Structure and emulsifying properties of whey protein isolate: Effect of safflower yellow concentration

Research on the preparation of soy protein isolate and whey protein isolate composite nanoparticles and their characteristics in high internal phase Pickering emulsions

This study investigated the role of thermal drive in the formation of soy protein isolate and whey protein isolate (SPI-WPI) complexes, as well as the stability effect of SPI-WPI complexes on high internal phase Pickering emulsions (HIPPEs). The shift in the peaks in the infrared spectrum and the change in fluorescence intensity indicated the interaction between these two proteins, which implies that SPI-WPI is not two dispersed groups of particles. Maximum emulsification activity (10.65 m2/g) and the absolute value of potential (37.87 mV) were achieved at an SPI to WPI mass ratio of 7:3. As the concentration and pH of the SPI-WPI complex increased, the droplets become evenly uniform and compact. It is predicted that the high concentration conditions are more favorable for the formation of a gel network structure. This research provides an effective strategy for HIPPEs stabilization using complex proteins.

Inhibitory Mechanism of Camellianin A against α-Glucosidase: In Vitro and Molecular Simulation Studies

α-Glucosidase is an important target for type II diabetes treatment, and the search for natural α-glucosidase inhibitors is currently a hot topic in functional food research. Camellianin A is the main flavonoid in the leaves of Adinandra nitida, but research on its inhibition of α-glucosidase is rarely reported. In view of this, the present study systematically investigated the inhibitory impact of camellianin A on α-glucosidase, combining the fluorescence method and molecular docking to explore their interaction, aiming to reveal the relevant inhibitory mechanism. The results indicated that camellianin A possessed excellent α-glucosidase inhibitory activity (IC50, 27.57 ± 0.59 μg/mL), and van der Waals force and hydrogen bonding dominated the binding process between camellianin A and α-glucosidase, with a binding-site number of 1. A molecular docking experiment suggested that camellianin A formed hydrogen bonding with Glu771, Trp391, Trp710, Gly566, Asp568, and Phe444 of α-glucosidase, consistent with the thermodynamic result. Our result can provide a reference for the development of natural α-glucosidase inhibitors.

Antioxidant stability and in vitro digestion of β-carotene-loaded oil-in-water emulsions stabilized by whey protein isolate-Mesona chinensis polysaccharide conjugates

The aim of this study was to investigate the delivery of functional factor β-carotene by emulsion stabilized with whey protein isolate-Mesona chinensis polysaccharide (WPI-MCP) conjugate. Results showed that the WPI-MCP complex had better antioxidant properties than WPI. Correspondingly, the emulsions stabilized by this complex also had better oxidative stability compared with protein emulsions alone. The particle size of WPI-MCP emulsion was smaller and had a better stability when MCP was added at 0.2 % (w/v). The sizes of WPI-MCP and WPI emulsions were 3594.33 and 7765.67 nm at pH 4, indicating improved emulsion stability around isoelectric point of WPI. At different NaCl concentrations, the absolute values of zeta-potential of WPI-MCP emulsions were larger than that of WPI emulsions except 0.1 % (mol/L) NaCl. The sizes of WPI and WPI-MCP emulsions were 2384.32 and 790.12 nm, respectively. During in vitro digestion, WPI-MCP stabilized emulsions slowed down the release of free fatty acids and achieved about 80 % bioaccessibility of β-carotene, indicating that WPI-MCP-stabilized emulsions encapsulating β-carotene can effectively control the release of bioactive substances. These studies have potential significance and value for the construction of food-grade emulsion delivery system.

Exploring the binding effect and mechanism of glycyrrhizin to ovomucin by combining spectroscopic analysis and molecular docking

Ovomucin (OVM) is an ideal natural macromolecular glycoprotein extracted from eggs with good adhesion. Based on the defect that glycyrrhizin (GL) has good antiviral activity but fast metabolism, this study aimed to explore the binding effect and mechanism of GL to OVM, using multi-spectroscopic techniques, isothermal titration calorimetry (ITC), and molecular docking. The adhesion ability of OVM to the hydrophilic interface and GL was first demonstrated by dual polarization interferometry (DPI) analysis and binding capacity assay, and the OVM-GL complex exhibited a similar affinity for the spike protein of COVID-19. The spectroscopic results show that GL can quench the inherent fluorescence and change the glycosidic bond and secondary structure of OVM. The ITC measurements suggested that the binding was exothermic, the hydrogen bond was the dominant binding force for forming OVM-GL. Finally, molecular docking results indicated that GL has hydrogen bond interaction with several amino acid residues located in α-OVM and β-OVM while embedding into the hydrophobic pocket of OVM via hydrophobic interactions. In conclusion, OVM can adhere to the hydrophilic interface and bind to GL through hydrogen bonding and hydrophobic interactions to form a stable complex, that is expected to be helpful in virus prophylaxis.

The Effects of Ethanol and Rutin on the Structure and Gel Properties of Whey Protein Isolate and Related Mechanisms

The effects of different levels of rutin (0, 0.05%, 0.1%, 0.2% and 0.3% w/v) and ethanol on the structure and gel properties of whey protein isolate (WPI) were examined. The results showed that the addition of ethanol promoted the gel formation of WPI. The addition of rutin increased the gel strength of WPI and maintained the water-holding capacity of the gel. Ethanol caused an increase in thiol content and surface hydrophobicity, but rutin decreased the thiol content and surface hydrophobicity of WPI. The particle size, viscosity and viscoelasticity of WPI increased at rutin levels of 0.2% and 0.3%, indicating that rutin caused cross-linking and aggregation of WPI, but rutin had no significant effect on the zeta-potential, indicating that electrostatic interactions were not the main force causing the changes in protein conformation and gel properties. Ethanol and rutin improved the gel properties of WPI possibly by inducing cross-linking of WPIs via hydrophobic and covalent interactions.

Non-covalent interaction between pea protein isolate and catechin: effects on protein structure and functional properties

The aim of this study was to investigate the effects of non-covalent interaction between pea protein isolate (PPI) and different concentrations (0.05–0.25%, w/v) of catechin (CT) on the structural and functional characteristics of protein.