Proteolysis in Model Sourdough Fermentations

Model wheat doughs started with six different lactic acid bacteria (LAB), with or without a commercial
baker's yeast culture, were used to study proteolysis in sourdough fermentations. Cell counts, pH,
and free amino acid concentration were measured. Sequential extraction of dough samples was
performed to separate wheat proteins. The salt-soluble protein fraction (albumins and globulins) was
analyzed by RP-HPLC and SDS-PAGE, whereas propanol-soluble (gliadins) and insoluble (glutenins)
protein fractions were analyzed by SDS-PAGE only. Multivariate statistical methods were used for
the analysis of results. The presence of yeasts and LAB affected RP-HPLC and SDS-PAGE patterns
of the salt-soluble fraction in a complex way. The only changes in the gluten proteins that could be
related to the presence of LAB were the appearance of new protein fragments (20 and 27 kDa) from
gliadins and the degradation of high molecular weight glutenin subunits.
Keywords: Wheat sourdoughs; proteolysis; lactic acid bacteria; yeasts