Effect of Chemical Environment on Soybean Protein-Lecithin Interaction and Stability of O/W Emulsions

J.R. WAGNER; TOMÁS, M. C.

Orlando, USA

Congreso; 100th AOCS Annual Meeting & Expo; 2009

merican Oil Chemists´ Society (AOCS)

The aim of this work was to study the effect of the chemical environment on soybean protein-lecithin interaction and the stability of O/W emulsions. O/W (25:75 w/w) emulsions were prepared with native(NSI) or denatured (DSI) soy isolates, lecithin (Lec), sunflower oil, protein-lecithin ratio (100:1-10:1), pH 2-7.The effect of pH, ionic strength and calcium salts were studied. The optical characterization of dispersions were determined. For DSI-Lec and NSI-Lec systems, creaming rate changed as a function of pH value. For DSI-Lec the stability increased at pH values not closed to the isoelectric point. The presence of Lec enhances the stability against to the coalescence process. It is interesting to consider the effect of the unfolding of 7S and 11S fractions by thermal treatment and their increased surface hydrophobicity on soybean proteins-Lec interaction. NSI-Lec emulsions at pH 2.0 presented an important initial emulsifying activity by denaturation of 11S fraction but the creaming rate was faster than those obtained for pH 5.5,7.0. The increase of ionic strength diminished the interactive effect of soy protein-lecithin systems with an enhance in creaming rate by flocculation/ coalescence of droplets. The increase in calcium concentration showed changes in emulsion stability due to the desestabilization of the interfacial film by charge screening of counterions.