Effect of Extruding Wheat Flour at Lower Temperatures on Physical Attributes of Extrudates and on Thiamin Loss When Using Carbon Dioxide Gas as a Puffing Agent

Abstract

ABSTRACT Wheat flour with 0.3% (w/w) thiamin was extruded on a twin‐screw laboratory‐scale extruder (19‐mm barrel) at lower temperatures and expanded using carbon dioxide (CO 2 ) gas at 150 psi. Extrusion conditions were die temperature of 80°C and screw speed range of 300–400 rpm. Control samples were extruded at a die temperature of 150°C and screw speed range of 200–300 rpm. Dough moisture content was 22% in control samples and 22 and 25% in CO 2 samples. Expansion ratio, bulk density, WAI, and %WSI were compared between control and treatment. CO 2 injection did not significantly increase expansion ratio. Bulk densities in the CO 2 extruded samples decreased when feed moisture decreased from 25 to 22%. The products using CO 2 had lower WAI values than products puffed without CO 2 at higher temperatures. The mean residence time was longer in CO 2 screw configurations than in conventional screw configurations. Thiamin losses were 10–16% in the control samples. With CO 2 , thiamin losses were 3–11% at 22% feed moisture, compared with losses of 24–34% at 25% moisture. Unlike typical high‐temperature extrusion, thiamin loss in the low‐temperature samples decreased with increasing screw speed. Results indicate that thiamin loss at lower extrusion temperatures with CO 2 injection is highly dependent on moisture content.