Studies on the lipids of flour V. —Effect of air on lipid binding

Abstract

AbstractLipid distribution in mechanically developed doughs was found to be sensitive to relatively small amounts of air present in the dough mixer atmosphere. In doughs mixed to high work levels, less than 5 % air present in the nitrogen‐air mixture fed into the mixing bowl was sufficient to cause a significant decrease in bound lipid. Although flour pigments were readily bleached by small amounts of air, lipid peroxides did not increase significantly until at least 50% air was present. Polyunsaturated free fatty acids were most susceptible to peroxidation although, at high work levels in air, peroxides were found in all lipid classes. While lipids bound during nitrogen mixing were readily released by subsequent mixing in air, the effect of air on lipid binding was not reversed by further mixing in nitrogen. Addition of peroxidised lipid to the dough did not prevent lipid binding in nitrogen‐mixed doughs and it was concluded that a mechanism of lipoxidase‐coupled site oxidation was responsible for the effect of air on lipid binding rather than the direct action of the lipid peroxides themselves.