On food and cooking the science and lore of the kitchen ( PDFDrive ) 1519
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betweenmolecules,andonwhetherwatercan
separatethemoleculesfromeachotherby
hydrogenbonding.Thewheatproteinsthat
formglutenwhenflourismixedwithwater
areakindofproteinthatabsorbsconsiderable
amountsofwaterbutdoesn’tdissolve,
becausemanyfat-likegroupsalongtheir
moleculesbondwitheachother,holdthe
proteinstogether,andexcludewater.
Similarly,theproteinsthatmakeupthe
contractingmusclefibersinmeatareheld
togetherbyionicandotherbonds.Onthe
otherhand,manyoftheproteinsinmilkand
eggsarequitesoluble.
ProteinDenaturation
Averyimportantcharacteristicofproteinsis
theirsusceptibilitytodenaturation,orthe
undoingoftheirnaturalstructurebychemical
orphysicalmeans.Thischangeinvolves
breakingthebondsthatmaintainthe
molecule’sfoldedshape.(Thestrong
backbonebondsarebrokenonlyinextreme
conditionsorwiththehelpofenzymes.)
Denaturationisnotachangeincomposition,
onlyachangeinstructure.Butstructure
determinesbehavior,anddenaturedproteins
behaveverydifferentlyfromtheiroriginals.
Proteinscanbedenaturedinmanyways:
byexposingthemtoheat—usuallyto
somewherebetween140–180ºF/60–80ºC—or
tohighacidity,ortoairbubbles,ortoa
combinationofthese.Ineachcase,the
unusualchemicalorphysicalconditions—
increasedmolecularagitation,orlotsof
reactiveprotons,orthedrasticdifference
betweentheairbubbleandtheliquidwallthat
surroundsit—breaksmanyofthebonds
betweenaminoacidsidegroupsthatholdthe
proteinmoleculeinitsspecificfoldedshape.
Thelongproteinsthereforeunfold,exposing
manymoreoftheirreactivesidegroupstothe
wateryenvironment.
