Identification and Organoleptic Contribution of (Z)-1,5-Octadien-3-one

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Identification and Organoleptic Contribution of (Z)-1,5-octadien-3-one to the Flavor of Vitis vinifera cv. Merlot and Cabernet Sauvignon Musts Lucile Allamy, Philippe Darriet, and Alexandre Pons J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b05293 • Publication Date (Web): 11 Feb 2017 Downloaded from http://pubs.acs.org on February 15, 2017

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Journal of Agricultural and Food Chemistry

Identification and Organoleptic Contribution of (Z)-1,5-octadien-3-one to the Flavor of Vitis vinifera cv. Merlot and Cabernet Sauvignon Musts

Lucile Allamy,†,‡, § Philippe Darriet,‡,§ and Alexandre Pons*,‡,§,♯

†

Château Latour, Saint Lambert, 33000 Pauillac, France.

‡

Université de Bordeaux, ISVV, EA4577 Œnologie, F-33140 Villenave d'Ornon, France.

§

INRA, ISVV, USC 1366 Œnologie, F-33140 Villenave d’Ornon, France.

♯

Seguin Moreau France, Z.I. Merpins, BP 94, 16103 Cognac, France.

*

Corresponding author (telephone: +33557575868; email: [email protected])

1

ACS Paragon Plus Environment


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ABSTRACT

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The main goal of this research was to identify key aroma compounds involved in the dried

3

fruits (prune and dry fig) aroma of musts. An odoriferous zone (OZ) was detected by gas

4

chromatography coupled with olfactometry (GC-O) and identified as (Z)-1,5-octadien-3-one

5

(geranium). A quantitation method by SPME-GC-MS (CI, MeOH) was developed and

6

validated for assaying this very fragrant ketone in musts for the first time (LOD: 0.15 ng/L;

7

LOQ: 0.5 ng/L). Concentrations of (Z)-1,5-octadien-3-one in musts marked by dried fruits

8

flavors reached 90 ng/L, thus exceeding its detection threshold (Dth 9 ng/L). Moreover,

9

sensory experiments showed that this compound contributes to the dry fig nuance at

10

concentrations ranging from 64 to 96 ng/L. Above that level, it contributes to the geranium

11

nuance of the must. It is also established its affinity with sulfur dioxide: 30 mg/L of sulfur

12

dioxide causes a decrease of concentration of 60%.

13 14

KEYWORDS: aroma compound, dried fruits, must, ripening, GC-MS, (Z)-1,5-octadien-3-

15

one

2


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INTRODUCTION

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The intensity and complexity of aromas are very important in wine quality and play a great part

18

in the global judgment of quality by consumers. Wine aromas take their diversity and

19

complexity from various origins and cascades of formation including biochemical and chemical

20

transformation or precursors found in grapes. For this reason, grape maturity can impact the

21

flavor of wine.1 When grapes are harvested at maturity, the aromas found in young red wines of

22

Merlot and Cabernet-Sauvignon suggest a complex mixture of odors of fresh red fruits such as

23

cherry or blackberry for Merlot, and strawberry or blackcurrant for Cabernet-Sauvignon.

24

However, when grapes are harvested earlier, vegetal, herbaceous odors dominate the flavors of

25

these red wines, whatever the cultivar.2 On the contrary, grapes that are harvested belatedly, are

26

overripe or have undergone a hot dry summer produce a characteristic shade of aromas of dried

27

fruits (dry fig, prune). These aromas are found in both musts and young wines.3

28

The volatile compounds associated with these fruity herbaceous flavors have received

29

considerable attention. Aroma compounds exist in berries as both free and bound volatile

30

compounds and are released thanks to chemical or biochemical mechanisms during

31

winemaking. They belong to several chemical families mainly including the terpenoids,

32

norisoprenoids, aliphatic aldehydes, alcohols, thiols, and pyrazines.4

33

It is now assumed that 2-methoxy-3-isobutylpyrazine (IBMP) is responsible for the green bell

34

pepper aroma of grapes and wines from Cabernet-Sauvignon.5 This compound, which is

35

present in high concentrations in green grapes, decreases during maturation, and its

36

concentrations are quite stable during winemaking. It is important for winemakers to monitor

37

it during maturation as it is one of the criteria determining the organoleptic quality of mature

38

grapes. The fruity aroma of red wines, including blackberry, strawberry or blackcurrant

39

nuances, has been widely studied, leading to the identification of several volatile compounds

40

involved directly or indirectly (synergy, antagonist, additivity) in this flavor.6,7,8 These fruity 3



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nuances that are rarely detected in must are produced by yeast during alcoholic fermentation.

42

For example, the organoleptic impact of several ethyl esters such as ethyl hexanoate and ethyl

43

octanoate9,10 has been demonstrated. The odorants of young red wines from various grape

44

varieties are known to participate in the fruity aroma of red wines.11,12 More recently, ethyl 2-

45

hydroxy-4-methylpentanoate was identified as a major contributor to the aroma of blackberry

46

in wine.13,14

47

In wines where oxidation during winemaking plays a role such as Port wine, VDN and Xeres,

48

the dried fruit flavor is well correlated with the level of a very fragrant lactone: 3-hydroxy-

49

4,5-dimethyl-furan-2-one (sotolon).15,16 Red wines made in reductive conditions can develop

50

dried fruit nuances during bottle aging. The flavor of such red “prematurely aged” wines is

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associated with a diketone: 3-methyl-2,4-nonanedione.17 In oxidized red wines, its

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concentration can exceed 300 ng/L, which is higher than its olfactory detection threshold (16

53

ng/L).18 It is also detected in Merlot and Cabernet Sauvignon musts where its concentration

54

ranges from some ng/L to more than 70 ng/L3 to impart a flavor of dried fruits. However,

55

owing to its high olfactory perception threshold in must (62 ng/L), its organoleptic impact has

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not been clearly demonstrated and the molecular markers of these dried fruit aromas remain to

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be identified.

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In this work, the identification of (Z)-1,5-octadien-3-one and the first results of its

59

quantitation in musts are described. In addition, its organoleptic contribution to the dried

60

fruits aromas in musts is discussed.

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MATERIALS AND METHODS

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Chemicals and reference compounds. Dichloromethane and methanol were provided by

63

Prolabo (Fontenay sous Bois, France). Absolute ethanol (≥99.9%) was obtained from Merck

64

(Darmstadt, Germany). Ammonium sulfate (≥99.9%), 2-octanol (99%) and tartaric acid

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(≥99.5%) were provided by Sigma-Aldrich (Saint-Quentin Fallavier, France). (Z)-1,5-

66

octadien-3-one solution in pentane was a gift from Nestlé® (Lausanne, Switzerland).

67

Origins of musts and wines. All samples of must and wines selected are listed in Table 1.

68

They were collected from wineries from different regions in France, from white and red vines.

69

Wine and must samples were kept at – 20°C until analysis. Before freezing, samples were

70

tasted and classified on a 0-to-10 scale by four wine professionals according to the intensity

71

of their dried fruit nuances. When the intensity was ≤ 5, the sample was considered flavorless.

72

Conversely, when the intensity was > 5, samples were considered to be marked by dried fruit

73

aromas. The samples were used for identification by GC-O-MS, development of the method,

74

quantitation and sensory analysis.

75

Must and wine model solutions. A must model solution was prepared with 220 g/L

76

glucose/fructose and 5 g/L tartaric acid adjusted to pH 3.5 (NaOH 5M). The wine model

77

solution was a mixture of 12% vol. bi-distilled absolute ethanol and 5 g/L tartaric acid

78

adjusted to pH 3.5 (NaOH 5M).

79

Liquid-liquid extraction. 100 mL of sample were extracted three times with

80

dichloromethane (10, 5, and 5 mL) and magnetic stirring (750 rpm) for 10, 5 and 5 min each

81

time in a 250 mL amber flask and separated in a funnel. The organic phases were collected

82

and dried by anhydrous ammonium sulfate and concentrated under nitrogen 6.0 (Linde gas,

83

France) flow (approximately 100 mL/min) in a graduated glass volume (Atelier Jean Prémont,

84

Bordeaux) to a final volume of 500 µL.

85

Gas-Chromatography coupled with Olfactometry and Mass Spectrometry (GC-O-MS).

86

The analysis was carried out using a Trace GC Ultra (Thermo Fisher, Waltham, MA, USA)

87

gas chromatograph and the detector was a mass spectrometer DSQ II (Thermo Fisher,

88

Waltham, MA, USA) functioning in EI mode. The Trace GC Ultra was equipped with a

5



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sniffing port (ODO-1) (Gerstel, Germany). One µL of each sample extract was injected into a

90

splitless PTV injector (150 °C and rate of 14.5 °C/sec until 230 °C for 1.20 min, purge time: 1

91

min, purge flow: 30 mL/min,) onto a BP 20 capillary column (SGE, France, 50 m, 0.22 mm

92

i.d., 0.25 µm film thickness). The program temperature was as follows: 45 °C for 1 min,

93

increasing by 3 °C/min to 230 °C, followed by a 20 min isotherm. The carrier gas was helium

94

(Linde gas, France), grade 5.3, with a constant flow rate of 1 mL/min. The capillary column

95

flow was split between the MS and ODO-1 (division ratio 1:1).

96

The temperatures of the ion source and transfer line were set at 210 °C. The electron energy

97

for the electronic impact (EI) mass spectra was 70 eV. The MS was operated in scan mode

98

(m/z from 45 to 250). Identification was performed by comparing linear retention indices and

99

mass spectrometric data for sample constituents with those of an authentic reference

100

compound.

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Quantitation of (Z)-1,5-octadien-3-one by Solid Phase Microextraction and Gas

102

Chromatography Mass Spectrometry with Chemical Ionization (GC-MS-CI).

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Head space solid phase micro-extraction (HS-SPME). Design of experiments (DOE).

104

Experiments were designed to distinguish optimal parameters of SPME by the use of

105

Minitab® 16 software (Paris, France). The independent variables and their levels (-1, +1)

106

used for DOE were as follows: incubation temperature during extraction (50, 60 °C),

107

extraction time (10, 30 min), ammonium sulfate content (1, 6 g) and sample volume (1, 5

108

mL). The DOE was based on 24 factorial designs, leading to 16 experiments carried out in

109

random order. It was performed in duplicate. Analysis of variance determined the optimal

110

parameters (p ≤ 0.05). The volume of extraction mixture was adjusted to 10 mL with ultrapure

111

water. Ketone concentration was set at 200 ng/L and media were must and wine model

112

solution. The impact of pH extraction mixture on the intensity of the peak of this ketone in

113

GC-MS was also evaluated. To do so, five acidified aqueous solutions containing 5 g/L of

6


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tartaric acid at pH 5 (NaOH 5M), pH 3.6 (NaOH 5M), pH 3 (NaOH 5M), pH 2 (HCl, 10M),

115

pH 1 (HCl, 10M) were evaluated during the SPME extraction step. This test was carried out

116

in triplicate.

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Optimized parameters. 6 g ammonium sulfate, 10 µL octan-2-ol (100 mg/L) as an internal

118

standard, 5 mL of aqueous solution (5 g/L tartaric acid with ultrapure water- Milli-Q,

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Millipore, Bedford, MA, USA) adjusted to pH 1 (37% HCl) and 5 mL of must were added

120

successively to a 20 mL amber vial. Before sealing, the vial head space was inerted by carbon

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dioxide to prevent oxidation during extraction. The vial was automatically placed in the

122

thermostatic enclosure of the autosampler (Combipal, CTC Analytics) at 50 °C for 5 min. A 2

123

cm fiber coated with Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CARB/PDMS -

124

Supelco, Saint-Quentin Fallavier, France) was introduced into the headspace sample for 30

125

min. After sampling, the fiber was thermally desorbed for 3 min into the GC injection port at

126

240 °C (with a 0.75 mm i.d. SPME liner).

127

Gas Chromatography coupled to Mass Spectrometry. A Varian 240-4000 GC/MS gas

128

chromatograph (Agilent Technologies, Santa-Clara, US) with a split/splitless injector and an

129

ion trap analyzer was fitted with a BP20 fused silica capillary column (SGE, 60 m, 0.25 i.d,

130

0.5 µm film thickness) for quantitative analysis of samples. Oven temperature was set at 40

131

°C for 1 min, increasing by 3 °C/min to 190 °C and 15 °C/min to 240 °C, followed by a 20

132

min isotherm. The carrier gas was helium (Linde gas, France), grade 5.3, with a constant flow

133

rate of 1 mL/min. The MS conditions were similar to those already described by Pons et al.

134

(2011)19. Methanol was selected as reactant gas for chemical ionization (CI) experiments.

135

Acquisition was divided into two segments: first segment (Z)-1,5-octadien-3-one (28-30.80

136

min, µSIS, m/z 125), second segment 2-octanol (30.8-32.5 min, full scan, m/z 69 to m/z 125).

137

Solutions of linear n-alkanes (C9-C25) were injected under the same conditions as those

138

reported above to determine the linear retention indexes (LRI). 7



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Method validation. Optimization and validation of the method included several parameters:

140

linearity of calibration curves, limit of detection (LOD) and limit of quantitation (LOQ). (Z)-

141

1,5-octadien-3-one stock solution in pentane was kept stable for several months at - 20 °C.

142

This solution was dissolved in ethanol (10 mg/L) for subsequent use. For these experiments,

143

Merlot must in which this ketone was not detected was spiked at eight concentrations and

144

analyzed with the abovementioned procedure. To assess the repeatability of the method, eight

145

identical samples spiked with 200 ng/L were analyzed. LOD and LOQ were defined as the

146

concentration that gave a signal-to-noise ratio (S/N) of 3 and 10, respectively. The linearity

147

was evaluated twice thanks to a series of eight points ranging from 0.5 to 480 ng/L.

148

Impact of sulfur dioxide on contents of (Z)-1,5-octadien-3-one. A must and a wine model

149

solution were prepared and spiked with 250 ng/L (Z)-1,5-octadien-3-one. 120 mL of each

150

sample were stored in the absence of oxygen in 125 mL amber glass bottles in the dark for 7

151

days. Half of the samples were sulfited at 30 mg/L of total SO2. These trials were conducted

152

in duplicate.

153

General conditions for sensory analyses. Sensory analyses were conducted in a tasting

154

room at our oenology research unit (ISVV, France) including ten individual booths. The room

155

is designed to limit external factors that could potentially disturb sensory analysis and

156

corresponds to the AFNOR (ISO 8589)20 standards for this type of equipment (sound

157

insulation, constantly regulated temperature, etc). In addition, all the tastings were carried out

158

in black glasses corresponding to AFNOR (ISO 3591)21 standards filled with 50 mL of

159

solution. In all experiments, glasses were labeled with three-digit random codes and presented

160

to the panelists in random order. The panel consisted of 25 judges, all wine professionals and

161

from our research unit (ISVV, France). There were 15 women and 10 men, age range 20-50

162

years. Judges were selected for their experience in assessing dried fruit aromas of musts and

163

red wines. 8


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Olfactory thresholds. Olfactory detection thresholds of (Z)-1,5-octadien-3-one were

165

determined. The odor detection threshold corresponded to the minimum concentration below

166

which 50% of 25 tasters statistically failed to detect the difference from the control. Detection

167

thresholds were established in a model solution with a composition similar to that of must or

168

wine and also in a Merlot must. There were determined twice for the Merlot must and three

169

times for the model must and model wine. Each session was performed at a 1-month interval.

170

The detection threshold was determined in model solutions and Merlot must with an

171

ascending procedure using the three-alternative forced-choice presentation method (3-AFC)

172

(ISO 13301)22: 0.12, 0.25, 0.5, 1, 2, 4, 8, 16 ng/L for wine model solution and Merlot must;

173

0.8, 1.6, 3.2, 6.4, 12.8, 25.6, 51.2, 102.4 pg/L for must model solution.

174

Sensory impact of (Z)-1,5-octadien-3-one in must. Sensory impact was studied by spiking

175

increasing concentrations of (Z)-1,5-octadien-3-one (0, 32, 64, 96, 128 and 240 ng/L) in

176

“dried fruit flavors free” Merlot must which did not contain sulfites. Beforehand, it has been

177

verified that this ketone was not detected (GC-MS) in the must. During the sensory analysis

178

test, samples were presented randomly to the judges. They were asked to evaluate the

179

intensity on a 0 (not perceivable) to 7 (strongly perceivable) scale of six descriptors

180

characteristic of the flavor of red must. Selected descriptors were “rose flower”, “strawberry,

181

blackcurrant”, “dry fig”, “geranium”, “herbaceous” and “hay”. To statistically assess the

182

sensory changes in each experiment, an analysis of variance to a factor on the reduced-centric

183

data was performed for each descriptor. ANOVA application conditions, homogeneity of

184

variance (Levene’s test) and normality of residuals (Shapiro-Wilk test) were verified thanks to

185

R software (R foundation for Statistical Computing, England). If these conditions were not

186

met, a bilateral statistical, non-parametric, Kruskal-Wallis test was applied (multiple pairwise

187

comparisons according to the procedure of Steem-Dwass-Critchlow-Flogner). The risk α was

188

set at 5%.

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Statistical analysis of quantitative analysis. Statistical data on the various (Z)-1,5-octadien-

190

3-one assays and on the SPME method for testing pH in the diluent solution were obtained by

191

analysis of variance (ANOVA), as in the sensory analysis described above. Statistical

192

significance was set at 1% (p < 0.01) and 5% (p < 0.05).

193

RESULTS/DISCUSSION

194

Identification of (Z)-1,5-octadien-3-one by GC-O-MS. Musts and wines from Merlot and

195

Cabernet Sauvignon grapes marked or not by dried fruit flavors were extracted with

196

dichloromethane. After concentration, two assessors analyzed the extracts by GC–O. The

197

traditional goal of this first approach was to detect and select odorant zones reminiscent of the

198

flavor of wine, i.e. reminiscent of dried fruit flavor. Aromagrammes obtained from this

199

analysis revealed more than 50 different odorant zones (OZ). As depicted in Table 2, one of

200

them reminiscent of geranium leaf was very intense and surprisingly specific to samples of

201

musts and wines marked by dried fruit flavors. Although the descriptor associated with this

202

OZ was far removed from those used to describe the odor of must and wine, its distribution

203

and intensity intrigued us so decided to study it.

204

By comparing the descriptor of the OZ as well its linear retention index (LRI) on a polar

205

column (OZ was not detected on an apolar column) with those reported in the literature, (Z)-

206

1,5-octadien-3-one was identified. LRI was 1380 on a polar column in the work of Mayer et

207

al.,23 1381 according to Delort et al.24, 1362 according to Darriet et al.25 and 1376 in our work

208

(Table S1). In apolar column, LRI is 98625. A co-injection of a diluted solution of this ketone

209

with an organic extract of must was analyzed and odors was compared by GC-O: this

210

injection validate the identification. Complementary analysis of the co-injected sample by

211

GC-O-MS revealed no chromatographic peak (EI) at the retention time of the OZ.

212

Indeed, the mass spectrum obtained in electronic impact mode was highly fragmented with a

213

low m/z ion at high intensity, making its identification in a complex matrix tricky by this 10


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ionization technique. Furthermore, the ability of chemical ionization (CI) with methanol was

215

evaluated as reactant gas to detect and quantify the compound, as in the work of Greger and

216

Schieberle.26 The mass spectrum of this ketone under CI revealed one intense peak at m/z 125.

217

Its has previously been validated in the laboratory to quantify another ketone present at trace

218

levels in wines: 3-methyl-2,4-nonanedione.19 Thanks to this approach, a clear peak was

219

obtained in CI (MeOH) mode (Figure 1).

220

(Z)-1,5-octadien-3-one was described for the first time in 1977 as being responsible for the

221

metallic odor of oxidized fat. 27 The occurrence of the (Z) form of 1,5-octadien-3-one in many

222

food products (to date the “trans” form has never been reported in nature) has been studied by

223

GC-O in tomato extracts,23 in Japanese green tea,28 in Cheddar cheese,29 in several varieties of

224

strawberries,30 in mushrooms,31 in soybean oil32 and olive oil.33 More recently, a study using

225

omission experiments showed that (Z)-1,5-octadien-3-one contributes to the flavor of fresh

226

apricot.26 In addition, its contribution to the particular marine, oyster-like note of oyster leaf

227

has been recently demonstrated.24

228

In grapes, its presence has been demonstrated by GC-O and it is associated with the

229

development of pathogens such as Uncinula necator, also called powdery mildew.25 To our

230

knowledge, it is reported for the first time its presence in musts and wines marked by dried

231

fruit nuances.

232

It might arise from the oxidation of precursors such as α-linolenic acid and their n-3

233

counterparts,34 eicosapentaenoic acid (EPA)35 or docosahexaenoic acid (DHA)36 in the

234

presence of copper ion or lipoxygenase. However, its formation pathway in grapes and wines

235

remains unknown.

236

Quantitation Method

237

(Z)-1,5-octadien-3-one has been reported in many food products but to our knowledge its

238

quantitation has received little attention.37 For this reason, a method was developed for its

11



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quantitation in must. The development trials of quantitation method in wines is not shown

240

because it was not sensitive enough: the LOD was 60 ng/L and the concentrations found in

241

wines are systematically much lower than LOD.

242

Sample preparation by solid phase micro-extraction (SPME). Parameters tested in an

243

experimental design to determine the best conditions for the extraction experiment were:

244

incubation temperature, extraction time, salt concentrations, volume of sample and pH of the

245

diluent solution.

246

Before designing the experiment, two fibers were tested: the first fiber with a coating of

247

Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CARB/PDMS) and the second with a

248

coating

249

(DVB/CARB/PDMS) has shown greater affinity for this ketone. Finally, the signal obtained

250

by GC-MS-CI is on average twice as high as with the second fiber based on PDMS/DVB

251

(result not shown).

252

Next, a factorial plan was designed to define the best parameters for extraction. The

253

independent variables and their levels (-1, +1) used for the DOE were as follows: incubation

254

temperature during extraction (60, 50 °C), extraction time (30, 10 min), salt content (1, 6 g)

255

and sample volume (1, 5 mL). When sample volumes are 1 mL or 5 mL, aqueous solution

256

volumes are 9 mL or 5 mL respectively. The tests were carried out on a Merlot must

257

supplemented with 200 ng/L (Z)-1,5-octadien-3-one.

258

Finally, by linear regression of the response to the parameters tested (Figure 2, Table 3), the

259

maximum response (maximal surface area) was obtained with +1 levels, except for

260

temperature of incubation, by using an extraction time of 30 min at 50 °C, with 6 g of

261

ammonium sulfate and 5 mL of must sample, which represent the best conditions for SPME.

262

Main effects were observed for sample volume, salt content and extraction temperature (p ≤

263

0.05), while extraction time had no significant effect on the intensity of the signal in our

with

Polydimethylsiloxane/Divinylbenzene

(PDMS/DVB).

The

first

fiber

12


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experimental conditions. The interactions between the different parameters tested show that

265

interaction between the volume of must and the extraction temperature were significant (p ≤

266

0.05). These two parameters had the greatest influence on the peak area of (Z)-1,5-octadien-3-

267

one.

268

Incidence of pH of aqueous solution. The impact of the pH of diluted must was evaluated with

269

water or acidified aqueous solutions (5 g/L tartaric acid) at pH 5, pH 3.6, pH 3.0 pH 2.0, pH

270

1.0 on the peak intensity of (Z)-1,5-octadien-3-one and 2-octanol. The pH of Merlot must was

271

3.65 and 3.60 with twofold dilution with ultrapure water, so the response of (Z)-1,5-octadien-

272

3-one with an aqueous solution (5 g/L tartaric acid) at pH 3.6 was tested. Figure 3 shows that

273

pH had a significant impact on the peak area (p < 0.001). A lower pH diluent solution gave

274

greater extractability resulting in higher peak intensity, whereas tartaric acid in water had no

275

effect on the extractability of the compound at pH 3.6. From a pH of 2, the area of the peak

276

significantly increased whereas the response of 2-octanol was constant and not significantly

277

different according to the pH (result not shown). Similar results concerning the effect of pH

278

were observed for (Z)-1,5-octadien-3-one and 2-octanol in the model must solution.

279

Method validation. Sample preparation, chromatographic separation and detection were

280

undertaken to validate the method. Repeatability of the assay was confirmed by a series of

281

eight extractions of a sample of a must spiked with 200 ng/L of (Z)-1.5-octadien-3-one.

282

Precision estimated in terms of (RSD) was 8%. The LOD and LOQ of the method were 0.15

283

ng/L and 0.5 ng/L, respectively. The linearity of the method was determined by plotting the

284

calibration curves of the corresponding peak areas, normalized by that of the internal

285

standard. In the concentration range (LOQ-480 ng/L), the control curve was linear (Table 4).

286

Detection thresholds. The measurement of detection thresholds with the three-alternative

287

forced-choice presentation method (3-AFC) is one of the most common techniques to

288

evaluate quantitatively the aromatic potency of aromatic compounds in musts and wines. The

13



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extremely low detection thresholds in water reported in the literature25, 27 led us to evaluate

290

these detection thresholds in different matrices (Table 5).

291

The detection thresholds were extremely low in all matrices and especially in the synthetic

292

must. The detection threshold in the synthetic must (0.0022 ng/L) was lower than that

293

reported in water (about 1 ng/L) 25, 27 and there was a "salting out" effect due to the presence

294

of high levels of hexoses (glucose and fructose) in the synthetic medium. The detection

295

threshold was 9 ng/L in a Merlot must. Therefore, this compound has a strong odor impact in

296

must.

297

Quantitation in musts. (Z)-1,5-octadien-3-one was quantified in many musts marked (DF) or

298

not (control) by dried fruit nuances. The samples were classified by the jury according to the

299

intensity of their dried fig and prune flavors (0-10 scale) and characterized as either being

300

marked (> 5) or not (0 - ≤ 5) by them. The distribution of (Z)-1,5-octadien-3-one in white and

301

red must samples is reported in Figure 4. In white Sauvignon musts, it was less than LOQ (
0.05), strawberry, blackcurrant (p = 0.653, p > 0.05) or hay (p = 0.187, p > 0.05). On the

324

contrary, the intensity of herbaceous, dry fig and geranium changed considerably as the

325

concentration increased. Indeed, the must spiked with 96 ng/L of (Z)-1,5-octadien-3-one was

326

perceived as less marked by herbaceous aromas (p = 0.0411, p < 0.05) than the control must

327

although it produced fig aromas (p = 1.98e-8, p < 0.05). Beyond 96 ng/L, the fig aromas

328

decreased significantly whereas geranium nuances increased (p = 4.35e-9, p < 0.05). At high

329

concentrations, (Z)-1,5-octadien-3-one gave the must its geranium nuances.

330

To throw light on the contribution of (Z)-1,5-octadien-3-one to the flavor of the must, each

331

panelist’s means and standard deviation were compared for each (Z)-1,5-octadien-3-one

332

concentration and are plotted in Figure 6 as a radar chart. The results show that the control

333

must was marked by herbaceous flavors and that increasing the concentration of (Z)-1,5-

334

octadien-3-one gradually modified the overall aroma of the samples. Fig and geranium

335

nuances were detected at very low intensity in the control must. However, fig dominated at 64

336

and 96 ng/L whereas geranium dominated at 240 ng/L. Finally, it is demonstrated that (Z)-

337

1,5-octadien-3-one has a very strong impact on the flavor of the must according to its

338

concentration.

15



Page 16 of 35

339

Impact of presence of sulfur dioxide on (Z)-1,5-octadien-3-one content in musts and

340

wines. Sulfur dioxide is commonly added to freshly crushed grapes to protect musts against

341

oxidation and to prevent the development of microorganisms other than S. cerevisiae. In

342

aqueous solutions, sulfur dioxide, which is mainly found as HSO3-, can bind to carbonyl

343

compounds in various ways, one of which leads to bisulphite adducts also known as

344

hydroxyalkylsulfonic acids that render them non-volatile and therefore odorless.

345

It was observed that must may contain high levels of (Z)-1,5-octadien-3-one so it was decided

346

to study the influence of SO2 on its concentrations in must. It was also studied its evolution in

347

wine containing SO2. A model must and a model wine with a composition close to the must

348

and a wine spiked with 250 ng/L of (Z)-1,5-octadien-3-one were used. Half of the samples

349

were also spiked with sulfur dioxide at 30 mg/L, a concentration often reached in must before

350

alcoholic fermentation. After 7 days, (Z)-1,5-octadien-3-one was assayed in the samples. The

351

results are shown in Figure 7. SO2 caused a sharp decrease in levels of (Z)-1,5-octadien-3-

352

one. Adding 30 mg/L of SO2 led to a 60% reduction in (Z)-1,5-octadien-3-one in a model

353

must and an 81% reduction in a model wine. Therefore, addition of SO2 forming a bisulphite

354

adduct in must and wine decreases the organoleptic impact of (Z)-1,5-octadien-3-one.

355

As proposed by Dufour and co-authors,38 addition of α,β-unsaturated carbonyl has a dual

356

effect since it initially produces a carbonyl adduct and ultimately a disulfonate. Reversible

357

binding occurs between the carbonyl functional group and bisulfite, whereas the addition of

358

bisulfite to the double bond of unsaturated aldehydes is irreversible.

359

In addition, Darriet et al.25 have already shown that yeast metabolism is able to reduce the

360

very odorant (Z)-1,5-octadien-3-one into the less odorant (Z)-5-octen-3-one, so the chemical

361

and biochemical mechanisms point to its instability in must and wine. However, it cannot rule

362

out that bisulfite adducts (ionized form at wine pH) are not assimilated by yeast and are used

363

as a sort of reservoir for other aldehydes and ketones, as recently observed by Bueno et al.39

16


Page 17 of 35


364

These adducts can be released progressively during aging as the level of free sulfur dioxide

365

decreases. Further investigation would likely throw light on this issue.

366 367

ACKNOWLEGMENTS

368

The authors would like to thank Château Latour for their financial support and Biolaffort Cie

369

and Seguin-Moreau for supporting the research activity of the laboratory.

370

Supporting Information. The table S1 is an example of olfactometric profil obtain in a

371

control red must of Merlot and in a red must of Merlot marked by dried fruits aromas (Dried

372

fruits red must). Analysis was carried out by GC-O-MS with polar colum (BP20) and by three

373

tasters.

374

REFERENCES

375 376

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10. Ferreira, V.; López, R.; Cacho, J. F. Quantitative determination of the odorants of

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methylpentanoate in red wines, a compound involved in blackberry aroma. Food

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Paris, France, 2010.

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parmi 3 (3-AFC). ISO13301. In Analyse Sensorielle; AFNOR: Paris, France, 2002.

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23. Mayer, F.; Takeoka, G.; Buttery, R.; Naim, M.; Bezman, Y.; Rabinowitch, H. Aroma

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fresh field tomatoes. ACS Symposium Series. 2002, 836, 144-161.

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24. Delort, E.; Jaquier, A.; Chapuis, C.; Rubin, M.; Starkenmann, C. Volatile composition

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of oyster leaf (Mertensia maritima (L.) gray). J. Agric. Food Chem. 2012, 60, 11681-

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25. Darriet, P.; Pons, M.; Henry, R.; Dumont, O.; Findeling, V.; Cartolaro, P.; Calonnec,

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A.; Dubourdieu, D. Impact odorants contributing to the fungus type aroma from grape

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berries contaminated by powdery mildew (Uncinula necator); incidence of enzymatic

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activities of the yeast Saccharomyces cerevisiae. J. Agric. Food Chem. 2002, 50, 3277-

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26. Greger, V.; Schieberle, P. Characterization of the key aroma compounds in apricots

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(prunus armeniaca) by application of the molecular sensory science concept. J. Agric.

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Food Chem. 2007, 55, 5221-5228.

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27. Swoboda, P.A.T.; Peers, K.E. Metallic odor caused by vinyl ketones formed in the

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Chem. 1977, 28, 1019-1024.

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30. Ubeda, C.; San-Juan, F.; Concejero, B.; Callejon, R.M.; Troncoso, A.M.; Morales,

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M.L.; Ferreira, V.; HernandeZ-Orte, P. Glycosidically bound aroma compounds and

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impact odorants of four strawberry varieties. J. Agric. Food Chem. 2012, 60, 6095-

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89−93.

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32. Guth, H.; Grosch, W. Comparison of stored soya-bean and rapeseed oils by aroma extract dilution analysis. Lebensmittel-Wissenschaft + Technologie. 1990, 23. 33. Reiners, J.; Grosch, W. Odorants of virgin olive oils with different flavor profiles. J. Agric. Food Chem. 1998, 46, 2754−2763.

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34. Ullrich, F.; Grosch, W. Identification of the most intense odor compounds formed

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during autoxidation of methyl linolenate at room temperature. J. Am. Oil Chem. Soc.

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1988, 65, 1313-1317.

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35. Haard N.F.; Simpson B. K. Utilization and influence on postharvest seafood quality. In Seafood Enzymes: Eds. Marcel dekker inc.; 2000.

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36. Hammer, M.; Schieberle, P. Model studies on the key aroma compounds formed by an

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oxidative degradation of ω-3 fatty acids initiated by either copper(II) ions or

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lipoxygenase. J. Agric. Food Chem. 2013, 61, 10891-10900.

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37. Guth, H.; W. Grosh. Furanoid fatty acids as precursors of a key aroma compound of

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green tea. In Progress in flavour precursor studies. Eds. P. Schreier and P.

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Winterhalter; 1992.

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38. Dufour, J.P.L., M.; Baxter, A.J.; Hayman, A.R. Characterization of the reaction of

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bisulfite with unsaturated aldehydes in a beer model system using nuclear magnetic

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resonance spectroscopy. J. Am. Soc. Brew. Chem. 1999, 57, 138-144.

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39. Bueno, M., Carrascón, V.; Ferreira, V. Release and Formation of Oxidation-Related Aldehydes during Wine Oxidation. J. Agric. Food Chem. 2016. 64, 608-617.

20


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489

SUPPORTING INFORMATION

490 491 492

Table S1. Olfactometric profil of a control red must of Merlot and a red must of Merlot marked by dried fruits aromas (Dried fruits red must). Analysis was carried out by GC-O-MS with polar column (BP20) and by three tasters. LRI

Control red must

Dried fruits red must

1004 1008 1038 1059 1061 1143 1197 1201 1246 1300 1308 1338 1376 1430 1448 1456 1499 1521 1564 1599 1653 1685 1721 1735

Strawberry Butter Rubber Strawberry Butter Herbaceous Plastic Cheese Plastic Mushroom Yeast Ham Cheese Vinegar Cooked potatoes Cooked vegetables Vegetal Vomit Earthy Honey Cheese Floral -

Strawberry Butter Rubber Strawberry Butter Herbaceous Plastic Cheese Plastic Mushroom Yeast Ham Geranium Vinegar Cooked potatoes Honey Floral Anise

21



Page 22 of 35

LIST OF FIGURES

Figure 1. Example of chromatographic separation of (Z)-1,5-octadien-3-one peak obtained by SPME-GCMS-CI (m/z 125) analysis of a Merlot must spiked (red) or not (black) with 64 ng/L of (Z)-1,5-octadien3-one (red) and developped formula of (Z)-1,5-octadien-3-one. Figure 2. Peak area (kCounts) of (Z)-1,5-octadien-3-one according to optimization of SPME parameters giving a minimum response (10 min, 60 °C, 1 g, 1 mL) and a maximum response (30 min, 50°C, 6g, 5 mL) for a must model solution. Figure 3. Impact of pH of aqueous solutions (Tartaric Acid 5g/L) (AS) and water aqueous solution (Water) on peak area of (Z)-1,5-octadien-3-one (200 ng/L) obtained by SPME-GC-MS (m/z 125). n = 3. Letters indicate statistical groups of ANOVA at (p < 0.001). Figure 4. Box-whisker plot of (Z)-1,5-octadien-3-one concentrations in White musts (n = 5, intensity of dried fruits aromas = 0), red musts marked (DF) (n = 8, intensity of dried fruits aromas > 5) or not (control) (n = 6, intensity of dried fruits aromas < 5) by dried fruit aromas. ANOVA (α = 0.01). Figure 5. Means of evolution of odor intensity of several descriptors at increasing (Z)-1,5-octadien-3-one concentrations in Merlot must. Letters indicate significantly different values at p < 0.05. Figure 6. Radar chart of sensory analysis in a control must spiked with increasing concentrations of (Z)1,5-octadien-3-one. Means are expressed on a 0 to 7 scale to evaluate intensity of rose flower, strawberry and blackcurrant, dry fig, geranium, herbaceous and hay aromas. ANOVA (**: α = 0.01; ***: α = 0.001). Figure 7. Impact of sulfur dioxide on levels of (Z)-1,5-octadien-3-one in a model must (A) and a model wine (B). ANOVA (α = 0.01).

22


Page 23 of 35


Figure 1.

23



Page 24 of 35

Figure 2.

24


Page 25 of 35


Figure 3.

25



Page 26 of 35

Figure 4.

26


Page 27 of 35


Figure 5.

27



Page 28 of 35

Figure 6.

28


Page 29 of 35


Figure 7.

29



Page 30 of 35

TABLES Table 2. List of Musts and Wines used in GC-O-MS Experiments for Identification of ( Z)-1,5octadien-3-one (1), Method Development in GC-MS (2), Sensory Analyses (3) and Quantitation of (Z)-1,5-octadien-3-one by GC-MS (4) Including Vintage, Vine, Appellation (AOC) and Intensity of Dried Fruit Aromas.

Code

Vintage

Type

Vine

Appellation (AOC)

M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17 M18 M19 W1 W2 W3 W4 W5 W6 W7 W8

2011 2011 2012 2012 2012 2012 2011 2011 2012 2012 2012 2012 2012 2012 2011 2006 2008 2016 2016 2011 2011 2012 2012 2012 2012 2012 2012

Must Must Must Must Must Must Must Must Must Must Must Must Must Must Must Must Must Must Must Wine Wine Wine Wine Wine Wine Wine Wine

Merlot Merlot Cabernet-Sauvignon Cabernet-Sauvignon Merlot Merlot Cabernet-Sauvignon Cabernet-Sauvignon Merlot Merlot Cabernet-Sauvignon Cabernet-Sauvignon Cabernet-Sauvignon Cabernet-Sauvignon Sauvignon Sauvignon Sauvignon Sauvignon Sauvignon Merlot Merlot Cabernet-Sauvignon Cabernet-Sauvignon Merlot Merlot Cabernet-Sauvignon Cabernet-Sauvignon

Pessac-Léognan Pauillac Saint-Julien Pauillac Pessac-Léognan Pessac-Léognan Pessac-Léognan Saint-Emilion Saint-Emilion Saint-Emilion Pessac-Léognan Saint-Emilion Pessac-Léognan Saint-Emilion Sancerre Sancerre Sancerre Bordeaux Bordeaux Pauillac Saint-Emilion Pauillac Saint-Emilion Pessac-Léognan Saint-Emilion Pessac-Léognan Saint-Emilion

Intensity of Dried fruit aromas 0 1 1 2 8 9 7 7 1 2 9 8 9 9 0 0 0 0 0 1 0 0 0 7 8 9 9

Analyses 1, 2, 3, 4 1, 4 1, 4 1, 4 1, 4 1, 4 1, 4 1, 4 4 4 4 4 4 4 4 4 4 4 4 1 1 1 1 1 1 1 1

30


Page 31 of 35


Table 3. Distribution of Odoriferous Zone Reminiscent of Geranium leaf in Musts and Wines Marked (DF) or not (Control) by Dried Fruit Aromas. N=4 for each modality.

LRI a 1376 a

Musts

Wines

Odor descriptors

Control

DF

Control

DF

Geranium leaf

Nd

*** b

Nd

*** b

LRI: Linear retention index in polar column (BP20) nd: undetected, b * low intensity, ** medium intensity, *** high intensity

31



Page 32 of 35

Table 4. Results of analysis of variance for parameters selected for optimization of SPME (volume of must (Must), amount of ammonium sulfate (Salts), the time of extraction (Time ext) and the temperature of extraction (T°C ext) and their interactions by a multivariate analysis of variance.

Parameters Must (mL) Salts (g) Time ext (min) T°C ext Interactions Must (mL)*Salts (g) Must (mL)*Time ext (min) Must (mL)*T°C ext Salts (g)*Time ext Salts (g)*T°C ext Time ext (min)*T°C ext

F 43.05 8.16 1.36 11.67

p value 0.001 0.036 0.297 0.019

3.44 0.65 9.71 3.66 2.61 0.43

0.123 0.458 0.026 0.114 0.167 0.542

32


Page 33 of 35


Table 5. Parameters of (Z)-1,5-octadien-3-one Calibration Curve in Musts.

LOQ

Compound

RSD

Calibration curve

R²

Linear range (ng/L)

(ng/L)

LOD (ng/L)

(Z)-1,5-octadien-3-one

8%

y=1.13x+8.91

0.9942

0.5-480

0.5

0.15

33



Page 34 of 35

Table 6. Olfactory Detection Thresholds of (Z)-1,5-octadien-3-one in Water, in a Synthetic Must (SM, n=3), in a Merlot Must (MM, n=2), and in a Synthetic Wine (SW, n=3).

Detection thresholds (ng/L±SD) References Water

SM

MM

SW

Personal results

-

0.0022±0.0004

9±2

1.2±0.4

[26]

1.2

-

-

-

[33]

0.7-0.9

-

-

-

34


Page 35 of 35


TOC graphic SPME-CI-GC-MS

(Z)-1,5-octadien-3-one

Dried fig flavors

Concentrations (ng/L)

GC-O-MS

White

Red Control

Red Dried Fruits

35


Identification and Organoleptic Contribution of (Z)-1,5-Octadien-3-one

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