Improvement of sorghum-wheat composite dough rheological properties and breadmaking quality through zein addition

Addition of sorghum flour to wheat flour produces marked negative effects o n rheological properties of dough and loaf volume. Although there are notab le differences in the chemical composition of sorghum proteins (kafirins) c ompared with wheat gluten that might imply poor functionality in breadmakin g systems, a larger constraint may be the unavailability of kafirins due to encapsulation in protein bodies. In this study, zein, the analogous maize prolamin to kafirin, was used to determine the potential effects of protein -body-free prolamins on dough rheology and baking quality of wheat-sorghum composite flour. Mixograms run at 35 degreesC (above the glass transition t emperature of zein) were significantly (P < 0.01) improved with addition of zein. Mixogram peak heights increased while mixing time decreased uniforml y with addition of zein. Dough extensibility studies showed an increase in maximum tensile stress, while baking studies showed an increase in loaf vol ume with increasing amounts of added zein. These data are supported by a pr evious study showing that, in a model system, zein mixed with starch can fo rm viscoelastic networks, and suggest that kafirin, if made available, coul d contribute to dough formation.