Karolien Decamps

Lipases and Their Functionality in the Production of Wheat-Based Food Systems

In the last several decades, food industries have increasingly used lipases as a result of the functional versatility of these enzymes and their potential beneficial effects in terms of processing and product quality. This review article discusses lipases and their functional effects during cereal-based food processing with a focus on the production of bread and cakes. Their dough and batter intermediates, respectively, are essentially semi-solid foams that upon baking are converted into solid cellular sponges. In both cases, the lipid fraction(s) from wheat (in the case of bread and cake), egg and/or bakery fat (in the case of cake) exert major roles in gas incorporation and stabilization in the cited semi-solid foams. An up-to-date overview on the (potential) substrates, the different lipase enzymes, their action mechanism, their functionality, and how they impact bread and cake quality is presented. We also hypothesize on how the observed effects can be interpreted in terms of the altered lipid chemistry.

The Bread Dough Stability Improving Effect of Pyranose Oxidase from Trametes multicolor and Glucose Oxidase from Aspergillus niger: Unraveling the Molecular Mechanism

Glucose oxidase (GO) and pyranose oxidase (P2O) improve dough stability and bread quality. We here studied whether their mode of action resides in cross-linking of proteins and/or arabinoxylan (AX) molecules through the production of H2O2. Evidence for both was deduced from a decrease in extractability of protein and AX from dough made with P2O, GO, or H2O2, using sodium dodecyl sulfate containing buffer and water, respectively. The addition of H2O2, P2O, or GO to a glutathione solution sharply decreased its sulfhydryl (SH) content. P2O or GO can trigger protein cross-linking through the formation of disulfide (SS) bonds. As a result thereof, SH/SS interchange reactions between low molecular mass SH containing compounds and gluten proteins can be hampered. Furthermore, a decrease in the level of monomeric ferulic acid (FA) esterified to AX in dough points to a role of FA bridges in cross-linking of AX molecules. Our results indicate that the molecular mechanism of dough and bread improvement by P2O and GO resides in cross-linking of gluten proteins and AX by formation of H2O2. They furthermore show that the extent of cross-linking upon addition of P2O or GO strongly depends on the concentration (and production rate) of H2O2.

Impact of pyranose oxidase from Trametes multicolor, glucose oxidase from Aspergillus niger and hydrogen peroxide on protein agglomeration in wheat flour gluten-starch separation.

The impact of pyranose oxidase (P₂O), glucose oxidase (GO) and H₂O₂ on gluten agglomeration during wheat flour gluten-starch separation was studied. Analysis of gluten aggregate sizes in batter formed from wheat flour dough revealed that increasing levels of oxidising agents gradually decreased the tendency of gluten proteins to form large gluten aggregates. Low enzyme levels increased arabinoxylan (AX) and starch retention on the sieves, due to physical incorporation of AX and starch in the gluten aggregates. Higher enzyme levels increased retention of starch and AX on the smaller and larger sieves, respectively. Extensive oxidation leads to physical incorporation of AX and starch granules in the small gluten aggregates. AX is also crosslinked and hence more easily retained on the top sieves. Our results confirm that the size of gluten aggregates and the level of AX crosslinking and AX and starch incorporation in gluten proteins depend on the concentration of H₂O₂.

Molecular Oxygen and Reactive Oxygen Species in Bread-making Processes: Scarce, but Nevertheless Important

In bread making, O2 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 O2 level is about 7.2 mmol/kg dough, of which a significant part stems from wheat flour. We speculate that O2 is quickly lost to the atmosphere during flour hydration. Later, when the gluten network structure develops, some O2 is incorporated in dough through mixing-in of air. O2 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 O2 consumption in yeastless dough is ascribed to oxidation of fatty acids by wheat lipoxygenase activity. In yeasted dough, about 70% of the O2 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) O2-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.

Pyranose Oxidase from Trametes multicolor Impacts Dough and Bread Microstructure

ABSTRACT Pyranose oxidase (P2O) improves wheat flour dough stability and bread quality. We related its effect on dough spread behavior to that on dough and bread crumb structure. Increasing P2O addition levels gradually reduced dough flow. High P2O addition levels further increased dough strength, significantly increased dough cell wall thickness, and decreased bread loaf volume. Taken together, affecting dough spread behavior impacts dough and bread (crumb) structure, and dough structure largely determines bread crumb structure.