Generation of aroma compounds during sourdough fermentation: applied and fundamental aspects

Sourdough has been used in bread production for more than 5000 years in order to improve the texture and flavour of baked cereals, and still today sourdough is very important to impart superior flavours to wheat and particularly rye bread. After an introduction into the history of sourdough, results of studies aimed at indicating (i) the influence of the dough and bread recipe, (ii) the regime used in dough fermentation, and (iii) the metabolic activities of sourdough bacteria and yeasts on the final bread aroma are summarized in this review. Based on quantitative results obtained from the same batch of flour, sourdough and rye bread, changes in the concentrations of key bread aroma compounds on the way from flour to bread are highlighted with respect to their contribution to the overall aroma. Based on correlations with the bread recipe, it is discussed how the flour and each technological step influences the final concentrations of selected odorants in the bread.