Potential of adding isolated pentosans from rye-bran to improve gluten-free bread properties

Rye flour, frequently used in breadmaking in combination with the sourdough fermentation, is highly rich in araboxylans (AXs), also referred to pentosans. AXs are the most important thickening components in rye flour and it is important to distinguish between water-extractable or soluble AXs, which are responsible for positive effects on water holding capacity, bread volume, crumb texture and staling, and water-unextractable or unsoluble AXs, which have an opposite effect. Although different hydrocolloids and other agent have been well investigated for their use in gluten-free breads, the use of pentosans has not been exploited yet in this respect. The aim of the study, therefore, was to improve the performance of gluten-free bread by the addition of different amounts of soluble pentosans. Pentosans were isolated from rye bran and analyzed for chemical composition, monosaccharides distribution and protein content. The gluten content was calculated, too, based on RP HPLC analysis and it was below 20 ppm. Baking experiments with various gluten-free raw materials (gluten-free wheat starch, amaranth, quinoa, millets and others) and different amount of pentosans were then tested. Dough rheological properties were characterized with a Micro-Z-Arm Mixer similar to Farinograph. The addition of pentosan isolates resulted in significantly (p<0.05) higher technological properties of the gluten-free dough systems: dough stability and extensibility were improved, gluten-free bread volume was higher, crumb firmness softer when compared the control bread (no pentosan addition). The results suggest that pentosans have a good potential to improve gluten-free bread quality.