Phase behavior of a meat-starch extrudate illustrated on a state diagram

The phase behavior of a meat-starch extruded system was illustrated on a state diagram. A mixture of meat and potato granules (1.48:1) was extruded with a twin-screw extruder. The extrudates were equilibrated at relative humidities between 0 to 88% and their glass transitions were determined. Starch and proteins were phase separated at macromolecular level and retained their own phase transitions. The state diagram of the system showed that proteins dictated the texture of the mixed system, with starch contributing to the high value of the mechanical properties. Water had a plasticizing effect on both biopolymers. At room temperature, the extrudates with a(w) < 0.32 were glassy, while those with a(w) > 0.57 were rubbery.