On food and cooking the science and lore of the kitchen ( PDFDrive ) 1124
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sizeofitsparticles.Thesmallertheparticles,
thelessnoticeabletheyaretothetongue,and
thesmootherthetexture.Also,thesmallerthe
particlesare,themoreofthemtherearetodo
theobstructingandthemoresurfaceareathey
havetotakeupalayerofwatermolecules:
andsothethickertheconsistencythey
produce.Suspensionsarealwaysopaque,
becausethesolidparticlesarelargeenoughto
blockthepassageoflightraysandeither
absorbthemorbouncethembacktowardtheir
source.Becausetheparticlesandwaterare
verydifferentmaterials,suspensionstendto
settleandseparateintothinfluidand
concentratedparticles.Cooksworktoprevent
separationbyreducingthevolumeofthe
continuousphase(drainingofforboiling
awayexcesswater),orbyaugmentingthe
dispersedphase(addingstarchorotherlong
moleculesorfatdroplets).
Nutbuttersandchocolatearesuspensions
ofsolidseedparticlesnotinwater,butinoils
andfats.
Thickening a liquid with food particles. In a
suspension, microscopic chunks of plant or
animal tissue are suspended in liquid, and
givetheimpressionofthicknessbyinterfering
withtheliquid’sflow.
ClearDispersionsandGels:Thickening
withMoleculesAsinglemicroscopic
fragmentofatomatocellwallormusclefiber
isbuiltupofmanythousandsof
submicroscopicmolecules.Notallofthe
largemoleculesinthosefragmentscanbe
teasedawayfromeachothersothattheyare
individuallydispersedinwater.Butthosethat
canbeextractedinthisway—starch,pectins,
suchproteinsasgelatin—areveryuseful
thickeningagents.Becausesinglemolecules
