Abstract
The use of exogenous maltogenic α-amylases or maltotetraogenic amylases of bacterial origin is common in wheat bread production, mainly as antistaling agents to retard crumb firming. To study the impact of maltogenic α-amylase and maltotetraogenic amylase on straight dough wheat bread, we performed a discovery-driven proteomics approach with commercial enzyme preparations and identified the maltotetraogenic amylase P22963 from Pelomonas saccharophila and the maltogenic α-amylase P19531 from Geobacillus stearothermophilus, respectively, as being responsible for the amylolytic activity. Quantitation of mono-, di- and oligosaccharides and residual amylase activity in bread crumb during storage for up to 96 h clarified the different effects of residual amylase activity on the sugar composition. Compared to the control, the application of maltogenic α-amylase led to an increased content of maltose and especially higher maltooligosaccharides during storage. Residual amylase activity was detectable in the breads containing maltogenic α-amylase, whereas maltotetraogenic amylase only had a very low residual activity. Despite the residual amylase activities and changes in sugar composition detected in bread crumb, our results do not allow a definite evaluation of a potential technological function in the final product. Rather, our study contributes to a fundamental understanding of the relation between the specific amylases applied, their residual activity and the resulting changes in the saccharide composition of wheat bread during storage.
Highlights
Wheat bread can be considered as an unstable multiphase food matrix subject to changes during storage: the flavor of fresh bread and the crispiness of the bread crust decrease, whereas crumb firmness and crumbliness increase
We combined discovery-driven proteomics with the quantitation of mono, di- and oligosaccharides in bread crumb and the determination of residual amylase activity to get insights into changes in sugar composition caused by the action of exogenous maltotetraogenic amylases and maltogenic α-amylases during straight dough wheat bread making and storage
We identified the specific amylases in two maltotetraogenic amylase and five maltogenic α-amylase preparations commonly applied in wheat bread making
Summary
Wheat bread can be considered as an unstable multiphase food matrix subject to changes during storage: the flavor of fresh bread and the crispiness of the bread crust decrease, whereas crumb firmness and crumbliness increase. The changes in the bread crumb, known as staling, lead to a loss of resilience and to firming [1], caused by water immobilization and redistribution processes. The retrogradation of amylopectin during storage immobilizes water, which leads to a decrease in freezable water in the bread crumb [2]. Water redistribution occurs via water migration from gluten to starch and from crumb to crust. These migration patterns lead to an additional decrease in freezable water and to an increase in crumb firmness [3, 4]. Amylose gelation occurs within hours, whereas that of amylopectin takes several days and involves reorganization of amylopectin side chains to form tightly
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