Effect of different oils and ultrasound emulsification conditions on the physicochemical properties of emulsions stabilized by soy protein isolate

The effects of different ultrasound emulsification conditions (20 kHz at 50-55 W cm-2, 40% amplitude for 2, 6, 12 or 18 min) on the physicochemical properties of soybean protein isolate-stabilized emulsions containing medium chain triglycerides (MCT), and long chain triglycerides (LCTs, palm, soybean and rapeseed oils) were investigated. It was found that MCT oil emulsions had the minimum droplet size (d4,3) of 0.5 ± 0.0 µm after ultrasound emulsification for 18 min. Moreover, results indicated that MCT oil emulsions had better emulsion stability (using distilled water as a water phase at neutral pH and room temperature) and higher adsorbed protein amounts at their interface than the LCTs emulsions. However, the absolute zeta (ζ)-potential values of MCT oil emulsions were the lowest among all the oil-in-water emulsions. Interestingly, the particle size of palm oil emulsion decreased after heat treatment at 90 °C for 30 min. In conclusion, high intensity ultrasound (HIU) could be considered as a useful emulsification technology to produce emulsions stabilized by soy protein isolate. However, the physicochemical properties of emulsions were different based on the types of oils as well as HIU time.