On food and cooking the science and lore of the kitchen ( PDFDrive ) 1123
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dividetheliquidintomanysmall,local
masses:andbydividing,theyorganizeand
collectitandgiveitakindofcoherencethat
itlackedbeforehand.Somethickeningagents
alsoliterallybindwatermoleculesto
themselvesandsotakethemoutofcirculation
altogether,andthistoohastheeffectof
reducingthefluidityofthecontinuousphase.
Inadditiontogivingwateryfluidsa
thickerconsistency,thesubstancesinthe
dispersedphasecangivethemtexturesof
variouskinds.Solidparticlesmaymakethem
grainyorsmooth,dependingontheparticle
size;oildropletsmakethemseemcreamy;
dispersedmoleculeswithatendencytoadhere
toeachothermaymakethemseemstickyor
slimy;airbubblesmakethemseemlightand
evanescent.
Therearefourcommonwaysofthickening
wateryfoodjuices.Eachproducesadifferent
kindofphysicalsystem,andlendsdifferent
qualitiestothefinishedsauce.
Cloudy Suspensions: Thickening with
Particles Most of our raw ingredients —
vegetables,fruits,herbs,meats—areplantor
animal tissues built from microscopic cells
thatarefilledwithwateryfluids.Thecellsare
contained within walls, membranes, or thin
sheets of connective tissue. (Dry seeds and
spicescontainnojuices,butarestillmadeup
of solid cells and cell walls.) When any of
these foods is broken apart into small pieces
bybeinggroundinamortarorpulverizedina
blender, they are turned inside out, so the
fluids form a continuous phase that contains
fragments of the solid cell walls and
connective tissue. These fragments obstruct
and bind the water molecules, and thus
thickentheconsistencyofthemixture.Sucha
mixtureofafluidandsolidparticlesiscalled
a suspension: the particles are suspended in
thefluid.Saucesmadefrompureedfoodsare
suspensions.
Thetextureofasuspensiondependsonthe
