Plant Pigments

Plant pigments are coloured substances produced by the plants and are important in controlling photosynthesis. they are important for humans, arrtecting our attention and providing us with nutrients.

1. Plant Pigments
Dr. Gitanjali, Assist Prof. Cum Scientist
Department of Food & Nutrition
College of Community Science
RPCAU, Pusa, Samastipur

2. Plant pigments
•Plantcompoundsthatareperceivedbyhumanstohavecolorare
referredtoasPIGMENTS.
•Pigmentsaremoleculethatabsorbspecificwavelengthoflightand
reflectsallothers.
•Pigmentsarecolouredandextractedfromplantmaterial,but
othersourcessuchasinsects,algae,cyanobacteriaandfungiare
alsoused.
•Extractedpigmentscanbeconcentratedusingeitherwateror
loweralcoholsforwater-solublepigmentsandorganicsolventsfor
lipophilicpigment.

3. Plant pigments
•Pigmentreferstonormalconstituentsofcells(or)tissues
thatimpartcolor
•Apigmentmayhavepropertiesbeyondthatofacolorant
forexample:
As energy receptors
Carriers of oxygen (or)
Protect against radiation

4. Plant pigments indigenous to food
Thechiefpigmentsoffruitsandvegetablescanbe
classifiedinto:
Chlorophylls
Carotenoids
Anthoxanthinsand
Anthocyanins

5. Chlorophyll
Thename“CHLOROPHYLL” wasoriginallyintended
todescribethosegreenpigmentsofthehigherplants
Chlorophyllsareofgreatimportanceinplantfoods
becauseoftheirroleinphotosynthesisand
TheformationofcarbohydratesfromCO2&H2O
Pigment

6. Chloroplast
Green pigments –Chloroplast
Two chlorophylls have been isolated ,
•chlorophyll a and
•chlorophyll b;
•and they occur in plants in the ratio of
approximately 3a:1b.
Chemically, they are very similar.
They belong to that group of important biological
pigments,
•The porphyrins

7. Cont:
•Theyarefairlylargemoleculescomposedof
•Fourpyrroleringsheldtogetherbymethane
carbons(-CH=)toformalargeflatmolecule.
•Inchlorophyll,Magnesiumatomisheldbya
nitrogenontwooftheringsbyordinarycovalent
bonds.
•Theothertwonitrogen'ssharetwoelectrons
withthemagnesiumtoformacoordinate
covalentbond.

8. Effect of cooking on Chlorophyll
Thecomplexstructureofproteinsmakeschlorophyllvery
susceptibletochemicalchangesincookingandconsequently
thepleasantgreencolorisdifficulttoretain.
Whenagreenvegetableisputinboilingwater,thegreen
colourbecomesbrighter.Thisisduetothegreatertranslucency
ofplanttissueduetoexplosionofintercellularaircollapseof
theintercellularspace.
Ascookingcontinuescompartmentalizationwithinthecellis
disrupted,cellconstituentsincludingorganicacidsdiffusefrom
thevacuolesthroughoutthecellandintothecookingwater.

9. Solubility of Chlorophyll
•Removalofthephytylgroupfromthemoleculeof
chlorophylliscatalyzedbytheenzymechlorophyllase
foundinsomevegetables.
Hydrolysisoftheesterlinkageyieldsacompound
chlorophyllidewhichiswatersoluble.
•Alimitedamountofchlorophyllideproducedduring
thestorageofcertaingreenvegetables
priortocookingaccountsfor
thelightergreentint

10. Heating of chlorophyll in the presence of organic acid
•Magnesiumpresentinthestructureofchlorophyllis
rathereasilydisruptedbythehydrogenmolecule.
•Apale-greenishgreycompoundknownaspheophytin-a
or
•Anolivegreenpheophytin-bresults.
•Nolongermaskedbytheintensegreenchlorophyll,
theyellowandorangepigmentsingreenplanttissue
showalongwiththegreen.
•Thiscombinationtogetherwithpheophytinsgivethe
vegetableamuddyolivegreencolour.

11. Flavonoids
Widelydistributedintheplantfoods
Thesearewatersolublepigmentspresentinvacuoles.
thesearepresentinjuicesoftheplants
Chemically,flavonoidscontaintwobenzeneringswitha3Cbridge.
TheCbridgeiscondensedthroughanoxygenatomintoan
intermediatering.
BenzeneringsholdtheOHgroups.
Flavonoidsareamongthebest-characterizedplantsecondarymetabolites
intermsofcolorationmechanism,biochemistry,geneticsandmolecular
biology
Flavonoidsareclassifiedas:
•Anthocyanins(red,blue,purple)
•Anthoxanthins(yellow)
•Thecatechinsleucoanthocyanins
•Thehighlightedoneschangetobrownishpigments.Theyarealsoknownas
foodTannins.

12. Subclasses of Flavonoids
1. Flavonols
2. Flavones
3. Isoflavones
4. Flavanones
5. Catechins
•Anthocyanins
C6–C3–C6 Compounds

13. Structure of Flavonoids
Flavonols& flavones
are very pale-yellow
& are invisible to the
human eye
As they absorb UV,
which insects
recognize, they give
color and patterns to
flowers to attract
insects

14. Anthocyanins
Watersolubleplantpigments
Colorvariesfromdeepredtopurpletoblue
presentinfruits,vegetableandflowers
Phyto-protectiveandpollinationattractants
Naturalfoodcolors
Anthocyninsaremembersofflavanoids
Phenolicphytochemicals
Anthocyaninsarehighlypronetoundergo
degradationandoxidation.

15. Anthocyanins
•Theyarefoundinthevacuolesoftheplantcells
•Theyoccurinplantcellsasglycosides.
•Examplesofanthocyaninsarecherries,redapples,variousberries,
bluegrapes,pomegranates,skinofradish&leavesofredcabbage
•Thecolourresultsfromthestructureofanthocyanidinswhichis
combinedwithmonosaccharideunits
•Thecarbohydratesarecommonlyboundedby
Glucose
Galactose
Rhamnose
Pentose
Incookeryandprocessingthesepigmentshavethetendencyto
leachoutinthecookingwater,buttheyarenotlostifthecell
wallsremainintact

16. Content of Anthocyanins in Food and Beverages

17. Effect of pH (Anthocyanins)
•AspHchanges
Thecolouroftheanthocyaninschangesfrom
crimson(pH3)tobrightgreen(pH14)
•Additionofalkali
Givesthepigmentabluishgreenshade
Thisshadeisprobablycausedbythepresenceof
anthoxanthinswithanthocyanins
•Ontheadditionofalkali
Theanthoxanthinsturnyellow,while
Theanthocyaninsturnbluewithamixtureof2
colorsappeargreen
Suchacolourcanbeseeninaredcabbage

18. Effect of Metal (Anthocyanins)
Specialenamelliningsofcansareusedwhencanning
anthocyanincontainingfruitsandvegetables.
Unusualcolorsrangingfromgreentostaleblue,developwhen
anthocyaninscontainiron,aluminum,tinandcopperions.
Theascorbicacidwithcopperorironacceleratestheoxidation
andundesirablecolorschangesofanthocyanincompounds.
Themetalironprecipitatesthepigment.
Ironreactswithanthocyaninstoformintenseblackcoloration.

19. Effect of the method of cooking
Anthocyaninsarewatersolublesappigmentswhichcanbeleached
fromavegetablebycookingwater.
•Thepigmentwillchangeintoadullunappetizingblue.
•Withtapwater,thepigmentschangetoanunattractiveblueor
greycolor.

20. Anthoxanthins
•Colorlessorpaleyellowpigments,closelyrelatedto
anthocyanins.
•Theyarealsowatersolubleandpresentinvacuolesofplantcells
•Widelydistributed
•Examples:cauliflower,onionsetc.
•Ingreenleafyvegetables,thecolorismaskedbychlorophyll.
•Anthoxanthinsareglycosides,whichonboilingwithacidsyield
monosaccharideandaflavoneoraflavonederivativesuchas
flavonal,flavanonal,orisoflavone.

21. Changes during cooking /processing
EffectofpH
•Thecolorofthevegetableturnswhitewithlittleacidaddedduring
cooking.
•Ifthewaterisslightlyalkaline,adistinctyellowcolorresults.
Effectofmetal
•Theycausethecookingwatertoturnyellowwhencookedin
aluminiumpans.
•Becausetheflavonesscavengealuminiumandformaflavone
aluminiumchelate.
Pearsandpotatoessometimesdevelopapinkishcolorintheircut
surfaces
•onstandingforawhileafterbeingpeeledorsliced.
•Thiscolorchangeisduetotheconversionofthepro-anthocyaninto
thepigmentedandcloselyrelatedcompoundcyanindin.

22. Tannins
•Darkcolorsinfoodsandastringencytastesareascribedto
tannins.Theyarecomprisedof
Catchins
Leucoanthocyanins
somehydroxyacids.
•Allofthemgivecolorswithmetalions.
•Cathechinsandlecoanthocyaninsarepresentinthetissuesof
woodyplantssuchasapples,peaches,grapes,almonds,pears.
•Presentincerealsandmillets.
•Teaandcocoacontaincatechinandepicatechin.
•Tanninsarereadilydispersedinhotwatertoformcolloidal
solutions.
•Whenafruitispressed,asapplesinthepreparationofcideror
grapesinmakingjuiceorwinetanninsflowoutinthejuice.

23. Tannins
•Theyhavelownutritionalvalueandareresponsiblefordecreasesinfood
intake,growthrateandproteindigestibility.
•Tannin-containingplantextractsareusedagainstdiarrhoea,diuretics,against
stomachandduodenaltumours,andasantiinflammatory,antiseptic,andanti
carcinogenicproperties.
•Inthefoodindustry,usedtoclarifywine,beerandfruitjuices.
•Thegrowthofmanyfungi,yeasts,bacteriaandvirusesisinhibitedbytannins.
•Theantimicrobialpropertyoftannicacidcanalsobeusedinfoodprocessingto
increasetheshelf-lifeofcertainfoods.
•Tanninshavealsobeenreportedtoexertotherphysiologicaleffects,suchas
toacceleratebloodclotting,reducebloodpressure,decreasetheserumlipid
level,producelivernecrosisandmodulateimmunoresponses.

24. Tannins
Intheextractionsuchasbrewingofteaorcoffeesomeofthetanninsare
extracted.
Whenteaorcoffeearebrewedwithhardwater,abrownprecipitateformson
thesurfaceoftheliquid.
Asthebeveragecools,itappearsthroughouttheliquid.Insteadofaclear,
sparklinginfusion,theteaorcoffeeisdistinctlymuddy.
Theprecipitateclingstothesideofthecupandthecolorisverynoticeable.
Thesetransformationsarecausedbythereactionsofthetanninsinthetea
andcoffeewithCaandMgionsofwater.
Ifironispresent,verydarkcomplexesareformed.
Thechangeincolorwhichoccurswhenlemonjuiceisstirredintoblackteais
alsotheresultofachangeinthetanninspresent.

25. Carotenoids
Carotenoidsarelipid-soluble,yellow–orange–redpigments
foundinallhigherplantsandinsomeanimals.
Animalscannotsynthesizecarotenoids.
Carotenoidscanbedividedintocarotenescontainingonly
carbonandhydrogen,andxanthophyllsmadeupofcarbon,
hydrogenandoxygen.
Carotenoidsarealsousedfornutritionalpurposesas
provitaminAagentsorasdietarysupplements.
Actsasantioxidants

26. Sources

27. Betalins
•Betalinsareredoryellowwater-solublepigments
colorinflowersorfruitsofthefamiliesof
Caryophyllales(includingcactus,amaranthusandred
beets).
•Advantageofbetalinscoloristhatitdoesnotdepend
onthepHandismorestablethanthatfrom
anthocyanins.
•Beetscontainpigmentsthatarecloselyrelatedto
anthocyanins.
•Betalainsareclassifiedintored(crimson)betacyanins
andyellowbetaxanthins.
Betacyanins(beetcolor)
Betanidinandbetanin.
Betaxanthins(yellowpigment)
BetacyaninsBetaxanthins

28. Betalins
•Althoughthesepigmentsareheldtightlywithincellsintheraw
vegetable.
•Theydiffuseratherrapidlyintothecookingwaterresultinginthe
highlypigmentedwaterassociatedwithboilingbeets.
•Thisproblemisaggravatedbycuttingbeetintosmallpiecesand
cookingleadingtodullcolorationintheboiledproduct.
EffectofpH
Betacyaninsturnintoareddishcolorinanacidicmedium.
InneutraloralkalinepHabrowinishbluepigmentresults.

29. Betalins