Rheological properties and stability of emulsions obtained by electrostatic interactions between soy protein isolate and sodium alginate with ultrasound application

Abstract

Colloidal particle systems based on natural biopolymers are being increasingly used as encapsulating or delivery systems for bioactive ingredients, or to modulate sensory properties of food. Most of these applications involve an emulsification step during processing. The heterogeneous aggregation of lipid droplets with polysaccharides can be used to create highly viscous emulsions or gels similar to, but with much lower oil content than conventional emulsions. This aggregation is induced by mixing a primary emulsion with oil droplets stabilized by a protein with a polysaccharide solution at a pH in which the biopolymers have opposite charges. The application of high intensity ultrasound with the purpose of changing functional properties of polymers has been extensively studied, and furthermore, the use of ultrasound is one of the methods that allow preparation of emulsions with reduced droplet sizes. Thus, this project aims to evaluate the stability and rheological properties of oil-in-water emulsions (O/W) stabilized by electrostatic interaction between a protein (soy protein isolate, SPI) and a polysaccharide (sodium alginate), searching to obtain systems with different textures. We propose to investigate creaming index, size and particle size distribution, and rheological behavior at steady shear of O/W emulsions prepared with SPI/sodium alginate, with different oil contents and with ultrasound application.