On food and cooking the science and lore of the kitchen ( PDFDrive ) 1407
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tendays,andproducesamilderflavor.
Bottomfermentationisthestandardtechnique
intheUnitedStates.Becausewarm
temperaturesencourageyeaststogenerate
particulararomacompounds(esters,volatile
phenols),topfermentationproducesfruity,
spicyaromas;cold,slowfermentation
producescrispbeerswithadry,breadyflavor.
Conditioning The treatment of beer after
fermentation varies according to the type of
fermentation that has taken place: brief for
fast top fermentation, prolonged for slow
bottomfermentation.
Top-fermentedbeerisclearedofyeastand
thenrunintoatankorcaskforconditioning.
Thegreenbeer,asit’scalledfreshfrom
fermentation,containslittlecarbondioxide,
hasasulfurous,harshflavor,andishazywith
thedetritusofdeadyeastcells.In
conditioning,asecondaryfermentationis
inducedbyaddingtothegreenbeereithera
smallamountofyeastandsomesugarorfresh
wort,orsomeactivelyfermentingwort(this
iscalledKräusening).Insidetheclosedcask
ortank,theliquidtrapsandabsorbsthe
carbondioxideproduced.Undesirableodors
canbeforcedoutofthebeerbyopeningthe
containerbrieflyandallowingsomegasto
escape.Thesetraditionaltechniquesare
sometimesreplacedbysimplypumpingpure
carbondioxideintothebeer—carbonatingit.
Somehopsorhopextractmayalsobeadded
atthispointtoaugmentaroma,bitterness,or
both.Afewdaysofcoolingandtheuseofa
“fining”agent—isinglass(fishgelatin),clay,
andvegetablegumsarecommon—
precipitatesuspendedproteinsandtannins
thatmightlaterformahazewhenthebeeris
chilledfordrinking;thisiscalled“cold
stabilization.”Thebeeristhencentrifugedto
removeanyremainingyeastandprecipitate,
filtered,packaged,andusuallypasteurized.
