THERMO-MECHANICAL AND BREADMAKING PROPERTIES OF WHEAT-SORGHUM FLOUR BLENDS

Abstract

Sorghum flour is a valuable ingredient for breadmaking. The thermo-mechanical properties of dough prepared out of wheat flour supplemented with 10, 20, 30, 40 and 50% sorghum flour and the bread characteristics in terms of specific volume, crumb firmness, resistant starch, total phenols and antioxidant activity were investigated. Water absorption and dough stability decreased when increasing the level of sorghum flour as a consequence of the dilution effect of gluten. Starch gelatinization speed was 0.50 Nm/min in case of wheat flour and increased up to 0.70 Nm/min for sample with 50% sorghum flour. In addition, gel stability during heating increased with the level of sorghum flour. Although wheat flour substitution by sorghum flour affected the specific volume of the bread and crumb firmness, the level of biologically active compounds in the final products was significantly increased. In particular, the addition of 50% sorghum flour caused the increase of the total phenols content and DPPH-RSA of bread from 122.41 to 527.59 μmol FAE/g d.w., and from 3.90 to 25.59%, respectively. Moreover, the content of resistant starch of the breads increased with the level of sorghum flour, most probably as a consequence of the presence of polyphenols from sorghum flour and of the interaction between sorghum starch and proteins.