Effects of Thermomoulding Process Conditions on the Properties of Agro-Materials based on Fish Myofibrillar Proteins

Rigid agro-materials were produced from powdered myofibrillar proteins by a thermomoulding process under low water content conditions. The effect of process conditions, water content of powder (from 2 to 32 g/100 g dry matter) and process temperature (from 150 to 250 °C) on the structural properties, dimensional and colour characteristics, and mechanical properties were studied using response surface methodology. Glassy translucent materials were obtained at low water content (2.2%) and low temperature (< -03200 °C). Increases in temperature and/or initial water content induced expansion, with the formation of air cells in material and foamed structure. The expansion yield (characterized by an increase in the specific volume from 0.8 to 6.1 mL · g-1) was greatly affected by the process conditions, and responsible for the observed changes in mechanical properties (from 22 to 195 N for maximum force). Relatively high thermal degradation of materials was observed for high temperature and low water content treatments, and attributed to caramelization or Maillard reactions.