Yeast and beer

Yeast and beer

In the absence of air, yeast cells transform sugars into carbon dioxide and alcohol. 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 industrial ethanol (including ethanol-based fuel). The different strains of yeast for alcohol thus have their specific features to adapt to certain substrates (fruit, grapes, grain, beet, malt), enhance particular flavours in the finished product, adapt to certain temperatures, resist high or low temperatures, etc.

Brewing

 

levure et biereThe first beers appeared “by miracle” in Ancient Times. Discover the indispensable role of brewer’s yeast in the production of this beverage.

 

According to historians, the first beers were accidentally brewed in Mesopotamia and Egypt and their fermentation was spontaneous. Air-borne wild yeasts fermented the must left in the sun and beer was born.

For a long time, wild yeasts present in the air spontaneously fermented brewing vats, hence yeast’s nickname of “gift of god”. Each region would brew its own type of beer as yeast in the air varies, depending on its location! The first scientific research on brewer’s yeast was conducted by Pasteur in 1876 (“Les études sur la Bière”) and allowed the selection and storage of the most appropriate brewing strains as well as the development of beer pasteurisation.

 

Nowadays, some beers are still spontaneously fermented (lambics, Gueuze) but most are fermented with high or low fermentation yeasts. They are distinguished by the temperature at which they ferment and therefore the types of beer that can be produced.

 

High fermentation yeasts are aimed at Ales which ferment between 15°C and 25°C. Low fermentation yeasts are used in lagers or Pils which are brewed at low temperature (7°C to 15°C) and are often kept to mature.

 

In brewing, yeast plays a major aromatic role and is often brewers’ secret ingredient. Depending on the temperatures used in fermentation, the same strain can produce different flavours.