The role of gluten proteins in the baking of Arabic bread

Fractionation and reconstitution/fortification techniques were utilised to study the role of gluten in Arabic bread. Glutens from two wheat cultivars of contrasting breadmaking quality were fractionated by dilute HCl into gli adin and glutenin. Gluten, gliadin and glutenin doughs from the good qualit y flour had higher G' and lower tan delta values than those from the poor q uality hour at all the frequencies examined. Interchanging the gliadin and glutenin fractions between the reconstituted hours showed that the glutenin fraction is largely responsible for differences in the breadmaking perform ance. Fortification of an average quality flour with the gliadin and gluten in fractions from the poor and good quality flours, at the levels of 1 % an d 2 % (protein to flour mass), induced marked differences in the mechanical properties of bread. The resilience of the leaves was not adversely affect ed by the addition of gliadins and increased, with a concomitant significan t (P<0.05) improvement in quality, at the 2 % level of fortification with g liadins from the good quality flour. Addition of glutenin resulted in leave s with leather-like properties that became particularly apparent at the hig her level of fortification; the observed deterioration in quality parallele d the increase in the elastic character of the doughs. It is suggested that highly-elastic doughs are not compatible with the rapid expansion of gases at the high-temperature short-time conditions employed in the baking of Ar abic bread and that there exists a threshold in dough elasticity beyond whi ch a rapid decline in quality takes place. (C) 1999 Academic Press.