Flour Treatment : Enzymes

5. Transglutaminase
Transglutaminase (TG) is able to crosslink protein chains either with adjacent loops of the same protein or with other proteins of the same or a different type. It requires lysine and glutamine groups as a target. Although lysine is a limited amino acid in wheat flour, there is sufficient lysine for the action of TG to take place. The result is a strengthening effect on the dough, similar to that of AA.

Since it is much more expensive than AA, TG is little-used. Its main use is in prolonged or retarded fermentation, when the enzyme has enough time to achieve its function even at a low dosage. Bauer et al. (2003) provide more detailed information on the function of TG.

6. Other Enzymes
Cellulase and β-glucanase are present as natural side activities in many enzyme preparations, e.g. xylanases. They do have some effect on the water-binding behaviour of dough, particularly from whole meal or rye flour containing larger amounts of fibrous components than standard bread flour. But their potential for improving the baking properties of white wheat flour, e.g. dough stability or volume yield, is only limited and negligible in comparison with other enzymes.

Glucose oxidase is often mentioned and has already been described above under oxidation. Glucose oxidase was the hope of many who wanted to omit potassium bromate or other oxidizing agents. A similar enzyme has recently been launched: hexose oxidase. The enzyme may be regarded as a glucose oxidase with less specificity, as it not only oxidizes glucose – which is a hexose, i.e. a sugar molecule with 6 (greek: hexa) carbon atoms – but also other hexoses such as galactose which can be found in flour in smaller amounts. So the effect does not differ significantly from glucose oxidase.
Fig. 127. Steamed bread baking trials with sulfhydryl oxide (SOX) in comparison with Ascorbic Acid

Arabinofuranosidase and sulfhydryl oxidase (Fig. 127) have also been tested for their possible suitability as flour improvers. So far they have not found wide distribution because of high costs or the lack of obvious benefits as compared to more common enzymes or ascorbic acid.

The development of microbial lipoxygenase as an alternative to the enzyme in soy and bean flour is a further highly interesting topic. Initial approaches failed because of the unsuitable pH optimum of the microbial enzyme and presumably the fact that it is not type II or III lipoxygenase. Only those are capable of oxidizing lipid-bound fatty acids which subsequently bleach lutein, the main carotenoid in the flour (see also Enzyme- Active Soy Flour).

Polymer-producing enzymes such as alternan sucrase or dextran sucrase produce hydrocolloids during the fermentation process. This results in increased water absorption and dough stability (Tab. 91) (Popper, 2002)

Tab. 91: Effect of alternan and alternan sucrase on the Farinogram


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