Brewing yeast

Microscope Saccharomyces cerevisiae

Brewing yeast - yeast used in brewing , preparations from brewer's yeast are also used as vitamin and immunomodulating dietary supplements , feed additives.

Pure brewer's yeast cultures were first isolated from wild-type yeast by E. Hansen at the Carlsberg Research Center, and soon after this, artificially bred strains began to be used in brewing instead of wild yeast that accidentally infected wort .

Depending on the conditions under which fermentation takes place, yeast is distinguished from the top (surface, warm) fermentation and the bottom (deep, cold) yeast. Top fermentation occurs at a temperature of 14-25 ° C and sometimes higher, while the "cap" rises above the surface of the wort. It is used to produce British ale , Weizen and a number of other beers. For bottom fermentation, temperatures of 6–10 ° C are optimal; yeast settles to the bottom with a dense precipitate.

However, the division into upper and lower yeast is not strict. For example, high yeast is able to adapt to low temperatures, at which, however, their activity decreases and they do not rise to the surface. Therefore, scientists and brewing practitioners evaluate and classify yeast strains according to a set of features. For taxonomy, the appearance of colonies developing on a solid nutrient medium and behavior during development in liquids, digestible (fermentable) sugars, alcohols and organic acids are evaluated. Brewers are important fermentation activity at different temperatures, the ability to flocculation , the degree of fermentation and, most importantly, the taste and other qualities of the resulting beer.

The strains of Saccharomyces cerevisiae are used for both top and bottom fermentation, and Saccharomyces pastorianus , Saccharomyces uvarum , Saccharomyces carlsbergensis are used for the bottom. Strains of S. carlsbergensis also differ in that they are able to ferment rafinose trisaccharide .

Some beers, such as the Belgian lambic , continue to be brewed using wild yeast (usually of the genus Brettanomyces ).

Ordinary brewer's yeast ceases to develop when the alcohol concentration reaches 10%, therefore, stronger beers are obtained using other races of yeast.