Effect of thermosonication on protein oxidation, aggregation, structure and storage stability of goat milk

Heat treatment is widely used in dairy processing but often induces protein oxidation and aggregation, compromising the nutritional quality and shelf life of pasteurized goat milk. This study systematically investigated the effects of thermosonication (moderate heat combined with low-frequency ultrasound) on protein structural stability, aggregation behavior, and storage performance in goat milk. Fresh skimmed goat milk was treated at 72, 75, 80, 90, or 125 °C with or without ultrasound (400 W, 1:1 duty cycle, 0–10 min). Thermosonication reduced carbonyl content from 20.26 to 12.03 nmol mg −1 at 72 °C after 10 min ultrasound, with 5 min sonication alone reducing carbonyls by approximately 29–32% across all temperatures. Dityrosine formation decreased and free sulfhydryl groups were partially restored with increasing sonication duration. Particle size decreased from approximately 1000 nm at 72 °C to the 10–100 nm range after 125 °C combined with 10 min ultrasound. Size-exclusion chromatography and SDS-PAGE confirmed dissociation of high-molecular-weight aggregates and recovery of β-casein. Zeta potential and surface hydrophobicity increased with sonication, reflecting improved colloidal stability and structural unfolding. Regarding microbial safety, raw goat milk exceeded 5 log CFU mL −1 by day 5, pasteurized goat milk by day 10, whereas 72 °C combined with 10 min ultrasound extended safe storage to day 18. These findings demonstrate that thermosonication effectively stabilizes goat milk proteins while prolonging shelf life, offering practical applications for the dairy industry.