Insoluble soybean polysaccharides as potential O/W emulsifying agent

PORFIRI, M.C.; VACCARO, J.; STORTZ, C.A.; NAVARRO, D.A.; WAGNER, J.R.; CABEZAS, D.M.

CABA

Conferencia; Conferencia Internacional de Proteínas y Coloides Alimentarios; 2017

Universidad de Buenos Aires

Proteins and polysaccharides play a key role in the structure formation and stabilization of oil-in water (O/W) emulsions. Proteins are commonly used as emulsifiers due to its ability to prevent droplet aggregation and coalescence. On the other hand, polysaccharides are often incorporated to stabilize the emulsion droplets against gravitational separation by increasing the viscosity of the aqueous phase or by the formation of a gel. Various studies report that polysaccharides may also interact with protein adsorbed at the interface enhancing the emulsion stability. In this way, only polysaccharides with sufficient hydrophobic character to adsorb strongly at the oil-water interface or those directly complexed with proteins are capable of making and stabilizing O/W emulsions.The aims of this work were to obtain different samples of insoluble soybean polysaccharides (ISPS) from defatted soy flour and to study their potential application as O/W emulsifier. In this regard, the insoluble residue (okara) resulting from an aqueous extraction (60ºC, pH 9.0), was submitted to an acidic extraction (pH 3.5, 120°C) without or with a pretreatment (high pressure homogenization or sonication treatment). The insoluble residues of these extractions were dried (oven, 70°C or vacuum post-treatment with 2-propanol, 40°C) yielding different ISPS samples. Aqueous dispersions of ISPS samples (1-2% w/w, pH 3 and 7), were used to prepare coarse and fine O/W emulsions. Emulsion stability against creaming and coalescence processes, and the rheological behavior were analyzed. ISPS samples obtained by okara pretreatment and vacuum dried post-treatment with 2-propanol produce emulsions with high values of flocculation degree, increase the stability of the particle size, and allow the formation of stronger gel-like emulsions. These pretreatments enable a better emulsifying activity of the insoluble-compounds with surface activity (proteins, polysaccharides-protein complexes and hydrophobic polysaccharides), probably by solubilization and elimination of low molecular weight polysaccharide and/or peptides fragments. Particularly, sample obtained by high pressures homogenization of the okara presented the best emulsifying properties and it was not significantly affected by variations in the pH of the emulsion. The results of this research work demonstrate a high potential of application of the ISPS samples as O/W emulsifier, under acid and neutral conditions, increasing the added value of an important by-product of the soybean industry.