Comparison of the extrusion cooking of a soya isolate and a soya flour

The effects of barrel temperature, die temperature and moisture content on soya extrusion were investigated using response surface analysis. Seven variables were measured, and a model derived for the effect of temperature and moisture content on pressure. Two samples were investigated, a soya flour (with a high protein dispersibility index) and a commercial soya isolate consisting of denatured protein. Differences between the samples are discussed. Changes along the length of the barrel, were investigated using a ‘dead stop technique’ and differential scanning calorimetry (DSC) revealed the points at which the major protein components in soya flour were denatured.