Lager fermentations take longer due to the lower temperature. The
name lager originates from the German word for store and describes the
period of secondary fermentation (storage) at low temperature which
these products undergo to improve yeast settling, clarification and CO 2
dissolution. In the past, this could last for several months, but with
modern techniques such as centrifugation and artificial carbonation it is
less protracted and is now complete within one to two weeks.
Depending on the product, beer from the fermenter can be subjected
to a variety of downstream processes. It may be run to casks where
priming sugars are added to stimulate the secondary fermentation neces-
sary in cask-conditioned beers, or it may be filtered prior to pasteu-
rization and kegging. Bottled and canned beers usually undergo a
combination of filtration and centrifugation before packing and
pasteurization.
Figure 9.13 Changes during the beer fermentation
(Reproduced courtesy of the Institute of Brewing)
354 Fermented and Microbial Foods