Effects of transglutaminase enzyme on fundamental rheological properties of sound and bug-damaged wheat flour doughs

Transglutaminase (TG) catalyzes the formation of nondisulfide covalent cros slinks between peptide-bound glutaminyl residues and epsilon -amino groups of lysine residues in proteins. Crosslinks among wheat gluten proteins by T G are of particular interest because of their high glutamine content. Depol ymerization of wheat gluten proteins by proteolytic enzymes associated with bug damage causes rapid deterioration of dough properties and bread qualit y. The aim of the present study was to investigate the possibility of using TG to regain gluten strength adversely affected by wheat bug proteases. A heavily bug-damaged (Eurygaster spp.) wheat flour was blended with sound cv . Augusta or cv. Sharpshooter flours. Dynamic rheological measurements, inv olving a frequency sweep at a fixed shear stress were performed after 0, 30 , and 60 min of incubation on doughs made from sound or blended flour sampl es. The complex moduli (G* values) of Augusta and Sharpshooter doughs blend ed with 10% bug-damaged flour decreased significantly after 30 min of incub ation. These dough samples were extremely soft and sticky and impossible to handle for testing purposes after 60 min of incubation. To test the possib ility of using TG to counteract the hydrolyzing effect of bug proteases on gluten proteins, TG was added to the flour blends. The G* values of TG-trea ted sound Augusta or Sharpshooter doughs increased significantly after 60 m in of incubation. The G* values of the Augusta or Sharpshooter doughs blend ed with bug-damaged flour increased significantly rather than decreased aft er 30 and 60 min of incubation when TG was included in the dough formulatio n. This indicates that the TG enzyme substantially rebuilds structure of do ugh hydrolyzed by wheat bug protease enzymes.