Mass Transfer Kinetics during Osmotic Dehydration of Pineapple Samples Coated with Pectin

wereȱsucroseȱconcentrationȱofȱtheȱosmoticȱsolution,ȱ

temperatureȱ duringȱ OD,ȱ timeȱ andȱ fruit-solutionȱ

SGȱ= f f

m s − m i s i

(g/100ȱgȱfreshȱsample)

ratio,ȱ whereȱ asȱ theȱ responseȱ variablesȱ keptȱ wereȱ

=

SG

× 100

m i

waterȱloss,ȱsolidȱgainȱandȱratioȱofȱwaterȱlossȱtoȱsolidȱ

WL

gainȱ(WL/SG)ȱwithȱdesiredȱconditionsȱofȱmaximumȱ

PRȱ=ȱ SG

waterȱloss,ȱminimumȱsolidȱgainȱandȱmaximumȱWL/

SGȱratioȱduringȱtheȱOD.ȱTheȱoptimizedȱconditionsȱ

WRȱ=ȱWLȱ–ȱSGȱ(g/100ȱgȱfreshȱsample)

obtainedȱ wereȱ 62°Brixȱ sucroseȱ concentration,ȱ whereȱ m ȱandȱ m ȱareȱtheȱinitialȱandȱfinalȱweightȱ(g)ȱ

i

f

temperatureȱofȱ30°Cȱforȱ6ȱhoursȱtimeȱusingȱ1:6ȱfruit-

ofȱtheȱsamples,ȱrespectively;ȱ z _i ȱandȱ z _f ȱareȱtheȱinitialȱ

solutionȱratioȱ(Singhȱ et al .ȱ2008).ȱAfterȱOD,ȱsamplesȱ andȱfinalȱmassȱfractionȱofȱwaterȱ(gȱwater/gȱsample),ȱ

wereȱtakenȱoutȱofȱtheȱosmoticȱmedium,ȱdrained,ȱthenȱ respectively;ȱ s andȱ s areȱtheȱinitialȱandȱfinalȱmassȱ

i

f

gentlyȱblottedȱwithȱfilterȱpaperȱtoȱremoveȱadheringȱ fractionȱ ofȱ totalȱ solidsȱ (gȱ totalȱ solids/gȱ sample),ȱ

solutionȱandȱweighed.ȱUncoatedȱsamplesȱwereȱalsoȱ respectively.

dehydratedȱosmoticallyȱbyȱusingȱsucroseȱsolutionȱforȱ

comparisonȱofȱtheȱmassȱtransferȱinȱcoatedȱsamplesȱtoȱ Statistical Analysis

thatȱinȱuncoatedȱsamples.

Allȱ theȱ experimentsȱ wereȱ carriedȱ outȱ inȱ triplicatesȱ

andȱ theȱ averageȱ valueȱ wasȱ takenȱ forȱ calculations.ȱ

Analysis of Moisture Content

Compositeȱ Rotatableȱ Designȱ (CRD)ȱ wasȱ usedȱ toȱ

Moistureȱ contentȱ ofȱ pineappleȱ samplesȱ wasȱ analyzeȱ theȱ resultsȱ toȱ determineȱ ifȱ theȱ differencesȱ

determinedȱ byȱ theȱ ovenȱ dryingȱ methodȱ (AOACȱ wereȱ significantȱ betweenȱ theȱ coatedȱ andȱ uncoatedȱ

1990).ȱSamplesȱwereȱweighedȱandȱplacedȱinȱanȱovenȱ samples.ȱ Factorialȱ Compositeȱ Rotatableȱ Designȱ

setȱatȱ70°C.ȱTheȱsamplesȱwereȱkeptȱinȱtheȱovenȱuntilȱ wasȱ employedȱ toȱ findȱ outȱ differencesȱ amongȱ theȱ

aȱ constantȱ weightȱ wasȱ reached.ȱ Theȱ samplesȱ wereȱ coatedȱsamplesȱatȱdifferentȱconcentrationsȱofȱcoatingȱ

cooledȱdownȱtoȱroomȱtemperatureȱinȱdesiccatorsȱandȱ solutions,ȱtwoȱdippingȱtimeȱ(60ȱandȱ120ȱs)ȱandȱtwoȱ

weighed.ȱTheȱmoistureȱcontentȱofȱtheȱsamplesȱwasȱ ovenȱdryingȱtimeȱ(10ȱandȱ40ȱmin).

thenȱcalculatedȱfromȱtheȱweightȱofȱtheȱsampleȱbeforeȱ

andȱafterȱdrying.ȱTheȱinitialȱmoistureȱcontentȱofȱfreshȱ Results and Discussion

pineappleȱsamplesȱvariedȱfromȱ90%ȱtoȱ93%ȱwetȱbasisȱ

(w.b.).

Water loss

Theȱ effectȱ ofȱ coatingȱ onȱ waterȱ lossȱ (WL)ȱ duringȱ

Mass Transfer Studies

ODȱ ofȱ coatedȱ andȱ uncoatedȱ pineappleȱ samplesȱ atȱ

Evaluationȱofȱmassȱexchangeȱbetweenȱtheȱsolutionȱ differentȱ concentrationsȱ ofȱ pectin,ȱ andȱ twoȱ levelsȱ

andȱ sampleȱ duringȱ ODȱ wereȱ madeȱ byȱ usingȱ theȱ ofȱdippingȱtimeȱandȱdryingȱtimeȱisȱshownȱinȱFigureȱ

parametersȱsuchȱasȱwaterȱlossȱ(WL),ȱsolidȱgainȱ(SG),ȱ 1.ȱTheȱhighestȱvalueȱ(48.86ȱg/100ȱgȱfreshȱsample)ȱofȱ

performanceȱratioȱ(PR)ȱandȱweightȱreductionȱ(WR).ȱ WLȱwasȱfoundȱduringȱmassȱtransferȱprocessȱinȱODȱ

Inȱorderȱtoȱcompareȱtheȱmassȱtransferȱbetweenȱtheȱ ofȱ pineappleȱ samplesȱ dippedȱ forȱ 120ȱ sȱ inȱ pectinȱ

coatedȱ andȱ uncoatedȱ samples,ȱ waterȱ lossȱ (WL),ȱ solutionȱ ofȱ 2%ȱ concentrationȱ andȱ laterȱ ovenȱ driedȱ

solidȱgainȱ(SG),ȱperformanceȱratioȱ(PR)ȱandȱweightȱ forȱ10ȱmin,ȱwhileȱtheȱminimumȱWLȱ(37.50ȱg/100ȱgȱ

reductionȱ (WR)ȱ wereȱ calculatedȱ accordingȱ toȱ theȱ freshȱsample)ȱwasȱobservedȱatȱ5%ȱconcentrationȱofȱ

followingȱequations:

pectinȱsolutionȱwhichȱwereȱdippedȱforȱ120ȱsȱfollowedȱ

byȱovenȱdryingȱforȱ40ȱminȱtoȱfixȱtheȱcoatingȱonȱtheȱ

m i z i − m f z f

sample.ȱAȱdifferenceȱofȱ11.36ȱ(g/100ȱgȱfreshȱsample)ȱ

=

WL

× 100 (g/100ȱgȱfreshȱsample)

wasȱ notedȱ inȱ theȱ ratesȱ ofȱ WLȱ betweenȱ theȱ highestȱ

m i

andȱlowestȱvalueȱofȱWL.

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