Molecular Oxygen and Reactive Oxygen Species in Bread-making Processes: Scarce, but Nevertheless Important
2016
Decamps, Karolien | Joye, Iris J. | De Vos, Dirk E. | Courtin, Christophe M. | Delcour, Jan A.
In bread making, O ₂ is consumed by flour constituents, yeast, and, optionally, some additives optimizing dough processing and/or product quality. It plays a major role especially in the oxidation/reduction phenomena in dough, impacting gluten network structure. The O ₂ level is about 7.2 mmol/kg dough, of which a significant part stems from wheat flour. We speculate that O ₂ is quickly lost to the atmosphere during flour hydration. Later, when the gluten network structure develops, some O ₂ is incorporated in dough through mixing-in of air. O ₂ is consumed by yeast respiration and in a number of reactions catalyzed by a wide range of enzymes present or added. About 60% of the O ₂ consumption in yeastless dough is ascribed to oxidation of fatty acids by wheat lipoxygenase activity. In yeasted dough, about 70% of the O ₂ in dough is consumed by yeast and wheat lipoxygenase. This would leave only about 30% for other reactions. The severe competition between endogenous (and added) O ₂-consuming systems impacts the gluten network. Moreover, the scarce literature data available suggest that exogenous oxidative enzymes but not those in flour may promote crosslinking of arabinoxylan in yeastless dough. In any case, dough turns anaerobic during the first minutes of fermentation.
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