Heat-induced polymerized whey protein (PWP) gels from whey protein isolate have limited application due to their high brittleness, but addition of polysaccharides in PWP gels can significantly improve their properties. Agaricus bisporus polysaccharide (ABP), as an anionic polysaccharide, exhibits excellent biological activities, but the formation mechanism of its composite hydrogels with PWP remains unclear. In this study, the effect of ABP concentration (0-4 g/100 mL) was investigated on physicochemical properties of PWP-ABP composite hydrogels including average particle size, zeta potential, surface hydrophobicity, intrinsic fluorescence spectrum and free sulfhydryl group content. The results demonstrated that as the ABP concentration increased, the average particle size of PWP-ABP composite hydrogels significantly increased from (76.22 ± 7.43) to (145.93 ± 8.20) nm (P < 0.05), and the absolute value of zeta potential rose from (35.60 ± 2.64) to (45.20 ± 1.40) mV, indicating that ABP enhanced the stability of the composite hydrogels through electrostatic repulsion. Additionally, the surface hydrophobicity decreased remarkably, and the free sulfhydryl group content significantly decreased (P < 0.05), confirming that ABP altered the tertiary structure of PWP via hydrophobic interactions and disulfide bond crosslinking. Synchronous rheology-Fourier transform infrared spectroscopy analysis revealed that ABP induced a red shift in the amide A region (3600-3200 cm^-1) of PWP, suggesting enhanced hydrogen bond formation; the fluctuations in the amide I band (1625 cm^-1) were attributed to electrostatic interactions. Molecular docking analysis showed that ABP binds to β-lactoglobulin via hydrogen bonds and two-dimensional correlation spectroscopy further validated the changes in O-H stretching vibrations. In conclusion, ABP optimizes the gel network structure of PWP through hydrophobic interactions, hydrogen bonds and electrostatic interactions, providing a theoretical foundation for developing functional food gel systems.

The present study aimed to investigate the gel characteristics of hydrogels formed by 10% (w/v) polymerized whey protein (PWP) and 0-0.75% (w/v) okra polysaccharide (OPS) through heat-induced gelation. The potential application of these hydrogels as thickening agents in goat yogurt was also assessed. Results demonstrated that the addition of OPS promoted the formation of a stable three-dimensional network structure in the PWP-OPS hydrogels, mediated by hydrogen bonding and hydrophobic interactions. Simultaneous rheology and FTIR spectroscopy analysis revealed conformational changes and the burial of aromatic amino acid residues during the heating process. Molecular docking and molecular dynamics simulations further confirmed the spontaneous polymerization and stable complex formation between PWP and OPS. The PWP-OPS hydrogels exhibited superior physicochemical properties and gelation characteristics compared to the individual components. When applied in goat milk yogurt, the incorporation of 1% PWP-OPS hydrogel (comprising 10% PWP and 0.75% OPS) significantly improved (P < 0.05) the texture, sensory attributes, and microstructure, as determined by texture profile analysis, electronic nose and tongue, and scanning electron microscopy. These findings provide a fundamental theoretical basis for the development and application of protein-polysaccharide hydrogels in dairy products.

This study aimed to investigate the difference between low-temperature sterilization methods including induced electric field (IEF) technology and the high-pressure microjet (HPM) and traditional thermal treatment including pasteurization and ultra-high temperature (UHT) sterilization on the sterilization effect and physicochemical properties of milk. The number of harmful colonies, particle size, thermal properties, protein secondary structure, and microstructure were characterized. Results demonstrated that low-temperature sterilization methods were equally effective as thermal sterilization methods. Differential scanning calorimetry results indicated that UHT treatment had enhanced the thermal stability of proteins in milk, while IEF treatment had improved the thermal stability of fats in milk. IEF sterilizing milk (IM) sample exhibited the largest particle size, followed by UHT sterilization milk (UM), raw milk (RM), and pasteurization milk (PM) according to the results of microstructure and size distribution. HPM sterilizing milk (HM) had the smallest particle size due to high pressure. Fourier transformed infrared spectra revealed that UHT sterilization changed the structure of milk protein due to the interactions between proteins, and protein-lactose. Conversely, the low-temperature sterilization methods had less effect on the protein structure. In conclusion, IEF and HPM have the similar sterilization effects to that of thermal sterilization methods, but have less effects on heat sensitive proteins, which has reference significance for the updating of sterilization technology in food field.