Transglutaminase Shows Better Functionality on High Digestible, High Lysine Sorghum-Wheat Composite Dough and Bread, Compared to Normal Sorghum-Wheat Composites

Abstract

Highly digestible high-lysine (HDHL) sorghum-wheat composites have previously been shown to produce better composite dough and bread compared to normal sorghum-wheat composites. This study aimed to test whether improved HDHL lines can provide further enhanced functionality through the effects of transglutaminase (TG) enzyme to improve dough rheological properties. Sorghum-wheat composite doughs were made using HDHL and normal sorghum flours at substitution levels of 10, 20, and 30%, with and without 0.15% TG. Rheological properties of dough were tested using a mechanical spectrometer at 0.05% strain amplitude (within the linear viscoelastic region) over a 0.01- 50 rad/sec frequency range. A more elastic system was observed in HDHL sorghum-wheat composites above 10% substitution levels compared to normal sorghum-wheat composite dough. Addition of TG to HDHL sorghum-wheat composites resulted in a decrease in phase angle values at all substitution level, indicating that TG increased the dough elasticity. However, TG did not change viscoelastic properties of normal sorghum-wheat composites. Bread from HDHL sorghum-wheat composites had significantly higher (P<0.05) loaf volume, compared to those made from normal sorghum-wheat composites. These results clearly show that HDHL sorghum has ability to produce dough with improved viscoelastic properties and higher quality bread; and, due to presence of protein body kafirins, addition of TG on HDHL sorghum-wheat composite further enhances dough rheological properties.