In this study, the effect of dynamic high-pressure micro-fluidization (DHPM) on the functional properties of egg white protein was investigated. The results showed that the pH of egg white protein reached a maximum value of 9.22 after one cycle of homogenization at 10000 psi, while the protein solubility reached a maximum value of 96.39% after one cycle of homogenization at 8000 psi. The gel hardness and chewiness of egg white protein reached their maximum values after two cycles of homogenizations at 13000 psi, significantly increasing by 55.32% and 28.93%, respectively, compared with the untreated control group (P < 0.05). The foaming capacity of DHPM-treated egg white protein reached a maximum value of 268.68% after two cycles of homogenizations at 6000 psi, which was 2.52 times that of the control group (106.02%)(P < 0.05). The foam stability reached a maximum value of 85.12% after three cycles of homogenization at 6000 psi, which was 2.07 times that of the control group (41.07%) (P < 0.05). The emulsifying activity reached a maximum value of 16.00% after three cycles of homogenizations at 8000 psi, which was two times that of the control group (8%) (P < 0.05). The emulsion stability reached a maximum value of 95.76% after three cycles of homogenization at 13000 psi, which was 13.01 times that of the control group (7.36%) (P < 0.05). Therefore, DHPM treatment can effectively improve the foaming and gelling properties of egg white protein. This study aims to provide a new theoretical basis and practical reference for the physical modification of egg white protein and to lay a foundation for furthering the application of DHPM in food protein processing.

Casein phosphopeptide-quercetin (CPP-QR) covalent and non-covalent complex were constructed, and the activity changes and difference mechanisms of these two complexes were explored after gastrointestinal digestion using dynamic simulation digestion and molecular dynamic (MD) simulation. Compared with CPP, the soluble calcium binding capacity of CPP-QR covalent and non-covalent complex increased by 44.35% and 34.57% respectively, and the DPPH· scavenging rate increased by 77.97% and 25.46% respectively after static simulation digestion. Thereinto, the activity of CPP-QR covalent complex was significantly better than that of CPP-QR non-covalent complex (P < 0.05). Under acidic conditions, the DPPH· scavenging rate of CPP-QR covalent and non-covalent complexes was higher than that of CPP (P < 0.05). While the antioxidant activities of two complexes decreased significantly at pH=8, they still exhibited markedly superior performance relative to CPP alone (P < 0.05). The CPP-QR covalent and non-covalent complex exhibited 66.72% and 70.72% higher inhibition rates than CPP against pepsin, and 83.85% and 46.60% higher inhibition against trypsin, respectively. MD simulation had revealed that the binding free energies were -60.71 kcal/mol for the non-covalent complex in the pepsin system versus -84.21 kcal/mol for the covalent complex in the trypsin system. The CPP-QR non-covalent complex has exhibited minimal radius of gyration (Rg) and root-mean-square deviation (RMSD) in pepsin systems, while the CPP-QR covalent complex had demonstrated superior stability with correspondingly minimal Rg and RMSD in trypsin systems. In conclusion, the soluble calcium binding capacity and DPPH· scavenging rate of the CPP-QR covalent complex were superior to those of the non-covalent complex and CPP. CPP-QR covalent complexes had higher stability in the intestinal phase due to their resistance to trypsin, while non-covalent complexes maintain higher activity during gastric digestion due to their resistance to pepsin and acid adaptation.

The foaming characteristics of rice bran protein (RBP)-ovalbumin (OVA) mixtures were investigated, and the physicochemical properties of the two proteins in solution and foam under specific pH and NaCl concentration were analyzed to elucidate the effects of the interaction between them on their foaming characteristics. The results showed that the two proteins had a synergistic effect on their foaming ability at pH 4.0, and the foaming ability and foam stability of the 3:1 mixture of RBP and OVA were significantly increased by addition of 1% NaCl. However, at pH 7.0, the two proteins showed no obviously synergistic effect on their foaming properties without NaCl, but instead showed an antagonistic effect when 1% NaCl was added. Under pH 4.0 and 1% NaCl conditions, the physicochemical properties of the two proteins in the solution and foam were complementary to each other. Therefore, the interaction between RBP and OVA can improve the foaming ability and foam stability of their mixtures from the perspective of different physicochemical properties.