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Howdolevelsofanthocyaninsinblueberrieschangeduetotemperatureandlocationoforigin?
GwennythCarroll
CandidateNumber:1203-0016
CentreNumber:1203
ChemistryExtendedEssay
InternationalBaccalaureate
WordCount:3992
InternationalSchoolofToulouse
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Abstract
Thisessayinvestigates:Howdolevelsofanthocyaninsinblueberrieschangeduetotemperatureandlocationoforigin?Blueberriesareagoodsourceofdietaryantioxidants,free-radicalscavengingchemicals.TheBriggs-Rauscherreactionwasusedtoanalyselevelsofanthocyanins(amainantioxidantinblueberries)insolutionsofblueberryjuiceandwater.Alongertimeforoneoscillationsignifieshigherlevelsofantioxidants,asittakeslongerforionstobuilduptoasuitableconcentrationforthereactiontooscillate.Arangeoftemperatures,from25°Cto75°C,ofablueberrysolutionsample,fromMorocco,wastestedaswereblueberrysolutionswithoriginsinCanada(wild),WashingtonState(organic),andSpain.
Theresultsofthetestusingblueberriesfromdifferentlocationsatthesametemperaturedemonstratesasizeabledifferenceinthetimeforoneoscillationcorrelatingwithasignificantdifferenceinlevelsofanthocyanins.TheCanadianwildblueberrieshavethehighestconcentrationofanthocyaninswithatimeforoneoscillationof60.1sfollowedbyWashingtonStateorganicblueberries(45.8s),Moroccanblueberries(10.2s)andfinallythelowestconcentrationofanthocyaninsintheSpanishblueberrieswithanoscillationtimeof9.0s.Thedifferenceinlevelsofanthocyaninscanbecontributedtothevarietyofblueberryandthecultivationpracticesusedtogrowthem.
Thetemperaturetestwasinconclusive.Howeverthegeneraltrend,whencombinedwithacademicresearch,indicatesthatlevelsofanthocyaninsinblueberriesdecreasewithtemperature.At25°Cthetimeforoneoscillationwas10.2swhileat75°Cthetimewas9.4s.Thismaybeduetotheslightincreaseintemperatureofthereactionsolutionsincreasingtherateofreaction,therebydecreasingthetimeforoneoscillation.Anthocyaninsarereportedtobethermo-sensitive,howeverdegradationhasbeenobservedabove70°Csoisoutoftherangeofthisexperiment.
WordCount:300
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TableofContents
Listoffigures 4
Introduction 5-7
Method 8-10
Assumptions 8
Variables 8-9
Preparationandreactionsummary 9-10
Problemsencounteredinpreliminary 10
DataCollection 11-17
Massofblueberryinblueberrysolution 11
Rawdata 12
ProcessingData 13,17
ProcessedData 13-14
Graphs 14-16
InterpretationandJustificationofData 17-20
Typeofblueberryaccordingtolocation 17-18
Temperature 19-20
Conclusion 20
UnansweredandAdditionalquestions 21
Evaluation 21-23
Justifyingrange 21
Limitations 21
RandomError 22
SystematicError 22-23
ErrorinDesignandData 23
Reliabilityofdata 23
Bibliography 24-25
Appendix 26-31
Method 26-29
Disposal 30
Safety 30
Preliminary 31
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ListofFigures
Figure1–Skeletalstructureofanthocyanins
Figure2–Anthocyaninscommonlypresentinblueberries,theirstructures,sugarmoieties,andcolour
Figure3–SummaryoftheBriggs-Rauscherreaction
Figure4–DiscussingControlVariables
Figure5–Massofblueberryjuicein100mlofdistilledwaterinpreparationofblueberrysolution
Figure6–Calculatinguncertaintyofblueberryjuiceinsolution
Figure7–Testforanthocyaninlevelsindifferentblueberrysamples–Rawdata
Figure8–Testforanthocyaninlevelsatdifferenttemperatures–RawData
Figure9–Examplecalculationofprocessingoscillationtimeanduncertainty
Figure10–Testforanthocyaninlevelsindifferentblueberries–ProcessedData
Figure11–Testforanthocyaninlevelsatdifferenttemperatures–ProcessedData
Figure12–Howthetimeforoneoscillationchangeswiththetypeofblueberry
Figure13–Howthetemperatureoftheblueberrysolutionaffectsthetimeforoneoscillation
Figure14–Howthetemperatureoftheblueberrysolutionaffectsthetimeforoneoscillation
Figure15–Howthetemperatureoftheblueberrysolutionaffectsthetimeforoneoscillation
Figure16–Ratiotocomparetherelativetimeforoneoscillationinblueberriesfromdifferentlocations
Figure17–PoliticalMapofWorldshowingtwodifferentregionsoforiginofblueberrysamples
Figure18–Differentcoloursoftheblueberrysolutions
Figure19–Thermaldegradationoftwocommonanthocyanins
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Introduction
Antioxidants,suchasanthocyanins,havebeen,‘ahottopicinrecentyears’accordingtoDr.MarizaSnyderandDr.LaurenClum(2011)inthescientificcommunityandthegeneralpublicduetotheirpotentialhealthbenefits.Theymayprotectagainstsomecancers,maculardegeneration,Alzheimer’sandatherosclerosis,amongstothers(WebMD,2014).
WildblueberriesfreshlypickedinNorthernCanadacannotcompare,inmyopinion,withcultivatedblueberriesboughtinFrance.This,combinedwithanarticleIreadaboutthehealthbenefitsofblueberries,sparkedmyinterestinwhetherlevelsofantioxidantsinblueberrieschangedwiththelocationoforigin.Asanavidbaker,Ienjoyusingblueberriesasatoppingorbakedinmuffinsorcrumbles,leadingtomycuriosityoftheimpactoftemperatureonlevelsofantioxidants.Theseinterestsledmetotheresearchquestion:
Howdotemperatureandlocationoforiginimpactthelevelsofanthocyanininblueberries?
Freeradicals(atomsormoleculeswithunpairedelectronssotheyareextremelyreactive)causedamageinthebodybyinhibitingthefunctionofcells(HusneyandRomito,2013)andbydamagingkeymoleculessuchasfats,proteinsandDNA(Smythies,1998).Antioxidantsstabilisefreeradicals,therebyprotectingthebody(HusneyandRomito,2013),by‘scavenging’freeradicalsandremovingthemorbyreactingwiththem(Smythies,1998).
Antioxidantsareagroupofchemicalsthatinhibitoxidation.Flavonoidsandphenols,togethercalledphytochemicals,areaclassofantioxidantstowhichthemajorantioxidantsinblueberries,anthocyanins,belong(Smythies,1998).TheyhavethebasicskeletalstructureofC6C3C6.(RoutrayandOrsat,2011).
AnthocyaninsoccurnaturallyinplantsasaprotectivemechanismagainstenvironmentalstressessuchasUVlightanddrought,intheformofglycosidesandacyloglycosides(RoutrayandOrsat,2011),ananthocyanidinmoleculepairedwithasugar(Webb,2014).
Figure1:Skeletalstructureofanthocyanins(RoutrayandOrsat,2011)
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Variationsinthechemicalstructureofanthocyaninsaremainlyduetodifferencesinthenumberofhydroxylgroupsandthenatureandnumberofthesugarmoiety(Nijveldtandothers,2001).
ThemostpredominateanthocyanininblueberriesisMalvidin-3-galactosidewhilewildblueberriesarereportedlythebestsourceofpeturidin-andmalvidin-basedanthocyanins(RoutrayandOrsat,2011).
On-goingresearchisexpandingknowledgeofthebenefitsofantioxidantsinblueberries.OnearticleintroducestheresearchofDavidLipsettandDr.BrianStaveley,whoarelookingintotheeffectsofblueberryextractonParkinsonDisease.Theresults,‘suggeststhatadietsupplementedwithblueberryextractmayindeedhaveapositiveimpactonafruitflymodelofParkinsonDisease.’(Foss,2014)
Figure2:Anthocyaninscommonlypresentinblueberries,theirstructures,sugarmoieties,andcolour(RoutrayandOrsat,2011)
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TheBriggs-Rauscherreactioncanbeusedtocomparerelativeamountsofantioxidantsinasampleofblueberrysolution.Developedbytwohighschoolteachersin1973,itisanoscillatingreactionwherethreecolourlesssolutionsarecombinedtoformaresultingsolutionwherethecolouralternatesbetweencolourless,amberanddeepblue.
Thecolourchangeswiththeoscillatingnatureofthereaction.WhentheconcentrationofI2ishigh,thesolutionappearsamber.WhentheconcentrationofI-ishigh,thesolutioniscolourless.WhentheI-andI2ionsareinequalconcentration,theybondwiththestarchresultingintheblue-blackcolour(UCSB,dateunknown).
Thecomplexreactionhasmanysub-reactions,howeverthesimplifiedreactionmechanismis:
IO3-+2H2O2+CH2(CO2H)2+H+->ICH(CO2H)2+2O2+3H2O
Asimplifiedoverallschemeis:
Figure3:SummaryoftheBriggs-Rauscherreaction(USCB,dateunknown)
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Method
[SeeAppendixI,pg26,forfullmethodandpreliminary]
TheBriggs-Rauscherreactionisthemostsuitablemethodinahigh-schoollabbecause,althoughnoabsolutevaluecanbecalculated,theresultsallowforacomparison.Inaddition,theBriggs-Rauscherreactionisrelativelysimpletoexecute,eventhoughthechemistrybehindthereactioniscomplex.
ThemethodhasbeenadaptedfromMIT(2012)andFarusi(2009),changingtheproportionofreactantsandalteringtheapparatusaswellasclarifyingtheprocedure.ThemethodformakingblueberryjuiceandintegratingitintothereactionwasadaptedfromFarusi(2009).
Assumptions
- Acomparisonbetweenthesamplescanbemadebecausethepreparationoftheblueberrysolutionwasconsistentsoanylossesofantioxidantswouldbeequivalent.
- Thedensityoftheblueberryjuiceisthesameaswaterso1g=1ml.- Thereisnoheatlosswhentheblueberryjuiceisheated,orduringreaction.- Theheatedblueberryjuicedoesnottransferthermalenergytothereactionsolution.- HeathasnoimpactontheBriggs-Rauscherreaction(orontheoscillationtime).- Anthocyaninsaretheonlyantioxidants.[Blueberriescanalsocontainotherantioxidantssuchas
VitaminCorQuercetin(Nijveldtandothers,2001).]
Variables
Twoindependentvariablesweretested.Thefirstwastheblueberryspecies,accordingtowhereitwasgrown.Fourdifferentlocationswerechosen;Canada(wild),WashingtonState(organic),SpanishandMoroccan.Thesecondwasthetemperatureoftheblueberryjuice.Sixdifferenttemperaturewerechosen;25°C,35°C,40°C,50°C,65°Cand75°C.Whenoneoftheindependentvariableswastested,theotherwaskeptconstant.
ThedependentvariablewasthetimeforasingleoscillationoftheBriggs-Rauscherreaction,measuredusingastopwatch.
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Figure4:DiscussingControlVariablesVariable Effectonexperiment Howtocontrol
Temperature(whentestingdifferentblueberries)
LevelsofantioxidantsavailablemaybeimpactedbytemperatureasmaytherateofreactionoftheBriggs-Rauscherreaction,sotheoscillationtimewithchange.
Keepingallsolutionsatroomtemperature,controlledtemperaturewhentestingdifferentblueberrytypes.
Originofblueberry(whentemperatureistested).
Thetypeofblueberrywillimpacttheoscillationtimebecauseitmaycontaindifferentlevelsofantioxidants.
Usethesameblueberrysolution,ofasingleblueberrytype,forallthetemperaturetests.
VolumeofsolutionsA,BandCreacted
Thevolumeofeachsolutionwillimpacthowmanymolesofreactantsareavailable,thereforewillimpacttherateofreaction,andasaconsequence,oscillationtime.
Glassmeasuringcylinderswereusedtomeasure50mlofthesolutionsforeachtrial.
Concentrationofthesolutions
Itwillalsoimpactthenumberofmolesofreactantsandthereforetherateofreactionandtheoscillationtime.
ThiswascontrolledusingthesamesolutionA,BandC(fromapreparedreservoirsotheconcentrationofthesolutionswerethesame)foreachtrial.
Volumeofblueberrysolution
Affecttheamountofantioxidantsavailableandthereforetheoscillationtime.
Controlledusinga3mlglassmeasuringcylindertomeasure1mlofblueberrysolutionfromareservoir(sotheconcentrationofblueberrysolutionwasthesame)foreachtrial.
Methodoftimingoftheoscillations
Thisdirectlyimpactstheoscillationtime.Thetimesforconsecutiveoscillationswerenotthesamesothetimeforfouroscillationscouldbedifferent.
Fouroscillationsweretimedforeachtrial.Theblueberrysolutionwasaddedafterthesecondoscillationandthetimerstarted.
Preparationofreactionsolutions
- 1LofSolutionAinavolumetricflasko 400mlofdistilledwaterand410mlof30%H2O2.o Distilledwatertoppeduptothe1Lmark.
- 1LofSolutionBinavolumetricflasko 800mlofdistilledwaterand43gofpotassiumiodate,warmedgentlyo 4.3mlof18Msulphuricacido Distilledwatertothe1Lmark
- 1LofSolutionCinavolumetricflasko 500mlofdistilledwaterwith16gofmalonicacidand3.4gofmanganese(II)sulphate
monohydrate,stirredo 0.3gofstarchin5mlofdistilledwaterinabeakeraddedto50mlofboiling(distilled)
waterinaseparatebeakerthenaddedtothevolumetricflasko Distilledwatertothe1Lmark
- Allsolutionskeptinfumecupboard
Preparationofblueberrysolution
- Blueberrysamplemashedwithpestleandmortarthenstrainedo 100mlofdistilledwateraddedto2gofblueberryjuice
- Eachtypeofblueberrysolutionpreparedseparatelyafterwashinganddryingpestleandmortar.
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Briggs-RauscherReaction
- 50mlofSolutionA,BandCwerecombinedina400mlreactionbeaker.o Colourcycleoscillatedtwicethen1mlofblueberrysolutionwasaddedwhenthecolour
changedfromambertocolourlessandthestopwatchwasstarted.o Afterfourcycles,thestopwatchwasstoppedandthetimerecorded.
- Repeatedfortheremainingthreeblueberrysolutions- Moroccanblueberrysolutionsampleheatedtosixdifferenttemperaturesandprocess(above)
repeated.
Problemsencounteredinpreliminary
Inthepreliminary,thefirsttrialconsistingof10mleachofsolutionsA,BandCand3mlofblueberrysolutionwasunsuccessfulasnocolourchangewasobserved.Whensodiumthiosulfatewasaddedtoquenchthereaction,thereactionsolutionturnedreddish-brownwithatintoflilacandeventuallycolourless.Thissuggestsareactionoccurredbecauseiodineionsweredisplacedtothesulphuricacidandthedeepcoloursuggeststhestarchwaseffective.Afterthefirsttest,potentialproblemswereidentified:thestarch,asitdoesnotalwaysreactaspredicted,aswellasthemalonicacid,whichwasoldsomayhavedegraded,andthechosenvolumeofreactants.Subsequenttrialstestedanewstarchsolution,whichresultedinafaintchangefromambertocolourlessafteralongtime,suggestingtheiodineandiodideionswerepresent.Howeverwhentheblueberrysolutionwasadded,theoscillationappearedtostopsuggestingtheantioxidantsintheblueberrysolutionsloweddowntheoscillationtothepointwhereitwasunrealistictomeasureasthecolourchangewastoofainttodetect.FinallyItriedusinglargervolumesofsolutionsA,BandC(50ml)withasmallervolumeofblueberrysolution(1ml)andthereactionsolutionoscillatedfromambertocolourlesshowevernodeepbluecolourwasobserved.Duringtheactualexperiment,thedeepbluecolourwasnotobserved.
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DataCollection
Massofblueberryjuiceinblueberrysolution:
Whenpreparingtheblueberrysolutions,theoretically2gofblueberryjuicewasdilutedwith100mlofdistilledwater.Howevertheactualmassofblueberryjuiceinthesolutionvariedslightly.
WashingtonState(organic)
Canadian(wild) Spanish Moroccan
1.91g+/-0.01g 2.06g+/-0.01g 2.08g+/-0.01g 1.99g+/-0.01g
Figure6:Calculatinguncertaintyofblueberryjuiceinsolution
Figure5:Massofblueberryjuicein100mlofdistilledwaterinpreparationofblueberrysolution.Theuncertaintyof0.01gisduetothemeasuringuncertaintyoftheapparatus
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Testforanthocyaninlevelsindifferentblueberrysamples–Rawdata
Initialreactionused50mlofsolutionsA,BandCand1mlofblueberrysolutionina400mlbeaker.TheVerniermagneticstirrerwassettosettingnine.
TypeofBlueberry Timeforfouroscillations(s)
+/-0.5s
Observations
WashingtonState 183.0 Theblueberriesweresmallerwithdarkflesh.Theblueberrysolutionappearedaredtransparentcolourwithparticlessuspendedinthesolution.Aftertheblueberrysolutionwasadded,theinitialoscillationwassignificantlylongerthanthefollowingthree(almost150s).Thelastthreeoscillationsweresimilarinlength.
Canadian 240.5 Theblueberriesweresmallerwithdarkflesh.Theblueberrysolutionappearedadarkpinkish-purpletransparentcolourwithparticlessuspendedinthesolution.Aftertheblueberrysolutionwasadded,theinitialoscillationwassignificantlylongerthanthefollowingthree(almost210s).Theinitialoxidation/reductionwaslongest.
Spanish 35.8 Theblueberrieswerelargerwithpaleflesh.Theblueberrysolutionappearedapaleyellowwithsignificantamountofparticlesatbottomofsolution.Relativelyquickandsteadyoscillationsafterblueberrysolutionadded.
Moroccan 40.7 Theblueberrieswerelargerwithpaleflesh.Theblueberrysolutionappearedapaleyellowtransparentcolourwithparticlessuspendedinthesolution.Thiswasthefastestreactionoscillatingfromamber-colourlesstodeepblueaftersodiumthiosulfatewasadded.
Figure7:Theuncertaintyintimingisgreaterthantheuncertaintyoftheapparatus,+/-0.01s,becauseofhumanerrorwhichhasnotonlyadelayedreactiontimebutisbasedonobservationssoIjudgedtheuncertaintytobe+/-0.5s.
Generalobservations:
Throughoutthereaction,bubbleswereobservedandtherewerefizzingsounds.Thereactionsolutionoscillatedfromcolourlesstoamber.Thefirstoscillation,withoutblueberrysolution,wasverylong.
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Testforanthocyaninlevelsatdifferenttemperatures–RawData
Inthistest,theMoroccanblueberrysolutionwasusedbecausetheoscillationtimewasmostsuitable,shortenoughtoallowforarelativelyquickreactiontimebutlongenoughtoallowforaccuratetiming.50mlofsolutionsA,BandCwereusedwith1mlofblueberrysolutionwiththemagneticstirrersettosetting9.
Temperatureofblueberrysolution(°C)+/-2°C
Timeforfouroscillations(s)+/-0.5s
25 40.735 39.740 31.150 39.265 38.075 37.5Figure8:Theuncertaintyinthetemperaturewasincreasedfromtheapparatusuncertaintyof+/-0.1°Cto+/-2°Cduetohumanerror.Theuncertaintyintimingisgreaterthanthemeasuringuncertainty,+/-0.01s,becauseofhumanerror
(reactiontimeandobservations)
ProcessingData
Fouroscillationsweretimedtoreducetheuncertaintyinthetimeforoneoscillation.
Testforanthocyaninlevelsindifferentblueberries–ProcessedData
TypeofBlueberry Timeforoneoscillation(s)+/-0.1sWashingtonState 45.8Canadian 60.1Spanish 9.0Moroccan 10.2
Figure10:Theuncertaintyinthetimeforoneoscillationistakenfromthepropagatederrorinthedataprocessing
Figure9:Examplecalculationofprocessingoscillationtimeanduncertainty.Errormustbepropagated.
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Testforanthocyaninlevelsatdifferenttemperatures–ProcessedData
Temperatureofblueberrysolution(°C)+/-2°C
Timeforoneoscillation(s)+/-0.1s
25 10.235 9.940 7.850 9.865 9.575 9.4Figure11:Theuncertaintyinthetemperaturewasincreasedfromtheapparatusuncertaintyof+/-0.1°Cto+/-2°Cduetohumanerror.Theuncertaintyinthetimeforoneoscillationistakenfromthepropagatederrorinthedataprocessing
Graphs
45.8
60.1
910.2
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
1(WashingtonState- organic) 2(Canadian- wild) 3(Spanish) 4(Moroccan)
Timeforo
neoscillation(s)+
/-0.1s
TypeofBlueberry(bylocation)
Figure12:Howthetimeforoneoscillationchangeswiththetypeofblueberry
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7.0
7.5
8.0
8.5
9.0
9.5
10.0
10.5
20 30 40 50 60 70 80
Timeforo
neoscillation(s)+
/-0.1s
TemperatureofBlueberryJuice(°C)+/- 2°C
Figure13:Howthetemperatureoftheblueberrysolutionaffectsthetimeforoneoscillation
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Therearetwopossiblelinesofbestfitforthetimeforoneoscillationvs.temperaturegraph.Onepossibilityisthatthepointat40°Cisanoptimumtemperaturefortheantioxidantsinblueberries.
Thesecondpossibilityisthatthepointat40°Cisanoutlier.Inwhichcasethelineofbestfitwouldappearsignificantlydifferent.
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ProcessingData
WashingtonState : Canadian : Spanish : Moroccan45.8s : 60.1s : 9.0s : 10.2s
45.8/9=5.088 : 60.1/9=6.677 : 9.0/9=1.000 : 10.2/9=1.1335.1 : 6.7 : 1.0 : 1.1
InterpretationandJustificationofData
Typeofblueberryaccordingtolocation
Thereisasizeabledifferenceinthetimeforoneoscillationdependingontheoriginoftheblueberries,fromtheCanadianwildblueberriesat60.1stotheSpanishblueberriesat10.2s.LookingattheratioofCanadian(6.7):WashingtonState(5.1):Moroccan(1.1):Spanish(1)clearlyshowsthattheCanadianblueberrieshadanoscillationtimenearly7timeslongerthantheSpanishones.Whentherearemoreanthocyaninsreactingwith,andstabilising(HusneyandRomito,2015),thefreeradicalspeciesofiodine(iodine,iodideandtri-iodide)createdduringtheBriggs-Rauscherreaction(Zaidan),ittakeslongertobuilduptohighenoughconcentrationstoeffectachangeinthesolution’scolour.Sothisrangeoftimeforoneoscillation,49.4s,suggeststhereisasignificantdifferenceinlevelsofanthocyaninsbetweensamples
TheWashingtonStateandCanadianblueberriesappeartohavesimilarlevelsofanthocyanins,withasignificantgapbetweenthesimilarlevelsoftheMoroccanandSpanishblueberries.
Thiscorrelateswiththegeographicaloriginoftheblueberries;NorthAmericaasopposedtoSouthernEuropeandNorthernAfrica(seeFigure17).Thisissignificantbecausegrowingconditions(climate,soilpHandfertiliser/soilnutrients)willbearedifferentsothesameblueberryspeciesareunlikelytogrownaturallyinthetwodifferentregions.
Figure16:Ratiotocomparetherelativetimeforoneoscillationinblueberriesfromdifferentlocations
Figure17:PoliticalMapofWorld(Geology.com,2007)showingtwodifferentregionsoforiginofblueberrysamples
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Bycomparingobservabledifferencesofcolourandsize(seeFigure7,pg12),itisevidentthatatleasttwoblueberryspeciesweretestedduringthisexperiment.AccordingtoRoutrayandOrsat(2011),‘Totalantioxidantcapacityandtotalphenolic…contenthavebeenfoundtobemoderatelyheritable.’andRiberaandothers(2010),‘Theevaluationofthetotalantioxidantactivityofhighbushblueberry…revealedthatfruittotalantioxidantactivityvariedamongdifferentblueberrycultivars.’Thissuggeststhatgeneticdifferencesbetweenvarietiesofblueberriesimpacttheanthocyanincontent,whichsupportsmyfindingssinceallthesampleshaddifferentoscillationtimes.
Cultivationpracticesalsoimpactthelevelsofantioxidants(RoutrayandOrsat,2011),ofwhichsoilpHisonefactor.Iattemptedtogetincontactwiththecompaniestodeterminethespeciesgrownandthesoilconditions.Disappointingly,noneofthecompaniesrepliedsoIcouldnotmakeadefinitelinktomyfindings.
Theuseoffertilisersalsoimpactlevelsofantioxidants.Organicfertilisersgenerallydonotprovidenitrogen,whichaffectslevelsofphenolicantioxidantsproducedbytheplant(MitchellandChassy,2004).However,studieshaveshownthatlevelsofphenolicantioxidantsdecreasewhenthereisanincreaseinnutrientavailability.Onetheorysuggeststhatthereisa,‘decreasedallocationofresourcestowardsproductionofexpendablemetabolitessuchasphenolicantioxidants,’whenplantgrowthisincreasedsothenaturalproductionofplant-defencemetabolitesisdisruptedbyexcessiveuseofpesticidesandinorganic,nitrogenrichfertilisers(MitchellandChassy,2004).Aseparatestudy(RoutrayandOrsat,2011),‘showedthetotalanthocyanincontentissignificantlyhigherinorganicallycultivatedblueberries.’Furthermore,accordingtoWebb(2014),antioxidantsareproducedasaresponsetoenvironmentalstressessuchasUVlight,coldtemperatureanddrought.Thiswouldsuggestthatwildblueberries,withfewernutrientsavailableandgreaterexposuretoenvironmentalstresses,havecomparablyhigherlevelsofphenolicantioxidantsthanorganicandinorganiccultivatedblueberries.Thissupportsmyfindingsasthewildblueberrieshavethehighestlevelsofantioxidantsfollowedbytheorganicblueberriesandthenthenitrogen-rich,stressfree,non-organic,cultivatedblueberries.
Whentheblueberrysampleswerepreparedtherewasasignificantdifferenceincolourbetweenthesolutions(seeFigure18).Thissupportstheideathatthesamplesaredifferentspeciesbutalsosupportsthedifferentlevelsofanthocyaninsfoundasdifferenttypesofanthocyaninsareresponsiblefordifferentcolours,mainlyred-orangeandred-blue(RoutrayandOrsat,2011).
Figure18:Differentcoloursoftheblueberrysolutions.
1isWashingtonState(organic),2isCanadian(wild),3isSpanishand4isMoroccan.
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Temperature
Keepinginmindthatalongeroscillationtimecorrelateswithhigherlevelsofanthocyanins,thegeneraltrendintemperature(seeFigure15,pg16)suggeststhathighertemperaturesledtolowerlevelsofanthocyanins.At25°C,thetimeforoneoscillationis10.2sandat75°Cthetimeforoneoscillationis9.4s,arangeof0.8s.
Theresultssuggesttherecouldbeanoptimumtemperatureforanthocyaninsinblueberriesasthetimeforoneoscillationdecreasesrapidlyto7.8sat40°C(seeFigure14,pg16).However,thistemperaturehastheshortesttimeforoneoscillationbyasignificantamount(1.6s),suggestingthatthelevelofanthocyaninsdroppedsuddenly,thencamebackup.Althoughthisispossible,itseemshighlyunlikely.Toverifythisresult,Iwouldneedtorepeattheexperiment.Infact,Ibelievethisreadingat40°Cisanoutlier,andassuch,shouldbeignored(seeerrorindata,pg23).
Thechangeintimeforoneoscillationduetotemperatureiswithinonesecondsuggestingthattemperaturehasverylittleimpactonthelevelofanthocyaninswithinthistemperaturerange.Theslightchangeinoscillationtimecouldbecreditedtothehighertemperatureoftheblueberrysolution,increasingtherateofreactionandresultinginadecreasedtimeoverall,ratherthanrelatingtolevelsofanthocyaninswithinthereactionsolution(seesystematicerror,pg22).
Researchhasfoundanthocyaninstobethermo-sensitive,howeverdegradationoftheanthocyaninshasbeenobservedover70°Cwhileheatingbetween40°C-60°Cisreportedtonothaveasignificanteffect(RoutrayandOrsat,2011).Thissupportsmytrendoflowerlevelsofanthocyaninsathighertemperaturesandexplainswhyonlyaverysmalleffectwasnoticedwhenheatingtheblueberryjuicebetween25°Cand75°C.
Therearedifferingopinionsastowhytemperaturesabove70°Cdecreaselevelsofanthocyaninsinblueberries.Temperaturesover70°Ccanleadtohydrolysis(RoutrayandOrsat,2011),areactionwherebondsinamoleculearebrokenwithwater(KimandHehir).AccordingtoPatrasandothers(2010),‘Degradationismainlyduetooxidation,cleavageofcovalentbondsorenhancedoxidationreactionsduetothermalprocessing.’Thoughlittleisknownaboutthemechanismfordegradationofanthocyanins,onemechanismproposedisapossiblethermaldegradationmechanismfortwocommonanthocyanins.Withheating,anthocyaninswouldbreakdownintoachalconestructurethentransformtoacoumaninglucosidewiththelossoftheB-ring(Patrasandothers,2010).(SeeFigure19pg20)
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Conclusion
Inconclusion,myresultssuggestthattheoriginoftheblueberries,whichcorrespondstothevarietyofspeciesandthecultivationpractices,hasasignificantimpactonthelevelsofanthocyaninspresent.Wildblueberrieshavethehighestlevelsofantioxidantsfollowedbytheorganicblueberriesandthenthenon-organic,cultivatedblueberries.
Theresultsfortheimpactoftemperatureonthelevelsofantioxidantsinblueberriesareinconclusive.
Figure19:Thermaldegradationoftwocommonanthocyanins(PatrasandOthers,2010)
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UnansweredandAdditionalQuestions
Theexpecteddeepbluecolourneverappearedinthereactionoscillation.Iwasunabletodeterminewhysowouldliketoexplorethisfurther.
Toextendthefirstresearchquestion,Icouldinvestigatelevelsofanthocyaninsusingthesameblueberryvarietiesindifferentlocationsordifferentvarietiesinthesamelocation.
TheinvestigationonthecorrelationbetweentemperatureandlevelsofanthocyaninsinblueberrieswasinconclusiveandIwouldliketoextendtherangetohighertemperatures,from70°Cto200°C,tocorrelatewithresearchonthistopic,andalsotosatisfymyinterestinwhethercookingtheblueberriesinmuffinsdecreasesthehealthbenefitsoftheblueberries.Dealingwithhighertemperatureswouldhavesafetyimplicationsinvolvingmoresevereburns.Topreventthis,Icouldusesiliconglovesandtongstotransferhotmaterials.
FinallyIwouldliketotestthedifferenceinlevelsofanthocyaninsbetweencultivated,processedandwildblueberriesseparatelyasthiswasavariablethatIwasnotabletokeepconstantinthisexperiment.
Evaluation
Justifyingrange
Iusedfourtypesofblueberries,asthiswasthemaximumnumberofdifferentvarietiesIhadavailabletomeinlocalstores.
Thetemperaturerangewastestedfrom25°Cto75°Cwithincrementscloseto10°Callowingmetotesthowthelevelsofanthocyaninschangedoverrelativelysmalltemperatureincrements.
FouroscillationsoftheBriggs-Rauscherreactionweretimedratherthanone,reducingtheuncertaintyforthetimeofoneoscillationasthetimewasnowdividedbyfour.
Limitations
Unfortunatelytherewerelimitationstotheexperiment.Firstofall,therewaslimitedmaterialavailable,especiallythemalonicacid,whichrestrictedthenumberoftrialspossibleandlimitedtherangeoftemperaturesthatcouldbetested.Thisiseasilyimprovedhadtheschoolbeenabletoordermorechemicals.Also,therewerelimitedvarietiesofblueberriesavailable.Toacquiremoresamples,itmaybepossibletoorderfrozenvarietiesfromagreaterrangeoflocations.
Theblueberriestestedwereallpackagedandthereforeprocessed.AccordingtoRoutrayandOrsat(2011),thereisahighprobabilitythatprocessingresultsinlossofanthocyanins.TheCanadianwildblueberrieswereflashfrozen;theprocessofstoragethatcausestheleastdeteriorationofantioxidants(RoutrayandOrsat,2011).MyresultssupportthisstatementastheCanadianblueberriescontainedthemostanthocyanins.Sincetheblueberriestestedwerenotprocessedinthesamemanner,theaccuracyofthecomparisonisreduced.Toimprovethis,freshblueberries(perhapsfromu-picks)canbetestedsoprocessingwillnothavereducedtheirlevelsofantioxidants.Or,toallowforafaircomparison,alltheblueberriestestedcouldbeprocessedinthesamemanner,suchasflash-freezing.
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RandomError
Randomerrorispresent,ascanbeseenbytheerrorbarsonthegraphshowinghowtemperatureaffectsthetimeforoneoscillation(seeFigures13,pg15).Theseareduetouncertaintiesintheapparatusandhumanerror.Thevolumesofreactantsareapossiblesourceofrandomerrorasthe50mlmeasuringcylindershaveanuncertaintyof+/-2mlwhiletheblueberryjuicewasmeasuredusinga5mlmeasuringcylinderwithanuncertaintyof+/-0.5ml.Humanerrorthroughinaccuratepouring,measuringandtransferringofsolutionscanalsoincreasetherandomuncertainty.Thiscanbereducedbymeasuringcarefullyandslowlyforagreaterdegreeofaccuracywhennearingthedesiredvolume.Forsmallervolumes(lessthan25ml)glasspipettescouldbeused,whicharemoreprecise,furtherreducinghumanerror.Althoughthereisopportunityforrandomuncertaintywhenpreparingthereactants,thisdoesnothaveaneffectonthecomparisonsmadeasthesamesolutionswereusedthroughouttheexperiment.
Significantrandomerror,causedbyhumanerror,isresponsibleforthevariationinmassofblueberryjuiceintheblueberrysolution(2.00g+/-4.5%.)Itwasdifficulttomeasureaccurately2gofblueberryjuicebecause,whenstrained,theblueberryjuicecamethroughinspurts.Toimprovethis,alargervolumeofblueberryjuicecouldbeblended,usingablender,makingitmoreviscousandallowingittopourmoresmoothlysothemasscanbemeasuredmoreaccurately.
Timingtheoscillationswasafurthersourceofrandomerror.Firstlythereisrandomerrorduetohumanreactiontimes.Thenthereishumanerrorassociatedwithstarting(andstopping)thestopwatchsinceitwasbasedonobservationswhenthesolutionchangedcolour(difficulttojudgeasthecolourchangewasnotdistinct)increasinguncertainty.Finally,thereisarangeoftimeratherthanapointintimewhentheblueberrysolutionwaspouredintothereaction,whichisasystematicerrorleadingtorandomerrorasitrequireshumanjudgementtodecidewhentostartthestopwatchsotherecordedtimecouldbeaboveorbelowthe‘true’time.Toreducetheseinaccuracies,theblueberrysolutioncouldbepouredquickly(toreducetheperiod)andthestopwatchstartedhalfwaythroughpouring.Inaddition,Icouldtime10oscillationstoreduceerror.Afinalimprovementwouldbetodeterminetheproportionsandvolumesofreactantsthatleadtoadistinctcolourchangetherebyimprovingtheaccuracyintimingoneoscillationbymakingthecolour-changemorerecognizable.
Duetothelimitationinmaterial,itwasnotpossibletodomultipletrialsforeachexperiment,leadingtoanincreasedrandomerrorasnoaveragecouldbecalculated.Thiscanbeimprovedbyhavingaccesstomorechemicals,asmoretrialswouldthenbepossible.
SystematicError
Systematicerrorwaspresentintheheatingmethod.Itwasdifficulttomaintainaconsistenttemperaturewhenusingthehotplate,whichmeanstheactualtemperaturesoftheblueberrysolutionswereconsistentlyabovetherecordedtemperatures,resultinginthetimeforoneoscillationtobefasterthanthe‘true’value.Onepossiblesolutionistoheattheblueberrysolutionsusingahotplate,onalowheat,sothetemperatureincreaseisgradual,makingiteasiertotakeareadingatthecorrecttemperature.
Solutiontemperatureisalsoasourceofsystematicerror.Astheheatedblueberrysolutionwasaddedtothecolderreactionsolution,thermalenergywouldbetransferredtothereactionsolution,sotheactualtemperatureislessthantherecordedtemperature.Inaddition,theslightincreaseintemperatureofthereactionsolutioncouldincreasetherateoftheBriggs-Rauscherreaction,thereforethetimeforoneoscillationwouldbefasterthanexpected.Howeveronlysmallvolumesof
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blueberrysolutionwereused,andallsamplesweretreatedthesameway,thereforethetemperaturechangeisnotgreatlysignificanceinthisexperiment.Athighertemperatures,moreenergywouldbetransferredtothereactionsolutionandthereforethetemperaturewouldincreasemoresignificantlytothepointwhereitmaybecomeaconcern.
Themajorityoftheblueberryskindidnotgrindintoajuicesoanyantioxidantpresentintheskinwillnotbepresentintheblueberrysolution.AccordingtoRibera(2010),‘Skinextractshavesignificantlyhighertotalantioxidantactivitythanthosedetectedforwholefruitandpulp.’Thisisasignificanterrorinthemethodbecauseitmeanstheresultsarenotanaccuraterepresentationofthelevelofantioxidantsintheentireblueberrybutonlyofthepulp.Thiscouldbeimprovedbyblendingtheentireblueberryinablendersotheantioxidantsintheskincouldalsobetested.However,asIammakingacomparison,andallsamplesweretreatedthesameway,myconclusionsarestillaccurate.
Anotherproblemencounteredwasthedifficultyinsynchronisingtheoscillationswithheatingtheblueberryjuice.Whenheatingwiththehotplate,thetemperaturewasalwaysincreasingsoIhadtojudgewhentostartthereaction(bycombiningsolutionsA,BandC)sothatthesecondoscillationcoincidedwiththecorrecttemperatureoftheblueberrysolution.Thissystematicerrorleadstorandomerrorastheactualtemperaturecouldbeaboveorbelowtherecordedtemperature.Asmentionedpreviously,animprovementwouldbetoheattheblueberryjuiceslowlysothatthetemperatureoftheblueberrysolutioncanbemaintainedwhenthereactionisstarted.
Errorindata
Thetemperaturerangewasnotbigenoughtoestablishastrongcorrelationwithexperimentaldata,asresearchsuggestsmostdegradationofanthocyaninsoccursattemperatureshigherthan70°C,whichwasanerrorintheplanning.
Thetrialat40°Cismostlikelyanoutlier,becauseIbelieveIonlytimedthreeoscillationsratherthanfour.HowevertherewasnotenoughmaterialtoretestwhenIsuspectedmyerror.
Reliabilityofdata
Thereissignificanterror,bothrandomandsystematic,inthisexperiment,decreasingdatareliability.However,theseuncertaintieshadlessofanimpactontheresultsthantheycouldhavehadbecausedatacomparisonsweremadewithnoabsolutevaluescalculated.Thismeansmyconclusionscanbeconsideredreliable.Noconclusioncouldbemadeontheeffectoftemperatureonlevelsofantioxidants,butthiswasduetoinconclusivedatanotunreliabledata.
Whenevaluatingtheimpactoftemperatureonlevelsofantioxidants,theoutlier(at40°Cwithatimeof31.1s)reducesthereliabilityofthedatabecauseitindicatesthepresenceofeitherhumanerrororanerrorinthemethod.Whenprocessingthedataanddrawingmyconclusions,Ichosetoignoretheoutlier.
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Bibliography
Journals
Nijveldt,Randothers(May14,2001)‘Flavonoids:areviewofprobablemechanismsofactionandpotentialapplications’,TheAmericanJournalofClinicalNutrition,volume74(4),pp.418-425
Ribera,A.Eandothers(2010)‘Antioxidantcompoundsinskinandpulpoffruitschangeamonggenotypesandmaturitystagesinhighbushblueberry(VacciniumcorymbosumL.)growninsouthernChile’,Journalofsoilscienceandplantnutritionvolume10(4),pp.509-536
Routray,W.andOrsat,V.(2011)‘BlueberriesandTheirAnthocyanins:FactorsAffectingBiosynthesisandProperties’,ComprehensiveReviewsinFoodScienceandFoodSafety,volume10,pp.303-320
Thalheimer,J(July2015)‘CelebrateSummerFruit’,TodaysDietitian,volume17(7),pp.20
Webb,D.(2014)‘Anthocyanins’,TodaysDietitian,volume16(3),pp.20
Websites
Andrew,J.AreAntioxidantsDestroyedbyHeat?Availableat:www.healthyeating.sfgate.com/antioxidants-destroyed-heat9263.html[Accessed:30July2015)
Bickelhaupt,D.SoilpH:WhatitMeans.Availableat:http://www.esf.edu/PUBPROG/brochure/soilph/soilph.htm[Accessed:13August2015]
Farusi,G.(09/12/2009)LookingforAntioxidantFood.Availableat:http://www.scienceinschool.org/2009/issue13/antioxidants[Accessed:01/06/2015]Foss,K.(April1,2014)CanblueberryextractpreventParkinson’s.Availableat:http://www.mun.ca/science/news.php?id=3305[Accessed:18August,2015]
Husney,A.andRomito,C.(11June2013)FreeRadicals.Availableat:www.webmd.com/hw-popup/free-radicals[Accessed:22July2015]
Kim,P.andHehir,G.Hydrolysis.Availableat:http://chemwiki.ucdavis.edu/Physical_Chemistry/Equilibria/Solubilty/Hydrolysis[Accessed:13August,2015]
MITopencourse.TheSplendorofOneChemicalReaction.Availableat:http://ocw.mit.edu/high-school/chemistry/demonstrations/videos/briggs-rauscher-reaction/briggs_rauscher.pdf[Accessed18August,2015]
Mitchell,A.E.andChassy,A.W.(2004)OrganicAgriculture:Doesitaffectantioxidantsandnutritionalquality.Availableat:www.soyconnection.com/newsletters/soy-connection/health-nutrition/articles/Organic-Agriculture-Does-It-Affect-Antioxidants-and-Nutritional-Quality[Accessed:1August2015]
Patras,A.andothers(2010)Effectofthermalprocessingonanthocyaninstabilityinfoods;mechanismandkineticsofdegradation.Availableat:www.acedemia.edu/1179480/Effect_of_thermal_processing_on_anthocyanin_stability_in_foods_mechanisms_and_kenetics_of_degredation[Accessed3August,2015]
Robertson,S.(December2,2014)WhatareFlavonoids.Availableat:www.news-medical.net/health/What-are-Flavonoids.aspx[AccessedAugust3,2015]
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UCSB.Briggs-RauscherOscillatingReaction.Availableat:www.people.chem.ucsb.edu/feldwinn/darby/DemoLibrary/DemoPDFs/Demo005.pdf[Accessed8September,2015]
WebMD.(July142014)Antioxidant–TopicOverviewAvailableat:http://www.webmd.com/food-recipes/antioxidants-topic-overview[AccessedJuly17,2015]
Zaidan,G.Briggs-RauscherReaction.Availableat:http://ocw.mit.edu/high-school/chemistry/demonstrations/videos/briggs-rauscher-reaction/[Accessed:13August,2015]
Books
Prasad,K.N.(2014)FightHeartDiseasewithvitaminsandantioxidants.Rochester,Vermont:HealingArtsPress
Smythies,J.(1998)EveryPerson’sGuidetoAntioxidants.NewJersey:RutgersUniversityPress
Snyder,M.andClum,L.(2011)Theantioxidantcounter:ApocketguidetotherevolutionaryORACscaleforchoosinghealthyfoods.UlyssesPress.
Illustrations
Figure1.Routray,WandOrsat,V(2011)SkeletalStructureofAnthocyaninsIn:BlueberriesandTheirAnthocyanins:FactorsAffectingBiosynthesisandProperties.[Diagram](Accessed2August,2015)
Figure2.Routray,WandOrsat,V(2011)Anthocyaninscommonlypresentinblueberries,theirstructures,sugarmoieties,andcolour.In:BlueberriesandTheirAnthocyanins:FactorsAffectingBiosynthesisandProperties.[Diagram](Accessed2August,2015)
Figure3.UCSB(Unknowndate)SummaryoftheBriggsRauscherreaction[Diagram]At:http://people.chem.ucsb.edu/feldwinn/darby/DemoLibrary/DemoPDFs/Demo005.pdf(Accessed9September,2015)
Figure17.Geoglogy.com(2007)PoliticalMapofWorld[Diagram]At:http://geology.com/world/world-map.shtml(Accessedon11.08.2015)
Figure19.Patras,Aandothers(2010)Thermo-degradationoftwocommonanthocyanins.In:Effectofthermalprocessingonanthocyaninstabilityinfoods.[Diagram]At:http://www.acedemia.edu/1179480/Effect_of_thermal_processing_on_anthocyanin_stability_in_foods_mechansim_and_kenetics_of_degredation(Accessedon2August2015)
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AppendixI
Method:
Apparatus
- 4differentvarietiesofblueberrieso FromSpaino FromMoroccoo FromWashingtonState(organic)o FromCanada(wild)
- Distilledwater(3litr)- Potassiumiodate(43g)- Malonicacid(16g)- Hydrogenperoxide(410mlof30%)- Sulfuricacid(4.3mlof18M)- Manganese(II)sulphatemonohydrate(3.4g)- Sodiumthiosulfate(20g)- Solublestarch(0.3g)- Volumetricflasks
o 31Lglassvolumetricflasko 4-640mlglassvolumetricflask
- Glassbeakerso 10mlbeakero 2100mlbeakero 7200mlbeakero 10400mlbeaker
- GlassMeasuringCylindero 1Lo 3500mlo 650mlo 10mlo 45ml
- MetalSpatula- 2-decimalbalance- Hotplate- 3Glassstirringrods- Magneticstirrerandstirrod(2”)- Smallbowl- Finestrainer- Pestleandmortar- DigitalThermometer- Boardmarker- Stopwatch- Fumehood- Largebucketandlid- Safetygogglesandgloves- SodiumBicarbonate
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JustificationofApparatus
- Distilledwater–ratherthantapwatertoreducechemicalsthatarepresentintapwater(suchaschlorine)thatcouldpotentiallyaffectthereaction.
- Volumetricflask–ratherthanabeakerbecausethevolumetricflaskonlyhasonelineindicatingthevolume,solesslikelytomeasuretothewrongline,andvolumetricflasksalsoallowformoreaccuratemeasurementsofvolume.
o Thevolumesofthevolumetricflaskswerechosentocorrespondtotheonemarkedline,sinceonlyonevolumecanbeaccuratelymeasuredusingaspecificvolumetricflask.
- Glassbeakers–usedinsteadofplasticbeakersbecausethegraduatedscaleontheglassissharpersoitiseasiertogetamoreprecisemeasurement.
o Volumeswerechosensothatthesolutionsmeasureddidnotfillthebeaker,toreduceriskofspilling,andsmallenoughtohaveappropriateincrementsinthescale.
- Glassmeasuringcylinder–usedinsteadofaplasticmeasuringcylinderbecausethegraduatedscaleontheglassissharpertomakethemeasurementsmoreprecise.IusedaglassmeasuringcylinderratherthanpipettesbecauseIcouldthenleavethepreparedsolutioninthemeasuringcylinderuntilIneededit
o Thesizewaschosentothesmallestpossiblevolumeforthemeasurementsothattheincrementsweremostappropriate,andcouldbeaspreciseaspossible.
- Metalspatula–usedtotransfersolidstoweighingboatsratherthanrisktouchingthechemicalswithmyhands.
- Two-decimalplacebalance–usedinsteadofaoneorzerodecimalplacebalancebecauseitismoreaccurate.Iusedthisinsteadofamoreaccuratebalancebecausetherandomuncertaintywaslargerthanthemeasuringuncertaintyoftheapparatus.
- Hotplate–usedinsteadofaBunsenburnerbecauseitiseasiertocontrolthetemperature.- Glassstirringrods–ratherthanmetalsoitdoesn’treactwiththereactionsolution- Magneticstirrer–ratherthanstirringrodbecauseitstirsmoreconsistentlyandallowsmeto
performothertasksatthesametime- Finestrainer–ratherthanfilterpaperbecausetheblueberrypulpwasnotliquidenoughto
strainthroughfilterpaper.- Pestleandmortar–ratherthanblenderbecausetheamountofblueberriesbeingcrushed
wastoosmallforablendertobeaffective.- Digitalthermometer–ratherthanaglassthermometerbecauseitismoreaccurate.- Stopwatch–ratherthanaclockasitishandheldsoeasiertomanoeuvreanditismore
accurate.- Sodiumbicarbonate–toneutralisesulphuricacidspills
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Procedure
Note:mustwearsafetygoggles/glassesandgloves,havebucketandlidready
1) Label450mlbeakerswiththevarietyofblueberrytobetested(onevarietyforeachbeaker)usingaboardmarker.
2) Mashonesampleusingapestleandmortar.Placea200mlglassbeaker,labelledwiththecorrespondingtypeofblueberry,onabalanceandzerothebalance.Straintheblueberryjuicefromthemortarintothebeakerusingafinestrainuntilthebalancereads2.00g.Setthesampleaside.Rinseanddrythepestleandmortarthenrepeatfortheothersamplesofblueberries.
3) Usinga100mlglassmeasuringcylinder,measure100mlofdistilledwaterandaddtothe200mlglassbeakerlabelledwiththefirstsampleandstirwithaglassrod.Rinseanddrytheglassrod.Repeatfortheremainingsamples.Thesearethefourblueberrysolutionstobetested.
4) PrepareSolutionAinaventedfumecupboard.- Label1Lvolumetricflask‘SolutionA–hydrogenperoxide’withaboardmarker.Label
one500mlglassmeasuringcylinder‘distilledwater’andanother‘30%hydrogenperoxide’.
- Measure400mlofdistilledwaterintothe500mlglassmeasuringcylinderlabelled‘distilledwater’andaddtothe1Lvolumetricflasklabelled,‘SolutionA–hydrogenperoxide.’
- Measure410mlof30%H2O2intothe500mlglassmeasuringcylinderlabelled‘30%hydrogenperoxide’andaddtothe1Lvolumetricflasklabelled,‘SolutionA–hydrogenperoxide.’
- Adddistilledwatertothe1Lvolumetricflaskuptothe1litremarkthengentlyswirlflask.
- Keepthesolutioninthefumecupboarduntilrequired.5) PrepareSolutionBinaventedfumecupboard.
- Labeladifferent1Lvolumetricflask‘SolutionB–Potassiumiodateandsulfuricacid’withaboardmaker.
- Labelthe1000mlglassmeasuringcylinder‘distilledwater’anduseittomeasure800ml,thentransferintothevolumetricflasklabelled‘SolutionB.’
- Placea50mlbeakeronathreedecimalbalanceandcalibrate(zero)thebalance.Then,usingametalspatula,weigh43gofpotassiumiodate(KIO3)intothe50mlbeakerandthentransferintothe1Lvolumetricflasklabelled‘SolutionB.’
- Addamagnetstirbartothe1Lvolumetricflasklabelled‘SolutionB’andplaceonmagneticstirapparatus(settomediumspeedsoitisnothittingside).
- Labela5mlglassmeasuringcylinder‘sulfuricacid,’thenuseittomeasure4.3mlof18Msulfuricacid.
- Heatthesolutioninthe1Lvolumetricflasklabelled‘SolutionB’onlowheatusingahotplate.Whilestirring(withthemagneticstirbar),addthe4.3mLofconcentratedsulfuricacid.
- Adddistilledwaterupto1L(todilutethesolution)andstir,usingaglassrod,untilalltheKIO3isdissolved.
- Removetheflask(labelled‘SolutionB’)fromtheheatandleavetocoolinfumehooduntilrequired.
6) PreparesolutionCintheventilatedfumecupboard- Labelathird1Lvolumetricflask,‘SolutionC–malonicacid,manganese(II)sulphate
monohydrateandstarch’usingaboardmaker.- Usingthe500mlglassmeasuringcylinderlabelled‘distilledwater’measure500mlof
distilledwaterandtransferintothe1Lvolumetricflasklabelled‘SolutionC’.
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- Placea50mlbeakeronathreedecimalbalanceandcalibrate(zero)thebalance.Then,usingametalspatula,weigh16gofmalonicacidintothebeakerandtransferintothe1Lvolumetricflasklabelled‘SolutionC’.
- Placeaplasticweighingboatonthebalanceandcalibratethebalance.Weigh3.4gofmanganese(II)sulphatemonohydrateintotheweighingboatandtransfertothe1Lvolumetricflasklabelled‘SolutionC.’
- Placethe1Lvolumetricflaskonamagneticstirrerplate(withamagneticstirbaraddedtothebeaker)setatmediumspeedsoitisnothittingthesides.
- Usingthe50mlglassmeasuringcylinderlabelled‘distilledwater’,measure50mlofdistilledwaterintoanew100mlglassbeaker(labelled‘starchsolution’)andbringtoaboilusingahotplate.
- Placeasecondplasticweighingboatonthebalanceandzeroit,thenweigh0.3gofstarchandtransferintoanother50mlbeaker(labelled‘starch’).Usingthesecond5mlglassmeasuringcylinder(labelled‘distilledwater’)measure5mlofdistilledwaterandtransferintothe50mlbeakerlabelled‘starch’.Usingaglassrod,stirthewaterandstarchintoapaste(slurry)
- Pourthestarchslurry(fromthebeakerlabelled‘starch’)intothe100mlglassbeaker(labelled‘starchsolution’)ofboilingwaterandheatfor2-3minutesuntilthestarchisdissolved.
- Pourthesolutioninthebeakerlabelled‘starchsolution’intothe1Lvolumetricflasklabelled‘SolutionC’
- Adddistilledwatertothe1Lvolumetricflasklabelled‘SolutionC’untilthe1Lmarkandleavetocoolinthefumehooduntilrequired.
7) Placea400mlbeaker(labelled‘reactionbeakertemperatureofblueberriestrial1’)onmagneticstirplateandputamagneticstirbarinthebeaker.
8) Label350mlglassmeasuringcylinders,‘SolutionA’,‘SolutionB’or‘SolutionC’withaboardmarker
9) Usinga50mlglassmeasuringcylinderlabelled‘SolutionA’,measure50mlofsolutionAandsetaside.RepeatforsolutionBandC(usingtheirrespective50mLmeasuringcylinders).
10) Usinga5mlglassmeasuringcylindermeasure1mloftheblueberrysampletobetested(andkeepinmeasuringcylinder.)
11) Transferthe1mlofblueberrysampleintoa10mlbeaker.Usingahotplate,heatuptheblueberrysampleto25°C,trackingthetemperatureasitincreaseswiththedigitalthermometer.
12) Whenthetemperatureoftheblueberryjuicenearsthetargettemperature,combinethepremeasuredsolutionsA,BandCintothebeakerlabelled‘reactionbeaker’andstartthemagneticstirrertosetting9.Letthereactiongothroughtwooscillations,thenaddtheheatedblueberrymixture(whenthesolutionturnsfromambertocolourlessthesecondtime)tothebeakerlabelled‘reactionbeaker’andstartthestopwatch.Lettheoscillationgothroughfouroscillationsaftertheblueberrysampleisadded,thenstopthestopwatchandrecordthetimeinatablewiththecorrelatingvarietyofblueberry/temperaturedependingonthetest.Thenstopthemagneticstirrer.
13) Putthereactionbeakerintothebucketandputonthelidtomoveintothefumecupboard,thensprinklesodiumthiosulfateintoreactionbeakertoreduceiodinetoiodideionsfordisposal.
14) Rinsethe5mlglassmeasuringcylinderandthe10mlglassbeaker(thatcontainedtheblueberrysample.)
15) Repeatsteps7to14forthesameblueberrysampleatdifferenttemperatures(35°C,40°C,50°C,65°Cand75°C).
16) Repeatsteps7to14fortheremainingthreeblueberrysamples,omittingstep10(donotheattheblueberryjuice)astrialsaretobeperformedatroomtemperature.
17) Cleanupexperimentareaandwipedowndesks.
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Disposal(MIT,2012)
- Reactionproducesalargeamountofelementaliodinethatmustbereducedtoiodideionsfordisposal.
o SprinklesodiumthiosulfateintothebeakercontainingtheBriggssolution(thereactionbeaker).Thiswillcausethesolutiontofoamup.Thereaction(betweentheiodineandthiosulfate)isveryexothermicsothebeakerwillbecomehot.Continuetosprinklethesodiumthiosulfateuntilthefoamingstops,indicatingthereactionhasstopped,andthesolutionwillbecomecolourless
o Waitfortheneutralisedsolutiontocoolthenthesolutioncanbedisposedofinaccordancetodisposallawsofyourspecificcountry.
Safety(MIT,2012)
- Iodineisproducedduringthereactionandvapourwillbegintoescapewhenreactionstopsoscillating.
o Vapourcanbeextremelyirritatingtoeyes,skin,mucousmembranesandlungso Asasafetyprecaution,havealargebucketwithlidhandy,andsetthereaction
beakerinthebucketwiththelidandplaceinthefumecupboardassoonasithasfinishedoscillating.
§ Quenchthereaction(instructionsin‘disposal’)- 30%hydrogenperoxideisastrongoxidizingagentthatcancauseseriousburnsifitcomesin
contactwithskin.o Rinseaffectedareaswithlotsofwaterfor15-20minutesthengetemergency
attentiono HydrogenPeroxideincontactwithotherchemicalscanresultinveryexothermic
(explosive)reactions.Keepaway(andstore)awayfromotherchemicals.- Sulfuricacidisastrongacidandcancauseburns.Ifthevapourisinhaled,itcouldcause
seriouslungdamage.o Neutralisespillswithaweakbase(ie.Sodiumbicarbonate)
- Malonicacidisastrongeye,skinandrespiratoryirritanto Wearsafetygogglesandworkinawell-ventilatedroom,keepingsolutionsinafume
cupboardwhennotinuse- Asasafetyprecaution,preparethesolutionsinaventedfumecupboardwearingsafety
gogglesandgloves.- DuringtheexperimentIamworkingwithboilingsubstances
o Becautiouswithequipmentandkeepawayfromtheedgeofdesks.o Ifyouspillinonyourskinrinsewithcoldwaterimmediatelyandseekmedical
attention.- Hotplateishotsomaycauseburns
o Asaprecaution,keepawayfromtheedgesoftablesandturnoffwhennotinuse.o Treatforburn(putaffectedareaundercold,runningwaterimmediately)andseek
medicalattentionifsevere.- Workingwithglasswarewhichmayshatterintosharpshards
o Asaprecaution,keepawayfromedgeso Sweepuppiecesaftermakingsurethechemicalsaresafe(neutralisethechemicals
first)o Ifinjuredseekmedicalattention.
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Preliminary
IusedtheMoroccanblueberrysolution(2.00g+/-4.5%in100mlofdistilledwater)forallpreliminarytests.10mlofsolutionA,BandCwereusedwith3mlofblueberrysolution,unlessotherwisementioned.
First,Icrushedtheblueberries–usingthepestleandmortar,andthenstrainedthemwithastrainerratherthantheblenderbecauseonlysmallmassesofblueberrieswereavailable.
Thefirsttrialwasunsuccessfulastherewasnocolourchange,sonovisibleoscillations.Whensodiumthiosulfatewasadded(toquenchthereaction)attheendofthefirsttrial,thereactionsolutionturnedreddish-brownwithsomepurple-lilacareasthateventuallyturnedcolourless.Thecolourchangesuggeststheiodineionsweredisplacedtothesulphuricacid,suggestingareactiondidoccur,anditturnedadeepbluecolourwhenthesodiumthiosulfatewasaddedsuggestingthestarchwasalsoeffective.Thismeanttherecouldbeaproblemwiththestarch,withthemalonicacid,orwiththevolumeofreactants,whichcouldbetoosmalltoallowoscillationstobeseen.
Thereforethesecondtrialusedanewstarchsolutionandeverythingelsewaskeptconstant.Initially,theresultswerethesameasthefirsttrial,withnocolouredoscillations.However,afterasignificantamountoftime,thereactionsolutionchangedfromfaintambertocolourlesssuggestingthatiodineandiodideionsarepresent.Whensodiumthiosulfatewasaddedtothereactionsolution,itturnedbrown-redwithapurpletinge,asbefore.
Howeverwhentheblueberrysolutionwasadded,thereactionappearedtostoposcillating.Toconfirmthereactionwasoscillating,Iwaiteduntilthereactionsolutionwasclearlyoscillating(movingbetweenpaleambertocolourless)beforeIaddedtheblueberrysolutionasecondtime.Whentheblueberrysolutionwasadded,acolourchangewasnotobserved.Eithertheantioxidantintheblueberrysloweddowntheoscillationtothepointwhereitwasunrealistictomeasureorthecolourchangewastoofainttodetect.
AtthispointIknewthatthereactionsolutionwasoscillating,withoutgoingthroughthedarkbluestage,buttherewasaproblemwhenIaddedtheblueberrysolution.
PossiblechangesthatIcouldmakeincludedusinglargervolumesofreactants(solutionsA,BandC),smallervolumesofblueberrysolutions,addingsodiumthiosulfatetothereaction(asacolourchangewasobservedwhenitwasadded)orchangingthemalonicacidtoacetone(becausethemalonicacidwasoldandmaybeoxidisedorgoneoff).
Whenonesmallpieceofsodiumthiosulfatewasaddedtothereactionsolution,beforetheblueberrysolutionwasadded,thesolutionchangedfromcolourlesstodarkpurplebecauseofthereactionbetweentheiodineandthiosulfate.Therewasafaintoscillationbetweendarkandslightlypalerpurplebeforebecominglighterandfinallyturningcolourless,suggestingtheoscillationreactionwasoccurring.Ibelievethisisbecausethesodiumthiosulfatehadcompletelyreactedatthatpoint.
FinallyItriedusinglargervolumesofthesolutionsA,BandC(100ml),withoutaddingthesodiumthiosulfate.Thereactionsolutionoscillatedfromcolourlesstodeeperamber.When3mlofblueberrysolutionwasaddedtothereactionsolution,thereweresmallbubblesandafaintyellowtingeafterasignificantamountoftime.Thenthereactionsolutionturneddarkblue.Therewasnooscillation.Thismaybebecausethelevelofantioxidantswastoohighsotheionswereallscavengedbeforethesolutioncouldoscillate.ThereforeIdecidedtousesmallervolumesofblueberrysolution(1ml)fortheactualexperiment.Duringtheactualexperiment,thedeepbluecolourwasnotobserved.
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