Plastification Behaviour of Different Native Starches

Abstract Based on physical and thermal conservation laws a quantitative variable is introduced, which allows evaluation of the thermomechanical starch plastification much more independent of the transformation procedure. By that method, a comparison of plastification behaviour during extrusion of native potato, maize and wheat starch without any additives is realized for the first time. The complete energetical balance of the extrusion process supplemented by microscopical investigations leads to an essential better understanding of thermomechanical proceedings during extrusion of starch or compounding of other polymers. After optimization of extruder and screw configuration the resulting data for the energy needed for the plastification of starch, i.e. for the transformation of native starch granules into a thermoplastic melt by extrusion, have been measured under constant conditions. On these adequat extrusion conditions the native, laminated starch granules of all three used starches have been destroyed completely during its plastification by extrusion. The specific energy input needed for the plastification of potato starch was about 650 kJ/kg, for maize 380 and for wheat starch 435 kJ/kg. In comparison of these results the energy input for melting of polyethylene high density was about 585 kJ/kg under same conditions.