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Gewählte Doctoral Thesis:

Doctoral Thesis - Institut für Lebensmitteltechnologie, BOKU-Universität für Bodenkultur, pp 153. UB BOKU obvsg FullText

Data Source: ZID Abstracts
The role of arabinoxylans (AXs) in rye and wheat bread-making has been widely studied, due to their beneficial contribution to the dough structure. Therefore, the aim of this investigation was to determine the potential of isolated rye AXs to imitate a rye bread-like structure by forming a stable hemicellulose network in different gluten-free (GF) bread formulations. For this purpose, a combination of different technologies such as extraction, enzyme and sourdough technology were thoroughly studied and combined to achieve stable AX network formation and hence a high-quality bread. On a first approach, the effect of different process parameters on the extraction yield and physicochemical properties of AXs was studied. First results showed that temperature had a stronger influence on the extraction yield and composition of the AXs than the pH. Further studies revealed that choosing the appropriate solvent could further solubilize AXs and limit their molecular damage (i.e. ferulic acid content). Enzymatic extraction delivered promising results for re-treating rye bran residues from previous extractions to increase the AX yield. Balanced process conditions allowed optimal yields of up to 3.81 g AX/100 g rye bran without compromising their functionality, which was later assessed in GF batters by rheological means as well as after baking. Viscoelastic properties of the batter were improved with the appropriate concentration of AXs. Its effect strongly depended on the chemical and structural properties of these polymers, which modified their interaction with other flour components in the batter. Addition of pyranose-2-oxidase to promote AX crosslinking did not always act synergistically with the AXs in the batter. Application of sourdough technology significantly improved the quality of GF bread and provided the optimal pH for AX gelation, when suitable starter cultures were employed. Baking trials revealed that AXs extracted with water generally improved the bread properties to a higher extent than alkaline-extracted AXs. Nevertheless, the best suitable AXs for GF baking were extracted with calcium hydroxide. Its extraction not only yielded AXs in higher amounts, but they were also able to produce breads with good functional properties. Overall, most of the extracted AXs showed a great potential to be used as natural structure-forming agents in GF breads.

Betreuer: Schönlechner Regine
1. Berater: Schreiner Matthias
2. Berater: D'Amico Stefano

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