REVIEWPAPER
NearInfraredSpectroscopy—AdvancedAnalyticalTool
inWheatBreeding,Trade,andProcessing
MilicaM.Pojić&JasnaS.Mastilović
Received:21February2012/Accepted:14June2012/Publishedonline:23June2012#SpringerScience+BusinessMedia,LLC2012
AbstractDuetoitssuitabilitytobeprocessedinwide
rangeoffinalproducts,wheathasanupmostsignificance
amongallcereals.Theglobalwheatmarketingarebecom-
ingincreasinglydemandingwithregardtoallaspectsof
wheatquality.Tofulfilthesedemands,eachlinkinwheat
productionchain—breeding,trade,andprocessingshould
besupportedbyobjectiveandreliablequalityassessment
toolsuchasthenearinfraredspectroscopy(NIRS)tech-
nique.Theaimofthispaperistosummarizetherecent
advancesintheapplicationsofNIRStechniqueforwheat
qualitycontrolapplicableinwheatbreeding,trade,and
processing.Althoughheavilyintertwined,eachlinkischar-
acterizedbyspecificNIRSapplications,withultimateaim—theproductionofconsumer-appealingandsafefinal
products.
KeywordsNearinfraredspectroscopy.Wheat.
Composition.End-usequality.Safety.Functionality
Introduction
Productqualityimprovementandtherationalizationofpro-
ductioninmanybranchesofindustryrequireapermanent
qualitycontrolofintermediateandfinishedproductsand
continuousmonitoringoftechnologicalprocesses.Different
techniquesofvibrationalspectroscopy(mid-andnearinfra-
redandRaman)haveproveditsapplicabilityforabove-
mentionedpurposes,wherethenearinfraredspectroscopy
(NIRS)appearedtobeparticularlyusefulduetothenumerousadvantagesitprovides.Theapplicationofthe
NIRStechniquesignificantlyreducesthetesttimeandcosts
anddoesnotrequiretheuseofchemicalsandsample
preparation,makingitsuperiorovertraditionalchemical
analyticalmethods,especiallyinindustrialqualitycontrol
andprocessmonitoringapplications(CenandHe2007;
McClure2007;Siesler2008).Theprerequisitefortheuse
oftheNIRSmethodisanappropriatecalibrationmodel
developedtorelatethecompound(orproperty)ofinterest
tothesample'sspectraldata.NIRScalibrationmodeldevel-
opmentisaverydemandingtaskduetothecomplexcom-
positionofanalyzedsampleswhichresultinsevere
overlappingofinterferingbandsrepresentingthecompo-
nent(s)(orproperties)ofinterest.Duetothesignificant
overlappingofNIRbands,theNIRspectralregionformany
yearswasmainlyusedforfundamentalresearchinchemis-
tryandphysicsandhadnoanalyticalapplication.Theinitial
applicationoftheNIRStechniqueinroutineanalysisis
relatedtothedeterminationofmoistureandproteinin
cereals,inthe'60s(MassieandNorris1965).Sincethen,
thepermanentdevelopmentoftheNIRSdevices,chemo-
metricstechniques,andcomputertechnologyhascontribut-
edtothedevelopmentoftheNIRStechniquethatis
currentlyusedfortestingawiderangeoffoodstuffs(Work-
man2008).TheNIRanalyticaltechniquehasdevelopedto
suchanextentthatnowadaysitusesdifferentspectral
ranges,differentwaysofrecordingandprocessingofspec-
tra,differentsamplepresentations,andvariousstatistical
methodsusedforcalibrationmodeldevelopment(Osborne
andFearn1986;BaetenandDardenne2002;Murray2004;
Pojić2010).
Overthepastdecade,theNIRSmeasurementshavebeen
extendedfromdeterminationofthecertainconstituents
presentinthesampletothedeterminationoffunctional
propertiesofsamples.Inthissense,thefunctionalproperties
aredefinedastheabilityofacommoditytomanifest
theM.M.Pojić(*):J.S.MastilovićInstituteofFoodTechnology,UniversityofNoviSad,BulevarcaraLazara1,21000NoviSad,Serbiae-mail:milica.pojic@fins.uns.ac.rsFoodBioprocessTechnol(2013)6:330–352DOI10.1007/s11947-012-0917-3propertiesinaccordancewithintendedpurposes.Sincethe
functionalityofthecommodityisstronglyaffectedbyits
physico-chemicalpropertieswhichdonotmanifestcharacter-
isticsabsorptioninNIRspectralregion,theuseofNIRSto
predictfunctionalityisbasedontherelationshipbetween
physico-chemicalpropertiesandcertainconstituenthaving
absorptionsinNIRregion(protein,oil,starchetc.)(Williams
2007).
Theobjectiveofthispaperistogiveanoverviewof
currentandmostimportantapplicationsoftheNIRS
techniqueinwheattechnology.
TheSpecificityofNIRSMethodology
PrinciplesofNIRS
NIRSisaspectroscopictechniquethatmeasurestheabsorp-
tionofNIRradiation(fromabout800to2,500nm)bythe
sample.DetectionofabsorbedNIRradiationbythesample
isconductedbymeasurementoftransmittance,reflectance,
interactance,and/ortransflectance,wherethesuitableacqui-
sitionmodeisdependentonthesampletypeandthecon-
stituentand/orpropertybeinganalyzed.Transmittance
modeinvolvesthemeasurementofradiationthatpasses
throughasample,whilstreflectancemodeinvolvesthe
measurementofradiationreflectedfromthesamplesurface.
Intransflectancemeasurement,theradiationistransmitted
throughthesample,reflectedfromadiffuselyreflecting
plateandthenagaintransmittedbackthroughthesample.
Interactancemodeinvolvesilluminationanddetectionat
laterallyseparatedpointsonthesample'ssurface(Osborne
2000).
WhensampleisexposedtoNIRradiation,theenergyof
chemicalbondsinvolvinghydrogen(CH,NH,OH,SH)is
changed.Duetoverycomplexcompositionoftheanalyzed
samples,differentorganicbondsinvolvinghydrogenabsorb
theNIRradiation.Asaresult,themolecularovertoneand
combinationbandsseenintheNIRspectralregionarevery
broad,overlapped,anddifficulttoassigntospecificchem-
icalcomponents(Fig.1).Consequently,theusefulspectral
informationcanonlybeextractedbyapplyingmodernche-
mometricsmethodsinthecalibrationdevelopmentprocess
resultingincalibrationmodelthatenablesthepractical
applicationofNIRS.Inthisregard,thecalibrationmodel
definestherelationshipbetweentheobtainedspectral
dataandthecontentofthecompoundorpropertyof
interestobtainedbyselectedreferencemethod.Beingan
indirectmethod,theperformanceoftheNIRSmethodis
highlydependentonthequalityofthereferencemethod
usedforbasisincalibrationdevelopmentprocess.
Therefore,thevalidationprocessshouldbeasmuch
comprehensiveaspossibletodemonstrateallthenecessarycharacteristicsoftheNIRSmethodforits
fitness-forpurpose,whereaccuracyisthecharacteristics
ofmostconcern(Pojić2006).Theaccuracyofthe
NIRSmodelsiscommonlydescribedbythecoefficient
ofdetermination(R2),standarderrorofcalibration
(SEC),standarderrorofcrossvalidation,and/orstan-
darderrorofprediction(SEP).Moreover,asbeingan
indirectmethod,standarderrorofreferencelaboratory
method(SEL)hasagreatimportanceforinterpretation
ofpredictiveabilityofdevelopedNIRSmodels,by
expressingtheratioofSECVvs.SELand/orSEPvs.
SEL(Hruschka2001).
ChemometricMethodsinNIRS
Duetotheabove-mentionedcomplexityofNIRspectrum,
NIRSanalysisrequiresextractionofrelevantinformation
frommanyvariableswhichisachievedbyapplicationof
chemometricswhichinvolvetheutilizationofmathematics,
statistics,andcomputationaltechniquestoNIRspectral
data.WhenappliedtoNIRS,chemometrictechniquescould
beroughlydividedintotechniquesusedforspectraldata
preprocessingandmultivariatetechniquesusedincalibra-
tionmodeldevelopment(Pasquini2003;LinandYing
2009;AgeletandHurburgh2010
).Fig.1NIRtransmittance(850–1,050nm)(a)andNIRreflectancespectrumofwheatflour(1,100–2,500nm)(b
)FoodBioprocessTechnol(2013)6:330–352331
