Sucrose metabolism and exopolysaccharide production in wheat and rye sourdoughs by Lactobacillus sanfranciscensis

The exopolysaccharide (EPS) produced from sucrose by Lactobacillus sanfranc iscensis LTH2590 is predominantly composed of fructose. EPS production duri ng sourdough fermentation, has the potential to affect rheological properti es of the dough as well as the volume, texture, and keepability of bread. I ts in situ production by L. sanfranciscensis LTH2590 was demonstrated durin g sourdough fermentation after the hydrolysis of water soluble polysacchari des. In wheat and rye doughs with sucrose addition the concentration of fru ctose in the hydrolysate of polysaccharides was significantly higher than t hat in the hydrolysate of control doughs or doughs without sucrose addition . EPS production by L. sanfranciscensis in wheat doughs was confirmed by th e determination of delta C-13 values of water soluble polysaccharides after the addition of naturally labeled sucrose, originating from C-3- and C-4-p lants. In rye doughs, evidence for EPS production with the isotope techniqu e could be demonstrated only by the determination of delta C-13 values of f ructose from water soluble polysaccharides. In addition to EPS formation fr om sucrose, sucrose hydrolysis by L. sanfranciscensis in wheat and rye sour doughs resulted in an increase of mannitol and acetate concentrations and i n accumulation of glucose. It was furthermore observed that flour arabinoxy lans were solublized during the fermentation.