11-07-2014, 06:52 PM
Yeast, Saccharomyces cerevisiae, was not identified and isolated until the mid-nineteenth-century. Louis Pasteur is most identified with explaining the role of yeast in fermentation. Until yeast was isolated by Pasteur it was impossible to produce a pure strain of yeast.
The yeast industry, particularly the bread yeast industry, is a product of advances in science and materials processing in the later decades of the nineteenth-century. Todays yeast catalogues for brewers and winemakers with their plethora of strains of S. cerevisiae is very recent. It has been furthered by DNA testing.
While we do speak, historically, of yeasted breads -- yeast has long been mentioned in texts as a fermenting agent -- that yeast was usually obtained from the brewer but the brewers did not have pure strains of yeast. Their fermentations were all contaminated to a greater or lesser degree with Lactobacilli and other contaminants. Lactobacilli are the primary fermenting agents in "sourdough" starters. Historic "yeasts" are probably best conceived of as mixes of S. cereevisiae and contaminates, often the bacterias of a sourdough cultures.
The yeast industry, particularly the bread yeast industry, is a product of advances in science and materials processing in the later decades of the nineteenth-century. Todays yeast catalogues for brewers and winemakers with their plethora of strains of S. cerevisiae is very recent. It has been furthered by DNA testing.
While we do speak, historically, of yeasted breads -- yeast has long been mentioned in texts as a fermenting agent -- that yeast was usually obtained from the brewer but the brewers did not have pure strains of yeast. Their fermentations were all contaminated to a greater or lesser degree with Lactobacilli and other contaminants. Lactobacilli are the primary fermenting agents in "sourdough" starters. Historic "yeasts" are probably best conceived of as mixes of S. cereevisiae and contaminates, often the bacterias of a sourdough cultures.
