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Impact of Wall Materials on Physico-Chemical Properties and Stability of Eggplant Peels Anthocyanin Hydrogels

Authors:
Nina Nicoleta Lazar at Universitatea Dunarea de Jos Galati
Nina Nicoleta Lazar
Mihaela Turturica at Universitatea Dunarea de Jos Galati
Mihaela Turturica
Elena Enachi at Universitatea Dunarea de Jos Galati
Elena Enachi
Vasilica Barbu at Universitatea Dunarea de Jos Galati
Vasilica Barbu
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Abstract and Figures

In this study, eggplant peel extract was used to obtain hydrogels. Two experimental variants were realized by varying the wall materials. Whey proteins isolate (WPI), citrus pectin (P), and sodium carboxymethylcellulose (CMCNa) were used as wall materials. The microcapsules were obtained by the gelation technique, followed by freeze-drying in order to obtain powders. Both experimental variants were analyzed in terms of phytochemical content, antioxidant activity, storage stability, and in vitro digestibility. Additionally, confocal microscopy was used to observe the encapsulation of the bioactive compounds from the eggplant peel extract into the selected matrices. The encapsulation efficiency of the powders varied from 64.67 ± 0.68% for variant 1 (V1) to 96.44 ± 3.43% for variant 2 (V2). Both powders presented high bioactive compound content with high antioxidant activity. V2 showed the highest stability within 28 days of storage, but also in the simulated digestive system.
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Inventions2021,6,47.https://doi.org/10.3390/inventions6030047www.mdpi.com/journal/inventions
Article
ImpactofWallMaterialsonPhysico‐ChemicalPropertiesand
StabilityofEggplantPeelsAnthocyaninHydrogels
Nina‐NicoletaCondurache(Lazăr)
1
,MihaelaTurturică
1
,ElenaEnachi
1
,VasilicaBarbu
1
,Gabriela‐ElenaBahrim
1
,
NicoletaStănciuc
1
,ConstantinCroitoru
2
andGabrielaRâpeanu
1,
*
1
FacultyofFoodScienceandEngineering,DunăreadeJosUniversityofGalati,DomneascăStreet111,
800201Galati,Romania;nina.condurache@ugal.ro(N.‐N.C.);mihaela.turturica@ugal.ro(M.T.);
elena.ionita@ugal.ro(E.E.);vasilica.barbu@ugal.ro(V.B.);gabriela.bahrim@ugal.ro(G.‐E.B.);
nicoleta.stanciuc@ugal.ro(N.S.)
2
AcademyofAgriculturalandForestrySciences,61MarastiBlvd,011464Bucharest,Romania;
c.croitoru@sodinal.com
*Correspondence:gabriela.rapeanu@ugal.ro;Tel.:+4-0336-130-177
Abstract:Inthisstudy,eggplantpeelextractwasusedtoobtainhydrogels.Twoexperimental
variantswererealizedbyvaryingthewallmaterials.Wheyproteinsisolate(WPI),citruspectin(P),
andsodiumcarboxymethylcellulose(CMCNa)wereusedaswallmaterials.Themicrocapsules
wereobtainedbythegelationtechnique,followedbyfreeze‐dryinginordertoobtainpowders.
Bothexperimentalvariantswereanalyzedintermsofphytochemicalcontent,antioxidantactivity,
storagestability,andinvitrodigestibility.Additionally,confocalmicroscopywasusedtoobserve
theencapsulationofthebioactivecompoundsfromtheeggplantpeelextractintotheselectedma‐
trices.Theencapsulationefficiencyofthepowdersvariedfrom64.67±0.68%forvariant1(V1)to
96.44±3.43%forvariant2(V2).Bothpowderspresentedhighbioactivecompoundcontentwith
highantioxidantactivity.V2showedthehigheststabilitywithin28daysofstorage,butalsointhe
simulateddigestivesystem.
Keywords:eggplantpeels;bioactivecompounds;hydrogels;anthocyanins
1.Introduction
Theagro‐foodindustriesgenerateannuallyoverwhelmingamountsofwastesby
theprocessingofvariousvegetablesandfruits[1].Untilafewyearsago,foodwaste
disposalwasnotamatterofconcern.However,theincreasingamountsofwastegener‐
atedandtheenvironmentalissuescausedbythemhavedrawnattention.Currently,
variousorganizationsaroundtheworldaretryingtofindsolutionstominimizefood
wasteswithlowereconomiccosts[2].Duetothehighcontentofproteins,lipids,sugars,
fibers,pectin,orphytochemicalcompounds,thefoodwastescanbetheidealsourcefrom
whichvalue‐addedfoodscanbeobtainedforfeedingthegrowingpopulation.Their
valorizationinvalue‐addedfoodproductsrepresentsanadvantageouswayofmanaging
thewastesproblems,turningthemfromwastesintoby‐products[1,2].
Thefruitandvegetableprocessingindustrygeneratesby‐productsespeciallyrichin
naturalantioxidants,suchaspolyphenols.Thesecompoundsareappreciatedfortheir
nutritionalandfunctionalproperties.Aregularintakeofphenoliccompoundsappearsto
reducetheriskfordevelopingcoronaryheartdisease,hypertension,diabetes,obesity,
gastrointestinaldiseases,etc.[3].Theirantioxidantactivitydelaystheformationof
off‐flavorsandrancidityinfoodproducts,makingthemtheperfectnaturalpreserva‐
tives.Theycanalsobeusedasnaturalpigmentsforfoodandbeveragecoloringorin
cosmeticsandnutraceuticals[4].
Citation:Condurache,N.‐N.;
Turturica,M.;Enachi,E.;Barbu,V.;
Bahrim,G.‐E.;Stanciuc,N.;
Croitoru,C.;Rapeanu,G.Impactof
WallMaterialsonPhysico‐Chemical
PropertiesandStabilityofEggplant
PeelsAnthocyaninHydrogels.
Inventions2021,6,47.https://doi.org/
10.3390/inventions6030047
AcademicEditors:FaridChemat
Received:10June2021
Accepted:28June2021
Published:29June2021
Publisher’sNote:MDPIstays
neutralwithregardtojurisdictional
claimsinpublishedmapsand
institutionalaffiliations.
Copyright:©2021bytheauthors.
LicenseeMDPI,Basel,Switzerland.
Thisarticleisanopenaccessarticle
distributedunderthetermsand
conditionsoftheCreativeCommons
Attribution(CCBY)license
(http://creativecommons.org/licenses
/by/4.0/).
Inventions2021,6,472of12
Aubergine,oreggplant,thenameunderwhichitisknownworldwide,isa
non‐tuberousSolanaceaefamilyvegetable.Solanummelongenaisatropicalfruitwithmul‐
tipleshapes,sizes,andcolors,andisveryperishableyetverytasty.Themostcommer‐
ciallyimportantoneisthepurplevariety(SolanummelongenaL.)duetotheanthocyanins
locatedinthepeels[5].
Theanthocyaninsareflavonoidswithred,blue,andpurplecolorsinfruits,vegeta‐
bles,andflowers.Theirbasicstructureiscomposedofaflavyliumcationtowhichdif‐
ferentsugars,hydroxylormethoxylgroupsareattached[6].Ofallthephenoliccom‐
pounds,anthocyaninsarethemostsensitive.TheyeasilydegradeathigherpH,temper‐
atures,oratprolongedexposuretolight,oxygen,enzymes,etc.[7].Theanthocyaninsare
alsosensitivetothedigestivesystemconditions,especiallywhenconsumedseparately
fromtheoriginalfoodmatrix,withonly1–2%oftheingestedamountbeingabsorbed[8].
Thelatestresearchesproposeencapsulationasamethodofincreasingthebioavailability
andbioaccessibilityofanthocyanins.Whenchoosingthesuitableencapsulationmethod,
thepropertiesofthebioactivecompound,encapsulatingmaterial,anddesiredfinal
productmustbetakenintoaccount[9].
Thepresentstudyaimedtoobtainfunctionalingredientsfromeggplantpeelsbio‐
activesforfoodornutraceuticalsapplications.Toextractthephenoliccompoundsfrom
theeggplantpeels,theultrasound‐assistedextraction(UAE)methodwasapplied.The
extractwascharacterizedintermsofphytochemicalcontentandantioxidantactivity.
Further,theextractwasusedforencapsulationbythegelationtechnique,followedby
freeze‐dryinginordertoobtainpowders.Sodiumcarboxymethylcellulose(CMCNa),
pectin(P),andwheyproteinisolate(WPI)wereusedaswallmaterialsindifferentcon‐
centrationsduetotheirabilitytoformhydrogelswiththree‐dimensionalnetworks.The
twoexperimentalvariantsresultingwereanalyzedintermsofencapsulationefficiency
(EE),totalanthocyanincontent(TAC),totalflavonoidcontent(TFC),totalpolyphenol
content(TPC),andantioxidantactivity.Themicrostructureofthepowderswasanalyzed
byconfocalscanninglasermicroscopy(CLSM).Theevolutionofphytochemicalsduring
thestoragestabilitytestwasalsomonitoredfor28days.Theinvitroreleaseprofileofthe
TACandantioxidantactivityundersimulatedgastricandintestinaljuiceswasalsoper‐
formed.
2.MaterialsandMethods
2.1.Materials
Wheyproteinisolate(proteincontentof95%)fromFonterra(NewZeeland).Ethanol
96%(EtOH)fromTitolchimica(Italy).HPLCpuritymethanol(MeOH),
2,2‐diphenyl1‐picrylhydrazyl(DPPH),glacialaceticacid(CH3COOH),sodiumnitrite
solution(NaNO2),potassiumchloridesolution(KCl),sodiumacetatesolution
(CH3COONa),aluminumchloride(AlCl3),sodiumhydroxide(NaOH),sodiumcarbonate
(Na2CO3),applepectin,sodiumcarboxymethylcellulose(CMCNa),
6‐hydroxy‐2,5,7,8‐tetramethylchromane‐2‐carboxylicacid(Trolox),Folin–Ciocâlteurea‐
gent,gallicacid,hydrochloricacid(HCl),sodiumbicarbonate(NaHCO3),Trizmabuffer,
thestandardsusedfortheHPLCanalysis,delphinidin3‐O‐glucoside,delphinidin
3‐O‐rutinoside,andcyanidin3‐O‐rutinosidewereobtainedfromSigma‐AldrichStein‐
heim,Germany.
2.2.Methods
2.2.1.BiologicallyActiveCompoundsExtraction
TheSolanummelongenaL.autochthonousvarietyfruitswerepurchasedfromalocal
marketinGalați,Romania.Thepurpleouterlayerofthefruitwerepeeledinuniform
strips,washedwithultrapurewater,driedwithpapertowels,andfrozen.Subsequently,
thepeelswerefreeze‐drieduntil90%dryweight(dw),at−42°C,underapressureof0.10
mBar,withaCHRISTAlpha1‐4LDplusequipment(Germany)for48h.
Inventions2021,6,473of12
ThebiologicallyactivecompoundswereextractedusingtheUAEmethoddescribed
byConduracheetal.[10].Briefly,1goffreeze‐driedeggplantpeelswasmixedwith15
mLofasolventmixturecomposedofEtOH96%andglacialaceticacid,ina4:1ratio.The
mixturewasexposedfor15mintoultrasoundsata40kHzfrequencyand25°Cona
Smartsoniccleanerultrasonicbath(MRC.LTD,Israel).Further,theextractswerecen‐
trifugedfor10minat14,000rpmand4°C.Theresultingsupernatantwasconcentratedto
drynessunderreducedpressureat40°C(AVC2‐18,Christ,ShropshireUK),andfinally
phytochemicallyanalyzed.
2.2.2.ExtractCharacterization
Theextractwascharacterizedintermsofyieldofextraction,TAC,TFC,TPC,and
antioxidantactivity,asdescribedbyTurturicăetal.[11].Inbrief,theTACsof10mg/mL
eggplantpeels’extractinultrapurewaterwerequantifiedusingthepHdifferential
method,andtheresultswereexpressedasmgdelphinidin3‐O‐glucoside(D3G)/gdw
[11].TheTFCwasanalyzedusingthecolorimetricmethodbasedonthecapacityofAlCl3
toformstablecomplexeswiththeflavonesorflavonols.Theresultswereexpressedas
mgcatechinequivalent(CE)/gdw[11].TheTPCswerequantifiedusingthecolorimetric
methodwiththeFolin–Ciocâlteureagent,andtheresultswereexpressedasmggallic
acidequivalents(GAE)/gdw[11].Thefreeradicalscavengingactivityoftheextractwas
measuredusingtheDPPH,andtheresultswereexpressedasmMtroloxequivalents
(TE)/gdw[11].Theyieldofextractionwascalculatedusingformula(1)asdescribedby
Sweretal.[12]:
EY=௘௫௧௥௔௖௧ ௪௘௜௚௛௧
௘௚௚௣௟௔௡௧ ௣௘௘௟௦ ௪௘௜௚௛௧×100(1)
2.2.3.HPLCAnalysisoftheAnthocyanins
Thechromatographicanalysisoftheanthocyaninsfoundineggplants,including
separation,identification,andquantification,wasmadebytheslightlymodifiedmethod
describedbyTurturicaetal.[11].TheusedHPLCsystemwasaThermoFinniganSur‐
veyorcontainingadiodearraydetectorandXcalibursoftware(FinniganSurveyorLC,
ThermoScientific,Waltham,MA, USA).Thevolumeusedfortheinjectionofthesamples
was20μLwithaflowrateof1.0mL/min.Beforetheinjection,thesampleswerefiltered
using0.22μmsyringefilters.Allstandardcompoundsusedinthisstudywereacquired
fromSigma‐Aldrich(Darmstadt,Germany)andwereofhighpurity(>95.0%).
2.2.4.EncapsulationoftheBiologicallyActiveCompoundsfromtheEggplantPeelEx‐
tract
Thebiologicallyactivecompoundsfromtheeggplantpeels’extractwereencapsu‐
latedinhydrogelsusingthemethoddescribedbySerrano‐Cruzetal.[13]withslight
modifications.Thehydrogelsare3Dnetworksmadefrompolymericchainscross‐linked
byphysicalorchemicalbonds,havingahighaffinityforwater[14].Inourstudy,two
experimentalvariantswereobtainedusingCMCNa,P,andWPIaswallmaterial.Forthe
firstvariant(V1),1.5%P,1.5%CMCNa,and3%WPIweredispersedinultrapurewater
duringtheagitationonamagneticstirrer(IKARCTBasic,StaufenGermany)for6hat45
°Cand450rpm.Forthesecondvariant(V2),2.25%P,2.25%CMCNa,and1.5%WPIin
ultrapurewaterwerealsohydratedfor6hat45°Cand450rpmontheheatingmagnetic
stirrer(Figure1).Bothvariantswereallowedtostandat4°Covernighttoensurethefull
hydrationofthewallmaterials,afterwhich25mg/mLofextractwasaddedineach
mixtureandhomogenizedfor2hat25°Cand450rpm.ThemeasuredpHofthemix‐
tureswas2.5duetotheextract.Thesampleswerefrozenat−80°C.Further,themixtures
werefreeze‐driedtoobtainstablepowderswithaAlpha1‐4LDplusequipment
(CHRIST,Osterode am Harz,Germany)for48h,at−42°Cunderapressureof0.10mBar
Inventions2021,6,474of12
untila94.37%dwforV1and96.31%dwforV2.Finally,thepowderswerecollectedand
packedinplastictubeswithlightprotectionandstoredat4°Cforlateranalyses.
V1
100mLultrapurewater
+1.5%P
+1.5%CMCNa
+3%WPI
Solubilization6h,45°C,450rpm
Overnightrest,4°C,dark
+25mg/mLeggplantpeelextract
Solubilization2h,25°C,450rpm
Freezing−80°C
Freeze‐drying48h,−42°C,0.10mBarpres‐
sure,94.37%dw.
V2
100mLultrapurewater
+2.25%P
+2.25%CMCNa
+1.5%WPI
Solubilization6h,45°C,450rpm
Overnightrest,4°C,dark
+25mg/mLeggplantpeelextract
Solubilization2h,25°C,450rpm
Freezing−80°C
Freeze‐drying48h,−42°C,0.10mBarpres‐
sure,96.31%dw.
Figure1.Theeggplantpeelextractencapsulationschemeusingthegelationtechnique.
2.2.5.PowderCharacterization
TheobtainedpowderswerephytochemicallyanalyzedintermsofinitialTAC,TFC,
TPC,andantioxidantactivity[11].Theencapsulationefficiency(EE)oftheanthocyanins
wasalsocalculatedbymeasuringtheTACandthesurfaceanthocyaninscontent(SAC)as
describedbyConduracheetal.[15].
TomeasuretheTAC,TFC,TPC,andantioxidantactivity,200mgofeachpowder
wasmixedwith7mLofmethanol/glacialaceticacid/distilledwater(25:4:21v/v/v).The
mixtureswerevortexedfor1minandsonicatedfor30minat25°Cand40kHzusingan
ultrasonicbath(MRC.LTD,Holon,Israel).Further,thesampleswerecentrifugedat14
000rpmfor10minat4°C,andthesupernatantwasanalyzed.
TheEErepresentsthecontentofanthocyaninsencapsulatedinthematrix,andit
wascalculatedasapercentageratiobetweenTACandsurfaceanthocyanincontent
(SAC).TheSACwasmeasuredbymixing200mgofeachpowderwith7mLofetha‐
nol/methanol(1:1v/v),vortexingfor1min,andcentrifugingat14,000rpmfor10minat4
°C.TheresultingsupernatantswereanalyzedusingthepHdifferentialmethod[11].The
EEwascalculatedusingEquation(2).
%EE=ሺ்஺஼ିௌ஺஼ሻ
்஺஼ x 100(2)
TAC—TotalAnthocyaninContent;SAC—SurfaceAnthocyaninContent.
2.2.6.StorageStability
TheencapsulatedpowderswereevaluatedregardingtheTAC,TFC,TPC,andan‐
tioxidantactivityduringstorageatroomtemperatureinplastictubeswithlightprotec‐
tion.ThebiologicallyactivecompoundswereextractedasdescribedinSection2.2.5.
Powdercharacterizationandthephytochemicalswereanalyzedafter28daysofstorage.
2.2.7.ConfocalLaserScanningMicroscopy(CLSM)
TheConfocalLaserScanningMicroscopytechniquewasusedtoobservetheen‐
capsulationprocessoftheeggplantpeelextracts’bioactiveswithintheselectedmatrices.
Inventions2021,6,475of12
Asananalysismethod,confocalmicroscopyallowsthemorphologyandstructureob‐
servationwithoutthefragmentationofthetargetedmicroparticles.CLSMwasper‐
formedusingaZeissconfocallasersystem(LSM710)equippedwithadiodelaser(405
nm),Ar‐laser(458,488,514nm),DPSSlaser(diodepumpedsolidstatee561nm)and
HeNe‐laser(633nm).TheobtainedpowderswerefluorescentlystainedwithRedCongo
(40μM),andthedistributionofthebioactivesintothepowdermatrixwasobservedus‐
ingaZeissAxioObserverZ1invertedmicroscopeequippedwitha40xapochromatic
objective(numericalaperture1.4).Furthermore,theFS49,FS38,andFS15filterswerealso
usedfortheanalysis.The3Dimageswererendered,classified,andanalyzedwiththe
ZEN2012SP1software(blackedition).
2.2.8.PowdersBehaviorinSimulatedDigestion
Thesimulatedgastrointestinaldigestionofthepowderswasperformedaccordingto
Oanceaetal.[16],at37°Cand150rpmonanSI‐300Rorbitalshakingincubator(Medline
Scientific,Chalgrove,UK).Thestaticmodelthatsimulatesthedigestioninthestomach
wasperformedtomeasurethebioavailabilityoftheanthocyaninsandtheantioxidant
activityfromthetwovariantsofpowders.Thegastricdigestionwasperformedfor2h
usingsimulatedgastricfluid(SGF)thatcontainedporcinepepsin(40mg/mLin0.1M
HCl)atapH=2.00.Theintestinaldigestionwasperformedusingintestinalfluid(SIF)
with2mg/mLpancreatinatPh=5.3.ThereleasewascalculatedusingEquation(3):
%Release=୧୬୧୲୧ୟ୪ ୡ୭୬ୡୣ୬୲୰ୟ୲୧୭୬
ୢ୧୥ୣୱ୲ୣୢ ୡ୭୬ୡୣ୬୲୰ୟ୲୧୭୬ ൈ 100(3)
2.2.9.StatisticalAnalysisofData
ThestatisticalanalysisofdatawasperformedusingtheMinitab17StatisticsSoft‐
ware.ThedifferencesbetweenthesampleswereassessedusingtheTukeytestwiththe
One‐wayANOVAmethod.Alltheexperimentswerecompletedintriplicates,andthe
resultswereexpressedasaveragevalueswithastandarddeviation.
3.Results
3.1.EggplantPeelExtractCharacterization
Eggplantpeelsarerichinbiologicallyactivecompounds,mainlyinanthocyanins.In
thepresentwork,thebioactivesfromtheeggplantpeelswereextractedusingtheUAE
method,withethanolasasolvent.Thiscombinationbetweenthemethod,solvent,and
acidhada74.79%extractionyield.Theobtainedextractwasanalyzedintermsofphy‐
tochemicalcontentandantioxidantactivity,andtheresultsarepresentedinTable1.The
extracthighlightedaTACof0.35±0.07mgC3G/gdw,aTFCof2.99±0.12mgCE/gdw,
andaTPCof12.79±0.66mgGAE/gdw.TheDPPHscavengingcapacityoftheextract
presented193.14±1.25mMTE/gdw.
Hosseinietal.[17]presentedaTACof0.43± 1.24mgD3G/gfwandaTPCof2.07±
4.20mgGAE/gfwaftertheconventionalextractionofbioactivesfromeggplantpeels
usingwater/ethanol/aceticacidina50:48:2ratio.Onthecontrary,Horincaretal.[18]
reportedhigherTAC,TFC,andTPCvaluesthanoursafterusingacidifiedethanolforthe
UAEextractionoftheeggplantpeelsbioactives.However,theantioxidantactivityon
DPPHfreeradicalreportedbythempresentedlowervaluesthanourextract.Jungetal.
[19]extractedthephenolicsfromdifferentpartsofeggplantandreportedaTPCcontent
of55.19±1.30mgGAE/gextractandTFCof6.19±0.28mgCE/gextract.Thedifferences
betweenourresultsandtheotherstudies’resultsareduetothephytochemicalvariabil‐
ityfromtherawmaterialandextractionconditions.Though,theobtaineddatafromTa‐
ble1confirmthattheeggplantpeelsarearichsourceofbiologicallyactivecompounds,
especiallyanthocyanins.

Inventions2021,6,476of12
Table1.Thephytochemicalcontentoftheeggplantpeelextract.
Phytochemical
Content
TAC
mgD3G/gdw
TFC
mgCE/gdw
TPC
mgGAE/gdw
AntioxidantActivity
mMTE/gdw
Eggplantpeelextract0.35±0.072.99±0.1212.79±0.66193.14±1.25
TAC=totalanthocyanincontent;TFC=totalflavonoidcontent;TPC=totalpolyphenolcontent;D3G=delphinidin
3‐O‐glucoside;CE=catehinequivalent;GAE=gallicacidequivalent;TE=troloxequivalent;dw=dryweight.
3.2.HPLCAnalysisoftheAnthocyanin
Inordertoachievethecharacterizationoftheeggplantanthocyaninprofileachro‐
matographicanalysiswasperformedbyusingtheHPLCtechnique(Figure2).Theiden‐
tificationandthequantificationofanthocyaninweremadedependingontheretention
timeandbycomparisonwiththeavailablestandardsandthedataexistingalreadyinthe
literature.
Theanthocyaninidentificationwasmadeat520nm,andthechromatographic
analysisrevealedthepresenceof11compounds:delphinidin3‐O‐rutinoside‐5‐glucoside
(Peak1),delphinidin3‐O‐glucoside(Peak6),delphinidin3‐O‐rutinoside(Peak8),cya‐
nidin3‐O‐rutinoside(Peak10),andpetunidin3‐O‐rutinoside(Peak11),whereaspeaks
2—5,7,and9wereunidentified.
Figure2.Chromatographicprofileofeggplantpeelextracts:Peak1—delphinidin
3‐O‐rutinoside‐5‐glucoside;Peak2—5:unidentified;Peak6—delphinidin3‐O‐glucoside;Peak
7—unidentified;Peak8—delphinidin3‐O‐rutinoside;Peak9—unidentified;Peak10—cyanidin
3‐O‐rutinoside;Peak11–petunidin3‐O‐rutinoside.
Theeggplantpeelextract(Figure2)revealedthatdelphinidin3‐O‐glucosideisthe
majoranthocyaninidentified,havingaconcentrationof82.51%.Theseresultsarein
agreementwiththoseobtainedbyAzumaetal.[20].Theymanagedtoidentifydel‐
phinidin3‐O‐rutinosideandnasuninasbeingthemajorcompoundsfoundintheegg‐
plantextract.Delphinidin3‐O‐rutinosidefolloweddelphinidin3‐O‐glucosideclosely,
withaconcentrationof66.94%.Theotheridentifiedanthocyanincompoundsvariedin
termsofconcentration,suchas:delphinidin3‐O‐rutinoside‐5‐glucoside—11.57%,cya‐
nidin3‐O‐rutinoside—5.08%,andpetunidin3‐O‐rutinoside—2.14%.Intheirstudies,Fe‐
rarsaetal.[21],Drancaetal.[22],andMauroetal.[23]managedtoseparateandidentify
onlyfiveanthocyaninsfromeggplantpeelextracts.Inourresearchconductedsofar,we
highlightedthatthemajoranthocyaninfoundineggplantisdelphinidin3‐O‐rutinoside.
Thisstudyrevealedahighconcentrationofdelphinidin3‐O‐glucoside.Thedifference
betweenthetwoisexplainedbyMauroetal.[23],therebypassingtodifferentstagesof
ripening,thedelphinidin3‐O‐rutinosideconcentrationindifferenteggplantcultivars
showasignificantdecrease.
0
50,000
100,000
150,000
200,000
250,000
300,000
0 5 10 15 20
Absorbanceat520nm,μAU
Time,minutes
12345
6
7
8
910 11
Inventions2021,6,477of12
3.3.EncapsulationEfficiencyandPowdersCharacterization
Theencapsulationefficiencyreferstothepotentialofwallmaterialtoentrapand
holdthecorematerialinsidethecapsule[24].Inourstudy,differentwallmaterialcon‐
centrationscausedsignificantdifferencesintheanthocyaninencapsulationefficiencies,
aspresentedinTable2(p<0.05).Thus,theencapsulationefficiencysignificantlyin‐
creasedwiththepolysaccharidesconcentration,rangingfrom64.67±0.67%forV1to
96.44±3.43%forV2(p<0.05).Ourresultsareinagreementwithotherstudies.Condu‐
racheetal.[15]reportedencapsulationefficienciesoftheeggplantpeelanthocyaninsin
CMC,P,andWPIrangingfrom69%to77%.Inthisstudy,anincreaseintheencapsula‐
tionefficiencywasalsoobservedwiththeincreaseoftheCMCconcentration.
HigherCMCandPconcentrationsalsoledtohigheranthocyanincontententrapped
inthepowders.Thus,V2presentedasignificantlyhigherTACthanV1(p<0.05).Onthe
contrary,significantlyhigherTPCandantioxidantactivityvalueswereobtainedforthe
variantwithhigherWPIconcentration(p<0.05).TheTFCwasnotsignificantlydifferent,
regardlessofthepowdervariant(p>0.05).AnoppositebehaviorwasreportedbyStan‐
ciucetal.[25],whoobtainedhigherpolyphenolconcentrationsandantioxidantactivities
forhigherpectinconcentrationsingrapeskinbioactive‐containingpowders.
However,fromTable2,itcanbeobservedthatbothpowdervariantsshowedhigh
encapsulationefficiencieswithhighantioxidantactivities.Thisleadsustoconcludethat
thewallmaterialcombinationssuccessfullyencapsulatedthephytochemicalsfromthe
eggplantpeelextract.
Table2.Characterizationoftheencapsulatedeggplantpeelsextract.
Phytochemical
Content
TAC
μgD3G/gdw
TFC
mgCE/gdw
TPC
mgGAE/gdw
AntioxidantActivity
mMTE/gdw
Encapsulation
Efficiency%
V150.41±2.13a1.53±0.06a8.03±0.18a41.96±0.28a64.67±0.67a
V294.94±7.94b1.64±0.14a7.22±0.18b36.60±0.83b96.44±3.43b
Foreachtestedphytochemicalandpowdervariant,valuesfromthesamecolumnthatdonotsharealetterarestatistically
differentatp<0.05basedontheTukeymethodand95%confidence.TAC—TotalAnthocyaninContent;TFC—Total
FlavonoidContent;TPC—TotalPolyphenolContent.
3.4.StorageStabilityofthePowders
Thepowderswerestoredatroomtemperaturefor28daysandwerecharacterizedin
termsofphytochemicalcontentandantioxidantactivity.ThechangesinTAC,TFC,TPC,
andantioxidantactivityofbothpowdervariantsduringstorageareshowninFigure3.
TheTACandTFCofbothpowdervariantsdidnotsignificantlychangeduringthe
28daysofstorage(p>0.05).Instead,theTPCofV2presentedasignificantincrease(p<
0.05),whiletheTPCofV1remainedconstant.Regardingtheantioxidantactivity,V1
showedsignificantlylowervaluesafter28daysofstorage,whileV2presentedsignifi‐
cantlyhighervaluesthantheinitialvalues(p>0.05).Similarbehaviorwasalsoreported
byMoseretal.[26].Theysuggestedthatthemicroencapsulationofgrapejuicecombined
withstorageatlowtemperaturesofferedstoragestabilitytotheanthocyanins.Onthe
contrary,Azarpazhoohetal.[27]reportedadecreaseintheTACofthepomegranate
peelsbioactivesmicroencapsulatedpowderastheperiodofstorageincreased.
However,fromFigure3,itcanbeobservedthatbothvariantsshowedlowantioxi‐
dantactivitiesandphytochemicalcontentvariationintime.Thisleadsustoconclude
thattheusedcombinationbetweenCMC,P,andWPIsuccessfullyencapsulatedthean‐
thocyaninsfromeggplantspeelextract,providingthemgoodstability.
Inventions2021,6,478of12

(a)(b)
(c)(d)
Figure3.TheTAC(a),TFC(b),TPC(c),andantioxidantactivity(d)stabilityoftheencapsulatedpowdersafter28daysof
storageatroomtemperature.Foreachtestedphytochemicalandpowdervariant,columnsthatdonotsharealetterare
statisticallydifferentp<0.05.TAC—TotalAnthocyaninContent;TFC—TotalFlavonoidContent;TPC—TotalPolyphenol
Content.
3.5.MorphologicalStructureofthePowders
Confocalmicroscopyisanexcellenttooltoinvestigatethemorphostructuralfea‐
turesofmicroencapsulatedpowders.UsingtheLSM710point‐by‐pointscanning
equipment,withtheDPSS(561nm)andHeNe(633nm)lasersandthecorresponding
filters(FS38WFandFS15WF,respectively),thesampleswereanalyzedinboththeirna‐
tiveform(toobservetheautofluorescenceemissionofthephytopigmentsfromtheegg‐
plantextracts)aswellasafterstainingofthesampleswithCongoRed,whichhasanaf‐
finityfortheproteincomponentofthemicroencapsulatingmatrix.Thus,thebioactives
fromtheeggplantexocarp,byencapsulation,generatedadigitiform,lacedappearancein
theV1variant(Figure4a)orcompactirregularscalesintheV2variant(Figure4b).In‐
terestingly,thesameplantextractdisplayeddifferentautofluorescentpropertiesde‐
pendingontheproportionofbiopolymersusedforthemicroencapsulatingmatrix,
probablyduetothetransientbondscreated.ThehigherpercentageofWPIintheV1
variantdeterminedaframeshiftoftheemissiontotherangeof640–680nm,whileinthe
presenceofamatrixricherinpolysaccharides(V2),theemissionspectrumofthephy‐
topigmentsintheextractappearedinthegreen‐yellowdomain(520–540nm).Similar
resultswereobtainedbyChanocaetal.[28]in2016whousedfluorescencelifetimemi‐
croscopytostudythesubcellularlocalizationofanthocyaninsinplantcells[28].Byla‐
belingwithCongored(Figure4c,d),thepowdersformedmoreorlesshomogeneous
biofilms.IntheWPInetwork(inred)predominantintheV1samplematrix,alargedi‐
versityofbioactives(ingreen)wasobserved(Figure4c).AstheWPIcontentdecreased
andthecontentofcarbohydratepolymersinthematrixincreased,thepowderbecame
morehydrophilic,finer,andmorehomogeneous,andthefluorescentlabelingwith
Congoredwasweaker.
aa
b
b
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100
150
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TAC,μgD3G/gdw
Time,days
V1
V2
aa
bb
0
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028
TFC,mgEC/gdw
Time,days
V1
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c
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TPC,mgGAE/gdw
Time,days
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cd
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mMTE/gdw
Time,days
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V2
Inventions2021,6,479of12
Figure4.Confocallaserscanningimagesofthemicroencapsulatedpowders:V1(a—native,
c—stained)andV2(b—native,d—stained).
3.6.PowdersBehaviorinSimulatedDigestion
Theanthocyaninshavethelowestbioavailabilityamongpolyphenols,withonly1–
2%ofthembeingabsorbedbythehumanbody.Theirabsorptionisaffectedbythe
physicochemicalconditionsfromthegastrointestinaltract,suchaspH,enzymes,and
microbiota[29].Thecombinationbetweenatop‐downmethodsuchasgelationanda
bottom‐upmethodsuchasfreeze‐dryingcanrepresentasolutiontoassureanintelligent
deliverysystemfortheeggplantpeelanthocyanins.
Inourstudy,theencapsulatedpowders’behaviorwasstudiedundersimulated
gastricandintestinalconditions.Theresultsobtainedfortheinvitrodigestibilityin
simulatedgastricfluid(SGF)showedthattheencapsulationmethodsandtheselected
coatingmaterialspresentedaprotectiveeffectontheanthocyaninrelease.InFigure5a,
weobservedaremarkableanthocyanincontentstability,withonly3%and7%releasefor
V1andV2,respectively,after120minofgastricdigestion.Aftertheintestinalfluidwas
added,anacceleratedanthocyaninreleasefromthematriceswasobserved(Figure5b).
Thus,theanthocyaninsfromV1completelyreleasedafteronly60min.ForV2instead,
theanthocyaninsstartedtograduallyreleaseintime.Thus,after30minofdigestion,half
oftheanthocyaninswerereleasedfromthematrix,reachingcompletereleaseafter120
minofdigestion.Itcanbenoticedahigheranthocyaninprotectiveeffectbythematrix
containinghigherCMCNaandPconcentration.
Conduracheetal.[15]reportedahighprotectiveeffectoftheanthocyaninsfrom
eggplantpeelsencapsulatedwithproteinsandpolymers,withamaximumof42%intes‐
tinalrelease.Instead,HuangandZhou[30]reportedthatacompletereleaseoftheen‐
capsulatedanthocyaninsfromblackriceoccurredafter20minofintestinaldigestion.
Inventions2021,6,4710of12
Intermsofantioxidantactivity,thereisareleaseofupto14%forV1and40%forV2
after120minofsimulatedgastricdigestion(Figure5c).Ifintheanthocyanin’scase,their
completereleaseinsimulatedintestinaldigestiontookplaceafteronly60minforV1,in
thecaseofantioxidantactivity,agradualreleaseisobservedforbothvariants(Figure
5d).Thereby,a50%releaseisobservedforbothvariantsafterthefirst30minofsimu‐
latedintestinaldigestion.Afterward,thereleasetookplacemoreslowly,reachingfull
releaseafter120minofdigestion.Theseresultsmaybeexplainedbythephenolicacids
formedduringthedegradationoftheanthocyaninsinintestinaldigestion[31].

(a)(b)
(c)(d)
Figure5.Invitrodigestibilityofencapsulatedanthocyaninandantioxidantactivityinsimulatedgastricfluid(a,c)and
simulatedintestinalfluid(b,d).
4.Conclusions
Thisstudyfocusedontheobtainingoffunctionalingredientsforfoodornutraceu‐
ticalsapplicationsbytheextractionandencapsulationofphenoliccompoundsfrom
eggplantpeels,mainlyontheanthocyanins.Thereby,theanthocyaninswereextracted
usingtheultrasound‐assistedextractionmethodandphytochemicallycharacterized.The
majoranthocyaninfromtheextractisdelphinidin3‐O‐glucoside.Further,thepresent
studyaimedtocomparetheimpactofthetwoencapsulationmatricesonthestabilityand
controlledreleaseoftheanthocyanins.Thus,thegelationtechniquecombinedwiththe
freeze‐dryingtechniquewasused,andthewallmaterialstestedinthisstudywerethe
CMCNa,P,andWPIindifferentconcentrations.Ithasbeendemonstratedthathigher
concentrationsofCMCNaandPintheencapsulationmatrixresultedinhigherantho‐
cyaninretention,encapsulationefficiency,andstoragestability.Theconfocalmicroscopy
revealedadigitiform,lacedappearanceintheV1andcompactirregularscalesintheV2
generatedbytheeggplantpeels’bioactives.Asthecontentofpolysaccharidesincreased
inthematrix,thepowderbecamemorehydrophilicandhomogeneous.Theinvitrodi‐
gestionstudyindicatedthateachtypeofmatrixexhibitedadifferentprotectionmecha‐
nismfortheanthocyaninandtheantioxidantactivityoftheencapsulatedpowders.A
higherpolysaccharideconcentrationinthematrixprovideshighanthocyaninstabilityin
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Time,min
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SGSrelease,%
Time,min
V1
V2
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0306090120
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SISrelease,%
Time,min
V1
V2
Inventions2021,6,4711of12
thegastricsystemandagradualreleaseintheintestinalsystem,whichcanleadtotheir
betterabsorption.
Ourresultscanbeusedinformulatingnewfunctionalfoodswithhighvalueadded.
Inthisregard,moreresearchwillbefurtheraddressed.
AuthorContributions:Conceptualization,N.‐N.C.;methodology,N.‐N.C.;software,N.‐N.C.,E.E.,
V.B.,andM.T.;validation,N.S.andG.R.;formalanalysis,N.‐N.C.,E.E.,V.B.,andM.T.;investiga‐
tion,N.‐N.C.;resources,G.‐E.B.,G.R.,andC.C.;datacuration,N.‐N.C.;writing—originaldraft
preparation,N.‐N.C.;writing—reviewandediting,G.R.,C.C.,andN.S.;visualization,G.‐E.B.;su‐
pervision,N.S.;projectadministration,G.‐E.B.;fundingacquisition,G.‐E.B.andG.R.Allauthors
havereadandagreedtothepublishedversionofthemanuscript.
Funding:ThisworkwassupportedbyprojectnumberPN‐III‐P1‐1.2‐PCCDI‐2017‐0569‐PRO‐SPER
(10PCCI)withinthePNCDIprogram.
InstitutionalReviewBoardStatement:Notapplicable.
InformedConsentStatement:Notapplicable.
DataAvailabilityStatement:Thedatathatsupportthefindingsofthisstudyareavailablefrom
thecorrespondingauthor(G.R.)uponreasonablerequest.
Acknowledgments:ThisworkwassupportedbytheIntegratedCenterforResearch,Expertiseand
TechnologicalTransferinFoodIndustry(BioalimentTehnIA),whichprovidedtechnicalsupport.
ConflictsofInterest:Theauthorsdeclarenoconflictofinterest.
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... The delphinidin-3-O-glucoside is the major anthocyanin identified (82.51%) in eggplant peel. Also, delphinidin-3-O-rutinoside-5-glucoside (11.57%), cyanidin-3-O-rutinoside (5.08%), and petunidin-3-O-rutinoside (2.14%) (Condurache et al. 2021) were also identified in eggplant peel. On the other hand, Colak et al. (2022) described that the delphinidin-3-(p-coumaroyl-rutinoside)-5-glucoside, known as nasunin, was the most common anthocyanin structure in the peel of eggplant. ...
... Due to the factors affecting bioavailability, this topic has become a hot topic for investigation (Husain et al. 2022). Several technologies have been tested to improve Table 3 Techniques to recovery of delphinidin in different sources the bioavailability, solubility, and stability of Dp, such as complexation with cyclodextrins (sulfobutylether-β-cyclodextrin) and microencapsulation, double emulsions, and nanoformulations (de Almeida Paula et al. 2018;Enache et al. 2020;Barkallah et al. 2021;Condurache et al. 2021;Sauer et al. 2021;). Improving bioavailability is essential to find applications as dietary supplements and nutraceuticals in the food and pharmaceutical industries. ...
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... Whey proteins are widely used as ingredients and additives in the food industry because of their nutritional and functional characteristics. Recently, these dairy proteins have been studied due to their capacity to form complexes with polyphenols, such as anthocyanins, leading to changes in structure, functionality, and nutritional value for both protein and anthocyanins (Condurache et al., 2021;Gowd et al., 2020;Khalifa et al., 2021). For instance, nanoparticles of β-lactoglobulin and anthocyanins extracted from red raspberry pomace were produced using a desolvation method combined with ultrasonication process leading to an encapsulation efficiency of approximately 77% . ...
Protein‐binding approaches for improving bioaccessibility and bioavailability of anthocyanins
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Color is an important characteristic of food. Over the last 15 years, more attention has been paid to natural colorants because of the rising demand for clean‐label food products. Anthocyanins, which are a group of phytochemicals responsible for the purple, blue or red hues of many plants, offer a market advantage. In addition, anthocyanin‐rich foods are associated with protection against cardiovascular disease, thrombosis, diabetes, cancer, microbial‐based disorders, neurological disorders, and vision ailments. However, the real health value of anthocyanins, whether as a natural colorant or a functional ingredient, is dependent on the ultimate bioaccessibility and bioavailability in the human body. Many animal and human clinical studies revealed that, after intake of anthocyanin‐rich foods or anthocyanin extracts, only trace amounts (< 1% of ingested content) of anthocyanins or their predicted metabolites were detected in plasma after a standard blood draw, which was indicative of low bioavailability of anthocyanins. Protein binding to anthocyanins is a strategy that has recently been reported to enhance the ultimate bioactivity, bioaccessibility, and bioavailability of anthocyanins as compared to anthocyanins delivered without a protein carrier. Therefore, in this review, we address anthocyanin properties in food processing and digestion, anthocyanin‐protein complexes used in food matrices, and changes in the bioaccessibility and bioavailability of anthocyanins when bound into anthocyanin‐protein complexes in foods. Finally, we summarize the challenges and prospects of this delivery system for anthocyanin pigments.
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... Higher polysaccharide concentrations than protein concentrations as carrier materials permitted the retention of higher amounts of phytochemical compounds from red OS extract. Our findings reached more satisfactory values for the phytochemical contents of the powders than those reported by Condurache et al. [41], who encapsulated bioactive components from eggplant peel extract using various combinations of sodium carboxymethyl cellulose (CMCNa), pectin (P), and whey protein isolate (WPI). They reported a TAC of 0.095 ± 0.01 mg delphinidin 3-O-glucoside/g DW, a TFC of 1.64 ± 0.14 mg catechin equivalent/g DW, a TPC of 7.22 ± 0.18 mg GAE/g DW, and antioxidant activity of 36.60 ± 0.83 mM TE/g DW for the powder with higher CMCNa and P concentrations. ...
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Article
  • Jul 2021
The development of frozen yogurt supplemented with an oily extract from carrot was the main focus of this study. The research aim converged from the fact that Daucus carota L. are among the worldwide most consumed vegetables, exhibiting numerous health benefits. Both analysed variants (the control sample and the fortified sample) presented high total carotenoids, β-carotene, and lycopene contents. The addition of the oily extract from carrot caused a significant increase of the total carotenoids, respectively the β-carotene contents. Also, these functional dairy products registered a slight increase in the antioxidant activity compared to the control sample, the fortified variant having the highest value (93.95±0.050%). The total polyphenols content varied depending on the analysed variant, from 0.122±0.006 to 1.712±0.008 mg/g dry weight (DW) while the content of total flavonoids varied from 0.065±0.001 to 0.780±0.002 mg/g DW. The carrot and blueberries’ HPLC profiles also highlighted the abundance of the bioactive compounds. The confocal microscopy analysis of the fortified frozen yogurt revealed a complex microstructure due to the diversity of the biochemical compounds, a microstructure that preserved the probiotic strain very well and comprised functional properties to the final product. The frozen dairy product enriched with carrot extract can be considered an innovative functional product as it was designed to provide the consumer with various beneficial effects based on its high content of biologically active compounds.
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Eggplant Peels as a Valuable Source of Anthocyanins: Extraction, Thermal Stability and Biological Activities
Article
Full-text available
  • Mar 2021
This study aimed to use eggplant peels as a potential source of anthocyanins with biological activities. Two different extraction methods were tested in order to obtain extracts with a high anthocyanin content. The selected methods were the solid–liquid extraction (SLE) and ultrasound-assisted extraction (UAE) methods. For each method, two concentrations of ethanol (EtOH) were used, while varying the extraction time and temperature. Based on the results, the extracts obtained by SLE using EtOH 96% after 30 min of extraction at 50 °C showed the highest anthocyanin concentration. The UAE allowed the best results with EtOH 96% after 30 min at 25 °C. Both selected extracts showed similar chromatographic profiles, with delphinidin 3-O-rutinoside as the major anthocyanin, but in a higher concentration in UAE. The extracts also presented inhibitory activity against lipoxygenase (LOX), lipase, and α-amylase, thus suggesting a possible involvement in reducing the risk of various disorders. The first order kinetic model was used to predict the changes that can occur in the anthocyanin content and antioxidant activity from the eggplant peel extract. The calculated kinetic and thermodynamic parameters confirm the irreversible degradation of phytochemicals.
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Extraction and characterization of bioactive compounds from eggplant peel using ultrasound – assisted extraction
Article
Full-text available
  • Jul 2019
This study followed the bioactive compounds extraction and the antioxidant potential of the eggplant peel, using three different solvents (ethanol, methanol and acetone). The successive extraction of total monomeric anthocyanin (TMA), total flavonoids (TFC), and total phenolic compounds (TPC) from eggplant peel was done by using an ultrasound – assisted extraction. The results showed that the highest bioactive compounds content was achieved for the methanol extract, which was characterized by 0.74 g D-3G/g d.w. of TMA, 5.48 g CE /g d.w. of TFC, 14.72 g GAE/g d.w. of TPC, compared to the ethanol and acetone extracts. Moreover, for the methanol extract, six anthocyanins were identified (delphinidin-3-rutinoside, delphinidin-3-glucoside, cyanidin-3-rutinoside, delphinidin-3-rutinoside-5-glucoside, malvidin-3-rutinoside-5-glucoside and petunidin-3-rutinoside), while for the ethanol extract, five anthocyanins were identified (all without malvidin-3-rutinoside-5-glucoside) and for the acetone extract only two anthocyanins were detected (delphinidin-3-rutinoside, delphinidin-3-glucoside). The antioxidant potential of the eggplant extracts was investigated by DPPH method. Results showed that the methanol extract had the highest antioxidant activity (51% inhibition of DPPH radical at a concentration 27.2 mM TE/g d.w.), followed by the ethanol and acetone extracts (39 % and 33% DPPH radical inhibition rate at a concentration 22.4 and 17.04 mM TE/g d.w., respectively). Ultrasound-assisted extraction is promising because the extracts rich in bioactive compounds can be obtained at low cost.
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Probing the Functionality of Bioactives from Eggplant Peel Extracts Through Extraction and Microencapsulation in Different Polymers and Whey Protein Hydrolysates
Article
Full-text available
  • Aug 2019
  • FOOD BIOPROCESS TECH
Eggplant peels (Solanum melongena L.) constitute a promising source of phenolic compounds, flavonoids, and anthocyanins that are beneficial for human health. The objectives of this study were to extract the polyphenolics from eggplant peels and microencapsulation in selected polymers, such as pectin, carboxymethylcellulose and whey proteins hydrolysates by freeze-drying. A combination of ethanolic with ultrasound-assisted methods was used for the extraction, leading to an extract with antioxidant activity of 157.82 ± 9.46 mmol Trolox/g dry weight. The next experiment was to obtain bioactive peptide, both by experimental and predictive methods, which were further used as coating materials. The bioinformatics tools were used for checking the susceptibility of α-lactalbumin and β-lactoglobulin for digestion with thermolysin. The anthocyanins were encapsulated in different combinations of selected polymers, with encapsulation efficiency up to 77.60 ± 1.92%, highlighting a higher microencapsulation efficiency of carboxymethylcellulose to incorporate anthocyanins. Our results suggested whey peptides had a role in regulating the microencapsulation patterns, whereas carboxymethylcellulose and pectin favored filamentous structuring and double encapsulation, respectively. The in vitro tests showed high biocompatibility of powders cultivated in a cell culture of murine fibroblasts. A significant protective effect in simulated digestion was observed, with a controlled release in the intestinal juice. Accelerated storage stability test showed an increase in antioxidant activity.
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Physicochemical and Phytochemical Characterization and Storage Stability of Freeze-dried Encapsulated Pomegranate Peel Anthocyanin and In Vitro Evaluation of Its Antioxidant Activity
Article
Full-text available
  • Feb 2019
  • FOOD BIOPROCESS TECH
The acidified ethanol extract of pomegranate (Punica granatum L.) peel bioactive compounds was freeze-dried and encapsulated using a combination of maltodextrin (MDX 5, 10, and 15%) with calcium alginate (0.1%) with a weight ratio (w/w) of 1:5 (extract/wall material). The effects of various parameters on pomegranate peel extraction (POPx) and POPx-encapsulated powder were analyzed on bioactive components, physicochemical, morphological properties, and storage stability. The results revealed that process yield was positively influenced by increasing MDX concentration, due to the increase on mixture content. Encapsulated powder with 15% MDX had the highest total phenolic compounds (TPC, 73.1 mg GA/kg), the total anthocyanin content (TAC, 40.2 mg c3g/kg dmp and antioxidant capacity by FRAP, 405 (Fe²⁺, μmol/l)), the DPPH assay (RSA, 65.1%), the lowest IC50, 0.56 ± 0.02 mg/ml, and the lowest glass transition temperature indicating that the highest antioxidant capacity among other wall materials. In respect to morphology, the particles of encapsulated powders with high concentration of MDX were larger and smoother. Stability and half-life of encapsulated powders were measured from 42 days of storage study at 4 °C and 25 °C, and 52 and 75% relative humidity. Storage tests revealed first-order degradation kinetics for anthocyanin. The TAC of the PoPx-microencapsulated powders with wall material of 15% and control decreased by 18% and 33%, respectively, after 42 days storage at 4 °C, while at the storage temperature of 25 °C, the decreases were in the order of 24% and 38%, respectively, over the same period of time. The highest anthocyanin content was observed in the freeze-dried MDX 15%-encapsulated powder at 4 °C storage temperature and 75% relative humidity with a half-life (t1/2) of 115 days, and the reaction rate constant (k) of 0.64 × 10⁻² min⁻¹.
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Enhanced stability of berry pomace polyphenols delivered in protein-polyphenol aggregate particles to an in vitro gastrointestinal digestion model
Article
  • Jun 2020
  • FOOD CHEM
Stability of polyphenol-protein aggregate particles, created by complexing polyphenols from blueberry and muscadine grape pomaces with a rice-pea protein isolate blend, was evaluated in an in vitro gastrointestinal model. Recovery index (RI; % total phenolics present post-digestion) was 69% and 62% from blueberry and muscadine grape protein-polyphenol particles, compared to 23% and 31% for the respective pomace extracts. Anthocyanins RI was 52% and 42% from particles (6% and 13% from pomace extracts), and proanthocyanidins RI was 77% and 73% from particles (25% and 14% from pomace extracts), from blueberry and grape, respectively. Protein-polyphenol particle digests retained 1.5 to 2-fold higher antioxidant capacity and suppressed the expression of pro-inflammatory cytokines, iNOS, IL6, and IL1β, compared to unmodified extract digests, which only suppressed IL6. Protein-polyphenol particles as a delivery vehicle in foods may confer better stability during gastrointestinal transit, allow protected polyphenols to reach the gut microbiota, and preserve polyphenol bioactivity.
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Structural Changes in Mulberry (Morus Microphylla. Buckl) and Chokeberry (Aronia melanocarpa) Anthocyanins during Simulated In Vitro Human Digestion
Article
  • Feb 2020
  • FOOD CHEM
Mulberry and chokeberry are rich sources of anthocyanins. In this study, the effect of the anthocyanin composition on the anthocyanin profile changes during in vitro digestion (mimicking the physiological conditions) was investigated by UHPLC-(ESI)-qTOF and UHPLC-(ESI)-QqQ. The antioxidant activity before and after in vitro digestion was elucidated. Cyanidin-3-O-glucoside and cyanidin-3-O-galactoside were dominant in mulberry and chokeberry, respectively. Moreover, the loss of cyanidin-3-O-galactoside in the chokeberry extract after digestion was greater than that of cyanidin-3-O-glucoside in the mulberry extract. After digestion, phenolic acids including protocatechuic acid and various cyanidin conjugates were newly formed because of decomposition and changes in the cyanidin-glycosides. The phenolic acid and cyanidin conjugate levels varied depending on the cyanidin glycoside sources in the colonic fraction. Finally, antioxidant activity before and after digestion was higher in the chokeberry extract than in the mulberry extract. Moreover, this activity continuously decreased until intestinal digestion but increased in the colonic fraction.
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Anthocyanins: New techniques and challenges in microencapsulation
Article
  • Feb 2020
  • FOOD RES INT
Anthocyanins are a bioactive compound belonging to the flavonoid classthatis present in human nutrition through plant-based foods. Due to their antioxidant properties, several health benefits related to their consumption are reported in the literature. The stability of the color and the properties of anthocyanins is strongly affected by pH, solvent, temperature, and other environmental conditions. In addition, the insufficient residence time of anthocyanins in the upper digestive tract causes apartialabsorption, which needs to be improved. These factshave led researchers to investigate new forms of processing that provide minimal degradation. Microencapsulation is a promising possibility to stabilize anthocyanin extracts and allow their addition to food products in a more stable form. The microcapsules can still provide a prolonged gastrointestinal retention time caused by the improvement of the bioadhesive properties in the mucus covering the intestinal epithelium. Although there are efficient and emerging techniques, anthocyanins microencapsulation is still a challenge for the food industry. The purpose of this work is to provide an overview of anthocyanins structure, absorptionand protection, and to show the main conventional and emerging microencapsulation methods and their pros and cons.
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Recovery of eggplant field waste as a source of phytochemicals
Article
  • Nov 2019
  • SCI HORTIC-AMSTERDAM
The influence of ripening stage was evaluated on fruit characteristics of three widely cultivated eggplant cultivars (Birgah, Black Bell and Black Moon), with the aim to characterize their fruit residual waste for phytochemicals extraction. At overripening stage, eggplant fruits showed the highest average weight, dry matter content and weight incidence of the pulp. Total anthocyanins concentration of the peel (mainly represented by nasunin) was higher at commercial ripening, whereas total polyphenols (most of all 5-O-caffeoylquinic acid) and steroidal glycoalkaloids (α-solasonine and α-solamargine) peaked at the overripening stage. Because of these modifications, every ton of fresh fruit gave up to 59 g of total anthocyanins, 1054 g CAE of total polyphenols and 252 g of total glycoalkaloids, depending on cultivar and fruit ripening stage. This study highlighted the possibility to manage the choice of cultivar and harvest time in the view of valorise this raw material for phytochemical extraction.
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Microencapsulation of anthocyanins through two-step emulsification and release characteristics during in vitro digestion
Article
  • Nov 2018
  • FOOD CHEM
An anthocyanin-rich double emulsion (w/o/w) was prepared via a two-step emulsification method. Anthocyanins from black rice extract were incorporated in the inner water phase and dispersed inside the middle oil phase, which was then dispersed into the outer water phase. Generation of the double emulsion was confirmed by optical microscopic analysis and its microencapsulation efficiency was 99.45 ± 0.24%. An in vitro digestion study was carried out to evaluate anthocyanin concentration changes and release characteristics of the double emulsion using simulated gastrointestinal fluids. After 2 h incubation in the simulated gastric fluid, the percentage of diffused anthocyanins was 3.66 ± 2.32%. These observations indicate that the double emulsion could control the release of anthocyanins in the stomach. During incubation in the simulated intestinal fluid, a total release of anthocyanins in the double emulsion was observed within the first 20 min. A pH-dependent degradation of anthocyanins was also evident.
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