Ultrasound-induced food protein-stabilized emulsions: Exploring the governing principles from the protein structural perspective

Consumers' growing demand for healthy and natural foods has led to a preference for products with fewer additives. However, the low emulsifying properties of natural proteins often necessitate the addition of emulsifiers in food formulations. Consequently, enhancing the emulsifying properties of proteins through various modification methods is crucial to meet modern consumer demands for natural food products. High-intensity ultrasound offers a green, efficient processing technology that significantly improves the emulsifying properties of proteins. This study explores how ultrasound treatment enhances the stability of protein-based emulsions by modifying protein structures. While ultrasonic treatment does not significantly affect the primary structure of proteins, it influences the secondary, tertiary, and quaternary structures depending on the type of protein, ultrasound parameters (type, intensity, and time), and treatment conditions. The results suggest that ultrasound treatment reduces α-helix content, decreases protein particle size, and increases β-sheet content, surface hydrophobicity, free sulfhydryl groups, and zeta potential, leading to a more stable protein-based emulsion. The reduced particle size and increased flexibility of proteins induced by ultrasound enable more rapid protein adsorption at the oil-water interface, resulting in smaller emulsion droplets. This contributes to the emulsion's improved stability during storage. Future research should focus on the large-scale application of ultrasonic treatment for protein modification to produce high-quality, natural foods that meet the evolving needs of consumers.