2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Studies have reported that thiamine destruction in extruded dough increases with temperature and residence time. The same studies have shown thiamine destruction to increase with higher screw speeds, which give shorter residence times. These apparently conflicting data suggest that shear may have an effect on thiamine degradation. This study proposes a method to quantify the effect of shear on thiamine degradation in extruded doughs. Average shear rate in the extruder was estimated for each screw speed by using the method of matching viscosities of Newtonian and non-Newtonian fluids. Wheat flour with 0.3% thiamine was extruded at constant moisture content, feed rate, and barrel temperature, while varying screw speed. Final thiamine concentration appears to be a function of shear. The method used in this study holds promise as a practical and efficient technique for estimating average shear rates and nutrient loss in products produced on larger extruders.