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Influence of high intensity ultrasound (HIUS) on the structure and properties of ovalbumin (OVA) were investigated. It was found that the subunits and secondary structure of OVA did not change significantly with HIUS treatment from the electrophoretic patterns and circular dichroism (CD) spectrum. The amount of free sulfhydryl groups increased and intrinsic fluorescence spectra analysis indicated changes in the tertiary structure and partial unfold of OVA after sonication increased. Compared with the untreated OVA, HIUS treatment increased the emulsifying activity and foaming ability, and decreased interface tension (oil-water and air-water interface), which due to the increased surface hydrophobicity and decreased the surface net charge in OVA, while the emulsifying and foaming stability had no remarkable differences. The increased particle size may be attributed to formation of protein aggregates. Moreover, the gelation temperatures of HIUS-treated samples were higher than the untreated OVA according to the temperature sweep model rheology, and this effect was consistent with the increased in surface hydrophobicity for ultrasound treated OVA. These changes in functional properties of OVA would promote its application in food industry.

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Edible gliadin nanoparticles (GNPs) were fabricated using the anti-solvent method. They possessed unique high foamability and foam stability. An increasing concentration of GNPs accelerated their initial adsorption speed from the bulk phase to the interface and raised the viscoelastic modulus of interfacial films. High foamability (174.2 ± 6.4%) was achieved at the very low concentration of GNPs (1 mg/mL), which was much better than that of ovalbumin and sodium caseinate. Three stages of adsorption kinetics at the air/water interface were characterized. First, they quickly diffused and adsorbed at the interface, resulting in a fast increase of the surface pressure. Then, nanoparticles started to fuse into a film, and finally, the smooth film became a firm and rigid layer to protect bubbles against coalescence and disproportionation. These results explained that GNPs had good foamability and high foam stability simultaneously. That provides GNPs as a potential candidate for new foaming agents applied in edible and biodegradable products.

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Protein hydrolysates, as surfactants, can scavenge radicals, but their poor distributions at the oil−water interface limit their storage stability. Therefore, we studied covalent interaction between rice protein hydrolysates and chlorogenic acid under alkaline conditions to improve the physical and oxidative stability of oil-in-water emulsions. Turbidity and particle size measurements demonstrated the formation of hydrolysates−chlorogenic acid complexes, and their covalent interaction resulted in the decrease and redshift of the fluorescence intensity. The emulsifying activity of the hydrolysates could be effectively improved after the covalent interaction with 0.025% chlorogenic acid. The modified emulsions possessed a notable physical stability according to the least changes in size (0.08 μm) and ζ-potential (3.34 mV) of the emulsion (P > 0.05). Moreover, the covalent interaction endowed modified emulsions with high oxidative stability to effectively inhibit lipid oxidative deterioration during storage. The adsorption of hydrolysates to the emulsion interface was increased by the adequate addition of chlorogenic acid, which resulted in the oil droplet being surrounded by a thicker interfacial film. The covalent interaction between the protein hydrolysates and chlorogenic acid could be used to construct natural emulsion systems with a higher physical and oxidative stability during storage.