Effects of glucose oxidase or lipase addition on dough consistency and oxygen consumption during mixing of unyeasted flour dough.Addition of glucose oxidase enhances dough oxygen consumption and promotes transient peaks of consistency. The delay of apparition of these peaks is shortened with increasing amounts of glucose oxidase added, with the amount of glucose added and with the peroxidase activity. Conversely, the delay of apparition of these peaks increases with increasing amounts of free ferulic acid added to the flour and when catalase activity is added to the dough. Results are discussed by hypothesizing that the glucose oxidase activity in the dough produces hydrogen peroxide and enhances peroxidase activity. This latter enzyme would catalyse macromolecular cross-linking by phenolic linkages. Addition of exogenous lipase promotes both dough consistency and dough oxygen consumption during mixing. Results are in agreement with the fact that lipase activity in the dough increases the polyunsaturated free fatty acid concentration, enhancing the flour endogenous lipoxygenase activity.

Continuous measurement of oxygen consumption during mixing of unyeasted wheat flour dough.A mixer-bioreactor has been developed. Its instrumentation allows continuous measurement of the torque and of oxygen consumption during mixing of unyeasted wheat flour dough. The oxygen consumption corresponds to 1.7 µmol . g -1 d.m. after 10 min and 3.3 µmol . g -1 d.m. after 1 h of mixing. Oxidoreductase activities are responsible for this consumption since it largely declines following treatment which denatures enzymes. Conversely, oxygen consumption increases when exogenous oxidoreductases are added to the flour. In addition, measurements of polyunsaturated fatty acids in aliquots of dough allow to show the link between their losses and the amount of oxygen consumed. An oxygen balance can be calculated. Thus, after 10 min of mixing, half of the oxygen uptake can be ascribed to the lipoxygenase system. Whereas, after 1 h, this enzyme activity explains only one third of oxygen consumption.