The Properties Of Soy Protein

The functional properties of soy protein are of great significance in improving food structure and developing new foods. The most important reaction of soy protein in food processing is the intramolecular reaction between the exposed residues on the surface of the protein molecule during the denaturation process. The globulin in the natural state is fully folded, and there are secondary structures in this molecule, such as α-helix, antiparallel β-sheet and β-turn structure. Among the residues of the amino acid side chain, the hydrophobic amino acid side chain is located inside the molecule to form a hydrophobic region, while the hydrophilic side chain is located on the surface in contact with water. In this way, the soy protein subunit molecule can be visually seen as an oil droplet, surrounded by a hydrophilic shell. Several different subunits with similar three-dimensional structures are aggregated into one molecule. Natural proteins are soluble in water because the hydrophilic side chains on the surface of the molecule can be in contact with water .The structure of this protein is destroyed during denaturation treatment such as heating. The destruction of the three-dimensional structure of a molecule is known as denaturation, and the degree of destruction depends on the type of protein and the method of denaturation treatment. For example, the quaternary structure of 11S is affected by ion concentration, pH and temperature. Like urea, most proteins are almost completely denatured; soy protein is heat-treated at 100 ℃, and only part of the three-dimensional structure is unfolded [11]. The functional properties of soy protein influence each other and act synergistically in the food system. For example, the solubility directly affects the emulsification properties; and the viscosity is related to the strength of water holding capacity and gelation.