Extrusion of feather keratin

Keratin obtained from poultry feathers was extruded at 120 degrees C using a combination of glycerol, water, and sodium sulfite as processing aids. Rheological properties were assessed as a function of water, glycerol, and sodium sulfite content as well as extruder die temperature. The lowest viscosity blends at a constant feather keratin concentration of 60 wt % were found at glycerol concentrations that were higher than the water concentration and sodium sulfite concentrations of 3-4 wt % of the feather keratin fraction. For the melt state, higher or lower sodium sulfite concentrations resulted in increased viscosity. In the solid state, it was observed that processing induced orientation increased the tensile properties of the extrudates. Raman spectroscopy and DSC showed that there was a transition from alpha-helix to beta-sheet at sodium sulfite concentrations of less than 4 wt %. At greater sodium sulfite concentration, increased crystallinity was found, because keratin chains could be extended more during processing.