EFFECTS OF BAKING ON WATER-SOLUBLE NONSTARCH POLYSACCHARIDES IN WHITE BREAD FRACTIONS

Water-soluble non-starch polysaccharides were extracted from white flour and dough as well as from crumb, inner crust and outer crust fractions of white bread, baked at 210 °C for 22 or 35 min. Results from the two baking experiments were very similar. Extracted polysaccharides were fractionated on DEAE-cellulose and by different solubility properties in aqueous saturated ammonium sulfate. Fractions isolated were characterized by sugar- and 1H-n.m.r. analysis, revealing the presence of arabinoxylan mixtures with widely different degrees of arabinose substitution. Arabinogalactanproteins isolated showed little variation in galactose/arabinose ratio (1·5–1·8). Highfield 1H-n.m.r, of arabinoxylan fractions was particularly useful for estimating the ratios of terminal arabinofuranosidic residues linked to xylose residues at O-2 and O-3 or solely at O-3. Water-soluble arabinoxylans had a higher degree of arabinose substitution in bread fractions than in the flour and dough, probably due to increased solubilization of highly substituted arabinoxylans during baking. © 1990, Academic Press Limited. All rights reserved.