Labels:text | black and white | paper | font | publication | number | document OCR: than others, and consequently became mentation and aging of the beer, and the increasingly selective. choosing col- varying flavors produced. Bottom- NEWSLETTER lected yeast that produced a superior fermenting lager yeast can ferment at By William Moore flavor in beer. This collected yeast origi- nally was all of the top-fermenting (ale) temperatures as low as 34 degrees F ., making possible a ferment very resis- type, until the early 1900's, when a tant to bacteria and wild yeasts (which brewer in Germany began to isolate find it impossible or very difficult to bottom-fermenting (lager) yeast. grow at colder temperatures) and a fer- Yeast According to theory, the few bottom- ment in which the yeast does not add a Without the lowly yeast, alcohol could fermenting lager yeast cells occuring lot of flavors to beer, because flavor naturally in collected yeast gradually affecting esters, acids, and fusel alcohols not exist. Yeast, a form of fungi, eats the became dominant in cultures used to fer- are increasingly produced by yeast as sugar compounds extracted from malt. ment European beers brewed at colder the fermentation temperature increases producing carbon dioxide, alcohol, and winter and spring temperatures, and the yeast's metabolism is acceler- flavor compounds. There are countless because top-fermenting yeast did not ated. Accordingly. partially because varieties of yeast in the world, most of reproduce at colder temperatures, leav- lager yeast can ferment at lower which produce a sour, cloudy beer. Beer ing room for the colder-fermenting temperatures, it can produce a beer with yeasts have been selected and refined lager yeast cells to grow and eventually minimal yeast-produced flavor com- through centuries of brewing as much dominate. Though the exact date is not pounds. When bottom-fermenting lager for the unique flavors they impart as for known and stories vary regarding the their ability to convert malt sugars to first isolation of bottom-fementing lager yeast is fermented at ale temperatures to make steam beer (60 to 75 degrees F.), alcohol and settle out in a timely manner at brewing temperatures. Many ad- yeast. it was probably first recognized it adds flavor-affecting esters and other by a monk named Benno Scharl, operat- compounds in perceptible amounts, vanced home brewers, probably due to the limited number of brewing yeast ing a small brewery outside of Munich. which combine to help give steam beer Germany around 1810. He was using a its unique robust flavor and aroma. strains commonly available. have rele- brewing yeast with unique characteris- Top-fermenting ale yeast, on the other gated yeast strain selection to an ties - it produced a large sediment of hand. will not ferment at temperatures afterthought, selecting between a single yeast on the bottom of the fermenter. below about 55 degrees F ., and can be strain of dried ale or lager yeast, with Mr. Scharl experimented in reusing used at temperatures as high as 80 far less discrimination than afforded the only the sedimented yeast in successive choosing of hops, grain, or malt extract. degrees F ., making ale yeast a forgiving fermentations, and his beer became and easy to use yeast for the home This overlooking of the single most regionally prominent for its excellent brewer. Like lager yeast, ale yeast important ingredient in brewing limits flavor. A larger brewery, Spatenbrau- imparts its own flavor to beer, particu- the brewer to the tastes of just one or two erei of Germany, began using this new larly when fermenting at the upper lim- yeasts, restricting flavor range as severely as if limited to one or two malt yeast and sent samples to Copenhagen, its of its temperature range. The where the famous microbiologist, Chris- difference in the flavors imparted by ale or hop varieties. Different yeasts can tian Hanse, isolated the yeast cells and and lager yeast are subtle. Given an ferment the same wort into dramati- cally different beers, with varying grew them into the first pure lager yeast identical wort fermented with a typical culture, known as Saccharomyces strain of ale and lager yeast at identical flavors and aromas; the home brewer Carlsbergensis. This new lager yeast was called normal homebrewing temperatures (60 should select yeast strains with the same to 75 degrees F.) the resultant beers critical eye given to malt and hops. "bottom-fermenting" because a major clearly have a different flavor, though There are two basic species of brewing ity of the yeast cells ( though some rise to this difference may be as much due to yeast, lager yeast (bottom-fermenting) the surface), settle out towards the end of the flavors imparted by a certain strain and ale yeast ( top-fermenting). Brewing yeast evolved through the centuries fermentation, while the older top- of ale or lager yeast as by the varying fla- from wild airborne yeast, and even fermenting ale yeast tends to rise vors created by the species ale yeast or towards the surface during fermenta- lager yeast as a whole today, Belgian lambic beers are still tion and remain suspended in the wort Although there are only two basic spe- brewed with wild yeast - the freshly longer. This difference in sedimentation cies of beer yeast, top-fermenting ale boiled wort is cooled, and doors above is due to the varying composition of ale yeast and bottom-fermenting lager the fermenters are opened to the outside and lager yeast's porous cell walls, yeast, within each species there are air, letting wild airborne yeast drift in to though the chemical nature of the differ- hundreds of different strains, each capa- start fermentation. Beer fermented ences is not known. Another main bio- ble of imparting its own unique flavor. with wild yeast has a very astringent logical difference between ale and lager Until recently, the home brewer has character, however, and brewers yeast is lager yeast's ability to ferment been limited to one or two good strains of through the centuries learned to save melibiose sugar, due to the presence of dried lager and ale yeast (Red Star yeast at the end of fermentation for use Lager Yeast and some of the English ale in the next batch. This saving of yeast melibiase enzymes in the lager yeast cell. although this lack of melibiose yeasts). This lack of yeast choices has was initially done to provide a faster sugar in lager beer is not perceptible to stifled many brewers, because flavor start to fermentation than drifting wild my taste. differences imparted by, say, two differ- yeast could provide, though brewers For the brewer, the most important ent strains of lager yeast. are often as came to realize that certain samples of differences between ale and lager yeast collected yeast produced better beer are the temperature required for fer- over STO Copyright @ 1986 William's Brewing Co.
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