Alteration in rheology and microstructure of O/W emulsions using controlled soy protein isolate-polysaccharide aggregation in aqueous phases

In this study, three different types of O/W emulsions were prepared by dispersing 20 wt% soybean oil in aqueous continuous phases, consisting 4 wt % SPI and 0.5 wt% polysaccharide (pectin, iota carrageenan , or kappa carrageenan) composition. The emulsions were heated to thermal denaturation temperature of SPI (90 °C, 30 min), and their rheology, microstructure, and particle size was deeply examined and compared with unheated systems. The results showed that the shear stress, viscosity, shear modulus, and the droplet size of heated emulsions were higher than those of unheated systems. This behavior suggested that thermal treatment exposes the positively charged and hydrophobic regions of SPI in acidic medium (pH 4), which allowed to attach the anionic polysaccharide strongly by electrostatic and hydrophobic interactions, especially in SPI-kappa carrageenan emulsion. This study may be useful for the creation of highly viscous O/W products having higher rheology and stability, but reduced total fat contents.