Improvement of functional properties of acid‐precipitated soy protein by the attachment of dextran through Maillard reaction

Abstract

SummaryThe functional acid‐precipitated soy protein (SAPP)–dextran conjugate was prepared by dry‐heated storage at 60 °C under 79% relative humidity (RH) for 5 days through Maillard reaction between the ε‐amino of lysine in soy proteins and the reducing‐end carbonyl residue in the dextran. The covalent attachment of dextran to SAPP was confirmed by SDS‐polyacrylamide gel electrophoresis and gel filtration chromatography. Functional properties of soy protein depend on the structural and aggregation characteristics of their major components (storage globulins 7S and 11S). The conjugate seemed to be predominantly formed by 7S, and the acidic subunits of 11S in soy protein. The emulsifying properties of the SAPP–dextran conjugate were about four times higher than those of SAPP. The solubility of the protein was not enhanced as a result of preheating, but rather it was not decreased when the conjugated protein was heated at 90 °C for 20 min due to the presence of the polysaccharide. The excellent emulsifying properties of SAPP–dextran conjugate were maintained even at pH 3.0 and were further improved at pH 10.0. The object of Maillard reaction is to guarantee the suitable reaction degree, and the resulting soluble conjugate can have excellent emulsifying properties.