Sourdough is combined with long-fermentation products with highly distinctive aromatic profiles owing to the high concentration of organic acids, notably acetic and lactic.
Pasteur’s discovery of the role of yeast in fermentation in 1857, and especially that of Saccharomyces cerevisiae, led to its rapid deployment, which saw Lesaffre build its first yeast factory in the Paris area in 1872. The discovery also helped subsequently in understanding the nature and functioning of sourdough, which had hitherto been used in bread production. Sourdough is, in effect, based on a symbiotic association between yeast and lactic acid bacteria. Sourdough and yeast both have something in common. They are both fermenting agents used to ensure that dough rises through the production of carbon dioxide.
Yeast and sourdough also participate in the development of bread flavours thanks to the action of organic acids and the aromatic compounds produced by both types of microorganisms. As in the case of yeast, the bacteria found in sourdough has been isolated, individually multiplied and combined according to need in ready-to-use and/or customised solutions.
Far from being antipathetic, yeast and sourdough are perfectly complementary, thus making it possible to better regulate fermentation activity and obtain a specific aromatic identity. Sourdough is, in effect, combined with long-fermentation products with highly distinctive aromatic profiles owing to the high concentration of organic acids, notably acetic and lactic. The rheology of the dough thus obtained is highly particular, resulting in a lower specific volume and a thicker crust. The lower pH helps to preserve bread due to the anti-fungal effect and limited rate of starch breakdown, which thereby delays the staling process.
Diversity and complementarity in the metabolism of sourdough microbiota
- The balance between yeast and lactic acid bacteria is essential for ensuring that every microorganism can express its full aromatic and fermentation potential.
- Sourdough can contain two types of lactic acid bacteria in order to obtain different aromatic profiles:
- Homofermentative bacteria produce only lactic acid, which acts as a taste enhancer, used especially in sweet applications;
- Heterofermentative bacteria produce both lactic and acetic acid. The latter produces typical sourdough flavours (plum, cinnamon), especially in rye flour.
Sourdough varieties
The microorganisms in sourdough, live sourdough and products obtained from fermentation marketed by Lesaffre are the direct result of its expertise in the field of yeast and fermentation.
- Starters are used to obtain sourdough with the desired characteristics for baking thanks to a careful choice of species and strains (usually a combination of yeast and bacteria). Lesaffre’s expertise assists the baker in the choice of substrates and process management.
- Ready-to-use live sourdough enables bakers to dispense with sourdough preparation. Lesaffre’s expertise in strain selection and fermentation processes helps to guarantee the desired characteristics. A process patented by Lesaffre is used to stabilise the live sourdough for up to 14 weeks at temperatures lower than 10°C, both for rye and wheat sourdough, the latter being traditionally less acidic.
- Devitalised sourdough comes in liquid or powder form and is a sourdough with and is a live sourdough with a deactivated biomass. This treatment helps to extend shelf-life for up to 12 months, while preserving the aromatic properties of the sourdough intact. Available on different substrates, these sourdough types can be combined to obtain unique aromatic profiles.
