Chemistry Reference
In-Depth Information
8.13 GeLatION
Sugarisessentialinthegellingprocessofjams,preserves,andjelliestoobtainthedesiredcon-
sistencyandirmness.Thisgel-formingprocessiscalledgelation,andthefruitjuicesareenmeshed
inanetworkofibers.Pectin,anaturalcomponentoffruits,hastheabilitytoformthisgelonly
inthepresenceofsugarandacid.Sugarisessentialbecauseitattractsandholdswaterduringthe
gellingprocess.Inaddition,acidmustbepresentintheproperproportions.Theoptimumacidity
isapHbetween3.0and3.5.Somerecipesincludelemonjuiceorcitricacidtoachievethisproper
acidity(Meschter1990).
Theamountofgel-formingpectininafruitvarieswithripeness(lessripefruithasmorepectin)
andthevariety(apples,cranberries,andgrapesareconsiderablyricherinpectinthancherriesand
strawberries). In the case of a fruit too low in pectin, some commercial pectin may be added to
producegelling,especiallyinjellies.Inrecipesthatusecommercialpectin,theproportionofsugar
maybeslightlyhigherorlowerthantheonepartfruittoonepartsugarratio(Beranbaum1985).
8.14 preSerVING
Preservesaremadewithcrushedorwholefruit.
Sugarpreventsspoilageofjams,jellies,andpreservesafterthejarisopened.Properlyprepared
andpackagedpreservesandjelliesarefreefrombacteriaandyeastcellsuntilthelidisopenedand
exposed to air. Once the jar is opened, sugar incapacitates any microorganisms by its ability to
attractwater.Thisisaccomplishedthroughosmosis(theprocesswherebywaterwilllowfroma
weakersolutiontoamoreconcentratedsolutionwhentheyareseparatedbyasemipermeablemem-
brane).Inthecaseofjelliesandpreserves,thewaterisdrawnfromthesemicroorganismstoward
theconcentratedsugarsyrup.Themicroorganismsbecomedehydratedandareunabletomultiply
and cause food spoilage. In jellies, jams, and preserves, a concentrated sugar solution of at least
65%isnecessarytoperformthisfunction.Becausethesugarcontentnaturallypresentinfruitsand
theirjuicesislessthan65%,itisessentialtoaddsugartoraiseittothisconcentrationinjelliesand
preserves(Meschter1990;Beranbaum1985).
8.15 COLOr reteNtION
Sugar helps retain the color of the fruit through its capacity to attract and hold water. Sugar
absorbs water more readily than other components, such as fruit, in preserves and jellies. Thus,
sugarpreventsthefruitfromabsorbingwater,whichwouldcauseitscolortofadethroughdilution
(Gates1981).
8.16 hIGh-FrUCtOSe COrN SYrUp
HFCSisusedinmanycommercialjelliesandiscomparableinsweetnesstosugar.Themajor
disadvantageofHFCSisthatitisaliquidandmaycontainasmuchas29%water.Theextrawater
maybeevaporatedintheinalstageofproduction,aprocessthatcausespartofthevolatilefruit
lavorstobelost.
Concentratedfruitjuicescouldalsobeusedasasweeteningingredientbecausetheyaresimilar
incompositiontosugarsyrups(Meschter1990).
Theadditionofcornsyruptosugarconfectionsbothinhibitssucrosenucleationandincreases
theinductiontimebeforetheonsetofnucleiformation.
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