The use of exogenous microbial enzymes is common in wheat bread making to help standardize dough and bread quality, reduce dough stickiness, increase mixing stability, improve bread volume and prolong shelf-life. While endogenous enzymes from wheat and yeast are also active in the dough, their activities are lost during baking due to heat-induced irreversible denaturation. In contrast, some exogenous enzymes, especially maltogenic α-amylases, are known to be heat-resistant, so that their activities may partially persist in the final product. According to legislation in the European Union, enzymes used as processing aids do not have to be labeled, because they are not classified as food ingredients of technological relevance in the final product. However, in case residual enzyme activity persists and this causes a functional effect in the product, the enzyme would have to be labeled.<br/>To clarify which exogenous amylases still have detectable residual activity in bread crumb, we added one selected α-amylase, maltogenic or maltotetraogenic amylase each to a model toast bread. Residual amylase activities were analyzed using standard test kits and starch hydrolysis products including glucose, maltose and oligosaccharides were quantitated by high-performance anion exchange chromatography with pulsed amperometric detection. Discovery-driven proteomics revealed the identities and relative proportions of the amylases in each preparation.<br/>The addition of each exogenous amylase led to characteristic changes in saccharide concentrations in bread crumb compared to the control. As expected, the main starch hydrolysis product was maltose, followed by glucose, maltotriose, maltotetraose and other oligosaccharides with up to eight glucose units. Five out of six α-amylases had no detectable residual activity in bread crumb 22 h after baking, whereas one α-amylase and both maltotetraogenic amylases had very low residual activity amounting to less than 4% of the applied activity. All five maltogenic α-amylases showed detectable residual activities ranging from 14-45% of the applied activity and the maltose concentrations also increased in these breads during storage for up to 96 h. All amylase preparations contained the main enzyme next to variable percentages of wheat flour or starch as carrier material. Overall, the changes in saccharide concentrations over longer storage periods might eventually result in a functional effect due to starch degradation.

Activity of endogenous and exogenous amylases in wheat bread

ACS Spring Meeting 2021

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