Mass Transfer Kinetics during Osmotic Dehydration of Pineapple Samples Coated with Pectin
levelsȱofȱdippingȱandȱdryingȱtimeȱisȱshownȱinȱFigureȱ bothȱtheȱdryingȱtimeȱatȱbothȱtheȱdippingȱtimeȱ60ȱandȱ
2.ȱ Theȱ lowestȱ valueȱ (7.76ȱ g/100ȱ gȱ freshȱ sample)ȱ ofȱ 120ȱs,ȱSGȱvalueȱdecreasedȱwithȱincreaseȱinȱtheȱovenȱ
SGȱ wasȱ observedȱ duringȱ massȱ transferȱ inȱ ODȱ ofȱ dryingȱtimeȱfromȱ10ȱtoȱ40ȱmin.ȱComparingȱtheȱmeanȱ
pineappleȱsamplesȱdippedȱinȱcoatingȱsolutionȱofȱ1%ȱ valuesȱ ofȱ twoȱ dippingȱ time,ȱ SGȱ valueȱ decreasedȱ
concentrationȱforȱ120ȱsȱandȱlaterȱonȱovenȱdriedȱforȱ withȱincreaseȱinȱtheȱdippingȱtimeȱfromȱ60ȱtoȱ120ȱs.ȱ
40ȱ min,ȱ whereȱ asȱ theȱ highestȱ valueȱ (12.07ȱ g/100ȱ gȱ Thisȱ mayȱ beȱ dueȱ toȱ theȱ factȱ thatȱ theȱ developmentȱ
freshȱsample)ȱofȱSGȱwasȱobservedȱinȱsampleȱdippedȱ ofȱcoatingȱwasȱmoreȱappropriateȱwhenȱtheȱsampleȱ
forȱ60ȱsȱinȱ5%ȱsolutionȱfollowedȱbyȱovenȱdryingȱforȱ wasȱdippedȱforȱmoreȱtimeȱandȱformationȱofȱproperȱ
10ȱmin,ȱindicatingȱaȱdifferenceȱofȱ4.31ȱ(g/100ȱgȱfreshȱ coatingȱpreventedȱtheȱgainȱofȱsoluteȱmoleculesȱintoȱ
sample)ȱinȱtheȱratesȱofȱSGȱbetweenȱitsȱhighestȱandȱ theȱ fruitȱ tissue.ȱ Therefore,ȱ coatingȱ developedȱ byȱ
lowestȱvalue.
dippingȱ theȱ samplesȱ intoȱ solutionsȱ forȱ moreȱ timeȱ
impededȱtheȱuptakeȱofȱsoluteȱmoleculesȱintoȱtheȱfruitȱ
Increasingȱtheȱconcentrationȱofȱtheȱcoatingȱsolutionȱ
sample.ȱ Thisȱ isȱ inȱ agreementȱ withȱ theȱ findingsȱ ofȱ
fromȱ0.5ȱtoȱ1%ȱledȱtoȱdecreaseȱinȱtheȱSGȱandȱthenȱ
LenartȱandȱDabrowskaȱ(1999)ȱinȱapplesȱusingȱpectin.ȱ
increasedȱupȱtoȱ5%ȱconcentration.ȱThisȱwasȱobservedȱ
SGȱ valueȱ alsoȱ decreasedȱ whenȱ theȱ meanȱ valuesȱ ofȱ
inȱ allȱ theȱ combinationsȱ ofȱ concentration,ȱ dippingȱ
dryingȱtimeȱwereȱincreasedȱfromȱ10ȱtoȱ40ȱmin.ȱThisȱ
andȱdryingȱtime.ȱThisȱmayȱbeȱdueȱtoȱtheȱreasonȱthatȱ
mayȱbeȱdueȱtoȱtheȱreasonȱthatȱovenȱdryingȱforȱlongȱ
selectingȱ theȱ concentrationȱ ofȱ theȱ coatingȱ solutionȱ
timeȱledȱtoȱstrongȱattachmentȱorȱfixationȱofȱcoatingȱ
atȱ 0.5%ȱ andȱ 1%ȱ levelȱ resultedȱ inȱ theȱ formationȱ ofȱ
toȱ theȱ pineappleȱ samples,ȱ whichȱ furtherȱ reducedȱ
coatingȱthatȱwasȱstrongȱenoughȱtoȱpreventȱtheȱentryȱ
theȱinfluxȱofȱsoluteȱmoleculesȱintoȱtheȱfruitȱsampleȱ
ofȱ soluteȱ moleculesȱ i.e.ȱ sucroseȱ duringȱ theȱ processȱ
duringȱ theȱ ODȱ process.ȱ Anotherȱ explanationȱ forȱ
ofȱ ODȱ ofȱ pineappleȱ samples.ȱ Atȱ theȱ concentrationȱ
thisȱphenomenonȱcouldȱbeȱthatȱoven-dryingȱstepȱinȱ
greaterȱthanȱ1%,ȱSGȱvalueȱincreasedȱandȱwasȱmoreȱ
theȱcoatingȱprocessȱcausedȱshrinkageȱofȱcellsȱwhichȱ
thanȱ theȱ valueȱ ofȱ SGȱ ofȱ coatedȱ sampleȱ ofȱ 0.5%ȱ
furtherȱcausedȱtheȱreductionȱofȱintercellularȱspacesȱ
concentration.ȱ Thisȱ wasȱ observedȱ inȱ allȱ theȱ valuesȱ
leadingȱtoȱdecreaseȱinȱtheȱuptakeȱofȱsucroseȱintoȱtheȱ
ofȱSGȱatȱallȱtheȱlevelsȱofȱconcentrationȱandȱatȱbothȱ
sample.ȱThisȱisȱconsistentȱwithȱtheȱfindingsȱofȱKhinȱ
theȱlevelsȱofȱdippingȱandȱdryingȱtimeȱunderȱstudy.ȱ
et al. ȱ(2007).ȱTherefore,ȱincreaseȱinȱbothȱdippingȱandȱ
ThereȱwasȱconsiderableȱcheckȱinȱSGȱbyȱusingȱcoatingȱ
dryingȱtimeȱcausedȱdecreaseȱinȱSG.
solutionȱ ofȱ bothȱ 0.5%ȱ andȱ 1%ȱ concentration.ȱ Theȱ
valuesȱofȱSGȱobtainedȱbyȱusingȱallȱtheȱcombinationsȱ Overall,ȱcoatingȱresultedȱinȱsubstantiallyȱdecreasedȱ
ofȱ concentrations,ȱ dippingȱ timeȱ andȱ dryingȱ timeȱ solidȱuptake,ȱthusȱleadingȱtoȱimprovedȱODȱprocess.ȱ
wereȱ lessȱ thanȱ theȱ SGȱ valueȱ ofȱ uncoatedȱ samplesȱ Thisȱ factȱ isȱ consistentȱ withȱ previousȱ findingsȱ inȱ
(12.45ȱ g/100ȱ gȱ freshȱ sample).ȱ Therefore,ȱ evenȱ byȱ potatoȱcubesȱ(Khinȱ et al. 2006a),ȱapplesȱ(Khinȱ et al
increasingȱ theȱ concentrationȱ ofȱ solutionȱ toȱ 5%,ȱ theȱ 2006b),ȱapplesȱ(LenartȱandȱDabrowskaȱ1999)ȱusingȱ
valuesȱ ofȱ SGȱ wereȱ lessȱ thanȱ theȱ uncoatedȱ sample.ȱ lowȱ methoxylȱ pectinate,ȱ inȱ strawberriesȱ (Matsukaȱ
SGȱwasȱincreasedȱasȱtheȱconcentrationȱwasȱincreasedȱ et al .ȱ2006)ȱusingȱsodiumȱalginate,ȱcarrageenanȱandȱ
fromȱ1ȱtoȱ2%ȱorȱaboveȱwhichȱmayȱbeȱdueȱtoȱpoorȱ guarȱgum,ȱandȱinȱpineapplesȱ(Singhȱ et al .ȱ2010)ȱusingȱ
developmentȱofȱcoatingȱonȱtheȱpineappleȱsamples.
sodiumȱalginateȱasȱcoatingȱagent.ȱStatisticalȱanalysisȱ
revealedȱ thatȱ theȱ valuesȱ ofȱ SGȱ atȱ allȱ theȱ levelsȱ ofȱ
Consideringȱ theȱ meanȱ valuesȱ ofȱ allȱ theȱ levelsȱ ofȱ
concentration,ȱ bothȱ theȱ dippingȱ andȱ dryingȱ timeȱ
concentration,ȱSGȱwasȱdecreasedȱasȱtheȱconcentrationȱ
differȱsignificantlyȱfromȱoneȱanother.ȱTheȱdifferenceȱ
increasedȱ fromȱ 0.5ȱ toȱ 1%ȱ andȱ thenȱ increasedȱ fromȱ
inȱtheȱvaluesȱofȱSGȱofȱtheȱcoatedȱandȱuncoatedȱsampleȱ
furtherȱincreaseȱinȱtheȱconcentrationȱupȱtoȱ5%.ȱItȱwasȱ
wasȱ statisticallyȱ significantȱ (p<0.05).ȱ Theȱ valuesȱ
foundȱthatȱmaximumȱdecreaseȱinȱSGȱwasȱobservedȱ
ofȱSGȱatȱbothȱtheȱdippingȱtimeȱ(60ȱandȱ120ȱs)ȱandȱ
inȱ pineappleȱ sampleȱ dippedȱ inȱ coatingȱ solutionȱ ofȱ
dryingȱtimeȱ(10ȱandȱ40ȱmin)ȱwereȱfoundȱstatisticallyȱ
1%ȱ concentration.ȱ Comparingȱ theȱ meanȱ valuesȱ ofȱ
differentȱfromȱeachȱother.
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