This enzyme’s catalytic reaction releases hydrogen peroxide which promotes the formation of disulpher crosslinks between the gluten proteins and the dough strengthening reaction of the water- soluble pentosanes, consequently producing significant changes in wheat dough rheology. Laccase also belongs to the oxidizing enzyme group and recently its use has drawn considerable interest. Because of the simultaneous strengthening of the arabinoxilnase and oxidising agents, the addition of laccase signifi cantly improves the quality of the gluten, bringing about marked changes in the rheological properties of the dough. These characteristics can also be modified by utilizing enzymes that promote cross-linking of the glutens. For example, transglutaminase is particularly reactive with high molecular weight gluetenin subunits. The crosslinking of the glutenin fractions generated a reaction that improved viscoelastic properties with positive effects on dough rheology. Several studies have shown that transglutaminase strengthens the dough by increasing mixing tolerance, decreasing the absorption of water and reducing the stickiness. Finally, this enzyme has been used in the production of rice fl our bread, providing a gluten network that can retain the gas produced during rising, resulting in an acceptable loaf specifi c volume and satisfying crumb structure. Further, the partial hydrolysis of triglycerides, along with the increase of monoglycerides, slows bread staling, but an excessive dose can generate off flavours. In general, enzymes provide the precursors for the fermenting and thermal reactions that produce the fl avour components of bread and their influence on this sensory characteristics are considerable. Amylase, for example, produces reducing sugars while protease produces peptides and amino acids. On the other hand, lipoxygenase gives unstable products decomposing to carbonyl compounds that produce off flavors. A recent study has demonstrated that through the use of different enzymes (for example alpha-amilase, protease and hemicellulase), it is possible to reduce the intensity of the water characteristics caused during freezing of partially baked bread. Finally, enzymes with different biochemical processes can be used in combination, obtaining significant synergistic effects on the behaviour of the dough and the quality of the final product.
Effects of the combination of different types of enzymes
Below are the results of a study of different enzymes that sought to analyse the synergistic effects on the bread dough and the final product. The study used enzymes capable of catalysing a cross-link between the glutens (transglutaminase, TG, glucoxidase, GO, and laccase, LAC) and others that reduced polysaccharide and gluten degrading enzymes (alpha-amylase, AMYL, xylanase, XYL, and protease, PROT). In particular, the tests were conducted according to a plan that include 32 levels of trials so that the singular effect as well as the interactions could be evaluated.
Viscoelastic properties of the dough
The study shows that, aside from GO and LAC, all the enzymes tested affected the viscoelastic properties of the dough. In particular, the results confirmed the strengthening effect of TG, while AMYL, ZYL and PROT promoted a similar increase in all dynamic moduli analysed (e.g., elastic, viscous, and complex). Furthermore, statistically significant interactions were observed only between TG and XYL and between AMYL and PROT. The addition of XYL to the samples containing TG demonstrated a good alternative to excessive strengthening of the dough.
