Use of durum wheat clear flour in vital gluten and bioethanol production

During milling of durum wheat (Triticum durum) into semolina used for pasta processing, certain amount of clear flour (5-15%) with low economic value is obtained. This study aimed at determining the suitability of durum clear flours for vital gluten and bioethanol productions. The durum clear flours were wet-processed into vital gluten by three wet-milling methods, namely dough-washing, dough-water dispersion and flour-water dispersion. Vital glutens with acceptable purities (71.0-82.1% protein, Nx5.7, dm), yields (9.8-14.3%, dm) and recoveries (48.7-76.8%) were achieved by the dough-water and flour-water dispersion methods. However, vital gluten by the dough-washing method could not be isolated satisfactorily. The dough mixing and breadmaking qualities of vital glutens from the clear flours were found comparable to the commercial vital gluten. The carbohydrate-rich remnants of the clear flours upon isolation of glutens were subjected to enzymatic hydrolysis and yeast fermentation, leading to ethanol yields and conversion efficiencies of 32.2-33.5% (g/g, based on clear flour solids) and 80.5-87.6%, respectively. In conclusion, except for the dough-washing method, vital gluten and bioethanol with acceptable purities, yields, recoveries and qualities can be produced by the dough-water and flour-water dispersion methods.