Abstract
The stabilizing behaviour of soluble soy polysaccharide (SSPS) on acidified dispersions of soy protein isolate (SPI) and SPI-stabilized emulsions was studied. SPI and SSPS suspensions were characterized via light scattering, surface charge measurement, turbidity, sedimentation analysis, and light microscopy. At acidic pH (pH 6-3), it was found the addition of at least 0.25 wt% SSPS was required to stabilize 0.75 wt% SPI suspensions against aggregation and phase separation, likely via steric repulsion. The mechanism of SPI-SSPS interaction was shown to be electrostatic in nature by testing the effects of increased ionic strength of the suspensions. The stabilizing effect of SSPS on SPI was then applied to 5% oil-in-water emulsions. The presence of SSPS stabilized the emulsions against droplet size increases and phase separation over time. Overall, the results demonstrated that it was possible for SSPS to stabilize SPI suspensions and that SPI-SSPS interactions may be used as a tool to stabilize O/W emulsions.
Highlights
An extensive amount of work has been performed on the characterization of oil-in-water emulsions stabilized by proteins, polysaccharides and protein-polysaccharide interactions, but little work has been performed on the characterization of such emulsions stabilized by soy protein isolate (SPI) and soy soluble polysaccharide (SSPS)
Surface denaturation may lead to the exposure of new hydrophobic or hydrophilic groups, which can result in increased attraction or repulsion, respectively, via hydrophobic interactions or electrostatic and/or steric repulsion [18]
Suspensions of 0.75 wt% SPI became destabilized at moderately acidic pH due to decreased solubility resulting from protein charge neutralization
Summary
An extensive amount of work has been performed on the characterization of oil-in-water emulsions stabilized by proteins, polysaccharides and protein-polysaccharide interactions, but little work has been performed on the characterization of such emulsions stabilized by soy protein isolate (SPI) and soy soluble polysaccharide (SSPS). Proteins are amphiphilic, having both hydrophilic and hydrophobic portions, making them surface active because they are able to interact with both the oil phase and aqueous phase in an emulsion and reduce the interfacial tension at droplet interfaces. As the coarse emulsion flows through the small gap between the valve (A) and the seat (B), there is a rapid increase in velocity accompanied by a decrease in pressure This produces a turbulent flow that disrupts the droplets at the discharge gap (D). This chapter summarizes the work done for the thesis, beginning with the experimental methods used to prepare and characterize the soy protein and polysaccharide suspensions and emulsions and finishing with the results and discussion
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