Abstract: In this study, highly stable algal oil-based nanoemulsions stabilized by a combination of soy protein isolate (SPI) and stevioside (STE) were prepared by pre-structuring the oil phase. The microstructure observation, differential scanning calorimetry (DSC) test, and rheological analysis of the algal oil-based oleogels showed that in algal oil with 4% (m/m) beeswax added, a large number of crystals were connected to form a stable network structure, thereby constructing a stable oleogel. The effects of algal oil pre-structuring on the formation and stability of algal oil-based nanoemulsions were investigated. The results showed that the addition of beeswax had no significant effect on nanoemulsion formation. With increasing concentration of beeswax in algal oil (up to 6%), the physical stability of nanoemulsions gradually increased; however, at a higher concentration (8%), more rigid gel network was formed, which destroyed the interfacial layer and in turn led to deterioration of the physical stability of the nanoemulsion. The results of thermal oxidation and photooxidation tests showed that oil phase structuring significantly improved the oxidative stability of the nanoemulsion, and the sample with 6% beeswax added in the oil phase displayed the highest oxidative stability. This study can provide technical support for the preparation of highly stable nanoemulsion-based delivery systems for algal oil in the food industry.

Key words: algal oil nanoemulsion; beeswax-based oleogel; oxidative stability; soy protein isolate; stevioside