Ultrasonic assisted oil-in-water emulsions stabilized by flaxseed protein isolate: influence of different oils

In this study, the physicochemical properties and stability of ultrasonic assisted flaxseed protein isolates (FPI) emulsions containing medium chain triglycerides (MCT), soybean oil, flaxseed oil, or docosahexaenoic acid (DHA) algae oil were investigated. The particle size distribution, zeta-potential, turbiscan stability index (TSI), and backscattering profiles were determined. The results showed that the emulsions containing flaxseed oil had the smallest droplet size and the lowest TSI value after 30 min ultrasonic treatment. Flaxseed oil emulsions showed the best storage stability with minimum clarified layer and cream layer after 10 days storage. MCT emulsions were more sensitive to salt, and less stable than other oil emulsions. Soybean oil, flaxseed oil, and DHA oil emulsions had good stability under low ionic strengths (0–50 mM NaCl), and became unstable under high ionic strengths (150 and 300 mM). Thermal treatment had great influence on the particle size distribution of emulsions. The particle size of the four oils emulsions increased after heating at 90 °C for 30 min. However, the particle size of DHA oil and flaxseed oil emulsions decreased after heating at 50 °C for 30 min. In conclusion, ultrasonic treatment is one of the effective ways to improve stability of FPI-stabilized emulsions, which are based on the oil type and ultrasound intensity. The effects of oil type and chain length on particle size and stability of FPI-stabilized emulsions could be further studied.