Isolation, modification and characterization of soluble arabinoxylan fractions from rye grain

Because of the positive role of arabinoxylans and especially their water-soluble fractions in establishing bread properties, it seems reasonable to use them as natural bread improvers. In this work, an adequate isolation procedure of water-soluble arabinoxylans from rye grain with efficient purification steps is presented, delivering 2.9 % yield from wholemeal with a content of arabinoxylan of approximately 70 % and an arabinose/xylose ratio of 0.7. Furthermore, soluble arabinoxylans were modified by enzymatic hydrolyses, cross-linking with peroxidase/H2O2 treatment and combination of both for developing preparations applicable for bread making with different quality profiles. Additionally, a detailed analysis of chemical composition and molecular dimension was carried out by HPLC, SEC, HPSEC and viscosity measuring. The preparation after cross-linking showed considerably higher molar mass values, lower solubility and higher viscosity with high Huggin's constant compared to the not modified sample. Otherwise, the combination of enzymatic hydrolysis and cross-linking resulted in the formation of arabinoxylan preparations with only slight degree of cross-linking and properties comparable with the only hydrolyzed sample.