Investigation of the effect of pentosan addition and enzyme treatment on the rheological properties of millet flour based model dough systems

The objective of this work was to investigate the possibility of a macromolecular network formation in gluten-free model dough systems based on millet flours (white and wholemeal) by the addition of rye bran arabinoxylan (AX) and enzyme treatment. To perform enzyme treatment pyranose-2-oxidase was applied, which was assumed to be able to initiate cross-links between AX molecules through H2O2 production. The effect of AX addition and enzyme treatment on the rheological properties of the model systems was studied by basic (oscillation measurement) and applied (micro-doughLab, Rapid Visco Analyzer and Mixolab) rheological methods. The molecular basis of AX crosslinking was investigated in lyophilized dough and/or gel samples by SE-HPLC and Scanning Electron Microscopy (SEM). The results showed that AX addition deteriorated the mixing and pasting properties in general, but these properties were significantly improved when it was combined with enzyme treatment. In some cases, enzyme addition itself also changed the behaviour of the model systems significantly, suggesting that the enzyme may have an effect on other flour components (e.g. proteins, starch), as well. The study of AX molecular weight distribution performed by SE-HPLC confirmed the appearance of a new peak in the higher molecular weight range when enzyme treatment was applied to AX dosed dough systems, supporting our initial assumptions. According to SEM images of dough and gel microstructures, significant association was observed between starch granules when AX and enzyme treatment were applied together indicating a possible formation of a macromolecular network.