;){kind=link}
Beer Fermentation
Lager Fermentations
Temperatures
Fermentation time-temperature profiles vary widely throughout the industry for lagers. Traditional lager brewing involves pitching the yeast between 5 and 6ºC and allowing the temperature to rise between 8 and 9ºC (23). This generally results in a better quality beer because low fermentation temperature retards the development of byproducts – esters, fusel alcohols, and diacetyl, all of which are inappropriate in lagers. However, the lag period is generally longer at lower fermentation temperatures. At the end of primary fermentation the temperature is reduced by 1 to 1.5ºC per day and transferred to the lager cellar between 4 and 5ºC (23).
More commonly, the yeast is pitched between 7 and 8ºC, and after a couple days the temperature is increased to 10 to 11ºC (23). Some brewers use the same starting temperature but then increased to 14 and 15ºC (22). Other breweries are known to pitch between 12 and 14ºC and then increase the temperature to as high as 18ºC.
Starting Tanks
Traditional European lager brewers, especially in Germany and Scandinavia, use a starting tank in which yeast is added to the cooled wort and the contents then allowed to stand for a period of up to 24 hours before racking (27). Traditionally, starting tanks were open vessels, but nowadays they are generally designed like regular closed-in fermenters.
The purpose in using a starter tank is to allow some undesirable solids to be removed by settling or flotation (32). The starter tank also removes trub particles that were not collected during trub separation, as well as hop resins that precipitate after cooling (23). Trub also contains polyphenols, ketones, and sulfur compounds that may be absorbed into the ferment and thereby affect the flavor of the beer. Knudsen reports that starting tanks are also used to more accurately measure wort volume, to mix yeast and wort, and to equalize temperature differences prior to transferring wort and yeast to the fermenter (22).
Click on the following topics for more information on beer fermentation.