Beer Styles: Fermentation temperature - part 15

October 28, 10:54 AMBeer ExaminerCharlie Papazian

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Fermentation bloom at a London's Young brewery in the 1980s.  During ferment
yeast produce heat and in this brewery cold water was piped (see below) through
the fermenting beer to keep temperature stable.  Photos by Charlie Papazian.

Most beer drinkers know beer is a naturally fermented alcoholic beverage.  Yeast is introduced into unfermented brewed “wort.”  Yeast population grows and then begins converting sugar into alcohol, carbon dioxide and beer flavor and aroma.

There are many critical factors that influence beer character during fermentation.  One of the most important and easily controlled pieces of the “brewing to style” and intent is temperature control.  

At the beginning and during the height of fermentation, yeast metabolism produces a lot of heat.  Surprised?  Don’t be.  When yeast metabolizes sugar, they burn energy, creating heat.  It’s important to keep temperatures stable at the desired level throughout the various phases of fermentation.

Elevated fermentation temperatures produce higher levels of fruity aromas and flavors.  These characters are called esters.  In some beer styles this is desirable.  Generally speaking with most classic lager styles esters are not sought; hence cool temperature fermentations are pursued.

Warmer temperature fermentations can also reduce head retention.  Also elevated levels of fusel alcohol (sometimes referred to as fusel oil or higher alcohols) are produced.  Minute quantities of these compounds contribute solvent-like aromas and flavors.  This is not desirable in any beer.

Photo left: Cold water was pumped through these pipes to cool fermentation at Young's brewery in the 1980s.  This brewery no longer exists. Photo by Charlie Papazian.

Lager yeasts produce lager style character at initial fermentation temperatures between 45 and 55 degrees F.  Lagering, storing and maturing these beers is best at temperatures between 38 and 32 degrees F.  

English styles of ales are traditionally fermented initially at about 70 to 74 degrees F.  They are matured later by "cellaring" at about 55 to 65 degrees F.  

Many fruity styles of Belgian ales are initially fermented at temperatures between 74 and 80 degrees F, depending on the degree of fruitiness desired.

The delicate character of German-style wheat beers must be very carefully controlled in order to produce the complex balance of ester, spiciness and other beer quality.  

In order to produce the bacterially and yeast derived “funk” and acidity of certain “wild” beer styles, warmer environments are required at specific stages of fermentation to nurture their metabolism.

Different yeast strains behave differently at various temperatures.  Brewers access various knowledge bases in order to determine which yeast is right for the character they are seeking.  Then they try it on their own system of fermentation.  Different shapes and configuration of fermentation vessels produce varying end results.

Brewing beer to style is both a science and an art.

Next: Beer Styles: Maturation beer goes from good to best - part 16