Chemistry Reference
In-Depth Information
7.1.2 raisin receive
TheAutonomousOrganizationforRaisinsinGreeceisresponsiblefortheprotection,cultiva-
tion, and growth of Corinthian raisins. From these black raisins, they withhold 15% of the total
raisinproductionanduseitforwinemaking,staidinproduction,andthreptin.
Raisinsarecollectedfromthebrokenplantstoensuretheiruseasstaidinandnotforotheruse.
InGreece,staidinismanufacturedmainlyfromCorinthianraisins,whichhavethelowestcost
and lowest transport and processing costs. However, in places such as Crete, where sultanas are
producedinlargequantities,itispossibletomanufacturestaidinfromsultanas.
Raisinjuiceconcentrateisanaturalsweetenerinsyruporpasteform,anditisproducedfrom
second-gradedryraisinsbyleachingthemwithwater.Driedraisinjuice,althougheasiertohan-
dleandhasmorepotentialapplicationsthanthesyrup,isnotavailableinthemarket.Papadakis,
Gardeli,andTzia(2006)producedraisinjuicepowderwithalab-scalespraydryer.Theproblemof
stickinessinthedryingchamberwasovercomethroughtheuseofmaltodextrinsof21,12,and6
dextroseequivalent(DE)asdryingaids.Foreachtypeofmaltodextrin,thedryeroperatingcondi-
tionsandtheminimumconcentrationofmaltodextrininthefeed,necessaryforsuccessfulpow-
derproduction,weredetermined.Themaximumratioofraisinjuicesolidstomaltodextrinsolids
achievedwas67:33andwasmadepossiblewiththeuseof6-DEmaltodextrin.Theinletandoutlet
dryingairtemperatureswere110°C,and77°C,respectively,andthefeedcontained40%w/wtotal
solids.Thephysicalandsensorypropertiesofallpowdersproducedweredeterminedandfoundto
besatisfactory;theonlyexceptionwastheirhighhygroscopicity.
7.1.3 raisin extraction
Raisinsareplacedinstainless-steelextractiontanksthatareverywellinsulatedandhaveapseu-
dobedfunctioningasailter.Thedistanceofthelongitudinalplatesthatcomprisethepseudobedis
modiiedaccordingtotheraisinsize.Theextractionprocesshasthefollowingfoursteps(Payne1994):
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Firststage
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Waterandraisinsarepouredintoeachtank.
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Coldwater,20°C-25°C,isused.
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Raisinsstayinthewaterfor12h.
Thesugarsolutioniscollectedfromeachtank.
Theirstsugarextractshouldhaveaconcentrationof20-25°Be.
•
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Secondstage
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Coldwaterispouredonlyintotheirsttank.
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Thesugarextractcollectedispouredintothesecondtank.
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Extractioncontinues,thesugarextractcollectedgoestothethirdtank,andsoon.
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Thesugarextractfromthesecondextractionshouldappearwithaconcentrationof10-15°Be.
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Thirdstage
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Coldwaterispouredonlyintotheirsttank.
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Reextractionofthesugarextractinthenexttankstakesplace.
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Extractionscontinueuntilthesugarextractinthelasttankhasaconcentrationof6-7°Be.
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Fourthstage
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Whentheconcentrationreaches6-7°Be,coldwaterispouredintotheirstextractiontank.
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Extraction starts, and steam insertion is carried out in the extract appearing in the region
betweenthepseudobottom(ilter)andthebottomofthetanktoachievethebesticingofraisins.
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Reextractionwithsteaminsertionfollowsatalowertemperatureinthesucceedingtanks.The
inalextracthasatemperatureof50°C-60°Cand10°Be-20°Be.
Thisextractionunderheatcontinuesuntiltheconcentrationoftheinalextractreaches3°Be-5°Be.
TheraisinextractionprocessisshowninFigures7.1and7.2.
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