BLEACHING OF WHEAT DISTILLERS GRAINS AND ITS FIBER AND PROTEIN-FRACTIONS WITH ALKALINE HYDROGEN-PEROXIDE

In experiments designed to develop high-fibre and protein ingredients from wheat-based stillages, organic solvents were only partially effec tive in pigment removal and colour improvement. However treatment of s tillage or stillage solids with alkaline hydrogen peroxide (AHP) reduc ed total colour differences to less than one half of the Delta E value s for controls. By mild drying of AHP-treated stillage products using acetone washing or freeze-drying, the residual colour was further redu ced to a light yellow colour on the Hunterlab scale. Also, adjusting o f pH before addition of hydrogen peroxide and, after AHP treatment,neu tralization before centrifugation resulted in even lighter colours for stillage and its fibre-rich and protein-rich fractions. In addition, the AHP treatment largely eliminated the yeasty taste and odour of sti llage from the fibre and protein fractions. The AHP treatments had min or effects on yield or composition of stillage or the fibre-rich and p rotein-rich fractions relative to controls. The APH-treated fibre-rich and protein-rich fractions contained low concentrations of residual H P, except for protein-rich fractions treated with 1.5 mol/L. HP.