UNCORRECTED PROOF
Food Con ol xxx (2017) xxx-xxx
Con en s lis s a ailable a ScienceDi ec
Food Con ol
jou nal homepage: www.else ie .com
ATR-FTIR as a po en ial ool o con olling high quali y inega ca ego ies
Rocío Ríos-Reina a, Raquel M. Callejón a, Celia Oli e -Pozo b, José M. Amigo c, Diego L. Ga cía-González b, ∗
aÁ ea de Nu ición y B oma ología, Facul ad de Fa macia, Uni e sidad de Se illa, C/P. Ga cía González n°2, E-41012, Se illa, Spain
bIns i u o de la G asa (CSIC), Campus Uni e sidad Pablo de Ola ide, Building 46, C a. de U e a, km. 1, E–41013, Se illa, Spain
cSpec oscopy and Chemome ics G oup, Depa men o Food Sciences, Facul y o Science, Uni e si y o Copenhagen, Roligheds ej 30, F ede iksbe g CDK-1958, Denma k
ARTICLE INFO
A icle his o y:
Recei ed 20 Decembe 2016
Recei ed in e ised o m 23 Feb ua y
2017
Accep ed 27 Feb ua y 2017
A ailable online xxx
Keywo ds:
Wine inega s
P o ec ed Designa ion o O igin
ATR-FTIR
PCA
Au hen ica ion
ABSTRACT
Cha ac e iza ion o wine inega s quali ied wi h a P o ec ed Designa ion o O igin (PDO) is c ucial o ce i y hei qual-
i y and au hen ici y. Spec oscopic echniques as Fou ie ans o m mid in a ed spec oscopy (FTIR) wi h A enua ed
To al Re lec ance (ATR) has been applied o in es iga e i s po en ial as a apid, cos -e ec i e and non-des uc i e ool
o cha ac e izing di e en ca ego ies o high-quali y inega s. Spec a om 67 wine inega s belonging o he PDOs
“Vinag e de Je ez” and “Vinag e Condado de Huel a”, including hei di e en es ablished ca ego ies, we e analyzed in
he 4000–600 cm−1 in a ed egion. Changes associa ed o ca ego ies we e obse ed in he egion 1800–900 cm−1. These
changes we e assigned o ce ain compounds ha inc ease du ing aging (e.g. ace ic acids, alcohols, es e s) o a e cha ac-
e is ic o Ped o Ximenez ca ego y (e.g. suga s, u u al). P incipal componen analysis ca ied ou on he mos ele an
spec al ea u es, e ealed ha aging o inega s clea ly a ec he ATR-FTIR spec a ob ained in each PDO.
© 2016 Published by Else ie L d.
1. In oduc ion
Vinega is a p oduc ob ained by a double e men a ion p ocess
(alcoholic and ace ous e men a ion o ace i ica ion) by using a wide
a ie y o me hods and di e en aw ma e ials (wine, honey, cide ,
e c.). In he pas , inega was conside ed as a seconda y p oduc in
he amily o e men ed p oduc s and lacked o any ecognized quali y
s anda d. Nowadays, inega is conside ed as a necessa y p oduc in
households all o e he wo ld and many consume s ega d i as high
quali y p oduc .
Wine inega is he mos commonly used inega in Medi e anean
coun ies and Cen al Eu ope. I is he esul o he con e sion o sug-
a s om g ape juice in o e hanol by yeas and he subsequen oxida-
ion o he e hanol by ace ic acid bac e ia (O dóñez, Callejón, Mo ales,
& Ga cía-Pa illa, 2013). The wine inega s a ailable in he ma ke
di e in aw ma e ials and p oduc ion p ocess. Conce ning he la -
e inega s can be p oduced by ei he a quick ace i ica ion sys em
o a slow adi ional p ocess (De la Haba, A ias, Ramí ez, López, &
Sánchez, 2014). The ime and ype o aging (in di e en kinds o
woods) a e o he sou ces o a iabili y and hey g ea ly a ec he ine-
ga quali y. Due o hese p ocesses, chemical modi ica ions ela ed
wi h aging and wi h he mic obiological ac i i y occu and hey p o-
ide speci ic and singula p ope ies o he inal p oduc , being highly
app ecia ed by consume s (Ma u o-Cu ido e al., 2012).
Some wine inega s a e adi ionally linked o a ce ain geog aph-
ical a ea, and hey a e p o ec ed by he Eu opean Union wi h a legal
∗Co esponding au ho .
Email add ess: [email p o ec ed] (D.L. Ga cía-González)
amewo k ha p o ides he ca ego y o “P o ec ed Designa ion o
O igin” (PDO). A p oduc wi h a PDO egis a ion means ha i is
p oduced, p ocessed and p epa ed in a gi en geog aphical a ea using
a ecognized know-how (Council Regula ion (EC) 510/2006). Conse-
quen ly, a PDO egis a ion p o ides an addi ional p o ec ion o con-
sume s agains alsi ica ions and i gua an ees some speci ica ions e-
la ed o hei chemical and senso y ea u es (Chinnici e al., 2009).
The p oduc ion o wine inega in Spain is cen e ed in Andalu-
sia (Sou he n Spain). Andalusia is a egion adi ionally associa ed
o wine cul u e whe e wine inega s ha e been p o ec ed by h ee
di e en PDOs because o hei unique cha ac e is ics: “Vinag e de
Je ez” (also known as “She y wine inega ”), “Vinag e Condado de
Huel a” and ecen ly “Vinag e Mon illa-Mo iles”. The i s wo PDOs
a e al eady well es ablished and widely comme cialized whe eas
“Vinag e Mon illa-Mo iles” was jus g an ed i s PDO s a us in 2015
(EU 2015/48) and hei inega s a e s a ing o appea on he ma ke .
Fu he mo e, wi hin each PDO, he e a e di e en ca ego ies acco d-
ing o hei aging ime and ype in wood ba els. The high quali y o
hese PDOs a e he consequence o he aw ma e ial (e.g. g ape a-
ie y, o igin), he wooden cask used (e.g. Ame ican Oak casks) and
he me hods o aging. Aging p ocedu es in hese PDOs comp ises he
“c iade as y sole a” (also called dynamic aging sys em) and “añada”
(also called s a ic sys em) sys ems. The inega in he i s sys em is
aged in di e en bu s in which aged and young inega s a e sequen-
ially mixed, while he inega in he second sys em is aged in a single
bu wi hou mixing wi h o he inega s.
The egula ion on PDO “Vinag e de Je ez” (BOJA, 2008a) de-
sc ibe h ee ca ego ies acco ding o aging ime in oak ba els by he
dynamic sys em “c iade as y sole a”: “Vinag e de Je ez” (aged in
wood a leas 6 mon hs),“Vinag e de Je ez Rese a” (wi h a mini
h p://dx.doi.o g/10.1016/j. oodcon .2017.02.065
0956-7135/© 2016 Published by Else ie L d.
UNCORRECTED PROOF
2 Food Con ol xxx (2017) xxx-xxx
mum aging ime o 2 yea s.), “Vinag e de Je ez G an Rese a” (aged
o 10 o mo e yea s). This egula ion also desc ibes semi-swee ca e-
go ies (i.e. “Ped o Ximenez”, “Mosca el”).
The egula ion on PDO “Vinag e Condado de Huel a” (BOJA,
2008b) also es ablishes he ollowing ca ego ies: “Vinag e Condado
de Huel a” (no aging), “Vinag e Viejo Condado de Huel a Sole a”
(aged a leas 6 mon hs), “Vinag e Viejo Condado de Huel a Rese a”
(aged a leas 2 yea s), all aged by he sys em “c iade as y sole a”. Fu -
he mo e, he e is one mo e ca ego y named “Vinag e Viejo Condado
de Huel a Añada” aged a leas 3 yea s bu in s a ic aging sys em.
These inega s ha e high p ices in he ma ke due o hei high
quali y, he long aging ime and hence, he high cos o hei p o-
duc ion. Tha explains ha hese p oduc s a e ulne able o aud
(Callejón e al., 2012; Sáiz-Abajo, González-Sáiz, & Piza o, 2004)
and new ools a e equi ed o igh agains alsi ica ion o mislabeling.
Fu he mo e, he g owing consume demand and he inc easing di e -
si y o wine inega s has aised a need o cha ac e ize hem and o p o-
ide an adequa e quali y con ol o de end hei iden i y (Ce ezo e al.,
2008; Liu, He, & Wang, 2008; Ma u o-Cu ido e al., 2012). Di e -
en senso y and physicochemical echniques such as gas-ch oma og a-
phy-mass spec ome y (GC-MS), a omic abso p ion spec ome y o
high-pe o mance liquid ch oma og aphy (HPLC) ha e been used o
cha ac e ize inega s (Ci lini, Caligiani, Palla, & Palla, 2011; Na e a,
Cas o, De Valme Ga cía-Mo eno, He nández, & Ga cía-Ba oso,
2003). Howe e , hese echniques a e o en expensi e and ime-con-
suming. Rapid me hods based on non- a ge ed echnique can p o-
ide a solu ion o ood au hen ica ion (Bae en & Da denne, 2002).
In pa icula , Fou ie ans o m in a ed spec oscopy (FTIR) has be-
come an impo an ool o quan i a i e analysis (Rod iguez-Saona &
Allendo , 2011). FTIR combined wi h chemome ics has gained wide
accep ance in he iden i ica ion o chemical compounds in oods o
au hen ici y and classi ica ion pu poses (G assi, Amigo, Lyndgaa d,
Foschino, & Casi aghi, 2014; Mo os, Iñón, Ga igues, & de la
Gua dia, 2008; Regmi, Palma, & Ba oso, 2012; Tay, Singh,
K ishnan, & Go e, 2002; Van de Voo , Ghe le , Ga cía-González, &
Li, 2008).
The use o an accesso y o A enua ed To al Re lec ance (ATR)
in FTIR s udies allows he di ec analysis o liquids in a simple and
non-des uc i e manne wi h enough sensi i i y (Gou inhas, de
Almeida, Ca alho, Machado, & Ba os, 2015; Ve sa i, Pa pinello,
Chinnici, & Meglioli, 2011). Thus, ATR-FTIR has p o en o be an ap-
p op ia e me hod o he au hen ica ion o se e al liquid oods such as
inega (Dong, Zheng, Jiao, Lang, & Zhao, 2016; Gue e o, Mejías,
Ma ín, Lo illo, & Ba oso, 2010), oli e oil, wine, milk o honey
(Bendini e al., 2007; Be in, Fe gusson, Pe y, Janik, & Cozzolino,
2006; Gou inhas e al., 2015; Kelly, Pe isco, & Downey, 2006;
Ta an ilis, T oianou, Pappas, Ko se idis, & Polissiou, 2008; Tena,
Apa icio-Ruiz, & Ga cía-González, 2014). Sca ce s udies ha e been
ca ied ou in he cha ac e iza ion o inega s belonging o PDOs
and wi h di e en aging imes, al hough some s udies al eady poin ed
ou he u ili y o di e en spec oscopic echniques (e.g. nea in a ed
and luo escence spec oscopy) in inega s udies (De la Haba, A ias,
Ram, í, ez, L, ó, pez, S, á, & nchez, 2014; Callejón e al., 2012).
The aim o his wo k was o s udy he po en ial o ATR-FTIR o
he cha ac e iza ion o wine inega ca ego ies (aged and swee ) es-
ablished in wo Andalusian PDOs (“Vinag e de Je ez” and “Vina-
g e Condado de Huel a”). Fo his pu pose, he mos ele an spec-
al bands we e iden i ied and he in o ma ion ha hey p o ided we e
assessed in e ms o chemical assignmen and inega cha ac e is-
ics. P incipal componen analysis (PCA) was used as unsupe ised
me hod in o de o explo e and compa e he da a s uc u e and o help
in he in e p e a ion o ATR-FTIR analysis.
2. Ma e ials and me hods
2.1. Samples
Six y-se en wine inega samples belonging o di e en ca ego ies
egis e ed as P o ec ed Designa ion o O igin, named “Vinag e de
Je ez” and “Vinag e Condado de Huel a”, we e collec ed om di e -
en wine ies o Andalusia (Spain). Samples we e di ided as ollows:
36 “Vinag e de Je ez” and 31 “Vinag e Condado de Huel a” includ-
ing samples o each es ablished ca ego y (Table 1).
2.2. Chemicals
Ace ic acid was ob ained om Me ck (Mad id, Spain), and i was
o analy ical quali y. Wa e was ob ained om a Milli-Q pu i ica ion
sys em (Millipo e, USA).
2.3. ATR-FTIR spec oscopy analysis
Spec al da a we e collec ed on a B uke Ve ex 70 FTIR spec-
ome e equipped wi h a DGTS de ec o (B uke Op ics, E lingen,
Ge many). The sampling s a ion was equipped wi h an o e head and
de achable mul i- e lec ion a enua ed o al e lec ance accesso y
(ATR, six bounces, Specac, O ping on, U.K.). This accesso y consis s
on a 45° angle ZnSe c ys al moun ed in a shallow channel o he sam-
ple. Each spec um was eco ded a he same empe a u e (22 °C) in
he egion o 4000–600 cm−1 by an a e age o 50 scans a a esolu ion
o 4 cm−1. Be o e scanning each sample, a backg ound spec um was
aken wi h an emp y ATR c ys al and eco ded in he compu e . Each
sample (250 μL) was sp ead uni o mly h ough he ATR c ys al us-
ing a mic opipe e. A e he analysis, he ATR c ys al was ho oughly
cleaned o elimina e he p esence o inega esidues be ween mea-
su emen s and hen wiped wi h co on. Spec a we e examined using
OPUS e sion 7.0 (B uke Op ics, E lingen, Ge many) and manipu-
la ed wi h OMNIC so wa e. Each sample was analyzed in iplica e.
2.4. Da a analysis
Da a p ocessing and s a is ical analysis was pe o med wi h MAT-
LAB e sion 8.4.0.150421 (R2014b) and PLS- oolbox e sion 7.0.2
(Eigen ec o Resea ch Inc., Manson, WA). Di e en p ep ocessing
me hods we e s udied p io o PCA including s anda d no mal a ia e
(SNV), i s and second de i a i e. Mo eo e , he spec a we e p op-
e ly no malized by mean cen e ing a e p ep ocessing. A e some i-
als and compu a ions, p ep ocessing was ound no o be necessa y.
The e o e, he aw spec a we e jus no malized by mean cen e ing.
Table 1
Wine inega samples analyzed in his s udy.
P o ec ed Designa ion o
O igin (PDO) Ca ego ies code
Aging ime
(mon hs) n
“Vinag e de Je ez” “Vinag e de
Je ez”
JCR ≥6 15
“Rese a” JRE ≥24 15
“G an Rese a” JGR ≥120 3
“Ped o Ximenez” JPX – 3
“Vinag e Condado de Huel a” “Condado de
Huel a”
CSC 0 10
“Viejo Sole a” CSO ≥6 7
“Viejo Rese a” CRE ≥24 10
“Viejo Añada” CAN ≥36 4
UNCORRECTED PROOF
Food Con ol xxx (2017) xxx-xxx 3
P incipal componen analysis (PCA) was applied o he
1500–900 cm−1 spec al egion o he o al o samples in iplica e in
o de o explo e he da a s uc u e and o iden i y he main sou ces o
a iabili y in he spec a. Full c oss alida ion (lea e-one sample-ou )
was applied, unde s anding as sample all he analy ical eplica es o
he same sample. Fac o loadings o each p incipal componen we e
used o assess abou he ela i e impo ance o each wa enumbe and
he co ela ion o hem wi h speci ic composi ional p ope ies acco d-
ing o hei ca ego y.
3. Resul s and discussion
3.1. In e p e a ion o ATR-FTIR wine inega spec a
The i s s ep in his wo k was o iden i y he mos ema kable
bands ela ed o he majo compounds ha cha ac e ize wine ine-
ga samples. Fig. 1 shows he ATR-FTIR spec a o some analyzed
inega s. Fo a compa a i e pu pose, a spec um o Millipo e Q-pu-
i ied wa e is shown, as well as a spec um o a mix u e o pu e
ace ic acid and wa e . In he i s one (Fig. 1, spec um A; Table
2), he in ense bands de ec ed in he egions o 3800–2790 cm−1 and
1685–1550 cm−1 we e mainly assigned o OH g oups o wa e .
The ATR-FTIR spec a o a s anda d o ace ic acid dilu ed in wa e
(Fig. 1, spec um B) showed he p esence o h ee new bands: one
a ∼1711 cm−1 assigned o he C O g oup o ace ic acid, and wo
bands nea ∼1410 and ∼1290 cm−1 explained by C O s e ching and
C O H in-plane bending espec i ely (Mo os e al., 2008; Sil a,
Feliciano, Boas, & B onze, 2014; Ta an ilis e al., 2008; Ve sa i e
al., 2011). Ace ic acid also abso bs a 3800–2790 cm−1 due o C
H and O H s e ching, al hough i is no obse able in he spec-
um o being o e lapped by O H abso p ion o wa e (Mo os e
al., 2008). Conce ning he spec a o inega samples (spec a C, D
and E in Fig. 1), all he bands associa ed o wa e and ace ic acid
we e he mos in ense ones. O he mino bands we e cha ac e is ics
o some speci ic kinds o inega s (Table 2). Thus, he egion a
1500–900 cm−1 also showed spec al bands assigned o complex in e -
ac ing ib a ions, esul ing in a unique inge p in o each inega .
Fig. 2 shows wo ATR-FTIR spec a co esponding o an aged
wine inega (Rese a ca ego y) and a “Ped o Ximenez” wine ine-
ga , bo h o hem om PDO “Vinag e de Je ez”. In addi ion o he
bands assigned o wa e and ace ic acid (spec al bands 1 o 6), he
egion 1500–900 cm−1 shows o he abso p ion bands assigned o C
O, C C, C H, C N, N H and C O g oups (S ua , 2004)
(Table 2). These bands we e p oduced by he p esence o ca boxylic
acids, aldehydes, es e s, e he s, alcohols and phenols and some ni-
ogen compounds p esen ed in wine inega (Callejón e al., 2008b;
S ua , 2004). All hese chemical g oups ha e been iden i ied in ine-
ga s and hey ha e an impac on quali y p ope ies (Callejón, Mo ales,
Sil a Fe ei a, & T oncoso, 2008a). Fig. 2.A and 2.B shows he a e -
age spec a ( egion 1160–900 cm−1) o he aged ca ego ies o “Vina-
g e de Je ez” and “Vinag e Condado de Huel a” espec i ely. Peaks
7, 8 and 9 (∼1085, ∼1045 and 1015 cm−1) we e assigned o alcohol
compounds, aldehydes, and some es e s and e he s as well as acids
(Dua e, Ba os, Almeida, Sp aul, & Gil, 2004; Nieuwoud , P io ,
P e o ius, Manley, & Baue , 2004; Ve sa i e al., 2011). These bands
we e ela ed o he a o emen ioned chemical compounds whose con-
cen a ion inc ease du ing aging (Mo ales, Tes aye, Ga cía-Pa illa,
Casas, & T oncoso, 2001; Mo ales, Tes aye, Ga cía-Pa illa, Casas,
& T oncoso, 2002; Tes aye, Mo ales, Ga cía-Pa illa, & T oncoso,
2002) being esponsible o he a ia ions in he abso bance in ensi-
ies ha a e shown in he egion 1160–900 cm−1 (Fig. 2.A and 2.B).
Vinega s wi h longe aging pe iod, such as “Vinag e de Je ez G an
Rese a” (JGR), “Vinag e de Je ez Rese a” (JRE), “Vinag e Con-
dado de Huel a Rese a” (CRE), and “Vinag e Condado de Huel a
Añada” (CAN), showed an inc ease in he in ensi y o he band a
∼1045 cm−1 (band 8) and a sligh inc emen a ∼1085 cm−1 (band 7).
These wo spec al bands we e explained by he p esence o alcoholic
and es e compounds (mainly e hanol and e hyl ace a e), whose unc-
ional g oups (C O) abso b a his ange o he spec um (Dua e
e al., 2004; S ua , 2004). The spec al di e ences obse ed in aged
ca ego ies ag ee wi h he ac ha aging
Fig. 1. Compa ison be ween ATR-FTIR spec a o Millipo e Q-pu i ied wa e (A), a pu e ace ic acid solu ion in wa e (B), and some inega samples (“Vinag e de Je ez” PDO) o
di e en ca ego ies: “C ianza” (C), “Rese a” (D) and “Ped o Ximenez” (E).
UNCORRECTED PROOF
4 Food Con ol xxx (2017) xxx-xxx
Table 2
Chemical assignmen o he bands obse ed in he ATR-FTIR spec a o wine inega s
(S ua , 2004; Ald ich lib a y; Sigma Sample lib a y).
Compounds P incipal G oup Iden i ied
Spec al Region
(cm−1)
Wa e O H band 3800–2790;
1685–1550
Ace ic acid C H, C O, C O
s e ching and C O H
in-plane bending
3800–2790;
1800–1680;
1475–1230
Acids C O s e ching 1300–1000
E hanol, Glyce ol C O s e ching 1100–1000
Alcohols (e.g. 1-hexanol,
2-me hyl-1-bu anol)
O H s e ching band, C
O s e ching
3600; 1575–900
Es e s (e.g. e hyl ace a e,
isoamyl ace a e, e hyl
p opanoa e)
Alipha ic and a oma ic C
O and C O s e ching
1700–1100
Suga s ( uc ose, glucose) O H, CH21065–1030
Aldehydes (e.g.
Benzaldehyde)
C O s e ching 1700–1600
Phenols (e.g. guaiacol,
eugenol, 4-e hylphenol)
C O, O H s e ching 1800–900
Fu u als C O, C C 1300–840 and
∼1020
p omo es se e al phenomena ha a ec s he chemical composi ion
o inega s (Callejón, Mo ales, Sil a Fe ei a, & T oncoso, 2008b).
The main changes in ol e wa e losses h ough wood po es, inc eases
in ace ic acid concen a ion, ex ac ion o phenolic compounds om
wood and o ma ion o a oma compounds, mainly es e s (Callejón e
al., 2008b; Ga cía-Pa illa, He edia, & T oncoso, 1999).
Fig. 2 also showed he spec a o a “Ped o Ximenez” inega ,
which is a pa icula swee ca ego y o PDO “Vinag e de Je ez”.
I s spec um showed a singula g oup o peaks in he egion o
1175–1000 cm−1 (band 10, Fig. 2). This kind o inega has a high
ca bohyd a e con en and hey su e a Mailla d eac ion ha induces
he condensa ion o he educing ca bohyd a es (glucose and uc-
ose) and ee amino acids p oducing an appea ance o b own pig-
men s and ola ile compounds (Casale, Sáiz Abajo, González Sáiz,
Piza o, & Fo ina, 2006). Thei cha ac e is ic bands in he egion o
1175–1000 cm−1 mainly esul ed om g ape suga s and u u al com-
pounds ha a e cha ac e is ics o hese swee inega s (Casale e al.,
2006). In ac , in p e ious s udies he spec a o glucose and uc ose
showed a majo peak a 1034 and 1062 cm−1 espec i ely (Si akesa a
& I udaya aj, 2000) and u u al a 1020 cm−1 and 1300–840 cm−1
(Dong e al., 2016) (Table 2).
3.2. P incipal componen analysis
In o de o check he abili y o he a o emen ioned bands o cha -
ac e ize Andalusian PDO inega s and o ind ou i he spec al p o-
ile o hese wine inega s may be consis en ly co ela ed wi h spe-
ci ic composi ional p ope ies and/o sample aging, p incipal compo-
nen analysis (PCA) was pe o med. PCA was used o de ec g oups
o samples, ou lie s and o p o ide a isual ep esen a ion o he e-
la ionships wi hin he samples and be ween hem (sco es) and he
a iables (loadings). PCA was ca ied ou wi h he spec al egion
1500–900 cm−1, p e iously p ep ocessed by mean cen e ing, o he o-
al o samples by iplica e om each PDO.
3.2.1. PDO “Vinag e de Je ez”
The wo i s p incipal componen s (PCs) o he di e en aged
ca ego ies and Ped o Ximenez inega s included in he “Vinag e de
Je ez” PDO explained 97.33% o he o al a iance. Fig. 3 shows he
sco es and loadings plo s in he plane de ined by PC1 and PC2. PC1
allowed he sepa a ion o he “Ped o Ximenez” samples. Addi ion-
ally, samples we e dis ibu ed along PC1 acco ding o hei aging (Fig.
3-A): “G an Rese a” wi h posi i e alues o PC1; “C ianza”, wi h
nega i e alues o PC1; and “Rese a” wi h bo h nega i e and posi-
i e alues o PC1. This di e ence is mainly due o he wide ange o
aging ime in hese inega s ( om 6 mon hs o >10 yea s). None he-
less, some o e lapping was obse ed in he PCA sco es plo since
aging is a ac o ha de elops wi h ime. Thus, “Rese a” inega s
(2–10 yea s) ha we e aged o sligh ly mo e han 2 yea s we e ob-
se ed close o “C ianza” ca ego y (6 mon hs–2 yea s). Simila e
Fig. 2. ATR-FTIR spec um o an aged wine inega (“Vinag e de Je ez Rese a”) and a swee inega (“Vinag e de Je ez Ped o Ximenez”). Two inse s (A and B) shows he
selec ed spec al ange o each PDO aged ca ego ies (“Vinag e de Je ez” and “Vinag e Condado de Huel a”). No e: (1) 3800–2790 cm−1; (2) 1800–1680 cm−1; (3) 1685–1550 cm−1;
(4) (5) (6) 1475–1230 cm−1 (7) ∼1085 cm−1; (8) ∼1045 cm−1; (9) ∼1015 cm−1; (10) 1175–1000 cm−1. The ac onyms o he di e en inega ca ego ies a e de ined in Table 1.
UNCORRECTED PROOF
Food Con ol xxx (2017) xxx-xxx 5
Fig. 3. Resul s o p incipal componen analysis ca ied ou wi h ATR-FTIR spec al da a o “Vinag e de Je ez” samples (in iplica e). The sco e plo s wi h and wi hou “Ped o
Ximenez” ca ego y (A and C espec i ely) a e shown as well as he co esponding loadings o he i s wo p incipal componen s (PC1 and PC2) (B and D). The ac onyms o he
di e en inega ca ego ies a e de ined in Table 1.
sul s we e ob ained in a p e ious wo k (Callejón e al., 2012) in
which inega s o di e en aging we e analyzed by luo escence spec-
oscopy. The loadings plo co esponding o he wo PCs wi h highe
amoun o o al a iance, PC1 and PC2 (Fig. 3.B), shows ha wo
speci ic egions o he spec a had mo e impo ance in he model
(1175–1000 cm−1 and 1475–1230 cm−1). PC1 (87.96% o he o al
a iance) was mainly associa ed wi h posi i e alues o he spec al
egion o 1175–1000 cm−1. This egion was asc ibed o he samples
wi h highe amoun o suga s om g ape-juice in hei composi ion
ha was cha ac e is ic o “Ped o Ximenez” inega s. These loadings
o PC1 explained ha Ped o Ximenez samples we e sepa a ed om
he es o inega s. In addi ion o his egion, PC2 loadings showed
posi i e alues a he abso p ion bands cha ac e is ics o ace ic acid
(1475–1230 cm−1) explaining ha he majo i y o wine inega sam-
ples wi h mo e aging ime we e loca ed in he posi i e side o PC2
(e.g. all “G an Rese a” and many “Rese a” samples).
Once he Ped o Ximenez samples we e explained and showed dis-
inc i e spec al cha ac e is ics, hey we e emo ed om he da a in
o de o ca y ou a di e en ia ion o he es o inega s (aged ca e-
go ies). Sco es and loadings o he i s wo PCs a e shown in Fig. 3.C
and 3.D, accoun ing o 95.98% o he o al a iabili y. Once again,
wo egions o he spec a whe e highligh ed in he loadings plo :
1475–1230 cm−1 and he wo peaks a ∼1085 cm−1 and ∼1045 cm−1.
The highes con ibu ions co esponded o he bands assigned o ace ic
acid and alcoholic, e he s and es e s compounds espec i ely, indi-
ca ing he ela ionship p e iously desc ibed (Fig. 2) be ween aging
ime and he inc ease o hese compounds. The p ojec ion on o he
educed space spanned by he PCs allowed he sepa a ion o “G an
Rese a” and “C ianza” ca ego ies (wi h posi i e and nega i e al-
ues o PC1 espec i ely) in he sco e plo (Fig. 3.C), while he sam-
ples o he “Rese a” ca ego y we e dis ibu ed be
ween he wo o he g oups, showing he impo ance o he aging in
he spec al cha ac e is ics.
3.2.2. PDO “Vinag e Condado de Huel a”
A PCA was ca ied ou wi h samples o all he ca ego ies o wine
inega comme cialized by “Vinag e Condado de Huel a” PDO (Fig.
4). The esul s ob ained we e simila o he PCA ca ied ou o “Vina-
g e de Je ez” samples. Fig. 4 shows he sco es and loadings plo s o
he i s wo p incipal componen s (PCs), accoun ing o 97.08% o
he o al a iabili y. The sco e plo (Fig. 4.A) shows ha PC1 ex-
plained mos o he a iabili y (81.39%) and allowed he di e en ia-
ion be ween wo g oups: he less aged inega s (“Vinag e Condado
de Huel a”) placed in he nega i e side o PC1, o he mos aged ine-
ga s (“Añada” and “Rese a”) in he posi i e side. Mo eo e , om
a concep ual s andpoin , i is possible o a he a i m ha he aging
di ec ion is no only PC1 bu i is he diagonal o he PC1 s PC2
plo , so ha mo e aged inega s esul in a simul aneous inc ease in
he sco es along bo h componen s. Once again, he e was an o e -
lapping o samples belonging o he in e media e ca ego y “Sole a”,
aged om 6 mon hs o 2 yea s, wi h he ca ego y immedia ely mo e
aged “Rese a”, aged o mo e han 2 yea s. In ega ds o he loadings
(Fig. 4.B), he highes con ibu ions o PC1 co esponded o he bands
assigned o ace ic acid (1475–1230 cm−1), and he posi i e loadings
o PC1 and PC2 we e assigned o alcoholic, e he s and es e s com-
pounds (1085 cm−1 and 1045 cm−1). These highligh ed egions con-
i med again he ela ionship be ween aging ime and he in ensi y o
hese bands. The loading p o ile shown in Fig. 4-B we e simila o
hose ob ained wi h he samples om “Vinag e de Je ez” PDO (Fig.
3-D).
These esul s sugges ed ha FTIR spec a could be used o iden-
i y he main di e ences be ween he es ablished ca ego ies o wine
inega s wi hin each PDO. The “ inge p in ” egion o inega spec

UNCORRECTED PROOF
6 Food Con ol xxx (2017) xxx-xxx
Fig. 4. Resul s o p incipal componen analysis ca ied ou wi h ATR-FTIR spec al da a o “Vinag e Condado de Huel a” samples (in iplica e). The sco e plo (A) is shown as
well as he co esponding loadings o he i s wo p incipal componen s (PC1 and PC2) (B). The ac onyms o he di e en inega ca ego ies a e de ined in Table 1.
a has demons a ed o p o ide impo an in o ma ion o cha ac e iz-
ing each wine inega .
In addi ion o he di e en ia ion o ca ego ies wi hin each PDO,
he spec al signals o he wo PDOs we e included in he same PCA
model. In his s udy, only he ca ego ies wi h he same ange o ag-
ing (>6 mon hs and >24 mon hs) we e conside ed since hey a e com-
pa able be ween PDOs (Table 1). Fig. 5.A shows he sco es plo o
he i s wo PCs, accoun ing o 93.98% o he o al a iabili y. The
sco es showed a clea di e en ia ion be ween he wo PDOs. These e-
sul s ein o ced ha wine inega s p oduced unde he speci ica ions
o PDOs ha e unique quali y and cha ac e is ics. The spec al load-
ings esponsible o di e en ia ion (Fig. 5.B) we e again loca ed in he
anges 1475–1230 cm−1 and 1175–1000 cm−1, al eady selec ed in p e-
ious PCA models.
4. Conclusions
In his s udy, FTIR p o ed o be use ul o a simple cha ac e i-
za ion o he es ablished aging ca ego ies o high quali y wine ine-
ga s p o ec ed unde PDO. The abili y o he spec al bands in dis in-
guishing inega s by hei ca ego ies and aging ime is mainly based
on a se ies o bands obse ed in he egion o 1500–900 cm−1. These
bands p o ided aluable in o ma ion abou changes ela ed o spe-
ci ic compounds du ing aging in wood ba els (ace ic acid, alcohols,
e he s, es e s, e c.). Since aging is a con inuous a iable, he in e me
dia e ca ego ies in aging (e.g. “Rese a”) we e o e lapped wi h he
o he ca ego ies o some ex en , while he spec al da a allowed a
clea sepa a ion o he mos and leas aged ca ego ies. This p oce-
du e also allowed cha ac e izing swee inega s (“Ped o Ximenez”
ca ego y) whose spec a we e clea ly di e en compa ed o aged ca -
ego ies, mos ly due o bands assigned o suga s and Mailla d com-
pounds (1175–1000 cm−1). Fu he mo e, he unique cha ac e is ics o
he Spanish PDO wine inega s, which di ec ly a ec he ATR-FTIR
spec a, also allowed he di e en ia ion be ween PDOs.
The ad an ages o his me hod (e.g. as , non-des uc i e and wi h
no-sample p epa a ion) would allow implemen ing his measu emen
as an addi ional con ol o PDO councils and p oduce s o assess he
ca ego y o he di e en wine inega s es ablished in each PDO, and
o moni o he aging p ocess wi h a simple and apid p ocedu e. The
chemical assignmen o he bands desc ibed in his wo k and he p e i-
ous knowledge o inega composi ion p o ided an addi ional chemi-
cal suppo o FTIR spec oscopy o his applica ion.
Funding
This wo k was suppo ed by he “Conseje ía de Economía,
Inno ación y Ciencia, Jun a de Andalucía” unde he p ojec
P12-AGR-1601 and by a FPU schola ship o he Minis e io de
Educación, Cul u a y Depo e.
Fig. 5. Resul s o p incipal componen analysis ca ied ou wi h ATR-FTIR spec al da a o “Vinag e de Je ez” (“J”) and “Vinag e Condado de Huel a” (“C”) PDOs. The sco es plo
(A) is shown as well as he co esponding loadings o he i s wo p incipal componen s (PC1 and PC2) (B). The ac onyms o he inega ca ego ies a e de ined in Table 1.
UNCORRECTED PROOF
Food Con ol xxx (2017) xxx-xxx 7
Acknowledgmen s
We would like o hank o he Regula o y Councils o he wine
inega PDOs o hei in aluable help wi h he acquisi ion o he sam-
ples o his s udy.
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