On food and cooking the science and lore of the kitchen ( PDFDrive ) 1126
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Thickeningaliquidwithlongfoodmolecules.
Dissolvedmoleculesofplantstarchoranimal
gelatin get tangled up with each other and
impedetheflowoftheliquid.
Emulsions:ThickeningwithDroplets
Thankstotheirverydifferentstructuresand
properties,watermoleculesandoilmolecules
don’tmixevenlywitheachother(p.797).
Neithercandissolveintheother.Ifweusea
whiskorblendertoforceasmallportionof
oiltomixintoalargeroneofwater,thetwo
formamilky,thickfluid.Boththemilkiness
andthethicknessarecausedbysmalldroplets
ofoil,whichblocklightraysandthefree
movementofwatermolecules.Theoil
dropletsthusbehavemuchasthesolid
particlesinasuspensiondo.Suchamixtureof
twoincompatibleliquids,withdropletsofone
liquiddispersedinacontinuousphaseofthe
other,iscalledanemulsion.Thetermcomes
fromtheLatinwordfor“milk,”whichisjust
suchamixture(p.17).
Emulsifiers In addition to the two
incompatible liquids, a successful emulsion
requires a third ingredient: anemulsifier. An
emulsifier is a substance of some kind that
coatstheoildropletsandpreventsthemfrom
coalescing with each other. Several different
materials can serve this function, including
proteins, cell-wall fragments, and a group of
hybrid molecules (for example, egg-yolk
lecithin)thathaveanoil-likeendandawatersoluble end (p. 802). To make an emulsified
sauce, we add oil to a mixture of water and
emulsifiers(eggyolk,groundherbsorspices),
andbreaktheoilupintomicroscopicdroplets,
which the emulsifiers immediately coat and
stabilize. Or we can begin with a premade
