Nontargeted GC-MS approach for volatile profile of toasting in cherry, chestnut, false acacia, and...

Research article

Received: 14 October 2013 Revised: 5 February 2014 Accepted: 6 February 2014 Published online in Wiley Online Library

(wileyonlinelibrary.com) DOI 10.1002/jms.3347

Nontargeted GC–MS approach for volatileprofile of toasting in cherry, chestnut, falseacacia, and ash woodBrígida Fernández de Simón,a Miriam Sanz,b Estrella Cadahía,a*Enrique Esteruelasb and Angel María Muñozb

By using a nontargeted GC–MS approach, 153 individual volatile compounds were found in extracts from untoasted, lighttoasted and medium-toasted cherry, chestnut, false acacia, as well as European and American ash wood, used in cooperage
for aging wines, spirits and other beverages. In all wood types, the toasting provoked a progressive increase in carbohydratederivatives, lactones and lignin constituents, along with a variety of other components, thus increasing the quantitativedifferences among species with the toasting intensity. The qualitative differences in the volatile profiles allow for identifyingwoods from cherry (being p-anisylalcohol, p-anisylaldehyde, p-anisylacetone, methyl benzoate and benzyl salicylate detectedonly in this wood), chestnut (cis and trans whisky lactone) and false acacia (resorcinol, 3,4-dimethoxyphenol, 2,4-dihydroxybenzaldehyde, 2,4-dihydroxyacetophenone, 2,4-dihydroxypropiophenone and 2,4-dihydroxy-3-methoxyacetophenone), butnot those from ash, because of the fact that all compounds present in this wood are detected in at least one other.However, the quantitative differences can be clearly used to identify toasted ash wood, with tyrosol being most prominent, but2-furanmethanol, 3- and 4-ethylcyclotene, α-methylcrotonolactone, solerone, catechol, 3-methylcatechol and 3-hydroxybenzaldehyde as well. Regarding oak wood, its qualitative volatile profile could be enough to distinguish it from cherry and acaciawoods, and the quantitative differences from chestnut (vanillyl ethyl ether, isoacetovanillone, butirovanillone, 1-(5-methyl-2-furyl)-2-propanone and 4-hydroxy-5,6-dihydro-(2H)-pyran-2-one) and ash toasted woods. Copyright © 2014 John Wiley &Sons, Ltd.
Additional supporting information may be found in the online version of this article at the publisher’s web-site.

Keywords: GC–MS; volatile compounds; non-oak woods; toasting

* Correspondence to: Estrella Cadahía, Departamento de Productos Forestales,Centro de Investigación Forestal (CIFOR), Instituto Nacional de Investigacióny Tecnología Agraria y Alimentaria (INIA), Apdo. 8111, 28080 Madrid, Spain.E-mail: [email protected]

a Departamento de Productos Forestales, Centro de Investigación Forestal(CIFOR), Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria(INIA), Apdo. 8111, 28080 Madrid, Spain

b Industrial Tonelera Navarra (INTONA), Departamento I+D+I, Polígono ‘La Moyuela’,Monteagudo, Navarra, Spain

353

Introduction

Wood has been used from time immemorial in the aging of winesand other alcoholic beverages. During this period, oak waschosen over other woods, not only for its organoleptic qualities,but also for its physical and mechanical properties, which allowfor the construction of a variety of containers, providing themwith resistance and porosity, together with the permeabilityneeded during aging. Regarding its extractable chemicalcomponents, quantitatively, ellagitannins are the most importantones, as they can represent up to 10% in dry weight of oakheartwood.[1] In addition, the oak heartwood also shows highlevels of low molecular weight phenolic compounds, such asellagic and gallic acids, in addition to a great variety of aromaticcompounds, such as phenolic aldehydes, phenolic ketonesisomers, volatile phenols, lactones, furanic compounds,pyranones and furanones among others.[2] However, the levelsof volatile compounds can vary greatly depending on oak speciesand geographical origin, as well as the processing that undergoesin cooperage, seasoning on the open-air and toasting at differentintensities.[2,3]

Since the end of last century, the need to reduce productioncosts, as well as the advance in technology, has led to developnew methodologies in the aging in cellar for different beverages.For instance, the use of oak wood chips with micro-oxygenationdirectly in wine can confer wood characteristics to wine faster

J. Mass Spectrom. 2014, 49, 353–370

and simpler, thus changing the classical concept of introducingwine into the wood. A great variety of oak wood pieces for thispurpose can be found on the market: chips, cubes, powder,shavings, granulates, blocks or segments and even staves.[4] Thequantity of added wood, time of contact between wood andwine, piece size, the way the wood is used and many otheraspects influence the sensorial and chemical characteristics ofthe wines produced, being considered the chemical compositionof the wood, especially the contents of volatile compounds andtannins, the most important factors.[5–9]

The interest in providing particular features to wines that canmake them stand out in a global market has led to attempt tofurther modifications. So, in the recent scientific literature, wecan find various papers relating to the use of woods other thanoak, not only in containers such as barrels, but also in pieces that

Copyright © 2014 John Wiley & Sons, Ltd.

B. Fernández de Simón et al.

354

enter into contact with the beverages. A different evolution ofthe phenolic and volatile composition, as well as of theorganoleptic properties, has been pointed out in beverages agedin barrels or in contact with chips made of different woods.[10–16]

Some authors even highlight the fact that wine or vinegar agedin non-oak barrels have had better organoleptic characteris-tics.[12,13,17] At this point, we should have tools that allow us torecognize the botanical species of wood pieces present whennon-oak wood alternative to barrel products are used, speciallytaking into account that only oak and chestnut are approvedby the International Organization of Vine and Wine in the agingof wine.At first view, their physical–mechanical characteristics, such as

color, fiber arrangement, texture, etc., would help us to discerntheir authenticity as they are different. In small wood pieces, suchas wood chips, it can be more difficult to appreciate thesedifferences, and if wood chips are toasted, this process will leadto greater similarity, especially in their color. Additional character-istics must therefore be evaluated. In our research group, wehave proposed the analysis of polyphenolic compounds as auseful tool.[15,18] Its effectiveness in nontoasted wood is moreconclusive, as the toasting process causes a significant decreasein the concentration of many of these polyphenolic markerswhich in many cases even disappear, and generates newcompounds. Because some differences in the volatile profile ofthese woods have been recently shown,[19–22] the objective ofthis work is to compare the volatile composition, by GC–MSnontargeted analyses of untoasted acacia, chestnut, cherry andEuropean and American ash heartwoods along with theirchanges during the toasting process at cooperage, with that ofoak wood found in the literature, in order to find out thefeasibility of these compounds as chemical markers to differentiatethe botanical origin of the wood.

Material and methods

Wood samples

Acacia (Robinia pseudoacacia), chestnut (Castanea sativa), cherry(Prunus avium) and ash (Fraxinus excelsior L. and F. americana L.)heartwood staves, for making barrels, were provided by ToneleríaIntona, SL (Navarra, Spain). The wood was naturally seasoned for24months and toasted in an industrial kiln specially designed fortoasting staves, at two intensities: 165 ºC for 35min and 185 ºCfor 45min. Samples were taken before and after toasting, usingten staves of each wood. The number of staves was chosen inthat way because our objective was to study the general volatileprofile of this wood both before and after toasting, without goingdeeply into their natural variation. Several wood pieces were cutout of each stave, and the pieces were ground, sieved and mixed,taking sawdust samples ranging from 0.80 to 0.28mm of size.

Chemicals

Reference compounds of the volatile identified and the internalstandards were obtained from commercial sources: SigmaChemical (St. Louis, MO); Aldrich Chimie (Neu-Ulm, Germany);Chem Service (West Chester, United States); Fluka ChimieAG (Buchs, Switzerland); Riedel-de-Häen (Seelze, Germany);Extrasynthese (Genay, France); and ABCR GmbH & Co. (Karlsruhe,Germany), with purity higher than 98%. All reagents used(ethanol, dichloromethane, tartaric acid, potassium bitartrate

wileyonlinelibrary.com/journal/jms Copyright © 2014 Jo

and anhydrous sodium sulfate) were purchased from Panreac(Barcelona, Spain).

Extraction of volatile compounds

Volatile compounds were extracted from wood following themethod modified by Cadahía et al.[2] from Chatonnet et al.[23]

Briefly, the sawdust samples (2 g) were soaked in 100ml of ahydro-alcoholic solution (12% ethanol, 0.7 g/l tartaric acid,1.11 g/l potassium bitartrate), for 15 days at room temperatureand darkness, in order to simulate the migration of compoundsduring wine aging. After the mixture was filtered, we added theinternal standards and 15 g of ammonium sulfate, and thesolution was extracted threefold with 15ml of dichloromethane.The organic fraction was dried on anhydrous sodium sulfate,concentrated to 0.5ml under nitrogen flux in a Kuderna-Danishapparatus (Sigma, St. Louis, MO) and analyzed by GC/MS. Fourinternal standards were used: 100μl of a solution of 3,4-dimethylphenol (20mg/l in 95% ethanol) (for volatile phenols),100μl of a solution of o-vanillin (1mg/ml in 95% ethanol) (forphenolic aldehydes and related compounds), 100μl of a solutionof γ-hexalactone (2mg/ml in 95% ethanol) (for furan derivativesand other heterocycles) and 50μl of a solution of 2-octanol(1mg/ml in 95% ethanol) (for aldehydes, alcohols and fatty acidswith a linear chain, C13 norisoprenoids and the remainingcompounds). In all cases, the samples were analyzed in duplicate.

GC–MS analysis

Analyses were performed using an Agilent 6890N gas chromato-graph (Palo Alto, CA) equipped with a quadrupole massspectrometer Agilent 5975B. Samples were injected (2μl) in splitmode (30 : 1), and volatiles were separated using a fusedsilica capillary column (SUPELCOWAX-10) (30 × 0.25mm i.d. and0.25-μm film thickness), supplied by Supelco (Madrid, Spain),and under the working conditions previously described.[24] Thepressure of the carried gas (helium GC grade) was 9 psi with alinear velocity of 1.1mlmin�1, the oven temperature was 45 °C,first increased at 3 °Cmin�1 to 230 °C held for 25min, and thenheated at 10 °Cmin�1 to 270 °C, and held at this temperaturefor an additional 21min. The injection temperature was 230 ºC.Detection was carried out by EI mode (70 eV), interphasedetection temperature was 290 ºC (MS source at 230 ºC and MSquad at 150 ºC) and scanning mass was ranged between35 and 400 amu. For each detected peak, a linear retention index(RI) was calculated using GC RI standards (hydrocarbons from C10to C35 used as internal standards) according to the method ofVan den Dool and Kratz.[25]

Among the detected compounds, 68 were identified bycomparing their RI and MS fragmentation patterns with thoseof commercial standards, and 76 were tentatively identified bycomparing their mass fragmentation with those in commerciallibraries (NIST 2.0 and Wiley 7) matching more than 95%, andwith those reported in the literature, also taking into accounttheir RI, structure and molecular weight.[2,26–36] Finally, ninecompounds remained unidentified.

Quantitative determinations were carried out by the internalstandard method, using peak areas obtained from selected ionmonitoring. The selected ions for each of the evaluatedcompounds are showed in Table 1. The concentrations of eachsubstance were measured by comparison with calibrations madewith pure reference compounds analyzed under the same

hn Wiley & Sons, Ltd. J. Mass Spectrom. 2014, 49, 353–370

Table

1.Volatile

compoun

dsin

extracts

from

untoastedan

dtoasteddifferen

twoodspecies

Peak

RIa

Compound

MSb

m/z

(%)

Calibrationc

Species

Toasting

SpxT

Furanderivatives

614

44furfural

96(100

),95

(95),3

9(90)

6.90

***(b

abbb)

27.8***(b

ba)

277***

1715

515-methylfurfural

110(100

),10

9(95),5

3(80)

1.81

72.2***(c

ba)

261***

9324

665-hyd

roxymethylfurfural

97(100

),12

6(75),1

09(13)

3.92

*(b

abab

ab)

144***

(cba)

293***

7221

695-acetoxymethyl-2-furfural

126(100

),79

(31),4

3(32),1

09(25)

3.61

*(b

aab

aab

)12

2***

(cba)

481***

5119

442,5-furandicarboxaldeh

yde

124(100

),1

23(55),9

5(40)

furfural

7.90

***(b

abaa)

31.6***(c

ba)

134***

2416

472-furanmethan

ol

98(100

),81

(53),9

7(50)

18.9***(b

bbaa)

18.8***(b

aa)

154***

1815

58methyl-2-furoate

95(100

),12

6(35),3

9(20)

1.86

145***

(cba)

430***

914

832-furylm

ethylketone

95(100

),11

0(48)

3.45

*(b

aab

bb)

35.1***(b

ba)

41.6***

1615

492-furyle

thylketone

95(100

),12

4(22)

1-(2-furanyl)-ethan

one

1.23

162***

(cba)

376***

5219

69furylh

ydroxymethylketone

95(100

),12

6(18)

1-(2-furanyl)-ethan

one

13.6***(b

abbb)

20.6***(c

ab)

699***

714

521-methoxy-2-ethoxyethyl-1-furan

97(100

),12

5(85),1

70(10),4

1(10)

furfural

5.39

**(b

abbb)

13.5***(b

ba)

465***

3417

511-(5-m

ethyl-2-furyl)-2-propan

one

95(100

),13

8(15)

1-(2-furanyl)-ethan

one

3.41

*(b

abbb)

72.2***(c

ba)

399***

4518

71(3E)-4-(2-furyl)-3-buten-2-one

121(100

),65

(75),1

37(65),9

4(50)

1-(2-furanyl)-ethan

one

4.21

*(b

abbb)

28.4***(b

ba)

451***

Other

carboh

ydrate

derivatives

4218

424-hyd

roxy-5,6-dihyd

ro-

(2H)-pyran

-2-one

114(100

),58

(60)

maltol

3.75

*(b

abbb)

24.6***(b

ba)

68.9***

7622

332,3-dihyd

ro-3,5-dihyd

roxy-

6-methyl-4H-pyran

-4-one

144(100

),43

(100

),10

1(70),7

3(30)

maltol

1.52

77.5***(c

ba)

108***

5019

38maltol

126(100

),71

(40),9

7(40),5

5(20)

6.06

**(b

bbaa)

157***

(cba)

629***

4018

22dihyd

romaltol

43(100

),128(76),5

7(27),7

2(27)

maltol

1.59

39.4***(b

aa)

23.5***

7321

88allomaltol

126(100

),69

(40)

maltol

3.74

*(abab

baa)

103***

(cba)

181***

8322

805-hyd

roxymaltol

142(100

),68

(35)

maltol

2.64

48.9***(c

ba)

189***

5619

901H

-pyrrole-2-carboxaldeh

yde

95(100

),94

(65),6

6(50),3

9(25)

4.50

*(b

babb)

34.2***(c

ba)

643***

5920

13Fu

raneo

l43

(100

),128(85),5

7(68),8

5(33)

4.19

*(b

bab

aab

)58

.6***(baa)

59.6***

6420

66unkn

own

128(100

),99

(80),5

7(40),9

8(35)

Furaneo

l2.47

57.6***(b

ba)

173***

3717

84cyclotene

112(100

),69

(50),5

5(50),8

3(25)

6.04

**(b

bbaa)

138***

(cba)

408***

2516

583-ethylcyclotene

126(100

),83

(45),8

4(40),5

5(38)

cyclotene

16.1***(b

bbaa)

28.4***(c

ba)

365***

2816

964-ethylcyclotene

97(100

),69

(65),4

1(50),1

26(42)

cyclotene

14.2***(b

bbaa)

25.0***(b

ba)

1137

***

3517

773,5-dim

ethylcyclotene

126(100

),69

(40),1

11(40),5

6(35)

cyclotene

18.9***(b

bbaa)

28.5***(c

ba)

737***

3817

953,4-dim

ethylcyclotene

126(100

),11

1(90),8

3(75),5

5(75)

cyclotene

16.3***(b

bbaa)

30.6***(c

ba)

872***

3016

984,5-dim

ethyl-2-ciclohexen

-1-one

82(100

),12

4(40),4

2(38),6

8(35)

cyclotene

11.8***(b

bbaa)

38.5***(c

ba)

909***

Lacton

es

1915

93γ-butyrolactone

42(100

),86(50),5

6(38)

0.97

31.0***(b

ba)

7.54

***

2916

96γ-ethoxyb

utyrolactone

57(100

),58(98),8

5(79)

γ-butyrolactone

1.29

107***

(cba)

37.4***

3317

16crotonolactone

55(100

),84

(58)

γ-butyrolactone

1.01

210***

(cba)

321***

2716

83α-methylcrotonolactone

41(100

),98(95),6

9(93)

γ-butyrolactone

11.4***(b

bbaa)

76.6***(c

ba)

449***

6020

26solerone

85(100

),43

(60),5

5(18),1

28(10)

γ-butyrolactone

6.01

**(b

bbaa)

58.1***(b

ba)

929***

4418

61tran

s-whiskylactone

99(100

),71

(30)

13.6***(b

abbb)

2.58

8.86

***

4819

28cis-whiskylactone

99(100

),71

(30),6

9(29),8

7(20)

26.8***(b

abbb)

1.06

10.1***

Nontargeted GC–MS volatile profile of toasted woods

J. Mass Spectrom. 2014, 49, 353–370 Copyright © 2014 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/jm

355

(Con

tinues)

s

Table

1.(Continued

)

Peak

RIa

Compound

MSb

m/z

(%)

Calibrationc

Species

Toasting

SpxT

Simpleph

enols

5319

78phen

ol94(100

),66

(35)

1.63

91.6***(b

ba)

30.9***

5419

80o-cresol

108(100

),107(90)

14.2***(b

bbaa)

30.2***(b

ba)

507***

6220

56p-cresol

107(100

),10

8(95)

11.9***(a

bbbb)

9.25

**(b

ba)

37.4***

6320

64m-cresol

108(100

),107(85)

13.9***(b

bbaa)

39.3***(c

ba)

179***

6821

533-ethylphen

ol

107(100

),12

2(40),7

7(30)

phen

ol

3.59

*(abbaab

ab)

0.66

1.55

105

2647

catechol

110(100

),64

(40),8

1(20)

phen

ol

4.73

*(b

bbaa)

62.5***(b

ba)

264***

101

2627

3-methylcatechol

124(100

),78

(70),12

3(40)

phen

ol

13.9***(b

bbaa)

47.9***(b

ba)

616***

110

2727

4-methylcatechol

124(100

),12

3(55),7

8(50)

phen

ol

6.05

**(b

bbaa)

39.3***(c

ba)

178***

126

2918

2-methoxy

hyd

roquinone

140(100

),12

5(80),9

7(60)

phen

ol

5.12

**(a

bbbb)

13.1***(b

ba)

19.8***

138

3058

resorcinol

110(100

),82

(20),8

1(20)

phen

ol

102***

(bbabb)

1.2

55.1***

4318

54phen

ylmethan

ol

79(100

),10

8(90),7

7(58),1

07(51)

20.8***(a

bbbb)

4.55

*(b

ba)

58.7***

4618

882-phen

ylethan

ol

91(100

),92

(65),1

22(38)

61.2***(c

ccab)

0.68

62.7***

6621

152-phen

oxyethan

ol

94(100

),77

(35),1

38(30),6

6(20)

0.52

0.67

0.43

4719

15ben

zothiazole

135(100

),10

8(30),6

9(18)

2.01

52.3***(b

ba)

14.3***

Mon

ometho

xyph

enols

4118

33guaiacol

109(100

),124(85),81(50)

8.57

***(b

bbaa)

64.6***(c

ba)

118***

4919

284-methylguaiacol

123(100

),138(100

),95

(35)

7.67

***(b

abaa)

46.1***(c

ba)

97.1***

5720

024-ethylguaiacol

137(100

),15

2(75)

3.19

7.09

*(b

aa)

3.42

**

6520

834-propylgua

iacol

137(100

),16

6(30),1

38(18)

4-ethylguaiacol

4.93

*(b

abab

aa)

110***

(cba)

112***

7121

654-vinylguaiacol

150(100

),13

5(73),1

07(48)

4-ethylguaiacol

10.5***(b

bbaa)

12.4***(c

ba)

10.5***

6721

39eu

gen

ol

164(100

),14

9(30),1

31(30),1

03(30)

44.9***(c

acbb)

5.66

*(b

ba)

70.3***

7522

26cisisoeu

gen

ol164(100

),14

9(32),1

31(28),1

03(28)

14.3***(b

bbaa)

52.1***(b

ba)

112.9***

8423

14tran

sisoeu

gen

ol

164(100

),14

9(32),1

31(28),1

03(28)

32.6***(d

dcba)

10.8***(b

ba)

29.0***

Dia

ndtrim

etho

xyph

enols

7722

37syringol

154(100

),13

9(47)

3.68

*(b

abab

aa)

168***

(cba)

360***

8523

224-methylsyringol

168(100

),15

3(72),1

10(30)

1.84

176***

(cba)

375***

8823

814-ethylsiringol

167(100

),18

2(56)

4-methylsyringol

1.95

100***

(bba)

44.1***

9124

524-propylsiringol

167(100

),19

6(35)

4-methylsyringol

2.39

53.4***(b

ba)

683***

9425

114-allylsyringol

194(100

),91

(25),1

19(22)

1.56

155***

(bba)

260***

109

2696

cisortran

s4-(1-propen

yl)syringol

194(100

)13

1(25),1

79(20)

4-allylsyringol

11.2***(b

baba)

24.5***(c

ba)

19.3***

111

2732

3,4-dim

ethoxyp

hen

ol

154(100

),13

9(80),1

11(55)

syringol

57.5***(b

babb)

1.63

25.2***

135

3026

3,4,5-trim

ethoxyphen

ol169(100

),18

4(66),1

41(50),6

9(32)

72.2***(a

bbbb)

5.48

*(a

bb)

176***

122

2857

3,4,5-trim

ethoxy-ben

zenem

ethan

ol

198(100

),12

7(30),9

5(20)

syringol

4.63

*(b

ababb)

2.65

2.89

*

Phenolicaldehydes

1114

93ben

zaldeh

yde

106(100

),10

5(92),7

7(90)

12.7***(b

bbaa)

17.5***(c

ab)

126***

2316

442-hyd

roxyben

zaldeh

yde

122(100

),12

1(95),6

5(40)

ben

zaldeh

yde

4.48

*(b

bbaa)

145***

(cba)

158***

112

2735

3-hyd

roxyben

zaldeh

yde

122(100

),12

1(90),9

3(55)

ben

zaldeh

yde

8.33

***(b

bbaa)

68.2***(b

ba)

246***

125

2978

4-hyd

roxyben

zaldeh

yde

121(100

),12

2(95),9

3(40)

ben

zaldeh

yde

0.47

355***

(cba)

179***


wileyonlinelibrary.com/journal/jms Copyright © 2014 John Wiley & Sons, Ltd. J. Mass Spectrom. 2014, 49, 353–370

356

Table

1.(Continued

)

Peak

RIa

Com

pound

MSb

m/z

(%)

Calibrationc

Species

Toasting

SpxT

139

2155

2,3-dihyd

roxyben

zaldeh

yde

138(100

),13

7(70),9

2(25)

2,4-dihyd

roxyben

zald.

3.36

36.6***(b

ba)

18.2***

6930

742,4-dihyd

roxyben

zaldeh

yde

137(100

),13

8(78),8

1(25),5

3(10)

37.6***(b

babb)

6.90

*(b

aa)

91.3***

9625

18vanillin

151(100

),15

2(95),1

09(22),1

23(18)

4.38

*(b

abbaa)

246***

(cba)

221***

124

2904

syringaldeh

yde

182(100

),18

1(55)

0.35

509***

(cba)

189***

141

3096

conife

raldeh

yde

178(100

),13

5(50),1

47(42),1

07(38)

9.05

***(b

bbaa)

81.3***(cba)

161***

153

3458

sinap

aldeh

yde

208(100

),16

5(52),1

37(38),1

80(25)

0.46

294***

(cba)

184***

5519

86p-an

isaldeh

yde

135(100

),13

6(65),7

7(30),1

07(18)

ben

zaldeh

yde

9.22

***(a

bbbb)

8.78

**(b

ba)

396***

5820

12cinnam

aldeh

yde

131(100

),13

2(75),103

(70)

vanillin

9.89

***(b

babb)

1.72

4.04

***

Phenolicketones

9725

18isoacetovanillone

137(100

),16

6(30),1

22(20),9

4(16)

acetov

anillone

7.16

***(b

abbb)

28.2***(b

ba)

356***

9925

65acetovanillone

151(100

),16

6(50),1

23(20),1

08(10)

2.52

353***

(cba)

436***

100

2617

isopropiovanillone

137(100

),18

0(20),1

22(16),9

4(12)

acetov

anillone

2.32

129***

(bba)

322***

106

2661

propiovanillone

151(100

),18

0(20),1

23(16),1

08(10)

acetov

anillone

3.88

*(ababaab

)87

.8***(b

ba)

151***

115

2770

butirovanillone

151(100

),12

3(20),1

08(15),1

94(5)

acetov

anillone

4.17

*(b

abbb)

38.8***(b

ba)

396***

7922

47p-an

isylacetone

121(100

),17

8(35)

acetov

anillone

8.27

***(a

bbbb)

5.84

*(b

ba)

19.8***

127

2927

isoacetosyringone

167(100

),19

6(50),1

23(10),1

06(10)

acetosyringone

2.08

96.7***(b

ba)

138***

130

2953

acetosyringon

e181(100

),19

6(45),1

53(15),6

5(15)

0.23

880***

(cba)

220***

133

2979

isopropiosyringone

167(100

),21

0(20),1

23(10),1

06(5)

acetosyringone

0.94

188***

(bba)

500***

134

3010

propiosyringone

181(100

),21

0(30),1

53(10),6

5(10)

acetosyringone

26.7***(a

bccc)

16.9***(b

ba)

29.6***

140

3085

butirosyringone

181(100

),22

4(15),1

53(12)

acetosyringone

1.82

96.6***(b

ba)

223***

Phenolicacidsan

desters

2015

95methylben

zoate

105(100

),77

(60),1

36(40),5

1(22)

ben

zaldeh

yde

12.4***(a

bbbb)

5.68

*(b

aba)

34.4***

9825

57methylvanillate

151(100

),18

2(52),1

23(18)

61.9***(a

ccbb)

4.21

41.9***

151

3215

methylhomovanillate

137(100

),19

6(20),1

22(13),1

80(8)

methylvanillate

3.74

*(b

abab

ab)

115***

(cba)

123***

128

2933

methylsyringate

181(100

),21

2(100

),14

1(12),1

53(9)

182***

(abbbb)

0.29

56.9***

145

3122

2-ethylhexyltran

s-4-methoxycinnam

ate

178(100

),16

1(50),1

34(15),2

90(9)

5.46

**(a

abbbb)

2.95

7.05

***

113

2737

ben

zylsalicylate

91(100

),22

8(10)

21.6***(a

bbbb)

4.56

15.3***

8923

89ben

zoicacid

105(100

),12

2(85),77

(70),5

1(30)

ben

zaldeh

yde

66.8***(a

bbbb)

2.66

407***

119

2833

tran

scinnam

icacid

147(100

),14

8(95),1

03(60)

homov

anillicacid

9.74

***(a

aabb)

5.07

*(b

aba)

17.5***

Phenolicalcoho

lsan

dether

132

2965

tyrosol

107(100

),13

8(24),7

7(20)

199***

(bbbaa)

0.98

55.5***

114

2764

vanillylalcohol

154(100

),93

(60),6

5(43),1

37(40)

6.45

**(b

abaa)

1.98

3.07

**

117

2805

homovanillylalcohol

137(100

),16

8(70),1

22(15),9

4(10)

9.62

***(b

bbaa)

30.0***(b

ba)

15.7***

150

3213

conife

ryla

lcohol

137(100

),18

0(71),1

24(58),9

1(35)

12.3***(b

aabb)

12.4***(c

ba)

13.2***

152

3304

dihyd

rosinap

ylalcohol

168(100

),16

7(90),2

12(70)

conife

ryla

lcohol

9.01

***(b

abbb)

12.9***(b

ba)

414***

7822

43p-an

isylalcohol

138(100

),10

9(95),1

37(70),7

7(70)

conife

ryla

lcohol

25.2***(a

bbbb)

0.46

8.19

***

129

2941

vanillylethylether

137(100

),18

2(75),1

38(50),1

23(18)

vanillin

18.3***(b

abbb)

9.95

**(b

ba)

354***

Aromaticketones

2216

20acetophen

one

105(100

),77

(65),1

20(30),5

1(22)

vanillin

2.8

85.5***(c

ba)

30.7***

120

2838

m-hyd

roxyacetophen

one

121(100

),13

6(70),9

3(70)

vanillin

5.80

**(b

bbaa)

83.8***(b

ba)

534***

(Con

tinues)


J. Mass Spectrom. 2014, 49, 353–370 Copyright © 2014 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/jms

357

Table

1.(Continued

)

Peak

RIa

Com

pound

MSb

m/z

(%)

Calibrationc

Species

Toasting

SpxT

131

2959

p-hyd

roxyacetophen

one

121(100

),13

6(35),9

3(35)

vanillin

5.74

**(b

babb)

19.1***(b

ba)

22.2***

7421

972,4-dihyd

roxyacetophen

one

137(100

),15

2(40)

vanillin

7.67

***(b

babb)

50.6***(b

ba)

535***

148

3140

2,6-dihyd

roxyacetophen

one

137(100

),15

3(50)

vanillin

10.7***(b

babb)

10.1***(b

ba)

233***

8222

772,4-dihyd

roxypropiophen

one

137(100

9),1

66(25)

vanillin

6.88

***(b

babb)

33.9***(b

ba)

509***

142

3101

2,4-dihyd

roxy-3-m

ethoxyacetophen

one

151(100

),18

2(30),1

23(18)

vanillin

9.11

***(b

babb)

9.72

**(b

ba)

26.5***

Linear

fattyacids

514

38aceticacid

60(100

),43

(100

),45

(100

)49

.5***(b

abbb)

0.28

13.9***

1515

45propan

oicacid

74(100

),73

(50)

9.65

***(a

bbaa)

16.8***(c

ba)

32.6***

2116

12butanoicacid

60(100

),73

(30),8

8(5)

0.97

31.0***(b

ba)

7.54

***

3217

11pen

tanoicacid

60(100

),73

(40)

7.84

***(b

bbaa)

7.87

**(a

ab)

6.18

***

3918

03hexan

oicacid

60(100

),73

(50),8

7(10)

9.95

***(b

bbaa)

4.83

*(a

ab)

6.99

***

6120

32octan

oicacid

60(100

),73

(80),1

01(40)

16.4***(a

bcbcbc)

0.29

9.58

***

8022

49decan

oicacid

60(100

),73

(90),1

29(30)

2.55

0.65

12.5***

9224

59dodecan

oicacid

73(100

),60(90),1

29(20),2

00(10)

2.2

23.8***(a

bc)

6.58

***

108

2682

tetrad

ecan

oicacid

73(100

),60(90),1

29(40),2

28(20)

6.56

***(a

abaa)

3.88

4.84

***

116

2785

pen

tadecan

oicacid

60(100

),73

(100

),12

9(50),2

42(40)

0.91

26.9***(a

bb)

4.21

***

123

2901

hexad

ecan

oicacid

73(100

),60(90),1

29(20),2

56(20)

3.59

16.7***(a

bb)

11.5***

143

3102

octad

ecan

oicacid

43(100

),60(80),7

3(80),2

84(30)

1.45

28.4***(a

bb)

4.74

***

146

3135

oleicacid

55(100

),60(80),7

3(60),2

64(20)

1.26

4.40

*(a

bb)

14.1***

C13

norisop

reno

ids

9525

953-oxo-α-io

nol

108(100

),10

9(35),1

35(20),1

52(18)

conife

raldeh

yde

14.0***(b

abbb)

3.13

7.14

***

107

2678

7,8-dihyd

ro-3-oxo-α-io

nol

43(100

),69

(80),1

08(80),1

35(70)

conife

raldeh

yde

29.8***(a

bccc)

4.33

11.2***

121

2846

6,7-deh

ydro-7,8-dihyd

ro-3-oxo-α-io

nol

149(100

),16

4(60),1

22(30)

conife

raldeh

yde

15.7***(a

cbcc)

9.29

**(a

bb)

11.6***

143

3108

vomifo

liol

124(100

),79

(10)

conife

raldeh

yde

3.05

14.1***(a

bb)

4.94

***

103

2643

dihyd

ro-3-oxo-β-io

nol

43(100

),109(80),1

37(60),1

52(50)

conife

raldeh

yde

48.7***(a

ccbb)

2.46

18.3***

104

2657

7,8-dihyd

ro-4-oxo-β-io

nol

137(100

),10

9(80),1

52(60),1

95(30)

conife

raldeh

yde

110***

(abbbb)

0.31

31.6***

Other

compo

unds

110

841-hexan

al44

(100

),56(90),5

7(60)

2.54

7.82

**(a

bb)

7.12

***

413

841-nonan

al57(100

),56

(60),7

0(35)

18.4***(a

aabb)

9.98

**(a

ab)

12.8***

1315

212-nonen

al41

(100

),43

(86),5

5(70),7

0(58),8

3(38)

25.9***(a

abcc)

4.5*

(aab)

22.5***

3117

052,4-decad

ienal

81(100

),41

(50)

2-ethyl-1-hexan

ol3.29

*(abbabb)

2.48

4.28

***

8723

701-hexad

ecan

ol

55(100

),83(90),7

0(80),9

7(70)

2-ethyl-1-hexan

ol1.27

18.9***(b

ca)

4.68

***

1014

892-ethyl-1-hexan

ol57(100

),83

(22),7

0(20)

4.32

*(b

babb)

8.02

**(a

bb)

20.5***

3617

81etan

ol-2-(2-butoxy

ethoxy)

57(100

),45

(95),7

5(20)

4.60

*(b

abbb)

25.3***(b

ac)

15.6***

814

541-acetyloxy-2-propan

one

43(100

),86

(18),1

16(8)

2-ethyl-1-hexan

ol1.61

85.8***(b

ba)

444***

313

581-hyd

roxy-2-butanone

57(100

),88

(12)

2-ethyl-1-hexan

ol10

.3***(c

ccba)

40.9***(c

ba)

177***

212

013-hyd

roxy-2-butanone

45(100

),43

(60),8

8(20)

2-ethyl-1-hexan

ol2.12

92.6***(c

ba)

101***

1415

211-acetyloxy-2-butan

one

57(100

),43

(92),1

01(10)

2-ethyl-1-hexan

ol4.65

*(b

bbaa)

177***

(cba)

498***

1215

20unkn

own

111(100

),13

9(85),18

4(15)

2-ethyl-1-hexan

ol2.4

62.9***(b

ba)

448***

7021

59caprolactam

55(100

),113(80),8

4(40),8

5(40)

2-ethyl-1-hexan

ol1.05

43.2***(b

ba)

9.79

***



358

Table

1.(Continued

)

Peak

RIa

Com

pound

MSb

m/z

(%)

Calibrationc

Species

Toasting

SpxT

8122

59methyldihyd

rojasm

onate

83(100

),15

3(30),1

56(30)

2-ethyl-1-hexan

ol0.41

3.69

2.98

*

136

3042

squalen

e69(100

),81

(60),9

5(20)

2-ethyl-1-hexan

ol3.88

*(b

abab

aa)

10.4***(b

ca)

5.61

***

2616

81α-terpineo

l59

(100

),93(60),1

21(50)

2-ethyl-1-hexan

ol3.16

0.72

4.09

***

Other

unknow

ncompo

unds

8623

38unkn

own

43(100

),57

(30),8

5(15)

2-ethyl-1-hexan

ol0.97

90.5***(b

ba)

91.4***

9024

15unkn

own

43(100

),69

(38),7

3(25),8

6(20)

2-ethyl-1-hexan

ol4.44

*(b

abbb)

21.8***(b

ba)

396***

102

2646

unkn

own

121(100

),11

9(62),1

37(30),13

8(30)

vanillin

121***

(cccab)

1.78

529***

118

2832

unkn

own

137(100

),16

4(60),2

24(50),1

49(35)

vanillin

7.65

***(b

abbb)

11.4***(b

ba)

417***

137

3056

unkn

own

167(100

),21

0(42),1

82(38),1

54(25)

vanillin

0.21

237***

(bba)

61.7***

149

3174

unkn

own

167(100

),19

8(30)

vanillin

4.27

*(a

babab

)89

.3***(b

ba)

44.5***

150

3183

unkn

own

167(100

),25

4(70),1

94(45),1

68(38)

vanillin

7.59

***(b

abbb)

9.39

**(b

ba)

430***

Retentionindex,m

assspectral

data,stan

dardusedin

quan

tification

,andF-values

from

thean

alysisofvarian

ce(ANOVA)results.

Lettersbetweenparen

theses

show

thedifferen

cesam

ongspecies,in

theorder

Prun

usavium,C

astaneasativa,Ro

biniapseudo

acacia,Fraxinu

sescelsioran

dF.am

erican

a;oram

ongtoastinglevel,in

theorder

seasoned

,lighttoastingan

dmed

ium

toasting.D

ifferen

tlettersden

ote

astatisticald

ifferen

cewith95

%confiden

celevel(Studen

tNew

man

–Keu

lsmultiplerangetest),withabeingthe

highestconcentration.

*Indicatesignificance

atp<0.01

.**Indicatesignificance

atp<0.00

1.***Indicatesignificance

atp<0.00

01.a

Retentionindex

inacarbow

axcolumn.b

Ions

used

forp

eakquantificatio

ninboldface.

cCalibrationusedwhen

thepure

reference

stan

dardwas

not

available.


J. Mass Spectrom. 2014, 49, 353–370 Copyright © 2014 John W

359

conditions. The corresponding calibration was made for eachcompound, and linear regression coefficients between 0.973and 0.9996 were obtained. In general, more than one linearregression was made for each compound, at different concentra-tion levels. The detection limits for these compounds in theseanalytical conditions were between 0.001 and 0.01μg g�1 ofwood, except for vanillyl and homovanillyl alcohol (0.05μg g�1)and γ-butyrolactone (0.03μg g�1). Calibration of a similarcompound was used when the pure reference standard wasnot available, as listed in Table 1. The variation coefficients ofduplicates were lower than 3%.

Statistical analysis

The obtained data were analyzed by carrying out univariate anal-ysis using two-way analysis of variance (ANOVA) (wood speciesfactor, toasting level factor and species and toasting together),and applying the post hoc Student Newman–Keuls multiplerange test. Multivariate canonical discriminant analysis (CDA)was also carried out using the program SAS (version 9.1; SASInstitute, Cary, NC). CDA finds canonical functions, linearcombinations of the quantitative variables that provide maximalseparation between defined groups, computing squaredMahalanobis distances between class means, and performingboth univariate and multivariate one-way analyses of variance.

Results and discussion

A total of 153 individual volatile and semi volatile compoundswere found in the studied woods and listed in Table 1 togetherwith their linear RI, fragmentation pattern and ANOVA results ofall obtained data, applied taking into account only the woodspecies, only the toasting intensity, and the two factors together.They can be distinguished as such: compounds arising fromwood carbohydrate and lipid degradation; low molecular-weightphenolic compounds arising from wood lignin degradation; C13norisoprenoids arising from carotenoids degradation;[26,33]

aldehydes, alcohols and fatty acids with a linear chain, whichwere natural wood components or derived from lipiddegradation;[31] and other compounds, revealing a wide varietyof chemical families.

The volatile profile obtained from each wood, along with itsevolution at two levels of toasting intensity commonly used atcooperages, shows some differences to that reported in literaturefor oak wood, American (Quercus alba) and European (Quercusrobur, Q. petraea, Quercus pyrenaica, etc.), and could be used asa useful tool to differentiate the botanical origin of the wood.Table 2 shows the average concentrations of some relevantcompounds in untoasted, light-toasted and medium-toastedwoods for the five studied species. The remaining data are inthe supplementary material.

Carbohydrate derivatives and lactones

The wood extracts were shown to possess a wide number ofmolecules (35) that showed heterocyclic structures (furanic com-pounds, pyranones and furanones), along with cyclopentanonesor cyclohexanones (Table 1). Among them, peak 64 presents abase peak at m/z 128 (Furaneol like-structure) and was includedas a carbohydrate derivative. Peaks 86 and 90 which remainedunidentified could be considered carbohydrate derivativesbecause they have m/z 43 as base peak, and m/z 57 or 69 ions,

iley & Sons, Ltd. wileyonlinelibrary.com/journal/jms

Table

2.GCquan

titative

evaluationofrelevantvo

latile

compoundsin

extracts

from

untoasted(UT),lighttoasted(L)an

dmed

ium

toasted(M

)differen

twoodspeciesa

μgg�1

ofwood

Cherry

Chestnut

Acacia

American

ash

Europeanash

Peak

Compound

UT

LM

UT

LM

UT

LM

UT

LM

UT

LM

Carbo

hydratederivatives

andlacton

es

6furfural

0.66

87.7

175

6.72

431

1675

0.92

20.7

714

1.31

26.5

62.1

0.54

26.5

63.6

17MF

0.07

14.0

29.4

0.19

29.0

75.8

0.10

7.48

91.3

0.11

15.3

17.1

0.05

15.2

14.9

93HMF

0.54

41.5

45.8

21.0

66.7

103

0.51

6.65

93.8

1.95

51.1

81.9

3.28

51.0

58.9

242-furanmethan

ol

0.16

1.48

1.42

0.10

0.26

1.25

0.18

1.99

6.90

0.52

32.2

30.4

0.29

32.2

26.1

162-furyle

thylketone

0.01

0.04

0.07

ndnd

0.26

nd0.03

0.23

nd0.11

0.16

nd0.11

0.14

71-methoxy-2-ethoxyethyl-1-furan

0.01

2.93

16.4

0.62

9.74

897

0.17

1.15

69.9

1.74

0.70

11.0

1.10

0.70

6.02

34MFP

nd0.31

1.51

0.03

0.92

4.26

nd0.06

1.49

nd0.68

0.85

nd0.68

0.93

45(3E)-4-(2-furyl)-3-buten-2-one

nd0.01

0.02

nd0.01

0.23

nd0.01

0.05

nd0.01

0.02

nd0.01

0.02

42HDP

nd0.84

1.50

nd1.27

20.73

0.07

4.21

5.21

nd0.49

2.18

nd0.49

1.90

50maltol

0.50

3.53

14.7

2.03

4.26

17.50

1.38

6.46

19.0

0.92

19.0

32.9

0.51

19.0

31.7

561H

-pyrrole-2-carboxaldeh

yde

nd1.04

1.38

0.02

1.51

1.65

0.04

2.69

15.7

nd1.36

3.43

nd1.36

2.96

64unkn

own

nd0.55

3.04

nd0.26

16.52

nd0.18

5.29

nd0.77

3.22

nd0.76

3.32

253-ethylcyclotene

nd0.02

0.41

nd0.05

0.29

nd0.05

0.56

0.03

2.33

5.15

0.03

2.33

4.61

284-ethylcyclotene

ndnd

0.07

ndnd

0.12

nd0.01

0.30

nd1.85

6.01

nd1.85

5.20

383,4-dim

ethylcyclotene

ndnd

0.07

0.01

0.04

0.08

nd0.03

0.10

nd0.43

0.74

nd0.43

0.79

304,5-dim

ethyl-2-ciclohexen

-1-one

nd0.06

0.15

nd0.16

0.29

nd0.07

0.35

nd0.73

2.45

nd0.73

1.91

33crotonolactone

nd7.76

30.2

1.62

7.41

57.0

0.04

7.52

30.7

2.09

13.6

23.3

1.09

13.6

22.8

27α-methylcrotonolactone

nd0.46

2.39

nd0.57

2.20

nd0.79

2.14

0.27

3.71

7.04

0.15

3.70

6.64

60solerone

nd1.17

7.07

nd1.65

5.08

nd1.68

6.31

nd1.93

39.6

nd1.92

33.2

Volatileph

enols

105

catechol

0.19

1.30

4.52

nd0.14

2.50

0.14

0.53

4.27

ndnd

21.5

ndnd

16.0

101

3-methylcatechol

nd0.09

0.22

nd0.04

0.41

0.01

0.26

1.01

ndnd

4.59

ndnd

4.83

126

2-methoxy

hyd

roquinone

0.63

2.80

5.87

0.36

0.60

2.74

0.54

1.91

4.45

0.63

1.80

3.57

0.25

1.80

4.22

138

resorcinol

ndnd

ndnd

ndnd

4.83

8.11

9.39

ndnd

ndnd

ndnd

41guaiacol

0.53

0.91

1.56

0.15

0.46

5.30

0.86

0.52

6.05

0.22

6.47

13.3

0.13

6.46

11.9

494-methylguaiacol

0.11

0.62

1.86

0.15

2.64

7.20

0.10

0.24

1.74

1.23

3.66

2.61

0.24

3.65

3.39

67eu

gen

ol

0.11

0.74

1.45

4.47

3.23

2.28

0.21

0.40

2.23

0.94

1.59

3.08

0.57

1.58

3.00

84tran

sisoeu

gen

ol

0.61

1.28

0.58

2.42

2.07

2.03

3.36

3.82

7.56

2.06

8.30

11.4

7.66

8.28

11.7

77syringol

1.49

2.13

4.98

0.29

1.41

13.60

1.89

1.26

20.9

0.92

7.47

23.6

0.63

7.45

23.0

854-methylsyringol

0.41

1.94

9.94

0.43

3.41

20.24

0.72

1.14

8.13

1.12

5.34

8.48

0.49

5.33

10.5

944-allylsyringol

0.56

2.05

9.63

4.58

3.58

8.60

0.77

0.96

15.4

0.74

1.66

7.32

0.55

1.66

7.21

109

cisortran

s4-(1-propen

yl)syringol

2.46

6.55

6.55

3.93

8.14

5.24

9.27

10.8

24.0

2.62

9.26

12.1

6.57

9.24

17.3

111

3,4-dim

ethoxyphen

olnd

ndnd

ndnd

nd1.83

1.17

0.72

ndnd

ndnd

ndnd

135

3,4,5-trim

ethoxyp

hen

ol

46.7

21.97

9.60

0.45

0.26

1.34

6.29

3.12

1.05

0.18

0.18

0.17

0.09

0.10

0.09

Phenolicaldehydesan

dotherligninderivatives

112

3-hyd

roxyben

zaldeh

yde

nd0.43

1.38

ndnd

1.92

nd0.24

3.68

0.05

2.17

10.7

0.41

2.16

8.94

692,4-dihyd

roxyben

zaldeh

yde

ndnd

ndnd

ndnd

16.7

91.7

89.3

ndnd

ndnd

ndnd



360

Table

2.(Continued

)a

μgg�1

ofwood

Cherry

Chestnut

Acacia

American

ash

Europeanash

Peak

Compound

UT

LM

UT

LM

UT

LM

UT

LM

UT

LM

96vanillin

2.42

45.0

91.7

16.7

71.5

143

3.48

19.2

106

13.9

76.3

187

10.3

76.1

160

124

syringaldeh

yde

6.93

115

535

38.4

114

311

10.4

56.7

420

37.0

98.0

351

19.9

97.8

376

141

conife

raldeh

yde

3.84

82.2

158

37.2

124

175

28.3

128

257

73.7

208

632

52.1

208

561

153

sinap

aldeh

yde

9.63

210

897

39.2

498

495

40.5

174

1120

30.5

331

744

18.3

330

980

55p-an

isaldeh

yde

0.18

0.45

4.36

ndnd

ndnd

ndnd

ndnd

ndnd

ndnd

97isoacetovanillone

0.62

2.42

9.46

1.96

24.0

83.6

1.86

3.41

26.8

3.58

5.60

8.57

1.85

5.59

8.92

99acetovanillone

0.34

1.52

8.61

0.41

1.66

17.7

0.33

1.02

9.59

0.90

4.24

17.4

0.37

4.23

14.6

115

butirovanillone

0.96

4.56

18.2

1.92

13.5

160

0.95

2.97

41.5

2.42

9.08

28.7

1.28

9.06

22.1

79p-an

isylacetone

0.03

0.18

0.21

ndnd

ndnd

ndnd

ndnd

ndnd

ndnd

133

isopropiosyringone

1.83

6.99

107

1.47

14.2

339

2.53

5.66

317

1.71

16.8

145

0.87

16.8

143.2

20methylben

zoate

0.04

0.77

1.58

ndnd

ndnd

ndnd

ndnd

ndnd

ndnd

98methylvanillate

5.68

7.11

7.39

0.06

0.25

0.75

0.08

0.12

0.46

0.15

4.39

4.83

0.08

4.38

2.96

128

methylsyringate

62.2

55.8

65.3

0.31

0.75

2.13

0.39

0.28

2.47

0.74

1.44

7.13

0.57

1.43

6.70

113

ben

zylsalicilate

4.46

0.69

0.61

ndnd

ndnd

ndnd

ndnd

ndnd

ndnd

89ben

zoicacid

24.6

34.5

76.9

0.86

1.15

0.83

0.94

0.53

1.68

0.55

1.01

1.52

0.39

1.01

1.28

132

tyrosol

0.64

0.84

0.31

0.32

0.39

0.43

0.18

0.13

1.85

28.4

21.2

26.0

24.7

21.2

27.3

152

dihyd

rosinap

ylalcohol

2.53

5.05

21.6

20.3

30.6

343

2.96

2.10

12.3

1.85

2.40

14.6

0.41

2.40

14.7

78p-an

isylalcohol

0.02

0.03

0.05

ndnd

ndnd

ndnd

ndnd

ndnd

ndnd

129

vanillylethylether

1.67

4.15

15.3

23.2

18.0

135

0.87

0.69

1.43

1.74

1.41

6.32

0.73

1.40

5.01

120

m-hyd

roxyacetophen

one

nd0.10

0.27

ndnd

1.80

ndnd

0.79

nd0.39

3.59

nd0.39

3.21

742,4-dihyd

roxyacetophen

one

ndnd

ndnd

ndnd

nd0.08

5.36

ndnd

ndnd

ndnd

148

2,6-dihyd

roxyacetophen

one

ndnd

ndnd

ndnd

2.60

5.64

37.0

nd0.69

0.61

nd0.69

0.29

822,4-dihyd

roxypropiophen

one

ndnd

ndnd

ndnd

nd0.04

1.38

ndnd

ndnd

ndnd

142

2,4-dihyd

roxy-

3-methoxyacetophen

one

ndnd

ndnd

ndnd

nd0.37

10.5

ndnd

ndnd

ndnd

Linear

fattyacids,C13

norisop

reno

idsan

dothercompo

unds

5aceticacid

25.0

25.0

24.0

90.2

75.7

103

22.1

23.0

9.04

15.0

20.0

31.0

13.5

19.9

32.8

15propan

oicacid

2.66

4.66

1.66

0.23

ndnd

0.91

1.10

2.96

0.27

4.45

7.31

0.22

4.44

9.94

39hexan

oicacid

1.58

2.93

1.67

1.57

1.26

1.00

1.56

0.99

0.67

6.17

4.41

0.88

6.54

4.40

1.08

123

hexad

ecan

oicacid

1.02

0.67

nd0.49

ndnd

1.08

ndnd

0.07

ndnd

0.10

ndnd

953-oxo-α-io

nol

0.14

ndnd

2.76

2.94

2.09

0.16

0.37

nd0.27

ndnd

0.20

ndnd

107

7,8-dihyd

ro-3-oxo-α-io

nol

0.30

0.18

0.17

0.15

ndnd

ndnd

ndnd

ndnd

ndnd

nd

103

dihyd

ro-3-oxo-β-io

nol

0.97

0.57

0.83

ndnd

ndnd

ndnd

0.20

0.32

0.54

0.05

0.11

0.38

104

7,8-dihyd

ro-4-oxo-β-io

nol

0.73

0.64

1.00

ndnd

ndnd

ndnd

ndnd

ndnd

ndnd

11-hexan

al0.96

0.31

0.32

0.99

0.66

0.14

0.89

0.23

0.20

0.75

0.32

0.24

0.32

0.28

0.14

81-acetyloxy-2-propan

one

nd3.09

20.0

nd0.59

60.6

0.04

0.72

26.3

nd4.69

10.70

nd4.68

13.5

31-hyd

roxy-2-butanon

end

0.14

0.95

nd0.08

0.82

nd0.52

1.93

nd2.17

3.09

nd2.17

7.75

aAverages

werecalculatedfortenwoo

dsamplesan

alyzed

induplicate.

bNot

detected.


J. Mass Spectrom. 2014, 49, 353–370 Copyright © 2014 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/jms

361


362

characteristics of unidentified compounds generated duringcellulose thermodegradation.[37] Most of these compounds havepreviously been found, in both untoasted or toasted oak wood([9,21,29,32–35] and references therein) with, as far as we know,the exception of 2-furyl ethyl ketone, 1-(5-methyl-2-furyl)-2-propanone (MFP), (3E)-4-(2-furyl)-3-buten-2-one, 4-ethylcyclotene, 3,4-dimethylcyclotene and 4,5-dimethylcyclohexen-1-one, which could be proposed as markers to differentiate oakwood from other species. However, the average concentrationsfor these compounds detected in untoasted and toasted studiedwoods (Table 2) were very low in all samples (<1μg g�1),except for MFP in medium-toasted cherry, chestnut and acacia,4-ethylcyclotene in light-toasted and medium-toasted Europeanand American ash wood, and 4,5-dimethylcyclohexen-1-one inmedium toasted ash wood. These three compounds, therefore,could be taken into account for purposes of authenticity,especially in regard to toasted woods.The concentrations of some of these compounds showed

significant differences related to wood species, allowing fordifferentiation among each of them, as can be deduced fromANOVA results in Table 1 when only the species were takeninto account. In chestnut wood, the concentrations of furfural,1-methoxy-2-ethoxyethyl-1-furan, furyl hydroxymethyl ketone,MFP, (3E)-4-(2-furyl)-3-buten-2-one, 4-hydroxy-5,5-dihydro-(2H)-pyran-2-one (HDP), and cis- and trans- isomers of whisky lactonewere significantly higher than in the remaining untoasted andtoasted woods. The levels of the first three compounds in oakwood were lower under similar toasting conditions, but theycan be achieved in more intense toasting.[9,21] Because MFPwas not found in oak wood, and toasted chestnut wood wasricher in HDP than toasted oak, from European and American or-igins,[38] these compounds could be considered as potentialmarkers to differentiate the two wood species.The whisky lactone cis- and trans- isomers also allow us to

distinguish oak and chestnut from the rest, because they havebeen identified in untoasted and toasted chestnut heartwood,although in very low concentrations (<0.7μg g�1), and arecharacteristic and even specific to the Quercus genus ([38] andreferences therein). The presence of these two isomers inchestnut wood was mentioned in ethanolic extracts (55%,pH 4.2) used to simulate brandy aging in chestnut woodbarrels,[39] as well as in red wines aged in chestnut barrels(33.7 μgl�1 of cis isomer and 21.3 μgl�1 of trans),[16] althoughbelow their perception threshold in red wines (54 and 370 μgl�1,respectively).[40] Despite the small concentration achieved, thesecompounds are involved in the characteristic aroma of chestnutwood, because they are part of the compounds identifiedby GC–O,[22] which is most likely due to their low odor threshold(1 and 20 μgl�1, respectively).[41]

European and American ash wood showed significant higherlevels of 2-furanmethanol, maltol, all compounds showingcyclopentanone and cyclohexanone structures, α-methyl-crotonolactone and solerone; the levels of 1H-pyrrole-2-carboxaldehyde were those only significantly higher in acaciawood, whereas none of these compounds was significantlyhigher in cherry wood. Very few data about the levels of thesecompounds in oak wood can be found in the literature, apartfrom those for maltol and cyclotene, which were similar intoasted oak and ash woods, and 2-furanmethanol, lactones and1H-pyrrole-2-carboxaldehyde, which were lower in oak woodthan in ash or acacia, respectively, even at high toastingintensities, as they were always under 2, 5 and 10μg g�1 in oak,


respectively.[9,21,32,35,36] These four compounds, therefore, couldalso contribute to the authenticity process together with theother cyclopentanone and cyclohexanone.

With the purpose of achieving an overall view of the influencethat the botanical species of wood has on the carbohydratederivatives and lactones composition, we carried out a CDA ofdata, grouping the samples in accordance only with species,not taking into account the toasting levels. The graphic represen-tation of the samples, in the space defined by the two maincanonical functions, allowed us to distinguish the four botanicalgenera: the first canonical function (Can1) separates chestnutwood from the others with cis and trans whisky lactone isomersand furfural as the most correlated variables, with positive coeffi-cients, whereas the second canonical function (Can2) separatesEuropean and American ash, with 3-ethyl, 4-ethyl, 3,5-dimethyland 3,4-dimethyl cyclotene and α-methylcrotonolactone beingthe most correlated variables, all of which with negativecoefficients (Fig. 1A and Table 3). Throughout Can3 (5.33% ofvariance) (supplementary material), the acacia wood samplesare separated from the others, with 1H-pyrrole-2-carboxaldehydeas the most correlated variable. Thus, the analysis of thesecompounds can be a useful tool to differentiate wood species,both untoasted and toasted.

A number of these compounds were either not detected inseveral nontoasted woods or showed very low concentrations.As a result of the toasting process, their concentrations increased,as multiple dehydrations and rearrangements of carbohydratesare produced when heating takes place, along with thesubsequent formation of furanic and pyranic derivatives, as wellas with cyclopentanone or cyclohexanone structures, includingspecific nitrogen compounds from Maillard reaction. Thus, theANOVA results in Table 1 showed significant differences for allcompounds when only the toasting intensity was taken intoaccount, with the exception of two whisky lactone isomers. Thiswas highlighted by the F-values (>100) of crotonolactone andγ-ethoxybutyrolactone, 2-furyl ethyl ketone, methyl-2-furoate,hydroxymethylfurfural (HMF) and 5-acethoxymethylfurfural, aswell as maltol, cyclotene and allomaltol.

The formation of these compounds under the two toastingapplied here also showed a relationship with the botanical woodspecies (Fig. 2A and Table 2), highlighting the high total levels offuranic derivatives in light-toasted chestnut wood (569μgg�1) andmedium-toasted chestnut (2802μgg�1) and acacia (1006μgg�1)woods, in contrast with those of medium-toasted cherry andAmerican and European ash woods (281, 227 and 190μgg�1,respectively). Furfural showed the highest concentrations in allmedium-toasted woods, underscoring its levels in chestnutand acacia woods, whereas the second was 1-methoxy-2-ethoxyethyl-1-furan in chestnut, and HMF in the other species,followed by HMF in chestnut, 5-methylfurfural (MF) in cherry andacacia and 2-furanmethanol in ash. Regarding the remainingcarbohydrate derivatives, their total levels were similar in light-toasted cherry, chestnut and acacia woods (between 9 and16μgg�1), and higher in ash wood (37.7 and 37.9μgg�1,American and European, respectively), while the levels in allmedium-toasted woods were similar (between 54 and 69μgg�1)but lower in cherry wood (26.7μgg�1). In toasted woods, maltolwas the most abundant, except in medium-toasted chestnut, inwhich HDP concentration was higher. In medium-toastedwoods, the second one was the unidentified peak 64 in cherryand chestnut, 1H-pyrrole-2-carboxaldehyde in acacia and4-ethylcyclotene in ash. As to the remaining lactones, their


Figure 1. Canonical discriminant analysis of volatile compounds in heartwood of different wood species, seasoned and toasted, taking into accountonly specie. (A) Carbohydrate derivatives and lactones, (B) volatile phenols, (C) phenolic aldehydes and other lignin constituents, and (D) fatty acids,C13 norisoprenoids, and remaining compounds. (♣) = Cherry; (□) = Chestnut; (Ο) = Acacia; (▲) = European ash; ( ) = American ash. n=150.


363

levels were once more low in toasted cherry wood (77 μg g�1),intermediate in chestnut (85 μg g�1) and high in acacia andash wood (95–97 μg g�1), with crotonolactone being the mostabundant in cherry, chestnut and acacia, and solerone in ash.As we can see, the particular characteristics of macromolecules(cellulose, hemicellulose and lipids) in each wood have a greatinfluence on the quantitative volatile profile of toasted woods,leading to a higher differentiation. Thus, ANOVA showed highF-values (>600) for most of studied compounds whenbotanical species and toasting intensity were taken intoaccount for grouping samples (Table 1), highlighting those of4-ethylcyclotene, solerone, 4,5-dimethyl-2-cyclohexen-1-one,other cyclopentanones, furyl hydroxymethyl ketone, 1H-pyr-role-2-carboxaldehyde and maltol. They are also some of thehighest correlated compounds with the canonical functions 2and 3, found to discriminate wood species, so toasting increasesthe statistical distances among studied woods.

Volatile phenols

Thirty-one volatile phenols arising from wood lignin degradation,such as phenol derivatives and a wide number of guaiacol(2-methoxyphenol) and syringol (2,6-dimethoxyphenol) deriva-tives, two trimethoxylated phenols and benzene compoundssuch as phenylmethanol, 2-phenylethanol, 2-phenoxyethanoland benzothiazole were identified in wood extracts. Amongthem, resorcinol and 3,4-dimethoxyphenol were only detectedin acacia woods; because their presence in oak wood wasnever established, they could be taken into account as tools todifferentiate acacia from the others woods and from oak.

Regarding quantitative differences related to species (Table 1),ash wood showed significantly higher concentrations of o- andm-cresol, catechol and its derivatives, 2-phenylethanol, guaiacol,


4-vinylguaiacol and cis and trans isoeugenol. Similar levels ofthese compounds could be detected in toasted oak wood([2,9,21,24,34–36,42,43], and references therein), with the exceptionof catechol and its derivatives, which, as far as we know havenot been detected in oak wood. Cherry wood showed significantlyhigher concentrations of p-cresol, 2-methoxyhydroquinone,phenylmethanol and 3,4,5-trimethoxyphenol, higher than thosefound in literature in oak wood, except those of phenylmethanol,similar in oak wood. Eugenol was the only compound showingsignificant higher concentrations in chestnut wood. However,their values were similar to those detected in oak wood,especially in relation to those from Q. pyrenaica.[9,24,38] In thegraphical representation of CDA carried out taking into accountonly species, we obtain a clear separation of samples grouped bygenera, as it was not possible to distinguish the two ash species(Fig. 1B and Table 3). Throughout Can1, cherry, acacia andchestnut wood samples are separate among them, showingcherry and chestnut the highest distances. Can2 separates ashsamples from the others. According to total canonical structure,3,4,5-trimethoxyphenol and p-cresol with negative coefficients,and eugenol with positive one, were the variables mostcorrelated to Can1, and resorcinol and 3,4-dimethoxyphenol, withnegative coefficients, and 2-phenylethanol, 3-methylcatechol, ando- and m-cresol, with positive ones, the most correlated to Can2.The statistical distances between acacia and chestnut samples werehigher throughout Can3 (23.8% of variance) (supplementarymaterial), with resorcinol, 3,4-dimethoxyphenol (positive) andeugenol (negative) as the most correlated variables. The analysisof volatile phenols can be a good tool to differentiatewood species.

The heat and moisture applied during toasting cause lignindegradation, as it is well-known ([21] and references therein), withthe formation of a multitude of different compounds in progres-sive stages, with the last being the formation of volatile phenols.


Table 3. Total canonical structure coefficients of the main discriminant variables in Can1, Can2 and Can3, obtained forvolatile compounds in all studied woods taking into account only wood species (Fig. 1)

Can1 Can2 Can3

Furan derivatives, other carbohydrate derivatives and lactones

Canonical correlation 0.9915 0.9726 0.9009

Eigenvalue 583 175 43

Percentage of total variance 72.17 21.64 5.33

Cumulative percentage 72.17 93.82 99.15

furfural 0.5394

2-furanmethanol �0.512

Furyl hydroxymethyl ketone 0.5676

1H-pyrrole-2-carboxaldehyde �0.5499

3-ethylcyclotene �0.5750

4-ethylcyclotene �0.5541

3, 5-dimethylcyclopentenolone �0.5286

3, 4-dimethylcyclopentenolone �0.5787

4,5-dimethyl-2-ciclohexen-1-one �0.6041

α-methylcrotonolactone �0.5169

trans-whiskylactone 0.5801

cis-whiskylactone 0.7078

Volatile phenols


Eigenvalue 41.95 22.47 20.75



o-cresol 0.5181

p-cresol �0.5118

m-cresol 0.5401

3-methyl catechol 0.5401

resorcinol �0.5691 0.7014

phenylmethanol �0.6704

2-phenylethanol 0.7097

eugenol 0.5302 �0.5945

3,4-dimethoxyphenol -0.5274 0.6500

3,4,5-trimethoxyphenol �0.8471

Phenolic aldehydes and other lignin derivatives


Eigenvalue 84.28 44.30 21.36



tyrosol 0.7301 0.5462

vanillyl ethyl ether �0.5483

propiosyringone �0.6054

2,4-dihydroxybenzaldehyde �0.7367

p-anisaldehyde �0.5133

methyl vanillate �0.7884

methyl syringate �0.9314

benzylsalicilate �0.6614

dihydrosinapic alcohol �0.5113

methyl benzoate �0.5559

benzoic acid �0.8397

Lineal fatty acids, C13 norisoprenoids and other compounds


Eigenvalue 12.26 9.95 5.48



acetic acid 0.5897 0.5663

(Continues)



364

0

Table 3. (Continued)

Can1 Can2 Can3

propanoic acid �0.5575

pentanoic acid �0.5528

hexanoic acid �0.5644

octanoic acid 0.5072

dihydro-3-oxo-β� ionol 0.8231

7,8-dihydro-4-oxo-β-ionol 0.9212

7,8-dihydro-3-oxo-α-ionol 0.6793

1-nonanal 0.6365

2-nonenal 0.6648

2,4-decadienal �0.5122

1-hydroxy-2-butanone �0.5217

The non-shown coefficients have values below 0.500.

Figure 2. Global valuation of volatile compounds by chemical families in heartwood of different wood species, untoasted (UT), light toasted (LT), andmedium toasted (MT). (A) Carbohydrate derivatives and lactones, (B) volatile phenols, (C) phenolic aldehydes and other lignin constituents, and (D) fattyacids, C13 norisoprenoids, and remaining compounds.


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Following the general structure of lignin in angiosperms, the firstvolatile phenols formed are those that are dimethoxylated,followed by the monomethoxylated and finally the simplerphenols, whose formation is important only at more intensetoasting.[34,44] In our woods, several volatile phenols were notdetected in some untoasted woods, such as 3-ethylphenol andcatechol derivatives, and most of them increase their concentra-tions during toasting showing statistically significant differences.Syringol and its 4-methyl, 4-ethyl and 4-allyl derivatives and4-propylguaiacol showed the higher F-values from ANOVA takinginto account only toasting intensity (between 100 and 176), andthis implies that toasting applied here has not been very intense.Only 3,4,5-trimethoxyphenol significantly decreases, especially incherry wood, which is possible due to oxidation reactions.[36,45]

The effect that the two toasting intensities applied here has onthe originated quantity of these compounds showed arelationship with the botanical wood species (Fig. 2B andTable 2), highlighting the higher total levels of simple and


mono-methoxylated phenols in medium-toasted ash woodextract (between 30 and 35 μg g�1), regarding the other woodspecies (between 6 and 21 μg g�1). Catechol was the mostabundant simple phenol in medium-toasted ash, resorcinol inacacia, and 2-methoxy hydroquinone in cherry and chestnut,whereas, with respect to those monomethoxylated, guaiacoland trans-isoeugenol were the highest in ash and acacia, and4-methylguaiacol and guaiacol in chestnut and cherry. Di andtrimethoxyphenols weremore abundant inmedium-toasted acacia(78.2μgg�1), intermediate in chestnut and ash (53–60μgg�1) andlower in cherry (44.2μgg�1), with syringol and 4-(1-propenyl)syringol in acacia and ash, syringol and 4-methylsyringol inchestnut and 4-methyl syringol, 4-allylsyringol and 3,4,5-trimethoxyphenol in cherry showing the highest concentrations.It seems that the individual lignin characteristics in each woodprovoke different volatile phenol profiles after wood toasting,leading to a higher differentiation among species and amonguntoasted and toasted woods. In fact, when botanical species and



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toasting intensity were taken into account to group samples forANOVA (Table 1), compounds like 3-methyl catechol, o-cresol orcatechol showed higher F-values, between 264 and 616, as wellas being some of the most correlated variables in CDA taking intoaccount only wood species: therefore, quantitative differencesamong species increased with toasting intensity. In addition,syringol and its 4-methyl, 4-propyl and 4-allyl derivatives alsoshowed high F-values, between 260 and 683, despite the fewdifferences found among species, which gives an idea about thestrong effect of toasting on their concentrations.

Phenolic aldehydes and other lignin constituents

An additional 45 compounds were identified, which also comefrom lignin degradation, such as benzaldehyde andacetophenone derivatives, or guaiacyl (2-methoxyphenol) andsyringyl (2,6-dimethoxyphenol) derivatives in structures such asC6-C1 (benzyl) and C6-C3 (cinnamyl). Peaks 118, 137, 149 and150 could be considered as lignin derivatives since they havem/z 137 or 167 as base peaks, characteristic of compoundsderived from guaiacol and syringol, respectively. In fact, themass spectrum of peak 137 is very similar to that ofisopropiosyringone. Peak 102 was also considered lignin deriva-tive, but this needs additional confirmation.From a quantitative point of view, the aldehydes were the

main ones; in particular, sinapaldehyde was the most abundant,followed by coniferaldehyde in ash wood and syringaldehyde inthe others, as well as in oak wood.[21] Vanillin was higher in ashbut did not show statistically significant differences with chestnutwood. Their levels were intermediate among those found inmedium-toasted oak wood from different species and origin,but lower than those found in more intense toasted oak.[9,38,42]

Some of these lignin constituents could contribute in authen-ticity determination because they were only detected in onebotanical species, and no data of its presence in oak heartwoodwere found: p-anisyl alcohol, p-anisyl aldehyde, p-anisylacetone, methyl benzoate and benzylsalicylate were characteris-tics of cherry wood, whereas 2,4-dihydroxy benzaldehyde, 2,4-dihydroxyacetophenone, 2,4-dihydroxypropiophenone and2,4-dihydroxy-3-methoxyacetophenone were only found inacacia wood. Therefore, in addition to p-anisaldehyde andbenzylsalicylate in cherry wood, and 2,4-dihydroxybenzaldehydein acacia wood that have already been described as possiblemarkers, the other compounds could also contribute to distin-guish botanical species.[14,18,21] Although cinnamaldehyde wasonly detected in acacia wood, it has also been detected in oakchips from several geographical origins.[42] In addition to theaforementioned compounds, in acacia wood, no other com-pounds were found showing significantly higher concentrationscompared with the other species (Table 1), but in cherry wood,compounds such as propiosyringone, methyl vanillate, methylsyringate and benzoic acid were significantly higher comparedwith the other wood species, highlighting the F-values showedby the last three, the highest in this group after tyrosol. In oakwood, propiosyringone and methyl vanillate can reach similaror higher levels,[9,38] but those for benzoic acid and methylsyringate were much lower,[21,36] so these compounds could betaken into account as tools to differentiate cherry from theothers woods and from oak. The presence of benzoic acid atappreciable levels in cherry wood has been used to explain thehigher levels of ethyl benzoate found in vinegars obtained byacetification in barrels of cherry wood, as well as in wines aged


in cherry wood barrels, compared with those aged in barrelsmade of other woods.[16,46]

Two phenolic ketones, isoacetovanillone and butirovanillone,in addition to dihydrosinapyl alcohol and vanillyl ethyl ether,were significantly higher in chestnut wood, and also higher thantheir levels in oak wood found in the literature.[9,35] Alañonet al.,[38] however, found levels of dihydrosinapyl alcohol higherin untoasted Q. petraea than in untoasted C. sativa, so this shouldbe better studied. Lastly, benzaldehyde, 2-hydroxybenzaldehyde,3-hydroxybenzaldehyde, coniferaldehyde, tyrosol, homovanillylalcohol and m-hydroxyacetophenone were significantly higherin ash wood. No data about 3-hydroxybenzaldehyde, tyrosoland m-hydroxyacetophenone in oak wood have been found,and those for coniferaldehyde and homovanillyl alcohol weresimilar or higher, but those for benzaldehyde and 2-hydroxybenzaldehyde were lower in oak than in ash wood.[9,21,42]

In the graphical representation of CDA carried out taking intoaccount only species, we found a clear distinction between bo-tanical genera, where cherry samples showing the largest statisti-cal distances relative to others throughout Can1 (Fig. 1C andTable 3), especially regarding chestnut wood, and methylsyringate, benzoic acid and methyl vanillate being the mostcorrelated variables, all of which with negative coefficients.Throughout Can2, ash, acacia and chestnut wood samples appearseparate among them, ash and chestnut showing the highestdistances, tyrosol being the most correlated variable showing apositive coefficient and vanillyl ethyl ether and dihydrosinapylalcohol showing negative coefficients. Moreover, acacia woodsamples are clearly separated from ash and chestnut throughoutCan3 (14.13% of variance) (supplementary material), with 2,4-dihydroxybenzaldehyde (with negative coefficient) and tyrosol(with positive) as the strongest correlated variables.

When the toasting process was applied to woods, theanalysis of variance of results showed statistical differences formost of those lignin constituents with respect to toastingprocess, increasing their concentrations significantly. Amongthem, it highlights F-values of acetosyringone, acetovanillone,syringaldehyde, 4-hydroxybenzaldehyde, sinapaldehyde andvanillin, between 880 and 246; the highest regarding allanalyzed compounds (Table 1). In addition, hydroxybenzaldehyde,isopropiovanillone, isopropiosyringone and methyl homovanillateshowed F-values higher than 100, similar to those for syringoland its derivatives. Taking into account that phenolic aldehydesand ketones were the products early obtained during thermaldegradation of lignin, the last step being the formation of volatilephenols in the order dimethoxyphenols, monomethoxyphenolsand simple phenols ([21,34], and references therein), our resultsconfirm that the toasted applied was not intense. Phenolic acidsand esters were less sensitive to toasting intensity, as only methylhomovanillate showed significance at p< 0.0001.

The lignin structure of each wood species provoked differ-ences in its degradation during toasting, regarding both theobtained compounds and their concentrations. This highlightsthe different profile of total levels in toasted chestnut (Fig. 2C):the highest levels of phenolic ketones (96.9 and 1143μg g�1),and alcohols and ethers (58.9 and 479μg g�1) at light andmedium toasting, whereas phenolic aldehydes levels were thehighest at light toasting and the lowest at medium toasting(813 and 1147μg g�1, respectively), regarding other species(phenolic ketones below 76 and 696μg g�1in light and mediumtoasting, alcohols and ether below 35 and 55μg g�1, andphenolic aldehydes below 725μg g�1 at light toasting and above



367

1700μg g�1 at medium toasting). Phenolic acids and estersshowed the highest total levels in cherry (175μg g�1) and thelowest in toasted acacia wood (28.4μg g�1), and aromaticketones were the highest in medium-toasted acacia (25.5μg g�1),intermediate in ash (3.95–4.54μg g�1), and lower in chestnut(1.94μg g�1) and cherry woods (1.55μg g�1). Clearly, the ligninin the studied woods has different constituents, reactingdifferently to the same toasting. On the other hand, despite thesedifferences in total contents, the F-values for individualcompounds were always smaller than 600, from ANOVA resultswhen botanical species and toasting intensity were taken intoaccount for grouping samples (Table 1). This illustrates that differ-ences among species in toasted woods were higher when itcame to carbohydrate derivatives and lactones, followed byvolatile phenols, with F-values above 600 for 82 compounds, re-spectively. Regarding these lignin constituents, the higher F werethose of 2,4-dihydroxyacetophenone, m-hydroxyacetophenone,2,4-dihydroxy propiophenone and isopropiosyringone, allthem above 500, followed by acetovanillone, dihydrosinapylalcohol, benzoic acid, p-anisaldehyde, butirovanillone,isoacetovanillone and vanillyl ethyl ether, between 350 and500. Because some of them are highly correlated tocanonical function obtained taking only species into account,we can deduce that toasting increased the statisticaldistances among species.

Linear fatty acids, C13 norisoprenoids and other compounds

We have also found 13 compounds identified as fatty acids with alinear chain; 6 C13 norisoprenoids compounds, arising fromcarotenoids degradation; 11 compounds including aliphaticaldehydes, alcohols and ketones and other five compounds,one of them not identified. On the whole, they showed statisticaldifferences between species (Table 1). With regard to acids, aceticacid was significantly higher in chestnut, octanoic acid in cherry,whereas pentanoic acid and hexanoic acid in ash wood, butshowing low F-values, except acetic acid. Showing between 110and 14 F-values, 7,8-dihydro-4-oxo-β-ionol, dihydro-3-oxo-β-ionol,7,8-dihydro-3-oxo-α-ionol and 6,7-dehydro-7,8-dihydro-3-oxo-α-ionol were significantly higher in cherry wood, and 3-oxo-α-ionolin chestnut wood. Although there were some differencesbetween species regarding the other compounds, they showeda low level of significance: 1-hydroxy-2-butanone was higher inash wood, ethanol-2-(2-buthoxyethoxy) in chestnut and 2-ethyl-1-hexanol in acacia. The CDA (Fig. 1D and Table 3) carried outwith the whole of these compounds does not allow for a cleardistinction among species in the space defined by Can1 andCan2: only cherry wood samples appear separated from theothers and only throughout Can1. The highest correlatedvariables to Can1 were dihydro-3-oxo-β-ionol, 7,8-dihydro-4-oxo-β-ionol, 7,8-dihydro-3-oxo-α-ionol and octanoic acid, all withpositive coefficients. Throughout Can2, a distribution ofremaining species can be observed, showing clear separationonly between chestnut and ash samples. Acacia samples appearin the middle of the two, almost separated but at very small dis-tances among them. The most correlated variables to Can2 were1-nonanal, 2-nonenal and acetic acid, with positive coefficients,and hexanoic, pentanoic, and propanoic acids, and 1-hydroxy-2-butanone with negative. Moreover, acacia wood samples areclearly separated from chestnut throughout Can3 (19.26% ofvariance) (supplementary material), with 2,4-decadienal (with anegative coefficient), and acetic acid (with positive), as the most


correlated variables. Therefore, it is also possible to distinguishthe wood from these species based on levels of these com-pounds, even though the statistical distances among groupswere lower than in other compound families.

It highlighted the concentration reached by acetic acid amongacids (Table 2), which was however lower than those detected inoak wood: from 1500μg g�1 in untoasted up to 250μg g�1 inhigh toasted.[35] Its formation has been reported to derive fromboth lignin and hemicelluloses.[34] Furthermore, Natali et al.[35]

proposed that the origin of propanoic acid could be the alkylchain breakdown of depolymerized lignin, increasing with thedegree of toasting, but that is true only in acacia and ash woods,its level in oak being intermediate between the two. In chestnut,it was only detected in untoasted wood, whereas in cherry wood,it increased at light toasting and decreased at medium toasting.Butanoic acid also increased significantly at medium toasting,except in acacia where it decreased, so we could expect the sameorigin. Nevertheless, it is difficult to discuss these data becausethe information found in the literature was extremely scarce,and most of these acids change their concentrations duringtoasting, increasing propanoic and butanoic acids, butdecreasing pentanoic, hexanoic, dodecanoic, pentadecanoic,hexadecanoic, octadecanoic and oleic acids, and without a signif-icant variation octanoic, decanoic and tetradecanoic acids[35]. C13norisoprenoids showed generally very low concentrations, notbeing detected in many samples, because they decreased duringtoasting,[33] the levels detected in oak wood being higher.[26]

Lastly, regarding the remaining compounds, aliphatic aldehydesand alcohols showed concentrations lower than 2μg g�1, similarto those detected in oak,[31,35,42] decreasing during toasting, withthe exception of 1-hexadecanol in ash wood. Concerningaliphatic ketones, all of their concentrations increased signifi-cantly with toasting, 1-acetyloxy-2-propanone being the mostabundant in toasted woods.

In a global perspective, toasting provoked changes in theconcentrations of most of these compounds, and this effect ismanifested differently depending on wood species, thedifferences among them increasing at higher toasting intensities(Fig. 2D and Table 2). Thus, total fatty acids decreased duringtoasting in cherry and acacia, increased in ash, and had minorchanges in chestnut. On the contrary, the increase of othercompounds, specifically aliphatic ketones and unknowncompound 12, was much more important in medium-toastedchestnut (up to 82.2μg g�1), with regard to other species(between 25 and 48μg g�1).

Volatile compounds as markers

Throughout the text, only a few qualitative differences in thevolatile composition of the five studied species have beendescribed, despite the large number of analyzed compoundsand diversity of the studied chemical structures. Therefore, wehave not detected in untoasted and toasted ash wood anyvolatile compound that can be used as a potential marker,because all compounds present in this wood are also detectedin at least one other. These results contrast with those obtainedin its polyphenolic composition that shows clear qualitativedifferences regarding the three other studied species andoak,[18,47] because a great variety of compounds such assecoiridoids, phenylethanoid glycosides, di and oligolignols canbe used to discriminate untoasted ash wood. As a result, thequantitative differences of volatile composition are the only



368

useful tools to identify toasted ash wood. Tyrosol stands outbecause it has the highest F-value relative to species, it is notsensitive to toasting, as well as shows high concentrations.Among others, all them toasting sensitive, 2-furanmethanol,3- and 4-ethylcyclotene, α-methyl crotonolactone, solerone,catechol, 3-methylcatechol and 3-hydroxybenzaldehyde showedgood F-values and concentrations high enough to be detectedin toasted ash wood. Because some of them can also be detectedin wines and other alcoholic beverages, especially tyrosol and2-furanmethanol, their effectiveness as markers in these casesneeds to be assessed.Regarding chestnut wood, only the two isomers of whisky

lactone showed qualitative differences as possible volatilemarkers, but these compounds are the most characteristic ofoak wood. As happens in ash wood, polyphenols, specificallygallotannins, are a good tool for identifying chestnut wood,but only when it is untoasted or light toasted.[18] Hence, toidentify toasted chestnut wood, we must again appeal to thequantitative differences in volatile compounds, such as vanillylethyl ether, dihydrosinapyl alcohol and isoacetovanillone,which showed high F-values relative to species and highenough concentrations in toasted wood. Butirovanillone, HDPand MFP, which showed lower F, could also be used becauseof their high concentrations in toasted chestnut.This is not the case of cherry wood, in which some volatile

compounds could be used as markers, also in relation to oakwood: p-anisyl alcohol, p-anisyl aldehyde, p-anisyl acetone,methyl benzoate and benzyl salicylate. However, with theexception of the last one, their concentrations were so low inuntoasted wood that their effectiveness could only be conclusivein toasted wood. Because of their high F-values relative tospecies, and their concentrations after toasting, methyl syringate,3,4,5-trimethoxyphenol and benzoic acid could contribute toimproving the identification of toasted cherry wood.Although some C13 norisoprenoids showed high F-values forsignificant differences among cherry wood and theremaining woods studied here, they cannot be used asmarkers in relation to oak.[26,33] For untoasted cherry wood,we must again turn to the polyphenols, by the large numberof them that can act as markers, among both low molecularweight compounds and flavonoids (procyanidin typecondensed tannins, flavanonols flavanones, chalcones, flavonolsand flavones).[18]

Lastly, acacia wood was the only wood showing sure volatilemarkers: resorcinol, 3,4-dimethoxyphenol, 2,4-dihydroxybenzaldehyde,2,4-dihydroxyacetophenone, 2,4-dihydroxypropiophenone and 2,4-dihydroxy- 3-methoxyacetophenone, the last three in toastedwood only, for which also contribute 1H-pyrrole-2-carboxaldehyde and 2,6-dimethoxyacetophenone. This,combined with the large number of polyphenols that can be agood tool to differentiate this wood from all others, untoastedand toasted,[18] makes acacia wood the more easily identifiedby its chemical composition.Most of the volatile compounds studied have been associ-

ated with different aromatic notes, and their contribution tothe aroma and flavor of wines, spirits and other beverages,has been the subject of several research studies ([22,43,48,49],and references therein). Consequently, these differentqualitative and quantitative volatile profiles displayed, regard-ing species and toasting intensity, will contribute withdifferent intensity and quality to the aromatic and gustativecharacteristics of aged beverages.


Conclusions

It was necessary to use a nontarget analysis method to findvolatile markers, because few compounds were characteristic ofa single wood species, and this only occurred in some of thestudied species. From the obtained results, we can deduce thatthe volatile profiles of wood used in cooperage is a useful toolto identify their botanical origin because they show cleardifferences among them, especially if they are toasted. Thetoasting provokes, in all types of wood, a progressive increaseof carbohydrate derivatives, lactones, lignin constituents andsome other components, directly related to its intensity. The finalprofiles of these molecules in toasted wood are also related tothe biopolymer structures of each wood, increasing the quantita-tive differences among species with toasting intensity.

The qualitative differences in the volatile profiles allow foridentifying untoasted and toasted woods from P. avium, C. sativaand R. pseudoacacia, but not those from Fraxinus spp., because allcompounds present in this wood are also detected in at least oneother. The quantitative volatile composition must be studied intoasted wood to identify those from ash.

Regarding data from oak wood, the qualitative volatile profilecould be enough to distinguish it from cherry and acacia woods,particularly for toasted wood, and quantitative differences toidentify chestnut and ash toasted woods.

Useful results potentially applicable to woods for cooperagewere achieved in this study, even though it was focused on twoparticular toasting levels, without going deeper into the naturalvariability of wood. In addition, further studies on differenttoasting intensities and/or different wood origin would benecessary for a better understanding of the influence that nonoak woods can have on the quality of aged wines.

Acknowledgements

This study was financed by the Spanish Ministerio de Ciencia eInnovación (Project INIA-FEDER RTA2009-0046), Tonelería Intona,SL, and the Navarra Government (Project: ‘Caracterización demaderas alternativas al roble en tonelería para uso alimentario’).Miriam Sanz received a contract from the Spanish Governmentthrough the Torres Quevedo program. The authors wish tothank Mr Antonio Sánchez for his help throughout thechemical analysis.

References[1] C. Viriot, A. Scalbert, C. L. M. Hervé du Penhoat, M. Moutounet.

Ellagitannins in woods of sessile oak and sweet chestnut.Dimerization and hydrolysis during wood aging. Pytochem. 1994,36, 1253–1260.

[2] E. Cadahía, B. Fernández de Simón, J. Jalocha. Volatile compounds inSpanish, French and American oak wood after natural seasoning andtoasting. J. Agric. Food Chem. 2003, 51, 5923–5932.

[3] P. J. Spillmann, M. Sefton, R. Gawell. The effect of oak wood source,location of seasoning and coopering on the composition of volatilecompounds in oak-matured wines. Aust. J. Grape Wine Res. 2004,10, 216–226.

[4] M. del Álamo. Effect des techniques de vieillissement accéléré dansla composition phénolique des vins rouges. Rev. Oenolog. 2007,122, 21–26.

[5] M. S. Pérez-Coello, M. A. Sánchez, E. García, M. A. González-Viñas, J.Sanz, M. D. Cabezudo. Fermentation of white wines in the presenceof wood chips of American and French oak. J. Agric. Food Chem.2000, 48, 885–889.

[6] A. B. Bautista-Ortín, A. G. Lencina, M. Cano-López, F. Pardo-Mínguez,J. M. López-Roca, E. Gómez-Plaza. The use of oak chips during the



369

aging of a red wine in stainless steel tanks or used barrels: effects ofthe contact time and size of the oak chips on aroma compounds.Aust. J. Grape Wine Res. 2008, 14, 63–70.

[7] B. Fernández de Simón, E. Cadahía, M. del Álamo, I. Nevares. Effect ofsize, seasoning and toasting in the volatile composition in toastedoak wood and in a red wine treated with them. Anal. Chim. Acta2010, 660, 211–220.

[8] I. Caldeira, O. Anjos, V. Portal, A. P. Belchior, S. Canas. Sensory andchemical modifications of wine-brandy aged with chestnut andoak wood fragments in comparison to wooden barrels. Anal. Chim.Acta 2010, 660, 43–52

[9] B. Fernández de Simón, I. Muiño, E. Cadahía. Characterization ofvolatile constituents in commercial oak wood chips. J. Agric. FoodChem. 2010, 58, 9587–9596.

[10] R. M. Callejón, M. J. Torija, A. Mas, M. L. Morales, A. M. Troncoso.Changes of volatile compounds in wine vinegars during theirelaboration in barrels made from different woods. Food Chem.2010, 120, 561–571.

[11] M. de Rosso, D. Cancian, A. Panighel, A. Dalla Bedona, R. Flamini.Chemical compounds released from five different woods used tomake barrels for aging wines and spirits: volatile compounds andpolyphenols. Wood Sci. Technol. 2009, 43, 375–385.

[12] G. Kozlovic, A. Jeromel, L. Maslov, A. Pollnitz, S. Orlic. Use of acaciabarrique barrels- Influence on the quality of Malvazika from Istriawines. Food Chem. 2010, 120, 698–702.

[13] F. Chinnici, N. Natali, F. Sonni, A. Bellachioma, C. Riponi. Comparativechanges in color features and pigment composition of red winesaged in oak and cherry wood casks. J. Agric. Food Chem. 2011,59, 6575–6582.

[14] M. Sanz, B. Fernández de Simón, E. Esteruelas, A. M. Muñoz, E.Cadahía, T. Hernández, I. Estrella, J. Martinez. Polyphenols in redwine aged in acacia (Robinia pseudoacacia) and oak (Quercuspetraea) wood barrels. Anal. Chim. Acta 2012, 732, 83–90.

[15] B. Fernández de Simón, M. Sanz, E. Cadahía, J. Martínez, E. Esteruelas,A. M. Muñoz. Polyphenolic compounds as chemical markers of wineaging in contact with cherry, chestnut, false acacia, ash and oakwood. Food Chem. 2014, 143, 66–76

[16] B. Fernández de Simón, J. Martínez, M. Sanz, E. Cadahía, E. Esteruelas,A. M. Muñoz. Volatile compounds and sensorial characterization ofred wine aged in cherry, chestnut, false acacia, ash and oak woodbarrels. Food Chem. 2014, 147, 346–356.

[17] H. Hillmann, J. Mattes, A. Brockhoff, A. Dunkel, W. Meyerhof, T.Hofmann. Sensomics analysis of taste compounds in balsamicvinegar and discovery of 5-acetoxymethyl-2-furaldehyde as anovel sweet taste modulator. J. Agric. Food Chem. 2012,60, 9974–9990.

[18] M. Sanz, B. Fernández de Simón, E. Cadahía, E. Esteruelas, A. M.Muñoz, T. Hernández, I. Estrella. Polyphenolic profile as a useful toolto identify the wood used in wine aging. Anal. Chim. Acta 2012,732, 33–45.

[19] R. Flamini, A. Dalla Bedona, D. Cancian, A. Panighel, M. de Rosso. GC/MS-positive ion chemical ionization and MS/MS study of volatilebenzene compounds in five different woods used in barrel making.J. Mass Spectrom. 2007, 42, 641–646.

[20] M. de Rosso, A. Panighel, A. Dalla Bedona, L. Stella, R. Flamini.Changes in chemical composition of a red wine aged in acacia,cherry, chestnut, mulberry, and oak wood barrels. J. Agric. FoodChem. 2009, 57, 1915–1920.

[21] B. Fernández de Simón, E. Esteruelas, A. M. Muñoz, E. Cadahía, M.Sanz. Volatile compounds in acacia, chestnut, cherry, ash, and oakwoods, with a view to their use in cooperage. J. Agric. Food Chem.2009, 57, 3217–3227.

[22] L. Culleré, V. Ferreira, P. Hernández-Orte, J. Cacho, B. Fernández deSimón, E. Cadahía. Characterization by gas chromatography-olfactometry of the most odor-active compounds in extractsprepared from acacia, chestnut, cherry, ash and oak woods. FoodSci. Technol. 2013, 53, 240–248.

[23] P. Chatonnet, I. Cutzach, M. Pons, D. Dubourdieu. Monitoringtoasting intensity of barrels by chromatographic analysis of volatilecompounds from toasted oak wood. J. Agric. Food Chem. 1999,47, 4310–4318.

[24] E. Cadahía, B. Fernández de Simón, R. Vallejo, M. Sanz, M. Broto.Volatile compounds evolution in Spanish oak wood (Quercus petraeaand Quercus pyrenaica), during natural seasoning. Am. J. Enol. Vitic.2007, 58, 163–172.


[25] H. Van den Dool, P. Kratz. A generalization of the retention indexsystem including linear temperature programmed gas-liquidpartition chromatography. J. Chromatog. 1963, 11, 463–471.

[26] M. A. Sefton, I. L. Francis, P. J. Williams. Volatile norisoprenoidcompounds as constituents of oak wood used in wine and spiritsmaturation. J. Agric. Food Chem. 1990, 38, 2045–2049.

[27] O. Faix, D. Meier, I. Fortmann. Thermal degradation products ofwood. A collection of electron-impact (EI) mass spectra of mono-meric lignin derived products. Holz Roh Werkst. 1990, 48, 351–354.

[28] O. Faix, I. Fortmann, J. Bremer, D. Meier. Thermal degradationproducts of wood. A collection of electron-impact (EI) massspectra of polysaccharide derived products. Holz Roh Werkst. 1991,49, 299–304.

[29] I. Cutzach, P. Chatonnet, R. Henry, D. Dubourdieu. Identifying ofvolatile compounds with a “toasting” aroma in heated oak used inbarrelmaking. J. Agric. Food Chem. 1997, 45, 2217–2224.

[30] M. D. Guillen, M. L. Ibargoitia. New components with potentialantioxidant and organoleptic properties, detected for the first timein liquid smoke flavoring preparations. J. Agric. Food Chem. 1998,46, 1276–1285.

[31] P. Chatonnet, D. Dubordieu. Identification of substances responsi-ble for the sawdust aroma in oak wood. J. Sci. Food Agric. 1998,76, 179–188.

[32] I. Cutzach, P. Chatonnet, R. Henry, D. Dubourdieu. Identifying newvolatile compounds in toasted oak. J. Agric. Food Chem. 1999,47, 1663–1667.

[33] M. F. Nonier, N. Vivas de Gaujelac, N. Vivas, C. Vitry. Characterizationof carotenoids and their degradation products in oak wood. Inci-dence on the flavor of wood. C. R. Chimie 2004, 7, 689–698.

[34] M. F. Nonier, N. Vivas, N. Vivas de Gaujelac, C. Absalon, Ph. Soulie, E.Fouquet. Pyrolysis-gas chromatography/mass spectrometry ofQuercus sp. wood. Application to structural elucidation of macromol-ecules and aromatic profiles of different species. J. Anal. Appl. Pyrol.2006, 75, 181–193.

[35] N. Natali, F. Chinnici, C. Riponi. Characterization of volatiles inextracts from oak chips obtained by accelerated solvent extraction(ASE). J. Agric. Food Chem. 2006, 54, 8190–8198.

[36] S. Vichi, C. Santini, N. Natali, C. Riponi, E. López-Tamames, S.Buxaderas. Volatile and semi-volatile components of oak wood chipsanalyzed by accelerated solvent extraction (ASE) coupled to gaschromatography-mass spectrometry (GC-MS). Food Chem. 2007,102, 1260–1269.

[37] E. Jakab, K. Liu, H. L. C. Meuzelaar. Thermal decomposition of woodand cellulose in the presence of solvent vapors. Ind. Eng. Chem.Res. 1997, 36, 2087–209.

[38] M. E. Alañón, L. Castro-Vázquez, M. C. Díaz-Maroto, M. S. Pérez-Coello.Aromatic potential of Castanea sativa Mill. compared toQuercus species to be used in cooperage. Food Chem. 2012,130, 875–881.

[39] I. Caldeira, M. C. Clímaco, R. Bruno de Sousa, A. P. Belchior. Volatilecomposition of oak and chestnut wood used in brandy ageing: mod-ification induced by heat treatment. J. Food Eng. 2006, 76, 202–211.

[40] R. C. Brown, M. Sefton, D. K. Taylor, G. M. Elsey. An odour detectionthreshold determination of all four possible stereoisomers of oaklactone in a white and red wine. Aust. J. Grape Wine Res. 2006,12, 115–118

[41] N. Abbot, J. L. Puech, C. Bayonove, R. Baumes. Determination of thearoma threshold of the cis and trans racemic forms of β-methyl-γ-octalactone by gas chromatography-sniffing analysis. Am. J. Enol.Vitic. 1995, 46, 292–294.

[42] M. E. Alañón, M. C. Díaz-Maroto, M. S. Pérez-Coello. Analysis ofvolatile composition of toasted and non-toasted commercial chipsby GC-MS after an accelerated solvent extraction method. Int. J. FoodSci. Technol. 2012, 47, 816–826.

[43] M. C. Diaz-Maroto, E. Guchu, L. Castro-Vazquez, C. de Torres, M. S.Pérez-Coello. Aroma active compounds of American, French,Hungarian and Russian oak woods studied by GC-MS and GC-O. Flav.Frag. J. 2008, 23, 93–98.

[44] M. Brebu, C. Vasile. Thermal degradation of lignin – a review.Cellulose Chem. Technol. 2010, 44, 353–363.

[45] J. L. Campbell, M. Sykes, M. A. Sefton, A. P. Pollnitz. The effects of size,temperature and air contact on the outcome of heating oakfragments. Australian J. Grape Wine Res. 2005, 11, 348–354.

[46] A. B. Cerezo, W. Tesfaye, M. J. Torija, E. Mateo, C. Garcia-Parrilla,A. M. Troncoso. The phenolic composition of red wine vinegar



370

produced in barrels made from different woods. Food Chem. 2008,109, 606–615.

[47] M. Sanz, B. Fernández de Simón, E. Cadahía, E.Esteruelas, A. M.Muñoz, T. Hernández, I. Estrella, E. Pinto. LC-DAD/ESI-MS/MS studyof phenolic compounds in ash (Fraxinus excelsior L. and F. americanaL.) heartwood. Effect of toasting intensity at cooperage. J. MassSpectrom. 2012, 47, 905–918.

[48] F. San Juan, J. Cacho, V. Ferreira, A. Escudero. Aroma chemicalcomposition of red wines from different price categories and itsrelationship to quality. J. Agric. Food Chem. 2012, 60, 5045–5056.


[49] P. Crupi, A. Coletta, D. Antonacci. Analysis of carotenoids in grapes topredict norisoprenoid varietal aroma of wines from Apulia. J. Agric.Food Chem. 2010, 58, 9647–9656.

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