Effects of twin-screw extrusion on soluble dietary fibre and physicochemical properties of soybean residue

Extrusion cooking technology was applied for soluble dietary fibre extraction from soybean residue. Response surface methodology (RSM) was used to optimise the effects of extrusion parameters, namely extrusion temperature (90–130 °C), feed moisture (25–35%) and screw speed (160–200 rpm) on the content of soluble dietary fibre. According to the regression coefficients significance of the quadratic polynomial model, the optimum extrusion parameters were as follows: extrusion temperature, 115 °C; feed moisture, 31%; and screw speed, 180 rpm. Under these conditions, the soluble dietary fibre content of soybean residue could reach to 12.65% which increased 10.60% compared with the unextruded soybean residue. In addition, the dietary fibre in extrude soybean residue had higher water retention capacity, oil retention capacity and swelling capacity than those of dietary fibre in unextruded soybean residue.