Phenolic Compounds in the Potato and Its Byproducts

19 Pages·2016·0.26 MB·English

International Journal o f
Molecular Sciences
Review
Phenolic Compounds in the Potato and Its
Byproducts: An Overview
HazalAkyol1,YleniaRiciputi2,EsraCapanoglu1,MariaFiorenzaCaboni2,3,*
andVitoVerardo4,5
1 DepartmentofFoodEngineering,FacultyofChemicalandMetallurgicalEngineering,
IstanbulTechnicalUniversity,Ayazag˘aCampus,Maslak,Istanbul34469,Turkey;
[email protected](H.A.);[email protected](E.C.)
2 DepartmentofAgro-FoodSciencesandTechnologies,AlmaMaterStudiorum—UniversityofBologna,
PiazzaGoidanich60,Cesena(FC)I-47521,Italy;[email protected]
3 Inter-DepartmentalCentreforAgri-FoodIndustrialResearch(CIRIAgroalimentare),UniversityofBologna,
PiazzaGoidanich60,Cesena(FC)I-47521,Italy
4 DepartmentofChemistryandPhysics(AnalyticalChemistryArea)UniversityofAlmería,
CarreteradeSacramentos/nAlmeríaE-04120,Spain;[email protected]
5 ResearchCentreforAgriculturalandFoodBiotechnology(BITAL),
AgrifoodCampusofInternationalExcellence,ceiA3,UniversityofAlmería,
CarreteradeSacramentos/nAlmeríaE-04120,Spain
* Correspondence:[email protected];Tel.:[phone]
AcademicEditor:AnaMariaGómezCaravaca
Received:28April2016;Accepted:24May2016;Published:27May2016
Abstract: Thepotato(SolanumtuberosumL.)isatuberthatislargelyusedforfoodandisasource
ofdifferentbioactivecompoundssuchasstarch,dietaryfiber,aminoacids,minerals,vitamins,and
phenolic compounds. Phenolic compounds are synthetized by the potato plant as a protection
response from bacteria, fungi, viruses, and insects. Several works showed that these potato
compoundsexhibitedhealth-promotingeffectsinhumans. However,theuseofthepotatointhefood
industrysubmitsthisvegetabletodifferentprocessesthatcanalterthephenoliccontent. Moreover,
manyofthesecompoundswithhighbioactivityarelocatedinthepotato’sskin,andsoareeliminated
aswaste. Inthisreviewthemostrecentarticlesdealingwithphenoliccompoundsinthepotatoand
potatobyproducts,alongwiththeeffectsofharvesting,post-harvest,andtechnologicalprocesses,
havebeenreviewed. Briefly,thephenoliccomposition,mainextraction,anddeterminationmethods
have been described. In addition, the “alternative” food uses and healthy properties of potato
phenoliccompoundshavebeenaddressed.
Keywords: Solanumtuberosum;potato;phenoliccompounds;healtheffects
1. Introduction
Thepotato(Solanumtuberosum)wasknownoutsidetheAndesfourcenturiesagoandhasturned
intoanecessarycomponentofmuchoftheworld’scuisine. Followingrice,wheat,andmaize,itis
thefourthlargestfoodcropintheworldandisveryimportantforhumanconsumption[1]. Itwas
estimatedthatthetotalworldpotatoproductionwas368milliontonsin2013;ofthat,112milliontons
wereproducedintheEuropeanUnion[2].
Thisstaplecropcontainsessentialaminoacids,vitamins,andminerals,andisthusreportedto
playasignificantroleinhumannutrition[3]. Manyvarietiesofpotatoesoffernutritionalquantitiesof
ascorbicacid(upto42mg/100g),potassium(upto693.8mg/100g),dietaryfiber(upto3.3%),and
otherhealthybioactivecomponents,withlesseramountsofprotein(0.85%–4.2%)[4]. Inparticular,
“resistant starch,” the dietary fiber that escapes digestion and absorption in the small intestine, is
Int.J.Mol.Sci.2016,17,835;doi:10.3390/ijms17060835 www.mdpi.com/journal/ijms
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fermentedbymicroorganismsinthelargebowel[5]. Moreover,inastudyithasbeenfoundthatboiled
potatoesshowedthehighestSI(satietyindex)scoreoutof38foodsgroupedintosixfoodclasses(fruit,
bakeryproducts,snackfoods,carbohydrate-richfoods,protein-richfoods,andbreakfastcereals)[6].
Inadditiontothat,thepotatoisanidealsourceofantioxidantsforthehumandiet[7]. Despitethe
growinginterest,littleinformationhasbeenreportedabouttheimportantphytochemicalspresentin
thiswidelyconsumedvegetableanditsprocessingbyproducts[8].
Theworldwideutilizationofpotatoesismovingfromfreshtoprocessedpotatoproductssuch
asmashedandcannedpotatoes, fries, chips, andreadymeals[9,10]. Thisindustrialprocessingof
potatoescreateshugeamountsofpeelasabyproductandthisgeneratesdisposal, sanitation, and
environmentalproblemslikeallotherindustrialwaste. Also,becauseoflegalrestrictions,thedisposal
ofthiswasteposesachallenge[11,12].However,potatopeelsareagreatsourceofphenoliccompounds
becausealmost50%ofphenolicsarelocatedinthepeelandadjoiningtissues[8,13].
Ontheotherhand,thereisgreatinterestintheutilizationofnaturalantioxidantsasfunctional
ingredients in food formulation because they guarantee the cell constituents’ protection against
oxidativedamageandlimittheriskofdegenerativediseaseslinkedtooxidativestress[14,15]. For
thesereasons,theuseofthesebyproductsfortheproductionoffoodingredientswithhighnutritional
valueincreasedand,consequently,theirrecoverymaybeeconomicallyattractive[11,16].
Ifaglobalhealthgoalistoexpandtheamountsofphytonutrientsconsumedinthediet,avaluable
approachcouldbetoimprovethenutritionalcontentofthephytochemicalsinthemostconsumed
crops, and/orusethebioactivecompoundsthatarecontainedinvegetablewaste[17]. Theuseof
potato peel is underscored as a source of natural antioxidants by many previous studies [9,18,19].
Consequently,thesebioactivecompoundscanbeaddedinfunctionalfoodorcanbeusedtogenerate
nutraceuticalsbyvirtueoftheirpotentialhealthbenefits.
2. PhenolicCompoundsinPotatoes
Phenoliccompoundsaresecondarymetabolitesproducedinplantsthathaveacommonstructure
basedonanaromaticringwithoneormorehydroxylsubstituents[20–22]. Thesecompoundscan
bedividedaccordingtotheirchemicalstructureintoflavonoids,phenolicacids,tannins,stilbenes,
coumarins,andlignans[23,24]. Theirpresenceaffectsthesensoryqualitiesofplant-derivedprocessed
foods,includingtaste,color,andtexture[25–27].
Potatoesaregoodsourcesofphenoliccompounds,withtotalphenoliccontenthigherthanother
widespreadfruitsandvegetableslikecarrots,onions,ortomatoesbecauseoftheirhighconsumption
rates[28]. Thegermplasmofthepotatoshowsastrikingvarietyintermsofthephenoliccompounds
profileandcontent[29]. Thephenoliccompoundsarepresentinthepotatopeelandflesh;however,
thepeelisreportedtohavethehighestamounts[30]. Phenoliccompoundspresentinpotatoesare
phenolicacidsandflavonoidsincludingflavonols,flavanols,andanthocyanins[3].
2.1. PhenolicAcids
Thepredominantphenolicacidsinplantsaresubstitutedderivativesofhydroxybenzoicacidsand
hydroxycinnamicacids. Caffeic,p-coumaric,andferulicacidsarethemostcommonhydroxycinnamic
acidsandfrequentlyoccurinfoodsasesterswithquinicacidorsugars[31]; hydroxybenzoicacid
derivativesaremainlypresentinfoodsintheglucosideforms,andp-hydroxybenzoic,vanillic,and
protocatechuicacidsarethemostcommonforms[31–35].
Phenolic acids are the most abundant phenolic compounds in potatoes [9,36–38]. Among all
these phenolic acids, chlorogenic acid, which is the ester of caffeic acid and quinic acid, has been
considerablydescribedinpotatoes[12,13,18,39,40]. Itconstitutes90%ofthephenoliccompoundsin
potatopeels[37,41]andexistsintheformofthreemainisomers,chlorogenicacid(5-O-caffeoylquinic
acid),neochlorogenicacid(3-O-caffeoylquinicacid),andcryptochlorogenicacid(4-O-caffeoylquinic
acid)[42]. Also,caffeicacidisquantifiedat25–72mg/100ginpotatoesbymanyresearchers[13,43–45].
Int.J.Mol.Sci.2016,17, 835 3of19
Otherphenolicacidssuchasferulicacid,gallicacid,andp-coumaricacidhavealsobeenquantified
in potatoes, ranging from 0 to 5 mg/100 g dry weight [8,9,36,46]; also, syringic acid, vanillic acid,
sinapicacid,andsalicylicacidarepresentinsmallquantities[3,9,31,38].
2.2. Flavonoids
Flavonoidsrepresentthemostcommongroupofplantphenoliccompoundsandtheirpresence
influencestheflavorandcoloroffruitsandvegetables. Thesixsignificantsubclassesofflavonoidsare
theflavones,flavonols,flavanones,flavan-3-ols,anthocyanidins,andisoflavones. Occasionallythey
canbefoundasaglyconesbutmostflavonoidsareattachedtosugars(glycosides)[29].
Inpotatoes,oneofthemostabundantflavonoidsiscatechin,rangingbetween0and204mg/100g
dryweight[36,47–50]. Flavonolslikequercetinandkaempferolrutinosearealsopresentinpotato
tubers[3,7,42,51,52]. Someauthorshavealsoreportedthepresenceofrutin[3,7,42,53].
Flavonoidsweremorethan30mgper100gfreshweightinwhitefleshedpotatoesandthislevel
isnearlydoubledinredandpurplefleshedpotatoesasaresultofanthocyanins[54]. Thecolorofred
andpurplepotatoesisderivedfromanthocyanins[55]. Anthocyaninsareasub-classofpigmented
flavonoids. Themostcommonanthocyanidins(thedeglycosylatedformsofanthocyanins)present
inpotatoesaremalvidin,petunidin,delphinidin,andpeonidininpurpletubersandpelargonidinin
redones[48,56]. Inadditiontothisanthocyanin,aglycones,cyanidin,andpetaninarealsofoundin
potatoes[51,57].
Thelevelsofphenoliccompoundsinpotatoescanvarygreatly[29]dependingonthecolorand
varietyofthepotatocultivars[43].Table1reviewstherangeofindividualphenoliccompoundcontents
reportedintheliterature.
Table1.Concentrationlevelsofthemainphenoliccompoundsinpotatoes.
PhenolicClasses PhenolicCompounds Range(mg/100gDryExtract) References
27.6 [43]
100.0–220.0 [53]
17.4–1274.6 [51]
47.0–283.0 [49]
chlorogenicacid
17.3–1468.1 [36]
21.0–40.0 [58]
60.0–292.0 [17]
0.2–2193.0 [3]
0.1–0.2 [53]
5.0–50.0 [49]
caffeicacid 1.1–172.4 [36]
2.0–6.9 [58]
0–41.6 [3]
0–9.2 [49]
coumaricacid
Phenolicacids 0–1.6 [36]
protocatechuicacid 0–7.6 [36]
vanillicacid 0–22.4 [36]
0.6–9.0 [49]
ferulicacid 0–3.9 [36]
0–1.4 [3]
16.0–27.0 [53]
3.1–163.3 [36]
cryptochlorogenicacid
8.0–59.0 [17]
0.1–168.3 [3]
2.9–9.9 [53]
49.2–91.2 [36]
neochlorogenicacid 0.5–1.5 [58]
3.0–11.0 [17]
0.1–87.6 [3]
Int.J.Mol.Sci.2016,17, 835 4of19
Table1.Cont.
PhenolicClasses PhenolicCompounds Range(mg/100gDryExtract) References
gallicacid 0–1.0 [36]
Phenolicacids
p-hydroxybenzoicacid 0–7.8 [36]
0.5–2.6 [53]
rutin 0.6–1.3 [17]
Flavonols 0–12.2 [3]
kaempferolrutinose 0.5–1.7 [17]
quercetin-3-o-glu-rut 2.5 [53]
43.0–204.0 [49]
Flavan-3-ols catechin 0–1.5 [36]
0–1.4 [3]
1.4–163.3 [51]
87.0 [59]
Anthocyanidins anthocyanins
953.8–1630.3 [60]
21.0–109.0 [56]
PhenolicClasses PhenolicCompounds Range(mg/100gFreshProduct) References
1.4–12.1 [39]
0.9–27.0 [31]
chlorogenicacid 0.4–34.0 [41]
0.4–30.1 [61]
8.7–28.6 [38]
0–1.2 [41]
caffeicacid 0.6–10.2 [61]
5.2–12.2 [38]
coumaricacid 0.8–6.5 [38]
0.2–0.5 [31]
Phenolicacids protocatechuicacid 6.1–10.3 [62]
1.9–2.0 [38]
vanillicacid 0.6 [31]
0.1 [31]
ferulicacid 0–0.1 [61]
1.5–4.9 [38]
0.2–0.5 [31]
syringicacid
0.9–1.7 [38]
p-coumaricacid 0.2–3.0 [31]
0.3–0.9 [31]
sinapicacid
0–0.4 [61]
gallicacid 0.5–0.6 [38]
3. EffectofHarvesting,Post-Harvest,andTechnologicalProcessesonPhenolicContent
The amount of phenolic compounds and their stability are dependent on several factors
such as agrotechnical processes, climatic conditions, ripeness during harvest, and post-harvest
manipulations[63],aswellasgenotype,storageconditionsafterharvest,andprocessingandcooking
methods[24,48,64–68]. Manypolyphenols,particularlyphenolicacids,aredirectlyimplicatedinthe
responseofplantstodifferenttypesofstressessuchasthermalstress,bioticstress,andinjuries,and
intheirtolerancetoexposuretoUVraysandozone[44]. Thesephytochemicalsshowantimicrobial
propertiesbyraisingconcentrationsafterpathogeninfectionandcontributetohealingbylignification
ofdamagedzones[69].
Thesebioticandabioticfactorscanaffectpotatoesandmaycauseaseriouseconomicproblem
in countries where potatoes are cultivated over large areas [1]. In the last decade, the effect of
environmental conditions such as location on the phenolic content of potatoes has been widely
Int.J.Mol.Sci.2016,17, 835 5of19
studied [50,60,70,71]. During tuber development, environmental conditions may influence the
phenylpropanoidpathwayandthepolyphenoliccompositioninpotatotubers[60]. Higherchlorogenic
acid levels were found in warm locations with regular periods of drought, in comparison with
high-altitudelocationsthatarebeneficialforpotatocultivation. Organicallygrownpotatoesreported
significantly higher levels of chlorogenic acids compared to conventional treatments [72]. On the
otherhand,thesestudiesdemonstratedthatthegenotypeofapotatohasmoreeffectonthephenolic
contentthanthelocation[50,70]. Navarreetal.[52]determinedthephenolicandantioxidantcapacity
ofdifferentpotatogenotypes.
Although wild species or primitive germplasm reported the highest phenolic content,
commercial/industrial cultivars are preferred because they have the agronomic characteristics to
beeconomicallypracticalandcouldeasilyandmorecommonlybeplanted. Moreover,itisknownthat
themostnoteworthyphenolicgenotypeswerecolored-fleshpotatoes;however,consumerchoiceisfor
white-fleshpotatoes,sotheyarethemostproduced. Thisencouragesnewharvestand/orpost-harvest
treatmentsinordertoimprovethephenoliccontent.
Forimprovingthephenoliccontentofpotatoes,someimplementationswereusedbeforeand
some after harvesting. Ngadze et al. [44] reported that calcium contributes to increase caffeic and
chlorogenicacidinpotatoes. Furthermore,calciumsoilamendmentalsoimprovedtheconcentration
ofpolyphenoloxidase(PPO)andperoxidase(POD)enzymes,whichareinvolvedinthephenolicsand
totalsolublephenolsmetabolism. SeveralauthorsdefinedtheroleofCa2+ inphenolicmetabolism;
Castañeda & Pérez [73] found that foliar application of 10 mM of CaCl increased phenylalanine
2
activity and resulted in the accumulation of phenols [44]. Other authors used a curing treatment
(10daysat16˝C)immediatelyafterharvest,obtainingahighphenoliccontentandPPOactivityin
potatoflesh;moreover,theyenhancedthefresh-cutcolorandthesensoryqualitiesaftercutting[69].
Afterharvest,storageconditionsalsoplayanimportantroleinphenoliccontents. WhileSingh&
Saldaña[38]indicatedthatphenoliccompoundsmaydegradeduringstorageconditions,manyother
studiesreportedthatcoldstorage(„4˝C)ofpotatoescausedanincreaseinthephenoliccontentorkept
itconstant[40,61,68]. However,asdescribedbyAndreetal.[74],highstoragetemperatures(10˝C)
decreasedthephenoliccontentsorhadnoeffect. Ontheotherhand,Külenetal.[40]demonstrated
thatstoragetimeisalsoveryimportantforphenoliccompounds. Theyfoundthatthetotalphenolic
content(TPC)ofpotatoeswashighatharvest,declinedaftertwomonthsofcoldstorage,increased
afterfourmonthsofcoldstorage,andfinallyincreasedtoalmostharvestlevelaftersevenmonthsof
coldstorage. TheresultsofBlessingtonetal.[47]wereinaccordancewiththeirdata,showingthatTPC
decreasedslightlyafterfourmonthsofcoldstorageinthe‘RussetBurbank‘varietyduringcoldstorage.
Furtherdetailedstudiesarerequiredtoclarifytheeffectsofcoldstorageonindividualpotatoclones.
Inadditiontotheharvestandpost-harvestcondition,cookingprocessesshouldbeconsidered
aswell. Thechemical,physical,andenzymemodificationsthatwereproducedduringcookingwill
changetheantioxidantcapacityanddigestibilityofpotatoes,whichlaterinfluencesthebioavailability
of phytochemicals to the postprandial glycemic response of the human body [75]. In a study of
Mulinaccietal.[76],thecontentsofphenolicacids,glycoalkaloids,andanthocyaninsaremeasuredin
freshandalsoinprocessed(boilingandmicrowavecooking)potatoesfromthreecultivars(Vitelotte
Noire,HighlandBurgundyRedwithpigmentedflesh,andKennebecwithwhitepulp). Differentfrom
theliteraturedata,itisindicatedthattheheatingtreatmentdidnotcauseanychangesinphenolic
acidscontentexceptforasmalldecreaseinanthocyanins. Also,Perlaetal.[54]studiedsomepotato
cookingmethodssuchasboiling,baking,andmicrowavingonphenoliccompoundsinfivecultivars
withdifferentskinandfleshcolorsaftersixmonthsofstorage. Thelevelofphenoliccompoundswas
reducedbythethreecookingmethodsbutboilingminimizedtheselosses.
Briefly,thecultivar,stageofmaturityofthetuber,cookingtemperatureandtime,andpresenceof
waterormoistureduringcookingallstronglyaffectthelossofphenoliccompoundsinpotatoes.
Int.J.Mol.Sci.2016,17, 835 6of19
4. ExtractionandDeterminationMethodsforPhenolicsinPotato
During the extraction of antioxidant compounds from plant materials, the selection of the
appropriateextractionconditionsrepresentsacrucialpoint[18]. Duringtheextraction,thedistribution
ofphenoliccompoundsinextractionsolventsshouldbemadetoreachtheappropriatedistribution
coefficient[75].Toextractphenoliccompoundsfrompotatoes,themostcommonmethodissolid–liquid
extraction [18,27,76]. Commonly, the extraction solvents used for potato phenolics are methanol,
ethanol,andaqueousalcoholmixtures[46,77–79]. However,thesetechniquesrequirealongextraction
timeandresultinlowyields[38]. Therefore,othermodernextractionandisolationtechniqueshave
beenappliedasalternativetechniquesforpotatophenolicextraction. Ultrasound-assistedextraction
(UAE),microwave-assistedextraction(MAE),andpressurizedliquidextraction(PLE)areafewof
thesemoderntechniques[45,62,80–82](Table2).
Table2. Overviewoftheextractionsystemsandanalyticalmethodsusedforphenoliccompounds
determinationinpotatoes.
Analytical
ExtractionSystem PotatoCultivar PhenolicCompoundsDescribed References
Technique
Chlorogenicacid,caffeicacid,
HPLC-DAD ‘Kufrichandromukhi’ [43]
gallicacid
9italiancultivars(‘Agata‘,
‘Primura‘,‘Arinda‘,‘Merit‘,
HPLCUV-Vis Chlorogenicacid [39]
‘Marabel‘,‘Jelli‘,‘Frinka‘,
‘Sponta‘,‘Agria‘)
Neochlorogenicacid,chlorogenic
acid,caffeicacid,
‘RangerRusset’ quercetin-3-o-glu-rut,rutin,
HPLC-MS [53]
‘NorkotahRusset’ kaempferol-3-o-rutinoside,
cryptochlorogenicacid,
quinicacid
Chlorogenicacid,neochlorogenic
HPLC-DAD, acid,cryptochlorogenicacid,
HPLC-MS, 23NativeAndeancultivars caffeicacid,protocatechuicacid, [51]
HPLC-FLD vanillicacid,ferulicacid,petanin,
rutin,kaempferol-3-o-rutinoside
Solid-liquid
extraction 320specialty Chlorogenicacid,caffeicacid,
HPLC-DAD [40]
potatogenotypes gallicacid,catechin
Chlorogenicacid,ferulicacid,
Notcited ‘RussetBurbank’ vanillicacid,caffeicacid, [83]
benzoicacid
Chlorogenicacid,caffeicacid,
‘Jasim’,‘Atlantic’,‘Jawan’,
HPLC-MS ferulicacid,p-coumaricacid, [41]
‘Superior’,‘Jopung’
trans-cinnamicacid
‘Nicola’,‘SieglindeF’, Chlorogenicacid,caffeicacid,
HPLC-DAD [49]
‘Isci4052’,‘Isci67’ ferulicacid,catechin
Gallicacid,caffeicacid,
HPLC Notcited(Indiancultivar) chlorogenicacid, [84]
protocatechuicacid
Neochlorogenicacid,
cryptochlorogenicacid,
13native
HPLC-DAD chlorogenicacid, [60]
Andeangenotypes
kaempferol-3-o-rutinoside,
quercetin
HPLC:HighPerformanceLiquidChromatography;UPLC:UltraPerformanceLiquidChromatography;DAD:
DiodeArrayDetector;UV:Ultravioletdetector;MS:massspectrometer.
Int.J.Mol.Sci.2016,17, 835 7of19
Table2.Cont.
Analytical
ExtractionSystem PotatoCultivar PhenolicCompoundsDescribed References
Technique
Gallicacid,neochlorogenicacid,
protocatechuicacid,catechin,
cryptochlorogenicacid,
HPLC ‘Karlena’ [36]
chlorogenicacid,vanillicacid,
caffeicacid,ferulicacid,
p-coumaricacid
‘Siecle’,‘PurpleMajesty’,
HPLCUV-Vis ‘Dakotapearl’,‘FL1533’, Chlorogenicacid,caffeicacid [13]
‘Vivaldi’,‘Yukongold’
‘Goldrosh’,‘Nordonna’,
‘DakotaPearl’,‘Norkotah’, Chlorogenicacid,caffeicacid,
HPLC-DAD,
‘RedNordland’,‘Sangre’, gallicacid,ferulicacid,catechin, [46]
HPLC-MS
‘Viking’,‘Dark p-coumaricacid,o-coumaricacid
RedNordland’
Chlorogenicacid,caffeicacid,
HPLC-DAD 8cultivars epicatechin,p-coumaricacid, [47]
vanillicacid,quercetin
Protocatechuicacid,gentisicacid,
gallicacid,chlorogenicacid,
HPLC-DAD ‘Sava’,‘Bintje’ [19]
salicylicacid,caffeicacid,ferulic
acid,p-coumaricacid
Chlorogenicacid,neochlorogenic
‘Bintje’,‘Piccolo’,
HPLC-DAD-MS acid,cryptochlorogenicacid, [17]
‘PurpleMajesty’
kaempferolrutinose,rutin
Chlorogenicacid,caffeicacid,
HPLC-DAD/
16cultivars 3-o-caffeoylquinicacid, [77]
APCI-MS
1-o-caffeoylquinicacid
Solid-liquid
extraction 5-o-caffeoylquinicacid,
4-o-caffeoylquinicacid,
HPLC-DAD-MS 13Italiancultivars [66]
3-o-caffeoylquinicacid,ferulic
acid,anthocyanins
‘PurpleMajesty’,‘Yukon Chlorogenicacid,caffeicacid,
UPLC-MS [61]
gold’,‘Atlantic’ ferulicacid,sinapicacid
Chlorogenicacid,rutin,
HPLC-DAD-MS 50cultivars [52]
kaempferol-3-rutinose
Chlorogenicacid,neochlorogenic
acid,cryptochlorogenicacid,
‘Vitelotte’,‘Luminella’, caffeicacid,ferulicacid,
UPLC-DAD [3]
‘Charlotte’,‘Bintje’ p-coumaricacid,syringicacid,
vanillicacid,catechin,rutin,
kaempferol-3-o-rutinoside
Gallicacid,protocatechuicacid,
gentisicacid,chlorogenicacid,
HPLC-DAD ‘Sava’ vanillicacid,syringicacid,caffeic [9]
acid,salicylicacid,p-coumaric
acid,ferulicacid
Chlorogenicacid,neochlorogenic
acid,cryptochlorogenicacid,
coumaricacid,genistin,
HPLC-DAD Notcited [85]
quercetin-3-β-D-galactoside,
naringin,naringenin,luteolin,
genistein,kaempferol,flavan-3-ol
chlorogenicacid,quinicacid,
UPLC-MS Notcited [86]
caffeicacid,methylcaffeate
HPLC:HighPerformanceLiquidChromatography;UPLC:UltraPerformanceLiquidChromatography;DAD:
DiodeArrayDetector;UV:Ultravioletdetector;MS:massspectrometer.
Int.J.Mol.Sci.2016,17, 835 8of19
Table2.Cont.
Analytical
ExtractionSystem PotatoCultivar PhenolicCompoundsDescribed References
Technique
Chlorogenicacid,neochlorogenic
HPLC-DAD-MS 15Colombiancultivars acid,cryptochlorogenicacid, [76]
caffeicacid
Chlorogenicacid,ferulicacid,
Solid-liquid HPLCUV ‘Agria’ gallicacid [18]
extraction
Chlorogenicacid,caffeicacid,
ferulicacid,coumaricacid,
‘Valfi’,‘BlaueElise’,‘Bore
HPLCUV cryptochlorogenicacid, [27]
Valley’,‘BlueCango’
neochlorogenicacid,p-coumaric
acid
Chlorogenicacid,caffeicacid,
‘Nicola’,‘Timo’,‘Siikli’,
HPLC-DAD ferulicacid,sinapicacid,vanillic [31]
‘Rosamund’,‘VanGogh’
acid,syringicacid
Protocatechuicacid,chlorogenic
HPLC-DAD ‘Agria’ acid,neochlorogenicacid, [62]
cryptochlorogenicacid
Chlorogenicacid,
HPLC-DAD 20potatocultivars petunidin-3-glucosidechloride, [81]
pelargonidin-3-glucopyranoside
‘Purple’,‘Innovator’, Chlorogenicacid,caffeicacid,
HPLC-MS [8]
‘Russet’,‘Yellow’ p-coumaricacid,ferulicacid
Chlorogenicacid,caffeicacid,
Ultrasound-assisted
HPLC-DAD ‘Penta’,‘Marcy’ gallicacid,p-coumaricacid, [15]
extraction
ferulicacid
Chlorogenicacid,caffeic,
4-hydroxybenzoic,p-coumaric,
HPLC-DAD ‘Diamond’ [87]
andtrans-o-hydroxycinnamic
acids
Chlorogenicacid,caffeicacid,
HPLC-DAD-MS ‘BlueBell’,‘Melody’ quinicacid,ferulicacid, [88]
cryptochlorogenicacid,rutin
Chlorogenicacid,caffeicacid,
HPLC-MS ‘Russet’ [42]
neochlorogenicacid
RP-HPLC Chlorogenicacid,caffeicacid,
‘BP1’ [44]
UV-DAD ferulicacid
Gallicacid,protocatechuicacid,
HPLC-DAD ‘Netherlands#7’ [69]
chlorogenicacid
Chlorogenicacid,caffeicacid,
gallicacid,protocatechuicacid,
HPLC-UV ‘Red’ [38]
syringicacid,ferulicacid,
coumaricacid
Microwave-assisted
extraction Chlorogenicacid,caffeicacid,
neochlorogenicacid,
HPLC-DAD ‘Calwhite’ [82]
cryptochlorogenicacid,ferulic
acid,p-coumaricacid
Pressurizedliquid HPLC-DAD ‘LadyClaire’ Caffeicacid [45]
extraction(PLE)+
solid-liquid HPLC-UV ‘Red’ Gallic,chlorogenicand [80]
extraction syringicacid
HPLC:HighPerformanceLiquidChromatography;UPLC:UltraPerformanceLiquidChromatography;DAD:
DiodeArrayDetector;UV:Ultravioletdetector;MS:massspectrometer.
Sonicationorultrasound-assistedextraction(UAE)isasimpleandefficientgreentechnologyfor
theextractionofphenoliccompoundsthatcouldbeusedasanalternativetoconventionalshaking
andwarmingsteps. Sonicationpermitsagreaterpenetrationofthesolventintothesamplematrix,
Int.J.Mol.Sci.2016,17, 835 9of19
increasingthecontactsurfaceareabetweenthesolidandliquidphase;asaresult,thesolutequickly
diffusesfromthesolidphaseintothesolvent,improvingtheextractionyield[55,89]. Also,UAEcan
providethepossibilityforimprovedextractionofheat-sensitivebioactivesandfoodcomponentsat
lowerprocessingtemperatures[90].
Theuseofmicrowave-assisted(MAE)extractionforfoodbioactiveshasincreasedsignificantlyin
recentyears[82,91–93]. InMAE,thedirecteffectofmicrowavesonmoleculesbyionicconductionand
dipolerotationpermitsanincreaseoftemperature,andbecauseofthatahighrecoveryofbioactive
compounds[94]. MAEisafast,selective,andenergy-savingmethodandrequiresloweramountsof
solventswhencomparedtoconventionalheatingmethods[82,95].
The pressurized liquid extraction (PLE) of phenolics has also been recommended as a green
extractiontechniqueforantioxidantsinpotatopeel[38,45]. Thistechnologyuseshighpressuresto
maintainwaterattemperaturesbetween100and374˝C;however,itrequirescomplexandhigh-cost
equipment in large-scale industrial extractions [82]. Nevertheless, the use of high temperatures
improvedthemasstransferandextractionrates,thusPLEgenerallyrequiresshorterextractiontimes
andalowerconsumptionoforganicsolventsthanconventionaltechniques[45,96].
Afterextraction,eventhoughtheanalysisofphenoliccompoundsisverychallengingduetothe
extensivediversityandreactivityofthesecompounds,novelseparationanddetectionmethods,suchas
hyphenatedtechniquesofhigh-performanceliquidchromatography(HPLC)withmassspectrometry
(MS),ultraviolet-visiblelight(UV-Vis),ornuclearmagneticresonance(NMR)spectroscopycanbe
usedsuccessfully[87,97]. Forthedeterminationoftotalphenoliccompoundsinthepotatotuberand
peel,themostcommonlyusedmethodistheFolin-Ciocalteumethod[70,74,98]. Ontheotherhand,
amongallthesemethodsHPLCisthemostfrequentlyusedfortheidentificationofindividualphenolic
compoundspresentinthepotato[13,18,31,38,80]. Thisanalyticaltechniqueacquiresahighdegreeof
versatilitynotfoundinotherchromatographicsystemsandallowsforseparatingawidevarietyof
chemicalmixtures[52].
5. UseofPotatoPeelExtractasanAntioxidant
Inthelastdecade,therehasbeenincreasingattentiongiventonewsourcesofnaturalantioxidant
phytochemicalsasaresultoftheirpotentialhealthbenefits,inadditiontotheirfunctionalproperties
intraditionallycommercializedproductssuchaspreservingcolorandflavorandhenceimproving
shelflife[99–101].
Lipidoxidationisoneofthemostimportantcausesoffoodqualitydeterioration;itgenerates
offodorsandoffflavors,decreasesshelflife,alterstextureandcolor,anddecreasesthenutritional
valueoffood[102]. Countlessmethodshavebeenintroducedtocontroltherateandextentoflipid
oxidationinfoods,buttheadditionofantioxidantsisoneofthemosteffective. Antioxidantshave
becomeacrucialgroupoffoodadditivesduetotheirabilitytoextendtheshelflifeoffoodswithout
anyadverseeffectontheirsensoryornutritionalqualities[32]. Generallysyntheticantioxidantssuch
asbutylatedhydroxytoluene(BHT)andbutylatedhydroxyanisole(BHA)areusedtocontroloxidation,
but these synthetic antioxidants are known to have carcinogenic and toxic effects on humans [16].
Therefore,theimportanceofreplacingsyntheticantioxidantswithnaturalingredientshasincreased
significantly[19].
Ontheotherhand,byproductsoffoodprocessingarealow-costrawmaterialfortheextraction
ofhealthycompoundssuchasdietaryfiber,naturalantioxidants,andnaturalfoodadditives[103].
Also,fruitandvegetablewasteandbyproductsarediscardedfrequentlyatacosttothemanufacturer.
Hence, useofthewasteasasourceofpolyphenolsmaybeofnoticeableeconomicbenefittofood
processors[101,104]. Inadditiontothis,sincetheconcentrationofphenoliccompoundsishigherin
thepeelthaninthepotatotuber,researchersgenerallyusedpeelsinsteadofusingthewholepotatofor
naturalfoodadditives[18,19,43].
Anumberofstudiesinvestigatedtheantioxidanteffectsofpotatopolyphenols(Table3). Most
ofthemsearchedfortheeffectondifferentoils[16,19,87]. KoduvayurHabeebullahetal.[16]used
Int.J.Mol.Sci.2016,17, 835 10of19
potatopeelextractforfishoilandoil-in-wateremulsionsandtheirresultsshowedthat‘Sava‘variety
potatopeelextractishighlyefficientatreducinglipidperoxidation. Inanotherstudyperformedby
Amadoetal.[18],ethanolicextractofpotatopeelwastewasusedtoevaluatetheabilitytolimitoil
oxidationand,accordingtotheresults,extracts(obtainedbyextractionwithamediumorhighethanol
concentration)wereabletostabilizesoybeanoilunderacceleratedoxidationconditions,minimizing
peroxide(PV),anisidine(AV),andtotoxvalues(TV)athightemperature.
Table3.Somematerialsinwhichpotatopeelswereusedasanantioxidantingredient.
Food PotatoType Criteria References
PotatoPeels(Solanum
ProcessedLambMeat tuberosumcv.‘Kufri TBARSandcarbonylcontent [43]
chandramukhi‘)
Potatopeels(Solanum Peroxidevalue,anisidinevalue,
Fish-RapeseedOilMixture
tuberosumcv.‘Sava‘ tocopherolconcentration,and [19]
andinOil-in-WaterEmulsions
and‘Bintje‘) sensoryevaluation
Potatopeels(Solanum
Soybeanoil,sunfloweroil Peroxidevalues,p-anisidine [16]
tuberosumcv.‘Diamond‘)
Peroxidevalue,volatiles,
carbonylcompounds,and
Mincedhorsemackerel PotatoPeels(Solanum
protectedagainstthelossof [9]
(Trachurustrachurus) tuberosum‘Sava‘variety
a-tocopherolandtryptophan
andtyrosineresidues
Potatopeelsandtubers
GroundSalmon (‘Purple‘,‘Innovator‘, TBARS [8]
‘Russet‘and‘Yellow‘)
Bothprimary(hydroperoxides)
Potatopeels(Solanum
Sunfloweroil andsecondaryoxidation [87]
tuberosumcv.‘Diamond‘)
products
Peroxide,totoxand
Soybeanoil Potatopeel(Agria) [18]
p-anisidinevalues
TBARS,Thiobarbituricacidreactivesubstances.
Therearesomestudiesthatcomparetheantioxidantactivityofpotatopeelextract(PPE)with
commercialantioxidants. Kanattetal.[43]foundthattheantioxidantactivityofPPEiscomparableto
butylatedhydroxytoluene(BHT).Also,Mohdalyetal.[87]estimatedtheantioxidanteffectofpotato
peelbymeasuringbothprimary(hydroperoxides)andsecondaryoxidationproducts,andcomparing
them with sesame cakes and sugar beet pulp in terms of the effect on sunflower oil. The results
showedthatpotatopeelsdisplayedmoreantioxidativeeffectthansesamecakeandsugarbeetpulp,
performingaswellassyntheticantioxidants(BHTandBHA).Albishietal.[8]alsofoundthatRusset
potatopeelwasmoreeffectiveininhibitingtheformationofTBARSthanBHA.
Someresearchersusedpotatopeelstolimitthelipidoxidationinmeat[8,9,43]. Kanattetal.[43]
addedpotatopeelextracttomeatbeforeirradiation;theextractwasabletoretardlipidperoxidation
withoutaffectingitsflavor/aroma,therebyimprovingitsstoragequality. Inastudyperformedby
Habeebullah et al. [9], potato peel was used in minced mackerel, a fatty fish particularly high in
n-3PUFA,asanaturalantioxidantsourceforretardinglipidandproteinoxidation[105]. Theresults
suggest that ethanol extracts of potato peel can be used as a natural additive to prevent lipid and
protein oxidation in chilled storage. Albishi et al. [8] also indicated that potato peel extracts were
efficientininhibitingtheoxidationofcookedsalmon;infact,thecontrolsamplesshowedhighTBARS
values after seven days of storage. On the other hand, more studies are needed to support this
hypothesisandextendtheutilizationoftheseextractsinfoods(suchasmeatandfishproducts)where
acomplexmixtureofproteins,lipids,pro-oxidants,andendogenousantioxidantsarepresent.