Twin-screw extrusion cooking of small white beans (phaseolus vulgaris)

Abstract

Dry small white beans (Phaseolus vulgaris) were ground and processed through a twin-screw extruder using three screw configurations of increasing energy intensity. Products were made over a moisture range of 150-250 g/kg, and barrel temperatures of 56-184°C. Results were examined by means of response surface methodology. Extrudate properties were significantly dependent (P < 0.10) on both the screw configuration and extrusion conditions used. In general, as the energy intensity of the configuration increased, expansion ratio, starting viscosity and hot viscosity increased, while bulk density, ending viscosity, and trypsin inhibitor activity decreased. All properties could be mathematically described as a function of the feed moisture content, the die temperature, and the specific mechanical energy consumption (SME) in Wh/kg, as determined on an 'as is' basis. R2 and overall P values ranged from 0.708-0.999 and 0.001-0.40, respectively. Residual trypsin inhibitor activity in the extruded products was low (<15%), and values below 10% were easily obtained. Trace amounts of ungelatinized starch granules could be found in all samples. © 1994 Academic Press.