Effects of the specific mechanical energy on the physicochemical properties of texturized soy protein during high-moisture extrusion cooking Original Research Article

Effects of the extrusion specific mechanical energy (SME) on the physicochemical properties including color parameters (L*, a*, b* and ΔE), textural properties (tensile strength, hardness, chewiness and degree of texturization), on-line viscosity at die, protein solubility, and the molecular weight distribution of texturized soy protein were investigated. A higher SME resulted in extrudates with lower L* but higher a*, ΔE, higher tensile strength, and hardness. The viscosity of dough at die decreased from 997.17 to 867.29 Pa s when SME increased from 819.70 to 1258.70 kJ/kg. The increasing SME also caused an increase of protein solubility in phosphate buffer solution by 15.30%. Increasing the SME resulted in higher content of low Mw subunits as well, which was evidenced by SDS–PAGE. It was concluded that increasing SME increased the proportion of smaller fractions, and led to darker and higher tensile strength products.