Fermentation produces amongst some other items carbon dioxide gas or CO2. Fermentation processes can happen more or less spontaneous (like in sourdough) or with more focused intention (as with yeast). Fermentation processes are not working very well in sugar rich or salt rich environments, hence it is dominantly used for bread and bread related items.
As fermentation happens due to living organisms they do require favourable conditions such as food (dextrin’s or maltose), temperature (between 10-50°C). With either yeast or sourdough (lactic acid bacteria and ‘spontaneous’ yeast) we will produce gasses, but also several by-products. Some of these by-products will a products its distinct flavours, and some are volatile (such as the ethanol produced) which will expand and evaporate during baking.
In order to have a finer distribution of gas cells doughs are not just fermented, but also are there different techniques used after a certain period (this will depend of the speed of fermentation, which is ‘simplistically put’ a function of time, temperature, level of sourdough/ yeast and yeast food) to fold, round, punch, sheet or other to ‘push out’ excess gasses, allowing dough layers to reconnect. This ‘mechanical’ process helps in developing not only a finer structure, but also more flavour.
In yeast based leavening we have a clear targeted functionality as we use only one type of fungi (Saccharomyces cerevisiae), where as in sourdough we will find different strains of bacteria and different yeast strains are present, this will naturally cause different volume and flavour development in the products.
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