This study aimed to investigate a novel technology for producing sheep milk cake using Dregea sinensis Hemsl. extract as a new coagulant. The processing conditions were optimized using one-factor-at-a-time and orthogonal array design methods. The sensory characteristics, physicochemical properties, color, texture characteristics and microstructure of the milk cake were evaluated in comparison with those of traditional acid-coagulated milk cake. The results showed that the optimal processing conditions, determined based on sensory score and yield, were as follows: curdling temperature 80 ℃, Dregea sinensis Hemsl. coagulant (DSHC) concentration 22.5%, calcium chloride concentration 0.015%, and pressing for 2 h at 3 kg/cm². The sensory score of the milk cake prepared under the optimized conditions was 83.25 ± 1.04, which was higher than that of acid-coagulated milk cake. The new milk cake contained (32.12 ± 0.39)% protein, (20.45 ± 0.25)% fat and (46.33 ± 0.41)% moisture, and its calcium, phosphorus and selenium contents were significantly higher than those of acid-coagulated milk cake (P < 0.05). Texture profile analysis indicated that the hardness, gumminess and chewiness were significantly better than those of the control group (P < 0.05). The gel network of the DSHC milk cake was more homogeneous and had better water retention capacity. These findings indicate that the novel coagulant DSHC demonstrates potential to replace traditional acid-induced coagulation processes. The product had a uniform color, good taste and strong milky flavor. Therefore, this process can serve as a new technology for the production of sheep milk cake.

To investigate the effect of electron beam irradiation (EBI) on the structure and functional properties of goat milk whey protein concentrate (WPC), WPC treated with different doses of EBI (0, 1, 3, 5, 7, 9, 11, 13, and 15 kGy) were analyzed for structural properties by determining particle size, zeta potential, surface hydrophobicity, fluorescence spectroscopy, color parameters, free sulfhydryl group, total sulfhydryl group, and carbonyl group content as well as using electrophoresis, Fourier transform infrared spectroscopy (FTIR), thermal stability, microstructure. The functional properties were evaluated by measuring the solubility, emulsifying, and foaming properties of WPC. The results showed a close correlation between structural and functional properties, with EBI exerting a dose-dependent effect on WPC. At a dose of 5 kGy, the average particle size of WPC was the smallest, measuring (309.17 ± 2.12) nm. Electrophoretic patterns revealed significant differences in the composition of WPC exposed to varying doses of EBI. FTIR results indicated the internal structure of WPC underwent unfolding and aggregation. Changes in intrinsic fluorescence intensity and surface hydrophobicity suggested that EBI induced protein unfolding and refolding, thereby affecting the exposure and masking of hydrophobic groups. Changes in free sulfhydryl group, total sulfhydryl group, and carbonyl contents indicated that EBI induced the cleavage and formation of disulfide bonds, as well as the oxidation of WPC. Scanning electron microscopy (SEM) observations showed puncture holes on the surface of WPC particles, indicating compromised surface integrity. These findings demonstrated that EBI induced the denaturation of WPC. An EBI dose of 5 kGy resulted in a significant increase in the solubility, foaming capacity, and emulsifying activity from (70.00 ± 1.93)% to (88.80 ± 1.58)%, from (113.8 ± 1.8)% to (119.5 ± 0.7)%, and (25.0 ± 0.3) to (33.3 ± 1.7) m²/g, respectively (P < 0.05). Thus, EBI treatment affects the structure and consequently the functional properties of WPC, providing technical support for the high-value utilization of WPC.

The effect of Astragalus polysaccharide (APS) on the formation and physicochemical properties of whey protein isolate (WPI) gel was systematically evaluated. It was found that visual appearance, gel strength, water-holding capacity, and swelling ratio of the APS-WPI gels were enhanced with increasing APS concentration. APS addition also notably promoted the enhancement in the absolute value of zeta potential with a simultaneous increase in size. Rheological results exhibited that APS-WPI gels had higher apparent viscosities, loss modulus, and storage modulus than native WPI. Scanning electron microscopy demonstrated that the water cavity structure of the gel network was denser when 1.2 g/100 mL APS was used. Additionally, disulfide bonds and hydrogen-bonding interactions between WPI and APS were considered the major contributing forces affecting the formation of APS-WPI gels, as confirmed by Fourier transform infrared spectroscopy and molecular forces. These results indicated that APS is effective in improving the gelling properties of WPI, which provides a reference for the potential application of a gelling agent in functional foods.

This study explored changes in the acidity of sheep milk across different lactation periods and the key factors affecting the acidity of sheep milk. The pH, titratable acidity, fat content, protein content and composition, total sugar content, mineral content, density, lactose content, fatty acid composition and content were analyzed, and the correlation between physicochemical indexes and acidity was investigated. The results indicated that the acidity of raw sheep milk was closely related to lactation stages. The highest acidity was observed in the early lactation period, which then gradually decreased as lactation progressed. Acidity changes were primarily associated with the protein content, fat content, fatty acid composition, total sugar content, lactose content, mineral content, and density of the milk. Among these, the protein content showed the strongest correlation with acidity changes, whereas fatty acid content had a relatively low correlation with acidity variations.

Milk-derived extracellular vesicles (MEVs), originating from mammary epithelial cells, are nanoscale doublelayered membrane vesicles transporting bioactive molecules like proteins, nucleic acids, and lipids, being crucial for intercellular communication and immune regulation. Although milk from minor animal species is not commonly found in the market due to its lower production, it possesses unique nutritional value and potential health benefits and is therefore worth exploring. This review covers the isolation and identification techniques, morphological characteristics, composition and biological characteristics of MEVs from goat, camel, yak, donkey, buffalo, porcine and horse milk. It points out the challenges and future directions in studying MEVs from minor dairy species, aiming to provide a theoretical foundation and scientific guidance for further research and application of MEVs so as to foster the development of the minor species milk industry.