Distribution of enzymes in wheat flour mill streams

The distribution of alpha-amylase, protease, lipoxygenase, polyphenol oxida se and peroxidase in wheat roller flour mill streams was studied. Break flo urs had relatively less alpha-amylase and protease activity than reduction flours both on flour weight and a protein basis. Among the different flour streams, the 5(th) and 6(th) reduction passage had the highest alpha-amylas e activity, while the 4(th) reduction passage had the highest protease acti vity. The lipoxygenase activity was concentrated mostly in the last break a nd the reduction streams, whereas polyphenol oxidase activity was highest i n break flour streams. Peroxidase activity was distributed unevenly among t he different mill streams. The lipoxygenase, polyphenol oxidase and peroxid ase were highly concentrated in different bran fractions. Except for protea se, the other enzymes were concentrated in the 'atta'. a milling by-product comprising refined flour, bran and shorts and are least active in semolina (farina). (C) 2001 Academic Press.