Plant-based Pickering emulsions using cellulose nanofibers and soy protein isolate: Stabilization and high environmental resistance

Soy protein isolate (SPI) can be used as a sustainable plant-based emulsifier to formulate edible oil-in-water emulsions. However, SPI-stabilized emulsions are highly prone to droplet aggregation when exposed to alterations in environmental or solution conditions such as pH, ionic strength, and temperature, which restricts their utilization in the food industry. In this study, this problem was overcome by preparing soy protein isolate-cellulose nanofiber (CNF/SPI) complexes as Pickering emulsifiers. These complexes are formed due to an electrostatic attraction between the cationic protein and anionic polysaccharides under the solution condition used (pH 3). The composition of the CNF/SPI complexes can be modulated to enable control over the oil droplet morphology. Emulsions formulated with the optimized CNF/SPI composition exhibit good environmental tolerance to changes in temperature (50–90 °C), pH (3–11), and ionic strength (100–500 mM). This improvement in stability is mainly attributed to the presence of thick and robust interfacial layers formed by the CNF/SPI complexes around the oil droplets. The potential of the CNF/SPI complexes as emulsifiers for application in food emulsions is assessed across various oil volume fractions and types. Overall, this research shows that CNF/SPI complexes can be used to overcome the limitation of traditional SPI emulsifiers, aiming at to be used in the formulation of next-generation sustainable plant-based foods.