Functional oxidation in bread making
As the bakery industry has grown larger and more industrialized, bakers have worked to increase consistency, freshness and naturalness, regardless of the quality and availability of wheat. This requires flexible ways to strengthen and modify wheat to maximize flour potential, while retaining the process tolerance demanded by plant bakeries.
Adaptable oxidative improver systems can meet the challenges of variable wheat quality and standardize product quality. To harness the natural variability of wheat flour, bakers use chemical oxidizing agents, such as azodicarbonamide (ADA), potassium bromate and ascorbic acid, to strengthen gluten proteins. These are highly effective in maximizing the potential from the wheat protein available.
However, many bakers have now turned to glucose oxidase, an alternative to such chemical agents, introduced in response to consumer demand for the reduction of chemical additives and legislative restrictions on their use. This has offered new benefits and the ability to create products with natural, easy-to-understand ingredient listings.
The baking quality of wheat flour is related to the quantity and properties of gluten proteins. These can be divided into two groups: monomeric gliadins and polymeric glutenins, of which there are roughly equal amounts. The interactions between the different glutenins, and the glutenins and gliadins, are critical to dough behavior. The presence and properties of very large glutenin aggregates, known as the glutenin macropolymer (GMP), is important for baking properties and the quality of flour. (Journal of Cereal Science, 37:1–7)
Arabinoxylans also influence dough and bread quality. The water-extractable arabinoxylan molecules increase the viscosity of the dough liquid phase, stabilizing the liquid films surrounding the gas cells. In addition, cross-linking of arabinoxylans may strengthen the gluten network. (Journal of Agricultural and Food Chemistry, 6(32):7848–7854)
Glucose oxidase affects dough properties via hydrogen peroxide formation. It acts on the glucose present in the dough to produce hydrogen peroxide that induces protein cross-links via disulfide bridges and arabinoxylan cross-links via ferulic acid bridges. However, when arabinoxylan chains are linked, it leads to increased water-binding capacity, which results in dryer dough. The extent of cross-linking in dough depends on the production rate and concentration of hydrogen peroxide.
High levels of hydrogen peroxide, especially during the mixing phase, can inhibit the formation of an extended gluten network. Mechanical shear during dough mixing will break some of the newly formed disulfide bridges, leaving fewer sulfhydryl groups to later form network linkages. These smaller aggregates will be less effective in stabilizing the dough structure than the gluten aggregates formed when lower levels of hydrogen peroxide are present. (Food Chemistry, 148:235–239)
Most common glucose oxidases on the market originate from Aspergillus sp. Recently, DSM developed a new glucose oxidase originating from Penicillium chrysogenum. Biochemical analyses of this new glucose oxidase have shown that this enzyme exhibits a self-regulating mechanism. A possibly larger and more extensive gluten network is formed, improving the overall strength of the gluten network. Moreover, it allows for the dough to become elastic, maintaining its ability to stretch.
During dough mixing and fermentation, DSM analysed samples for gluconic acid content, a direct indication of the amount of hydrogen peroxide formed by the enzymatic reaction of glucose oxidase (see Figure 1). At the onset of making dough, glucose oxidase from Penicillium (PenGox) and from Aspergillus (AspGox) show similar profiles of hydrogen peroxide formation. Differences are noticeable at the end of the mixing phase, where the dough containing PenGox shows lower levels of hydrogen peroxide production. This will avoid over-oxidation of the gluten network that might result in the formation of smaller aggregates as opposed to the formation of an extended gluten network.
This difference provides regulated oxidative power during the mixing process and means PenGox is suitable for bread-making processes, such as the Chorleywood bread process. It allows dough to remain soft and pliable, improves stability during fermentation and ensures the final bread has a nice, fine crumb structure. This creates opportunities for use of glucose oxidase to replace chemical oxidizers, or in applications such as frozen dough.
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