On food and cooking the science and lore of the kitchen ( PDFDrive ) 1125
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aresomuchsmallerandlighterthanintact
starchgranulesandcellfragments,theydon’t
settleoutandseparate.Andtheyaretoosmall
andtoowidelyseparatedtoblockthepassage
oflightrays:sounlikesuspensions,molecular
dispersionsareusuallytranslucentandglassylooking.Ingeneral,thelongerthemolecule,
thebetteritisatobstructingwatermovement,
becauselongmoleculesmorereadilyget
tangledupineachother.Soasmallquantity
oflongamylosestarchmoleculeswilldothe
samethickeningjobasalargequantityof
shortamylopectin(p.611),andlonggelatin
moleculesthickenmoreefficientlythanshort
ones.Thickeningwithmoleculesoften
requiresheat,eithertoliberatethemolecules
fromthelargerstructures—starchmolecules
fromtheirgranules,gelatinmoleculesfrom
meatconnectivetissue—ortoshakeout
compactlyfoldedmolecules—eggproteins
—intotheirlong,extended,tanglyform.
Solid Dispersions: Jellies When the water
phase of a food fluid has enough thickening
moleculesdissolvedinit,andthefluidisleft
undisturbed and allowed to cool, those
moleculescanbondtoeachotherandforma
loose but continuous tangle or network that
permeates the fluid, with the water
immobilized in pockets between the network
molecules. Such a network thickens the fluid
tothepointthatitbecomesaverymoistsolid,
or agel. It’s possible to make a solid — if
wobbly—jellythatis99%waterandjust1%
gelatin. If the gel is made from dissolved
molecules,thenitwillbetranslucent,likethe
dispersion from which it is formed. Familiar
examplesaresavoryjelliesmadefromgelatin
andsweetjelliesmadefromfruitpectin.Ifthe
solutionalsocontainsparticles—theremains
of starch granules, for example — then the
jellywillbeopaque.
