3,000 years before our era, Egyptians and Babylonians knew, using sourdough, how to utilise the fermentation of wild yeast to make alveolated bread different from the traditional, compact, flat cakes.
The era of " mysterious fermentation " was to last until the 19th century when Pasteur identified yeast as the micro-organism responsible for alcoholic fermentation.
Today, the yeast produced industrially and used worldwide by bakers is a strain from Saccharomyces cerevisiae. From only one cell, the genetic and biochemical characteristics of which are analyzed and carefully controlled in the laboratory, the yeast manufacturer has to propagate life and produce, in a fermentation tank , billions of cells which will enable the baker to initiate the complex mechanism of fermentation in dough which will be rapidly deprived of oxygen.
Nowadays, in the hands of the yeast manufacturer, yeast is no longer the sourdough, the properties of which are not very well known. Knowledge of the molecular structure of the Saccharomyces cerevisiae genes as well as its chemical heredity opens promising ways for new fields of application. The yeast manufacturer does not only select the right yeast for its fermentation capacity and its industrial productivity : he can also domesticate the existing strains by modifying or developing their genetic potential, and can create new and highly specialized yeast.
This is an absolute necessity, as the baker requires more stable and more " process-tolerant " yeast on account of the technological evolution of bread-making and new consumption trends. Accept the pH variations of sourdough and osmotic pressure in sweet dough; tolerate fungistatic agents for the sandwich-loaf shelf life; survive negative cold inside a frozen lump of dough - such is the ordeal the yeast must get though in the baker’s kneading machine.
And that is not the end of it !
After giving all his attention to the properties of the dough and its tolerance until it is put into the oven, today the baker has rediscovered the taste of bread which only a long and well monitored fermentation can produce. Are essential secondary fermentations possible without having to use the laborious techniques required by sourdough or poolish methods to develop the flavour of bread ?
It is the challenge facing yeast makers and requires that yeast can produce unchanged carbon dioxide associated with an accelerated synthesis of the aromatic volatile substances.