Influence of enzymes on the evolution of fructosans in sourdough wheat processes

The effects of white wheat flour, sourdough starters (multiform and purl strain) and enzymes (amylase/pentosanase and/or lipase) on amounts and composition of fructosans during a breadmaking process were investigated. Samples yielded a crude extract of fructosans close to 3%, of which about 30% was pure fructosans. In dough and bread samples the presence of yeast invertase split a considerable amount of fructosans, and further treatment with this enzyme during the measurement procedure did not yield more fructosans. Treatment with an inulinase showed the presence of inulin-type linkages in flour, the amount depending on the flour source. As expected, fermentation reduced the amount of fructosans. Different trends were observed with each starter, and some interactions appeared between type of flour and enzyme addition. Characterisation of fructosans by size exclusion chromatography revealed five fractions with apparent molecular weight (MW) between 25000 and 192 Da; fructosans isolated from dough and bread samples had the same MW distribution but a different relative proportion of each fraction, and differed from those obtained from flour.