The effects of high-intensity ultrasonic treatment on emulsification, rheological properties, and flow behavior of liquid egg yolk

High-intensity ultrasonic (HIU) treatment has been used to improve and modify the functional properties of food. HIU potentially inactivates microorganisms in food and modifies the physicochemical properties via the cavitation effect. This study evaluated the combination of different HIU power intensities, temperatures, and times for their effects on diluted liquid egg yolks’ physicochemical properties and rheological and flow behavior. The results showed that Salmonella enteritidis and Escherichia coli in the diluted liquid egg yolks were significantly destroyed as HIU power was increased, and complete destroyed conditions were achieved at 210 W, 60°C for 6 or 9 min. Moreover, the emulsifying activity index of the diluted liquid egg yolks increased significantly at 45 and 60°C under the 75 W HIU treatment, whereas the maximum emulsifying stability index was obtained at 30°C, 210 W for 9 min. Yolk viscosity was positively correlated with HIU power intensity and temperature; the same trend was observed for flow behavior and shear stress. The fluid dynamics of the storage modulus (G′) for the 150 and 210 W HIU treatments increased significantly following the increase in temperature to 45 and 60°C, and G′ > loss modulus (G″). However, free hydrogen sulfide group content also increased significantly after the HIU treatment. Thus, this study revealed that the HIU treatment effectively destroyed the bacteria population in the diluted liquid egg yolk while maintaining or improving the emulsification properties. Moreover, the diluted liquid egg yolk flow parameters apply to egg yolk product manufacturing processes.