Bioconversion of brewer's spent grains by reactive extrusion and their application in bread-making

A characteristic of industrial brewing is the production of large quantities of spent grains resulting from the mashing process. This residue is used mainly as animal feed. This study aimed to enzymatically modify the mashing residue by associating an innovative extrusion bioconversion process and compare the effects of the treatments on bread-making. Modification of spent grains with two types of commercial enzymes was evaluated. Bread was made with treated spent grains (TSG) and untreated spent grains (USG), which were later directly added with enzymes in the same concentrations during dough preparation. The bioconversion process modified the structure of arabinoxylans and allowed the formation of water-soluble arabinoxylans. The production of reducing sugars increased, indicating the increase in the production of residual xylose and in the water solubility index. Bread prepared with USG together with the enzymes directly added to the dough had larger specific volume and was softer than that made with TSG. The sensorial preference of the panel did not vary for the different treatments used.

► Modification of brewer's spent grains was promoted by extrusion with hemicellulases. ► Modified grains showed properties indicating arabinoxylan hydrolysis. ► The promoted modifications did not allow better performance in bread- making. ► Adding the hemicellulases to unmodified grains in bread- making gave better results.