Effects of ultrasound-heat pretreated egg white powder addition on the quality, gel properties, and metatranscriptomic profiles of yogurt.

Egg white powder incorporation into high-protein yogurt may interfere with starter culture performance and acid-induced gel formation. This study prepared egg white powder by ultrasound-heat pretreatment followed by spray drying (UHSD-prepared egg white powder) and evaluated its effects on set-type yogurt. Compared with fresh egg white, the UHSD-prepared egg white powder exhibited a 90.3% reduction in apparent lysozyme activity. Yogurt containing 1% UHSD-prepared egg white powder exhibited improved texture, water-holding capacity, and viscoelastic properties, whereas 4% addition increased pH, reduced titratable acidity, and decreased some texture parameters. Metatranscriptomic analysis revealed greater transcript representation of lactic acid bacteria-related taxa in the 1% group, while the 4% group exhibited reduced transcriptional representation of glycolysis/gluconeogenesis, pyruvate metabolism, glycoside hydrolases, and glycosyltransferases. UHSD-prepared egg white powder showed potential as a functional ingredient to modulate yogurt quality. Further comparison with conventional spray-dried egg white powder is needed to clarify the specific contribution of ultrasound-heat pretreatment.