Reference Number: 133
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.
SIGNIFICANCE OF THIS STUDY
The paper highlights the main volatile flavours present in both the sourdough starter and sourdough bread. The authors found that in sourdough bread, the amounts of alcohols, esters and diacetyl were shown to be much lower than in the corresponding sourdough. The level of esters in the bread was also very low implying that most of them are evaporated during baking. However, the content of 3-methylbutanal clearly increased during baking. Sensory evaluation of sourdough rye bread crumb suggested that a most intense and bread-like flavour was related 3-methylbutanal and other compounds such as to propanone, benzylalcohol and 2-phenylethanol. When comparing the type of lactic acid bacteria that drive flavour profiles, the authors found that the sensory evaluation of sourdough wheat bread crumb showed that bread made from sourdough fermented with the heterofermentative L. sanfranciscensis had a pleasant, mild, sour odour and taste, whereas sourdough bread fermented with the homofermentative L. plantarum had an unpleasant metallic sour taste. But, when this sourdough was supplemented with the sourdough yeast S. cerevisiae, the bread received a more aromatic flavour. It showed a higher content of 2- and 3-methylbutanol, methylpropanoic acid, 3-methylbutanoic acid and 2-phenylethanol, which may be involved in the more aromatic flavour. The type of flour also can influence the type of volatile flavour compounds that are released. For example, previous reports have shown that rye flour already contains certain aroma compounds, which ‘survive’ the baking process and thus, may contribute to bread aroma. The most striking aroma compounds that were associated with rye sourdough breads were potato-like smelling methional, the mushroom-like smelling 1-octen-3-one, and the fatty, tallowy smelling (E)-2-nonenal. Similarly, in wheat, the most striking aroma compounds revealed were vanillin, followed by fruity furanone, roasty notes of 4,5-epoxy-2-decenal, and the fatty, tallowy smelling 2-nonenal.