Effects of microbial transglutaminase on the quality of wheat bread supplemented with hull-less barley flour

The impact of microbial transglutaminase (MTG) on the quality of wheat bread supplemented with 20, 35 and 50% of hull-less barley flour was investigated. The MTG was added at five different levels (0, 0.5%, 1%, 1.5% and 2%; W/W). To increase the concentration of lysyl residues and possibly enhance the extent of cross-linking of protein matrix by MTG, a commertial soy protein isolate (SPI) was added at a level of 3% (w/w) in combination with MTG. Bread samples were evaluated in terms of loaf volume, specific volume, color characteristics, and rate of staling during 72 h. High cross-linking effect of MTG on wheat proteins significantly decreased the loaf volume of wheat breads. Though substitution of wheat flour by hull-less barley flour decreased the loaf volume, but increasing levels of MTG at higher substitution levels (35 and 50%) could increase the loaf volume due to dilution effect of barley flour on wheat gluten proteins. Moreover the addition of SPI along with MTG had improving effects on the bread loaf volume and in all the samples MTG, decreased the degree of color. The values obtained for staling of MTG treated barley breads after 72h were lower than those of their sespective contents. The results showed the ability of MTG in the formation of cross-links between barley, wheat, and soy proteins. Therefore, MTG can be used to improve the quality of hull-less barley breads.