Electronic nose discrimination, analytical identification, and sensory confirmation of flavor impact components in citrus juices

103 Pages·1998·3.7 MB·English

by  Bazemore, Russell A.

ELECTRONICNOSEDISCRIMINATION,ANALYTICALIDENTIFICATION,AND
SENSORYCONFIRMATIONOFFLAVORIMPACTCOMPONENTSINCITRUS
JUICES
By
RUSSELLALBERTBAZEMORE
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTL\LFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
^ 1998
ACKNOWLEDGMENTS
Iwouldliketoacknowledgemyparents,WilburandEdwinaBazemore,fortheir
continuedsupportandencouragementandDr.RussellRouseffforhisguidanceand
patience.Additionally,Iwouldliketoexpressmyappreciationto:Dr.UlrichHartmond
andDr.PrashanthiJellafortheirtimeandeffortasOsmepanelists;Dr.DanKingand
MarkWalshatSunPureCorporationforsupplyingorangejuiceandchemicalstandards;
Dr.MinaMcDanielatOregonStateUniversityforsharingtheOsmesoftware,Dr.Phil
ShawatUSDACitrusandSubtropicallabforservingasapanelistandadvisor,Alpha
M.O.S.,Neotronics;andAromaScanforsupplyingelectronicnoses;JoePiperof
Neotronicsfortechnicalexpertise;andtotheHuntBrothersforanacademicfellowship
andtheHerlongsforacademicsupport.
ii
TABLEOFCONTENTS
HUB
ACKNOWLEDGMENTS
//
USTOFTABLES vi
USTOFFIGURES v/7
CHAPTERS
1 Introduction 1
ElectronicNose 1
GasChromatography-Olfactometry 2
SensoryStudies 3
VolatileExtraction 4
Linalool 4
Summary 4
Chapter2 5
DiscriminationofGrapefruitJuiceVarietalDifferencesbyanElectronicNoseEquipped
withMetalOxideSensors 5
Introduction 5
MaterialsandMethods 8
SamplePreparation 8
SensoryAnalysis 8
ElectronicNoseAnalysis 9
StatisticalAnalysis 9
ResultsandDiscussion 9
SensoryScreening 10
FruitPigmentationandSensorResponse 13
StudyImplications 15
CorrelationwithOtherStudies 15
FutureStudies 16
^
CHAPTER3
DiscriminationofThermallyTreatedOrangeJuicesbyanElectronicNoseEquipped
withOrganicPolymerSensors j7
m
Introduction 1^
IdentificationofOrangeJuiceComponents 18
AromaActivitiesofOrangeJuiceComponents . 18
MaterialsandMethods . 19
HeatTreatment 1^
ElectronicNoseAnalysis 20
StatisticalAnalysis 21
ResultsandDiscussion 22
LLCaaorttreeeSSlaeetaaissooonnnWvis.thEaOrtlhye-rMiStdudies .^, 222244
Implications 27
FutureWork 28
CHAPTER4 29
ComparisonofUnpasteurizedOrangeJuiceAnalysisBy"ElectronicNose,"Sensory
TastePanelandHeadspaceGC 29
Introduction 29
MaterialsandMethods 30
"ElectronicNose"Analysis. 31
SPMEExtractionandGCFIDAnalysis. 32
SensoryAnalysis. 33
ResultsandDiscussion 33
MultisensorVolatileAnalysis. 33
GCFIDHeadspaceAnalysis 34
MSeentshoordyCAonamlpyasriisson . 3357
TemperatureandHumidityControl 37
Conclusion: 38
CHAPTER5 S9
AnalysisofEarly-MidSeasonOrangeJuiceVolatilesusingSolidPhaseMicroextraction
andGasChromatography-Olfactometry 39
Introduction 39
SuccessiveDilutionGasChromatography-Olfactometry(GCO) , 41
TimeintensityGC-0 41
MaterialsandMethods 42
HeatTreatment 42
MicrobiologicalCount 42
SPMEExtractionandGCFID/MSanalysis. 43
Liquid-LiquidExtraction 43
OsmeAnalysis 44
GC-Olfactometer 45
ResultsandDiscussion 46
OsmeAnalysis 46
MicrobiologicalCounts 47
IV
1
ComparisonofExtractionMethods 48
Conclusion 50
CHAPTER6 58
IdentificationandConfirmationofImportantAromaActiveVolatilesinUnpasteurized
andHeatAbusedValenciaOrangeJuices 58
Introduction 58
FlavorImpactComponents 58
HeatAbusedJuiceFlavor 59
GCOStudies 60
DescriptiveAnalysis 60
MaterialsandMethods 61
JuiceProcurement 61
HeatTreatment 62
VolatileExtraction/OilAnalysis 62
GCOanalysisA'olatileIdentification 62
SensoryAnalysis 63
InitialTesting 63
Recombination 64
ResultsandDiscussion 64
Brix/AcidandOilLevel 64
GCO 65
ComparisonofGCOResultsWithOtherStudies 66
Sensory 67
Recombination 67
Conclusion 73
\
CHAPTER7 75
SourcesandStabilityofLinaloolinValenciaOrangeJuice 75
Introduction 75
MaterialsandMethods 76
VolatileExtractionandGCAnalysis/OilAnalysis 77
Sensory 77
ResultsandDiscussion 78
OilLevels 78
LinaloolLevels 78
HeatTreatmentEffect 79
ComparisonwithPreviousStudies 80
Sensory 80
Conclusion 8
SUMMARY 82
CHAPTER8 82
LISTOFREFERENCES 84
BIOGRAPHICALSKETCH 92
LISTOFTABLES
Table page
Table3-1 Early-Midjuices:StandardizedcoefficientsforCanonicalVariableswith
EigenvaluesandCumulativeProportionofVarianceExplainedbyFunctions 21
Table3-2LateSeasonJuices:StandardizedCoefficientsforCanonicalVariableswith
EigenvaluesandCumulativeProportionofVarianceExplainedbyFunctions 26
Table3-3MahalanobisDistancesofVOandVI80fromGroupCentroid 26
Table5-1 ResultsfromGCOanalysisofearly-midunpasteurizedandexcessively
pasteurizedjuices 50
Table5-2 TenmostaromaactivecomponentsinEarly-Midorangejuiceheadspace 54
Table6-1Unpasteurizedandheatabusedmodelsolutioncomponents 65
Table6-2MostaromaactivecomponentsinunpasteurizedValenciajuice 69
Table6-3MostaromaactivecomponentsinheatabusedValenciajuice 70
Table6-4MeanscoresfromDescriptiveAnalysisofthreeValenciajuices 72
Table6-5Recombination-meanscores 74
Table7-1 ResultsfromDAofpeeledunpasteurizedjuice,unpeeled,unpasteurizedjuice,
andFMCextractedjuice. 81
vi
LISTOFFIGURES
Figure page
Figure2-1 Discriminantanalysisofmetaloxidesensorresponseto24varietiesof
grapefruitjuicewithvarietiesFloridaRedandNatsudaidaiindicated Eachsample
replicated6times. 11
Figure2-2Discriminantanalysisofgrapefruitjuicesensorresponsegroupedashedonic
categorieswith (0)indicatingscores1-4,(Qindicatingscores5-7,and(^)
indicatingscores8and9. 12
Figure2-3 Discriminantanalysisofsensorresponseto3ofthemostfavoredandthe3
leastfavoredgrapefruitjuicesgroupedasindividualcultivar. 14
Figure3-1Discriminantanalysisofearly-midunpasteurized pasteurizedfor8
seconds ( ),pasteurizedfor120seconds(^)andpasteurizedinexcessof180
seconds (^) 23
Figure3-2Discriminantanalysisoflateseasonunpasteurized(%),pasteurizedfor8
seconds ( ),120seconds(0),excessof180seconds(^) 25
Figure4-1 Cannonicaldiscriminantanalysisofelectronicnosesensordatafromjuices
agedfor0,3,6,9,and12daysatat2°C. 34
Figure4-2 CannonicaldiscriminantanalysisofheadspaceGCpeakareasfromjuices
storedfor0,3,6,9,and12daysat2°C. 35
Figure4-3Analysisofvarianceonsensorypanelresultsindicatedthereweresignificant
differences(p<.05)betweenthejuicefrozenatday0(a)andallothers(b,c),and
betweenthejuicefrozenatdays12(c)andallothers(a,b). 36
Figure6-1 GCFIDchromatogram(top)andGCOOsmegram(bottom)from
unpasteurizedValenciaorangejuice. 71
Figure7.1 Concentrations(mg/L)oflinaloolin6typesofValenciaorangejuice:
peeled-unpasteurized,peeled-pasteurized,peelintact-unpasteurized,peelintact
-pasteurized,FMC-unpasteurized,andFMC-pasteurized 79
vii
AbstractofThesisPresentedtotheGraduateSchool
oftheUniversityofFloridainPartialFulfillmentofthe
RequirementsfortheDegreeofMasterofArts
ELECTRONICNOSEDISCRIMINATION,ANALYTICALIDENTIFICATION,AND
SENSORYCONFIRMATIONOFFLAVORIMPACTCOMPONENTSINCITRUS
JUICES
By
RussellA.Bazemore
December,1998
Chairman:RussellL.RousefF
MajorDepartment:FoodScienceandHumanNutrition
Orangeandgrapefruitjuiceswereevaluatedforflavorcharacteristicsusing
sensorytechniquesandcomparedwithresultsfromthreedifferentelectronicnoses.
Volatilecomponentswereextractedfi'omjuicesusingbothsolidphasemicroextraction
(SPME)andliquid-liquidextraction. Volatileswerecharacterizedbygas
chromatography-olfactometry(GCO)andidentifiedbyGCandmassspectrometry(MS).
A12metaloxidesensorENoseutilizingmultivariatestatisticalanalysis(MVSA)
coulddistinguishbetween26differentgrapefruitjuicecultivars. A12organicpolymer
sensorENoseexhibitedsomesuccessindiscriminatingbetweenorangejuices(OJ)
exposedtodifferentheattreatments(unpasteurized,heatedto96°Cfor:8seconds,120
seconds,andinexcessof180seconds)butwaslesssuccessfulindiscriminatingbetween
OJfromdifferentcultivars. A32organicpolymersensorarrayENoseutilizingMVSA
coulddifferentiatebetweenunpasteurizedOJ(UPOJ)storedfor0,3,6,9,and12daysat
2°C. ResultsfromCanonicaldiscriminantanalysisofENosedataweresimilartothat
viii
fromsensorypanel,andfromheadspaceGCdatafromtheidenticalUPOJstoredfor
differenttimes.
HeadspacearomacomponentsfromUPOJandheatabusedearly-midseasonOJ
wereextractedusingSPMEandanalyzedusingGCO. Eighteenaromapeakswere
commontobothheattreatedandUPOJ. Sixaromaactivepeakswereobservedinonly
UPOJheadspace. Fivedifferentaromacomponentswereobservedinheatabusedjuice.
GCOanalysisofliquid-liquidextractsfromunpasteurizedandseverelyheatedValencia
juicefound23aromapeakscommontobothsamples,butfound17peaksonlyinUPOJ,
and2peaksonlyintheheatabusedsample.
Recombinationof8intensearomacontributorsofUPOJ,plus4additional
componentsreportedinOJ,addedtomodeljuicesolutionsdidnotdiffersignificantly
(p<.05)inorangearomaandflavorfromanUPOJpreviouslyfrozen.
Theprimarysourceoflinalool,amajorflavorimpactcompound,inValencia
orangejuicewasfromthepeeloilwhichistypicallyintroducedduringjuiceextraction.
Highestconcentrationsoflinaloolwerefoundinjuiceswhichexperiencedthemostpeel
macerationduringextraction.
ix
CHAPTER
1
INTRODUCTION
In1998,citruswasworthanestimated$1,015,703,000inthestateofFlorida.
Orangeswerethemostimportantcitrusfruitwithanestimatedvalueof$876,042,000or
86%ofthetotalFloridacitrusmarket(Greuderetal.,1998). Itisironic,givenorange
juices'enormouseconomicvalue,thesmallnumberofpublishedstudiesconductedthat
haveaddressedorangejuicearomavolatiles,theirimportanceinjuicequality,andthen
followedupwithsensorystudiesthatsoughttoconfirmanalyticalfindings. Thisresearch
wasconductedtodeterminetheeffectivenessof"electronicnose"instrumentationin
differentiatingcitrusjuicesbasedonheadspacecomponents,toidentifyaromaactive
volatilesresponsibleforfreshandheatabusedorangejuiceflavors,andtodeterminethe
sourceoflinaloolinValenciaorangejuiceandtheeffectofheattreatmentonlinalool
concentration.
ElectronicNose
, ,, .
Sensoryanalysishasbeenthehistoricalmethodofchoiceformeasuringflavor
differencesbetweenfoodsamplesproducedbydifferentprocessingconditions. Ata
minimum,sensoryanalysisrequiresseveralpanelistsforstatisticallysignificantresults,and
additionaltimetosetup,conduct,andstatisticallyevaluatedata. Ifdescriptiveanalysis