On food and cooking the science and lore of the kitchen ( PDFDrive ) 1183
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purees.Butbotharemarvelsofmouth-filling
pleasure.
SaucesThickened
withDropletsofOil
orWater:Emulsions
Thesauceswe’veexaminedsofarareliquids
thickenedwithafinedispersionofsolid
materials:proteinmolecules,starchgranules
andmolecules,particlesofplanttissueand
cell-wallmolecules.Averydifferent
thickeningmethodistofillthewater-based
liquidwithdropletsofoil,whicharemuch
moremassiveandslow-movingthan
individualmoleculesofwater,impedetheir
motion,andsocreateathickandcreamy
consistencyinthemixtureasawhole.Sucha
dispersionofoneliquidinanotheriscalledan
emulsion.ThewordcomesfromtheLatinfor
“tomilkout,”andreferredoriginallytothe
milkyfluidsthatcanbepressedfromnutsand
otherplanttissues.Milk,cream,andegg
yolksarenaturalemulsions,whilesauce
emulsionsincludemayonnaise,hollandaise
sauce,beurreblanc,andoil-and-vinegarsalad
dressings.Modernchefshaveappliedthe
basicideatothethickeningofallkindsof
liquids,andoftenactuallydescribetheresult
onthemenuasanemulsion,awordthat
lingersonthetonguelongerthansaucedoes.
Emulsifiedsaucesofferaspecialchallenge
tothecook:unlikesaucesthickenedwith
solids,emulsionsarebasicallyunstable.
Whiskoilandalittlevinegartogetherina
bowl,andthevinegarformsdropletsinthe
oil:buttheysoonsinkandcoalesce,andina
fewminutesthetwoliquidshaveseparated
again.Cooksnotonlyhavetoformthe
emulsion,theyalsohavetopreventthe
emulsionfrombeingundonebythebasic
incompatibilityofthetwoliquids.
TheNatureofEmulsions
