Abstract: The purpose of this study was to investigate the effects of sodium starch octenyl succinate (SSOS) as emulsifier and soy protein isolate (SPI) as co-emulsifier on the oxidative stability of nanoemulsion. The ultrasonic emulsification method was used to prepare flaxseed oil nanoemulsion. The results showed that the optimum preparation conditions were as follows: ultrasonic power of 600 W, core-to-wall ratio of 1:1.5, pulse mode of 8 s, and ultrasonication time of 20 min. The nanoemulsion obtained under these conditions was characterized by high embedding rate ((75.1 ± 4.9)% to (74.6 ± 4.2)%), low particle size ((244.0 ± 3.0) to (246.8 ± 4.5) nm) and high absolute zeta-potential value ((−67.2 ± 3.0) to (−69.3 ± 4.0) mV). With the addition of SPI, the peroxide value (PV) and thiobarbituric acid reactive substances (TBARS) value of the nanoemulsion were significantly reduced, and the oxidative stability was remarkably improved. This could result from the fact that SPI could increase the hydrophobicity of the mixed emulsifier, preventing flaxseed oil from contacting with oxygen radicals in the aqueous phase. This study will provide a new idea for improving the water solubility and oxidative stability of flaxseed oil, and provide a theoretical basis for extending the shelf life of flaxseed oil and promoting its application in the food field.

Key words: flaxseed oil; sodium starch octenyl succinate; soy protein isolate; nanoemulsion; ultrasonic emulsification