneresis and increased the meltability without resulting in significant differences in textural properties compared with the control group (full-fat). This study demonstrated that high internal phase emulsion gels stabilized by whey protein and pectin could be used as a fat replacer in the development of low-fat cheese products.

Milk fat globules (MFGs) originate from mammary epithelial cells, with the lipids and proteins in the milk fat globule membrane (MFGM) maintaining the stability of MFGs through electrostatic repulsion and steric hindrance. Components of the membrane possess specific nutritional properties. Reconstruction of the fat globule interface is critical to the quality of liquid dairy products. Hence, this article critically summarizes and uncovers commonalities among recent studies on the mechanism of milk fat globule interface construction during milk processing. Homogenization disrupts the structure of the MFGM, leading to its rearrangement. Additionally, thermal treatment alters protein structure and induces the lateral separation of lipid domains in the membrane. Meanwhile, the thermal response of proteins and lipids in the MFGM leads to the loss of its components. Exogenous additives participate in the reconstruction of the MFGM by improving the oil-water interface and enhancing the stability of MFGs. Future studies should focus on the connection between the mechanism of MFGM construction and the macroscopic system, as well as optimizing specific processing conditions to obtain higher-quality dairy products.