Yeast is one of the most useful compounds in the field of biotechnology, due to its role in fermentation. Many different types of yeast are used, such as baker’s yeast in bread production, and Brewer’s Yeast in beer fermentation.
Brewing Yeasts are classified into “top-cropping” and “bottom-cropping” groups. Top-cropping Yeasts, such as S. cerevisiae, received their name due to their ability to form a foam at the top of the wort, or liquid extract, during fermentation. Such Yeasts are used to produce various ales. Bottom-cropping Yeasts, in contrast, are used to produce lager-type beers, and ferment at lower temperatures.
Yeast is one of the earliest domesticated organisms, as archaeologists have found evidence of baking chambers for bread made with Yeast, and drawings of ancient bakeries and breweries. Anton van Leeuwenhoek first microscopically observed yeast in 1680, but in 1857, Louis Pasteur observed the process of fermentation by Yeast in a broth. By the late 18th century, two Yeast strains were identified and used in brewing – S. cerevisiae and S. carlsbergensis.
In 1825, a method was created to remove liquid so Yeast could be prepared in solid blocks. Then, in 1867, the filter press was invented to increase the separation of solid from liquid.