On food and cooking the science and lore of the kitchen ( PDFDrive ) 1408

TheDifferentFlavorofBeeronTap
Bottled and canned beers and ales are
generally cold stabilized and pasteurized
(at140–160ºF/60–70ºC)tosurviveextreme
temperatures during shipping and storage,
while keg beers, which are kept
refrigeratedcontinuously,maynotbe.This
iswhybottleandkegversionsofthesame
beer can taste very different. However,
even keg beer is a world apart from the
traditionalcask-conditionedbeer.Kegbeer
hasbeenclearedofallitsyeastbeforethe
keg is filled, while in cask conditioning,
the new beer and the yeast that will help
mature it are sealed together in the cask.
Cask-conditioned beer is thus in contact
withyeastuntilthemomentit’sdispensed,
and its flavor reflects this. Cask beer is
fragile and has a drinkable life of about a
month, compared with three months for
kegbeer.
LageringTheconditioningprocessfor


bottom-fermentedbeerissomewhatdifferent.
TheoriginalBavarianlagerwaspackedinice
andallowedtorestincontactwithitsyeast
dregsforseveralmonths.Theyeastslowly
producedcarbondioxide,whichhelpedpurge
thebeerofsulfuryoff-odors.Today,some
traditionallagersarestillagedforseveral

months;butbecausestoragehastheeconomic
disadvantageoftyingupmoneyand
materials,thetendencyistolagerthegreen
beerattemperaturesjustabovefreezingfor
twotothreeweeks.Carbondioxidemaybe
pumpedintopurgeundesiredaromas;and
centrifuges,filters,andadditiveshelpclarify
thebeer.Asareplacementforwoodencasks,
somebeechorhazelwoodchipsmaybe
thrownintothetankforflavor.
Additives More than 50 additives are
permitted in American beer, including
preservatives, foaming agents (usually
vegetable gums), and enzymes — similar to