On food and cooking the science and lore of the kitchen ( PDFDrive ) 1180
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removewaterandconcentrateit,thehigh
temperaturesbreakthealreadyenzymedamagedmoleculesintosmallerpiecesthat
arelessefficientthickeners,andthepaste
requiresthatmuchgreaterreductiontoobtain
thedesiredthickness.Ifinsteadtherawpuree
iscookedquicklyclosetotheboil,theresult
isathickersaucethatrequireslesssubsequent
reduction.Thepectinandcelluloseenzymes
aredenaturedandbecomeinactive,whileat
thesametimethecellwallsaredisruptedby
theheat.Thecell-wallpectinsthatescapeinto
thefluidphaseduringtheconcentration
heatingarelongermoleculesandmore
efficientthickeners.
TheThickeningComponentsof
Tomatoes
TotalSolids, PectinandHemicellulose
%byweight
Content,%byweight
Rawtomatoes 5–10 0.5–1.0
Cannedtomatopuree 8–24 0.8–2.4
Cannedtomatopaste 40 4
TomatoEnzymesandFlavorInadditionto
tomatoenzymesthataffecttexture,thereare
enzymesthataffectflavor:andinthecaseof
flavor,someinitialenzymeactivitycanbe
desirable.Thefresh,“green”-smelling
molecules(hexanalandhexanol,p.274)that
areanimportantelementinripetomatoflavor
aregeneratedbytheactionofenzymeson
fattyacidswhenthefruittissueiscrushed,
eitherinthemouthorinthepot.Rapid
cookingtotheboilminimizesthisfreshflavor
element,whileallowingtherawpureetositat
roomtemperature—inaMexicansalsa,for
example—oronlyslowlyheatingit,will
causetheaccumulationoftheseflavor
moleculesinthepuree.Amethodthathome
cookssometimesuseistohalveorquarter
tomatoes,thenbaketheminaslowovento
removewater,andfinallycookthem
relativelyquicklyintoasauce.Thistechnique
