On food and cooking the science and lore of the kitchen ( PDFDrive ) 1467
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FormsofHeatTransfer
Cookingcanbedefinedinageneralwayas
thetransformationofrawfoodsinto
somethingdifferent.Mostoften,wetransform
foodsbyheatingthem—bytransferring
energyfromaheatsourceintothefoods,so
thatthefoodmoleculesmovefasterand
faster,collideharderandharder,andreactto
formnewstructuresandflavors.Ourvarious
cookingmethods—boiling,broiling,baking,
frying,andsoon—achievetheirvarious
effectsbyemployingverydifferentmaterials
asthemediumthroughwhichtheheatmoves,
andbydrawingondifferentformsofheat
transfer.Therearethreewaystotransferheat,
andanacquaintancewiththemwillhelpus
understandhowparticularcookingtechniques
affectfoodsthewaytheydo.
Conduction:DirectContact
Whenthermalenergyisexchangedfromone
particletoanearbyonebymeansofa
collisionoramovementthatinduces
movement(forexample,throughelectrical
attractionorrepulsion),theprocessiscalled
conduction.Thoughit’sthemost
straightforwardmeansofheattransferin
matter,conductiontakesdifferentformsin
differentmaterials.Forexample,metalsare
usuallygoodconductorsofheatbecause,
whiletheiratomsarefixedinalattice-like
structure,someoftheirelectronsarevery
looselyheldandtendtoformafree-moving
“fluid”or“gas”inthesolidthatcancarry
energyfromoneregiontoanother.Thissame
electronmobilitymakesmetalsgood
electricalconductors.Butinnonmetallic
solidslikeceramics,conductionismore
mysterious.Itseemsthatheatispropagated
notbythemovementofenergeticelectrons—
insolidsofionic-orcovalent-bonded
compounds,theelectronsarenotfreetomove
