Yeast and fermentation
In the absence of air, yeast cells transform sugars into carbon dioxide and alcohol.
From the different yeast strains, researchers are able to produce beer, wine or even ethanol-based fuel!
The history of beer is like the history of bread
As luck would have it! Like bread, beer was discovered accidentally thousands of years ago. And who solved the mystery?
The first beers were “accidentally” brewed in Mesopotamia and Egypt. Air-borne wild yeasts fermented the must left in the sun and beer was born. But, as with bread, the Egyptians made beer empirically.
It was not until Pasteur (him again!) and his studies on beer in 1876 that the whole process was understood. He allowed the selection and storage of the most appropriate yeast strains as well as the possibility of pasteurisation. Even now, some beers are fermented spontaneously but most are fermented with high fermentation strains (between 15°C and 25°C) or low fermentation strains (between 7°C and 15°C).
Taste above all
A specific strain gives each type of alcohol its distinctive traits.
The same yeast is not used to ferment beer or whisky, or to make bread. Researchers have selected specific strains to make beer, wine, spirits and even ethanol-based fuel. All these yeasts for alcohol reveal specific flavours. In brewing, yeast plays a major aromatic role and is often brewers’ secret ingredient.
Yeasts are used to activate fermentation, create bubbles (champagne) or act on the degrees of alcohol. Yeasts also release specific flavours (banana so sought after in Beaujolais wine) and enhance certain tastes (the typical tastes of Chardonnay or Sauvignon for example). Yeasts also characterise certain wines by toning down acidity, giving more smoothness and even prevent certain white wines from turning brown!