Uniaxial Extensional Viscosity During Extrusion Cooking from Entrance Pressure Drop Method

Uniaxial extensional viscosity of cornmeal at moisture contents of 30 and 35% (dry weight basis) and temperature of 160 and 180 o C was estimated from entrance pressure drop measurements during extrusion cooking. The value of the sheat component of the entrance pressure drop was an order of magnitude below that of the extensional component. Food doughs exhibited sheat thinning and extension thinning behavior during processing conditions used. Increasing moisture and temperature decreased extensional viscosity at highet extension rates. The Trouton ratio ranged from 25 to 50 and was affected by product moisture content, barrel temperature, and deformation rate