Emulsifying properties of soybean soluble polysaccharide

Soybean soluble polysaccharide (SSPS) is an ingredient extracted from the by-product of the isolation of soybean protein. The objective of this work was not only to study the emulsifying properties of SSPS, but also to determine if different extraction conditions would affect the behavior of the polysaccharide when adsorbed at oil/water interfaces. For this reason, three types of soy polysaccharide, SSPS-L, SSPS-H, and SSPS-M were investigated. Emulsions prepared at pH 3.5–5.0, containing 20% soybean oil and concentrations of SSPS above 4% were stable to creaming for 30 days, for all the SSPS tested. In spite of the presence of galacturonic acid in SSPS, the emulsions were not affected by changes in pH or by addition of CaCl2 (5–25 mM) or NaCl (5–25 mM). Among the three SSPS tested, SSPS-L extracted at 120 °C and pH 3 for 2 h showed the best emulsifying properties forming stable emulsions at a concentration of 4% and up to 50% oil. Differences in the thickness of the adsorbed layer were found depending on the type of SSPS. The thickness of SSPS calculated after hemicellulase or pectinase treatment was estimated to be about 17 nm (SSPS-L), 21–24 nm (SSPS-H), and 30–36 nm (SSPS-M), respectively. The enzymatic degradation of SSPS resulted in oil droplet aggregation, indicating that oil droplet stabilization occurred mainly via steric repulsion.