Improving interfacial properties, structure and oxidative stability by ultrasound application to sodium caseinate prepared pre-emulsified soybean oil

The effect of high-intensity ultrasound on the interfacial properties and structure and the oxidative stability of a pre-emulsion prepared by sodium caseinate (SC) as well as on a high level of soybean oil was evaluated. Compared to the control emulsion, ultrasound treatments for 3, 6 and 9 min significantly decreased the average droplet size (P<0.05) and produced more stable emulsions with no creaming phenomenon. Ultrasound-induced emulsions had much lower interfacial tension and Turbiscan stability index. Ultrasound treatment significantly enhanced the adsorbed proteins concentration (P<0.05); moreover, SDS-PAGE showed that the content (band intensity) of alpha s(1)-, alpha s(2)-, and beta-casein were increased. Ultrasound treatment led to a decrease in peroxide value and thiobarbituric acid reactive substance during 14 d of storage. The 6 min of ultrasound-induced emulsion had higher content of interfacial proteins (P<0.05) than other ultrasound-induced emulsions. Transmission electron microscopy revealed that 6 min of ultrasound treatment created a thicker and more compact interfacial protein films in the SC-stabilized emulsions. Ultrasound treatments improved interfacial properties and oxidative stability of SC-prepared pre-emulsified soybean oil.