3-Alkenoic Acids, (E)-3-Alken-1-ols, and (E)-3 ... - ACS Publications

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Journal of Agricultural and Food Chemistry

Structure-odor Relationships of (E)-3-Alkenoic acids, (E)-3-Alken-1-ols and (E)-3-Alkenals

†

Katja Lorber , Andrea Buettner

†‡*

†

Department of Chemistry and Pharmacy, Emil Fischer Center, University of ErlangenNuremberg, Schuhstr. 19, 91052 Erlangen, Germany, [email protected] ‡

Department of Sensory Analytics, Fraunhofer Institute for Process Engineering and Packaging

(IVV),

Giggenhauserstr.

35,

85354

[email protected]

*Address for correspondence Phone +49-9131-85 22739 E-mail [email protected]

ACS Paragon Plus Environment

Freising,

Germany,


1

Abstract

2

(E)-3-Unsaturated volatile acids, alcohols, and aldehydes are commonly found as

3

odorants or pheromones in foods and other natural sources, playing a vital role in the

4

attractiveness of foods but also chemo-communication in animal kingdom. However, a

5

systematic elucidation of their smell properties, especially for humans, has not been

6

carried out until today. To close this gap, the odor thresholds in air and odor qualities of

7

homologous series of (E)-3-alkenoic acids, (E)-3-alken-1-ols and (E)-3-alkenals were

8

determined by gas chromatography-olfactometry. In the series of the (E)-3-alkenoic

9

acids the odor quality changed successively from sweaty via plastic-like to sweaty and

10

waxy. On the other hand, the odor qualities in the series of the (E)-3-alken-1-ols and

11

(E)-3-alkenals changed from grassy, green to an overall citrus-like, fresh, soapy and

12

coriander-like odor with increasing chain length. With regard to their odor potencies, the

13

lowest thresholds in air were found for (E)-3-heptenoic acid, (E)-3-hexenoic acid, and

14

(E)-3-hexanal.

15 16

Keywords

17

Gas chromatography-olfactometry, odor threshold in air, odorant, pheromone, retention

18

index, odor activity, odor intensity


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19

Introduction

20

Many important food odorants, but also a large number of other odor active compounds,

21

are formed, besides various other biosynthetic pathways, as major or minor products

22

during the lipid oxidation process, such as the autoxidation or enzymatic oxidation of

23

linoleic acid.1, 2 (E)-3-Nonenal is one of these aroma compounds, eliciting a fatty odor

24

quality.1 (E)-3-Pentenoic acid, (E)-3-nonenoic acid, (E)-3-decenoic acid and (E)-3-

25

decenal are formed during deep-fat frying, where oxidative and thermal decompositions

26

of fatty acids can take place.3 Furthermore, (E)-3-hexenoic acid is predominantly bio-

27

converted into (E)-3-hexen-1-ol, and (E)-3-octenoic acid partially into (E)-3-octen-1-ol by

28

the highly metabolic active fungus Botrytis cinerea.4 Some compounds comprising the

29

mentioned structural features have previously been identified in food. (E)-3-Hexenoic

30

acid has been detected in rhubarb5, soy sauce6 and breadfruit7, to name just a few.

31

(E)-3-Decenoic acid was identified in siraitia grosvenorii8, a herbaceous perennial vine

32

of the Cucurbitaceae family, and (E)-3-undecenoic acid in black tea9. In the homologous

33

series of the (E)-3-alken-1-ols nearly all compounds have been identified in food, except

34

(E)-3-undecen-1-ol and (E)-3-dodecen-1-ol. Just to mention some of them, (E)-3-

35

penten-1-ol was detected in Parmigiano Reggiano cheese10, (E)-3-hexen-1-ol and (E)-

36

3-octen-1-ol in yellow passion fruit11 and (E)-3-nonen-1-ol in pepper12. (E)-3-Hexenal

37

was identified in yellow passion fruit11, pink guava13 and baked potato14, inter alia, and

38

(E)-3-nonenal in oyster leaf15. Yet, it is possible and maybe even likely that the

39

compounds still undiscovered in food such as (E)-3-octenoic acid, (E)-3-dodecen-1-ol

40

and (E)-3-pentenal are naturally existing but are not yet detected due to their potentially

41

low concentrations, instability or the difficulty of extraction from their respective matrix.



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Besides the occurrence in food, some of the mentioned compounds also matter in the

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entomology. (E)-3-Penten-1-ol is a plant attractant for the fruit fly, Ceratitis capitata.16

44

(E)-3-Dodecenoic acid is secreted by the anal glands of phlaeothripine thrips as a

45

repellent,17 and (E)-3-hexen-1-ol and (E)-3-octen-1-ol are part of

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secretion from male Florida woods cockroaches, Eurycotis floridana.18

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Although many substances belonging to the homologous series of (E)-3-alkenoic acids,

48

(E)-3-alken-1-ols and (E)-3-alkenals have been identified in food, no odor thresholds

49

and odor qualities, respectively, have been described for most of these compounds so

50

far. Therefore, the aim of this work was to provide analytical and sensory data on these

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compounds for future investigations. Furthermore this study compiles comparative data

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on the odor thresholds in air and odor qualities to clarify structure-odor relationships of

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the target compounds.


the defensive

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Materials and Methods

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Chemicals. Malonic acid, trimethylamine, nonanal, decanal, hydrochloric acid, diethyl

56

ether, magnesium sulfate, lithium aluminium hydride (1M in THF), Dess-Martin

57

periodinane, sodium bicarbonate and sodium thiosulfate were purchased from Sigma-

58

Aldrich (Steinheim, Germany), n-hexane from Acros Organics (Geel, Belgium), sodium

59

hydroxide from Carl Roth (Karlsruhe, Germany), and silica gel (Normasil 60, 40 – 63

60

µm), dichloromethane and ethyl acetate from VWR International GmbH (Darmstadt,

61

Germany). (E)-3-Pentenoic acid (entry 1), (E)-3-hexenoic acid (entry 2) and (E)-3-

62

hexen-1-ol (entry 10) were purchased from Sigma-Aldrich (Steinheim, Germany), (E)-3-

63

heptenoic acid (entry 3), (E)-3-octenoic acid (entry 4), (E)-3-nonenoic acid (entry 5) and

64

(E)-3-decenoic acid (entry 6) from TCI Europe (Zwijndrecht, Belgium). All chemicals

65

were used without further purification.

66

Nuclear Magnetic Resonance (NMR) Spectra.

67

recorded in CDCl3 on an Avance 360 spectrometer, 360 MHz, and Avance 600, 600

68

MHz (Bruker Biospin, Rheinstetten, Germany) at room temperature operated at 360 or

69

600 MHz (1H) and 90 or 150 MHz (13C), with tetramethylsilane (TMS) as internal

70

standard.

71

GC-FID, GC-Olfactrometry (GC-O) and GC-Electron Impact-Mass Spectrometry

72

(GC-EI-MS). GC-FID and GC-O analyses were performed with a Trace GC Ultra

73

(Thermo Fisher Scientific GmbH, Dreieich, Germany) by using the following capillaries:

74

FFAP (30 m x 0.32 mm fused silica capillary, free fatty acid phase FFAP, 0.25 µm;

75

Chrompack, Mühlheim, Germany) and DB5 (30 m x 0.32 mm fused silica capillary DB-5,

1

H and


13

C NMR spectra were


76

0.25 µm; J & W Scientific, Fisons Instruments). The samples were applied by the cool-

77

on-column injection technique at 40 °C. After 2 minutes, the temperature of the oven

78

was raised at 10 °C/min to 240 °C, then raised at 40 °C/min to 280 °C (DB5), or at 10

79

°C/min to 240 °C (FFAP), respectively, and held for 5 minutes. The flow rate of the

80

carrier gas helium was 2.5 mL/min. At the end of the capillary, the effluent was split in a

81

ratio 1:1 (by volume) into an FID and a sniffing port using two deactivated but uncoated

82

fused silica capillaries (50 cm x 0.32 mm). The FID and the sniffing port were held at

83

250 °C, respectively. GC-EI-MS analyses were performed with an Agilent MSD 5975C

84

(Agilent Technologies, Waldbronn, Germany) and a Thermo ITQ 900 (Thermo Fisher

85

Scientific, Dreieich, Germany) with the capillaries described above. Mass spectra in the

86

electron impact mode (EI-MS) were generated at 70 eV.

87

Retention indices (RI). Retention indices were determined by the method previously

88

described by Van den Dool and Kratz (1963).19

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Panelists. Panelists were trained volunteers from the University of Erlangen (Erlangen,

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Germany), exhibiting no known illness at the time of examination and with audited

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olfactory function. In preceding weekly training sessions the assessors were trained for

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at least half a year in recognizing orthonasally about 90 selected known odorants at

93

different concentrations according to their odor qualities, and in naming these according

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to an in-house developed flavor language. Furthermore the panel is trained every two

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weeks on specific attributes with the help of specifically developed sniffing sticks; in the

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course of this training, all panelists also have to fill the same questionnaire (hedonic,

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intensity) to obtain insights into their specific sensitivities or insensitivities which are


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systematically recorded. Based on these tests, panelists are tested regularly if they

99

comply with the established flavor language.

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Odor threshold values. Thresholds in air were determined by GC-O with (E)-2-decenal

101

as internal standard.1, 20, 21 Of every dilution, 2 µL were applied for injection into the GC

102

system. The thresholds were determined by five panelists (one male, four female), with

103

each experiment being conducted once. GC analyses were performed on capillary

104

FFAP as already described. The purity of all commercial available and synthesized

105

compounds was taken into account in the GC/O experiments. All synthesized

106

compounds were further checked for potential olfactorily active impurities by sniffing

107

each single substance on both capillaries of different polarity, to exclude interferences.

108

Odor quality determination. The odor qualities, determined during GC-O evaluation,

109

were related to odor qualities of commercially available reference compounds. Panelists

110

were asked to freely choose the respective odor quality descriptors based on the in-

111

house developed flavor language (cf. panelists). No additional descriptors were supplied

112

to the panelists. The panelists determined the qualities during sniffing of FD 1 solution

113

(injection of 2 µL). The panelists were instructed to record any changes in odor qualities

114

in all following dilutions.

115 116

Syntheses, general procedures:

117

(E)-3-Alkenoic acids (7 and 8, Figure 1a). Malonic acid (1 eq.) was dissolved in

118

triethylamine (1.5 eq.) in a round-bottom flask fitted with a reflux condenser, a dropping

119

funnel and a nitrogen inlet tube. The corresponding aldehyde (1 eq.) was added slowly



Page 8 of 41

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over a period of 0.5 h under continuous stirring at room temperature. The contents were

121

then heated to 80 °C and maintained at this temperature for 3 h. The product was then

122

acidified with dilute HCl (1 mL/mmol malonic acid) and extracted with diethyl ether

123

(1 mL/mmol malonic acid) three times. The ether extracts were thoroughly washed with

124

distilled water and dried over anhydrous magnesium sulfate. After evaporation of the

125

solvent the residue was purified by column chromatography (silica gel, eluent:

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hexane/EtOAc = 4/1) to give the pure product.22

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The mechanism follows a Linstead modification of the Knoevenagel reaction.22-26

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(E)-3-Alken-1-ols (9 and 11 to 16, Figure 1b). Under nitrogen atmosphere LiAlH4 (1 eq,

129

1M/THF) was added to an ice cold solution of (E)-3-alkenoic acid (1 eq) in THF

130

mL/mmol acid). The reaction was allowed to warm to room temperature. After two hours

131

the reaction mixture was cooled in an ice bath, and water (4 mL/mmol acid) was added

132

slowly. NaOH (3 M) and water (4 mL/mmol acid each) were added and the resulting

133

mixture was extracted with CH2Cl2 (8 mL/mmol acid) three times. The combined organic

134

layer was washed with brine (8 mL/mmol acid) and then dried over MgSO4, filtered and

135

evaporated to get the corresponding (E)-3-alken-1-ol as an oily substance.27

(3

136 137

(E)-3-Alkenals (17 to 24, Figure 1c). A solution of (E)-3-alken-1-ol (1 eq) in CH2Cl2 (1

138

mL/mmol alcohol) was added drop-wise to a suspension of Dess-Martin periodinane

139

(1.1 eq) in CH2Cl2 (2 mL/mmol Dess-Martin periodinane). After a few minutes, in some

140

cases the reaction mixture started to boil and was allowed to do so for about five

141

minutes. After that the obtained suspension was stirred for three hours at room

142

temperature. It was then filtered through a glass frit and the filtrate was washed with


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saturated aqueous NaHCO3 solution containing Na2S2O3 (25%) (3.5 mL/mmol alcohol).

144

The resulting clear solution was dried over MgSO4, filtered and the CH2Cl2 was

145

removed by using a rotary evaporator to give the corresponding (E)-3-alkenal as a

146

colorless to pale yellow oil.28



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Results and Discussion

148

The median odor threshold values in air, the odor threshold range and the main odor

149

qualities of the homologues (E)-3-alkenoic acids, (E)-3-alken-1-ols and (E)-3-alkenals

150

are given in Tables 1a, 1b, 1c and Figures 2a, 2b, 2c. For the interested reader, besides

151

the median odor threshold values, the geometric mean values are given in Tables 2a,

152

2b and 2c. In the following, only the median values are discussed, because they appear

153

to be the more representative ones: In this study, of the number of single values is

154

limited, and some of these single values more strongly deviate from those of the other

155

panelists. Such deviations would influence the geometric mean more significantly than

156

the median. Nevertheless, when comparing the geometric mean and the corresponding

157

median values it becomes evident that both values show the same overall tendencies,

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and, if compared with each other, the differences are quite low, with only a few

159

exceptions (e.g. (E)-3-decenoic or (E)-3-dodecenoic acid).

160

Regarding the median odor thresholds the lowest can be found for (E)-3-pentenal with

161

3.03 ng/LAir, followed by (E)-3-heptenoic acid with 3.6 ng/LAir and (E)-3-hexenoic acid

162

with 4.13 ng/LAir. Due to the, at times, quite broad spreading of the individual threshold

163

values, no clear insights about potential minima in the OT values can be deduced.

164

Thereby, clustering or, on the other hand broad spreading of the OT values of individual

165

panelists is not evenly distributed amongst substances. As can be seen in Table 1a and

166

Figure 2a, the OT range of (E)-3-pentenoic acid is much higher than for the

167

homologously related (E)-3-hexenoic acid and (E)-3-heptenoic acid. Clustering of the

168

OT values for these six and seven carbon atom compounds is also much more narrow

169

than that of the OTs of the substances of the same series with longer chain lengths. The


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widest clustering was observed for (E)-3-octenoic acid, followed by (E)-3-nonenoic and

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(E)-3-decenoic acid. From eleven and twelve carbon atoms onwards the broadness of

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the clustering decreases again. A similar pattern was observable in case of the

173

homologous series of the (E)-3-alken-1-ols (Table 1b and Figure 2b). However, despite

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the wide spreading of the odor threshold for (E)-3-penten-1-ol, the clustering range of

175

the alkenols was not as wide as in the case of the (E)-3-alkenoic acids. Table 1c and

176

Figure 2c present the values for the (E)-3-alkenals. Again, there is a comparable pattern

177

to the (E)-3-alkenoic acids and (E)-3-alken-1-ols, with a quite wide spreading of the OT

178

ranges is for each single substance in this homologous series. Albeit, it needs to be

179

kept in mind that a larger panel number, or an untrained panel might lead to changes in

180

the order of threshold ranking, and might lead to a distinct change of the spreading and

181

clustering.2, 29-33

182

When comparing all three homologues series, the series with the lowest median odor

183

thresholds was the series of the (E)-3-alkenals, followed by the (E)-3-alkenoic acids.

184

However, when looking at the single odor thresholds of all five panelists independently

185

(Tables 1a, 1b, 1c OT range, Tables 2a, 2b, 2c) enormous differences between the

186

respective values of the individual panelists can be observed. Especially when

187

regarding the series of the (E)-3-alkenoic acids huge variances between individual

188

values can be found. The lowest OT of 0.27 ng/LAir for (E)-3-hexenoic acid and the

189

highest of 17 ng/LAir span a threshold range of a factor of 63. An analogously broadly

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distributed pattern can be found for (E)-3-penten-1-ol with a threshold range from 26 to

191

1655 ng/LAir, which corresponds to a factor of 64, and (E)-3-nonen-1-ol with a range

192

from 7 to 459 ng/LAir, which relates to a factor of 66 between the most extreme values.



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Nevertheless, despite these partly huge differences the ranking of the thresholds of the

194

single panelists of a homologous series was in many cases comparable (cf. Tables 2a,

195

2b, 2c). For instance, for four out of five panelists, the lowest individual OT of the (E)-3-

196

alkenoic acids was that of (E)-3-heptenoic acid. On the other hand, the highest

197

individual OT in case of the (E)-3-alken-1-ols was that of (E)-3-penten-1-ol, again for

198

four of the five panelists.

199

Compared with other studies, like Czerny et al. 2011, in which the odor thresholds

200

range “only” from a factor of 2 to 8, the differences between the odor thresholds of the

201

individual panelists in this study might seem very huge. However, in the case of Czerny

202

et al. 2011, it needs to be highlighted that only two panelists participated in the

203

experiments. Furthermore, only aromatic compounds, and more precisely phenol

204

derivatives, were investigated, and not open-chained substances like in the present

205

study.21 Accordingly, a satisfactory comparison would be hard to achieve.

206

The main odor quality in the series of the (E)-3-alkenoic acids changes noticeable with

207

increasing chain length from sweaty for (E)-3-pentenoic and (E)-3-hexenoic acid, over

208

plastic-like for (E)-3-heptenoic to (E)-3-decenoic acid, to waxy for (E)-3-undecenoic and

209

(E)-3-dodecenoic acid. (E)-3-Penten-1-ol and (E)-3-hexen-1-ol of the homologous

210

series of the (E)-3-alken-1-ols show a green odor, changing with increasing chain length

211

to citrus-, cleanser-like for (E)-3-hepten-1-ol to (E)-3-nonen-1-ol, ending up in a

212

cleanser-like smell for (E)-3-decen-1-ol to (E)-3-dodecen-1-ol. The (E)-3-alkenals start

213

also with a green odor quality for the short-chain (E)-3-pentenal to (E)-3-heptenal,

214

shifting to citrus-like for (E)-3-octenal, fatty for (E)-3-nonenal, and finally to coriander-

215

like for (E)-3-decenal to (E)-3-dodecenal. When regarding the individual odor qualities


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named by each panelist (Tables 3a, 3b, 3c), there are similarly broadly distributed

217

patterns in the individual naming of the odor characters as observed for the individual

218

odor thresholds, and they vary enormously. The odor quality descriptions of (E)-3-

219

pentenoic acid ranges from sweet, flowery over sweaty to pungent, plastic-like. The (E)-

220

3-dodecen-1-ol is described either as citrus-like, musty from another, or herb-like,

221

depending on the evaluating panelist. Only in the case of the (E)-3-alkenals the variety

222

is not that broad with most panelists having reported the terms green for (E)-3-pentenal

223

and (E)-3-hexenal, soapy for (E)-3-heptenal and (E)-3-octenal, soapy, coriander-like for

224

(E)-3-nonenal and coriander-like for (E)-3-decenal, (E)-3-undecenal and (E)-3-

225

dodecenal.

226

One explanation for these discrepancies in the odor thresholds and odor qualities

227

between the single panelists could be the inter-individual interaction of the respective

228

odorant with the receptors. There are reports on inter-individual differences in receptor

229

expression in humans that might be related to the observed differences.34,

230

needs to be kept in mind that numerous odorants do not only activate one receptor but

231

a number, and that receptors can also be activated by a range of odorants.36,

232

inter-individual patterns in activation resulting from that coding might also be divergent

233

between different subjects. However, apart from the direct binding of an odorant to the

234

respective receptors in the olfactory system, there might also be inter-individually

235

different effects related to the so-called peri-receptor events, meaning that odorants

236

may be bio-transformed e.g. by Cytochrome P 450 metabolization prior to interacting

237

with the target receptor sites. This biotransformation of aroma compounds can alter the

238

quality and quantity of the substances and might lead to differences in odor threshold as


35

It also

37

The


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well as odor quality.38-43 Accordingly, the investigated compounds, bearing e.g. double

240

bond moieties, might be prone to metabolic attack as has been previously shown for

241

other unsaturated compounds by Schilling et al..38, 39, 43, 44

242

Here, it might be worth to draw some comparison between the substances investigated

243

within this study with other related substance groups but differing in degree of

244

saturation. Tables 4a, 4b and 4c provide a compilation of literature data and own data of

245

the present study for direct comparison of the impact of the double bond configuration

246

(either E or Z), or the impact of saturation of the double bon on the respective OT

247

values. Unfortunately, available data for a straight-forward is not comprehensive.

248

Nevertheless, from the few reported (Z)-3-compound values it becomes clear that the

249

(Z)-3- configuration obviously represents a very favorable moiety in terms of high odor

250

impact. In contrast to this, the (E)-3-configuration obviously does not impart the same

251

effect, and is even, in several cases, to be regarded as less odoriferous than even the

252

saturated analoga. Nevertheless, these conclusions would need to be further

253

substantiated by future studies, filling the missing data of Tables 4a-c.

254

To sum up, our study demonstrates that some of the investigated compounds in the

255

series of the (E)-3-alkenoic acids, (E)-3-alken-1-ols and (E)-3-alkenals show low odor

256

thresholds or high odor potencies and interesting odor qualities. In consideration of the

257

fact that many of the 24 investigated substances have already been identified in food, or

258

generally in nature, some of the currently unreported substances may be also promising

259

candidates to be discovered as natural compounds in future studies. The analytical data

260

compiled in this study, such as retention indices, mass spectra, odor thresholds in air or

261

odor qualities can aid at their future discovery. Moreover, this study aims at raising


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future attention to this substance class, not only in terms of some of the compounds

263

being potentially important odorants in food but also with regard to other biological

264

meaning that has not been investigated comprehensively to date.

265

In view of this, one needs to keep in mind that chemo-sensorically active compounds

266

can serve a number of purposes in nature such as communication between and across

267

species, resulting e.g. in chemo-attraction or -repulsion. As an example, another

268

interesting field of research is the potential biological meaning of the target compounds

269

investigated within the present study in relation to entomology. As mentioned in the

270

introduction, some of the investigated compounds have already been shown to function

271

as pheromones, attractants or repellents in insects. Accordingly, it would be of high

272

interest to have a closer look on such possible functionalities of the compounds of the

273

current study, and to also establish the respective structure-response relationships in

274

view of insect behavior. Comprehensive substance libraries as generated in the current

275

study will aid the targeted and systematic discovery of such effects in future

276

investigations.



277

Abbreviations

278

GC-O

Gas chromatography - Olfactometry


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Acknowledgments

280

We thank all members of our working group for their participation in the sensory

281

analyses, although the odors were not always pleasant.



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Associated content

283

Supporting Information

284

Spectroscopic data (MS-EI, NMR), yield and purity of all synthesized compounds as

285

well as a table with the concentrations of the FD1 solutions and figures of the individual

286

odor thresholds are documented separately. This material is available free of charge via

287

the Internet at http://pubs.acs.org.


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References

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421



422

Figure captions

423

Figure 1a: Synthetic route leading to the (E)-3-alkenoic acids

424

Figure 1b: Synthetic route leading to the (E)-3-alken-1-ols

425

Figure 1c: Synthetic route leading to the (E)-3-alkenals

426

Figure 2a: Influence of the chain length on the odor thresholds of (E)-3-alkenoic acids

427

Figure 2b: Influence of the chain length on the odor thresholds of (E)-3-alken-1-ols

428

Figure 2c: Influence of the chain length on the odor thresholds of (E)-3-alkenals


Page 22 of 41

Page 23 of 41


Table 1a. Retention indices (RI), odor thresholds (OT) and odor qualities of (E)-3-alkenoic acids Odorant

RIa

OT [ng/Lair]

Odor qualitiesb,c

Previously identified ind

DB5

FFAP

median

range

(E)-3-Pentenoic acid

988

1842

28

3.6 – 56

sweaty, sweet

n.r.

(E)-3-Hexenoic acid

1075

1928

4.13

0.27 – 17

sweaty, cheesy,

rhubarb5, soy sauce6,

sweet

guava leaves45, snake fruit46, fish sauce47, breadfruit7

(E)-3-Heptenoic acid

1153

2026

3.60

0.49 – 14

plastic-like,

n.r.

waxy, pungent (E)-3-Octenoic acid

1245

2134

34

7.7 – 138

plastic-like, waxy

n.r.

(E)-3-Nonenoic acid

1335

2237

68

8.6 – 137

waxy, sweaty,

n.r.

plastic-like (E)-3-Decenoic acid

1422

2341

66

3.9 – 132

sweaty, plastic-

siraitia grosvenorii8

like, pungent (E)-3-Undecenoic acid

1525

2461

24

4.6 – 94

waxy, pungent,

black tea9

acidic, sweaty (E)-3-Dodecenoic acid

1627

2565

34

3.3 - 68

waxy, plastic-,

n.r.

vomit-like a

Retention indices were determined as described by Van den Dool and Kratz (1963).19

b

Odor qualities as perceived at the sniffing port.

c

Underlined attributes are the main odor qualities. These were named by the majority of the panel.

d

n.r.: Compound has not been reported previously.



Page 24 of 41

Table 1b. Retention indices (RI), odor thresholds (OT) and odor qualities of (E)-3-alken-1-ols

Odorant

RIa

OT [ng/Lair]

Odor qualitiesb,c


DB5

FFAP

median

range

(E)-3-Penten-1-ol

645

1274

414

26 - 1655

grassy, green fresh

Parmigiano Reggiano cheese10

(E)-3-Hexen-1-ol

777

1355

69

9.0 – 138

green, musty,

yellow passion fruit11, rose48,

grassy, clover-like

olive oil49, oyster leaf15

(E)-3-Hepten-1-ol

865

1445

114

28 – 227

citrus-like, cleanser

South African red wine50

(E)-3-Octen-1-ol

958

1548

62

8.0 – 124

citrus-, cleanser-like,

yellow passion fruit11

fresh (E)-3-Nonen-1-ol

1058

1647

57

7.0 – 459

citrus-like, soapy,

pepper12

cleanser-like (E)-3-Decen-1-ol

1156

1750

61

30 – 484

citrus-like, green,

yellow passion fruit11

cleanser-like (E)-3-Undecen-1-ol

1257

1859

23

11 – 181

cleanser-like, fresh

n.r.

(E)-3-Dodecen-1-ol

1350

1954

104

52 – 207

fresh, green,

n.r.

cleanser-like a


b


c


d



Page 25 of 41


Table 1c. Retention indices (RI), odor thresholds (OT) and odor qualities of (E)-3-alkenals

Odorant

RIa

OT [ng/Lair]

Odor qualitiesb,c


DB5

FFAP

median

range

(E)-3-Pentenal

716

1056

3.03

3.0 – 48

grassy, green, cheesy

n.r.

(E)-3-Hexenal

805

1135

4.96

0.62 – 10

fresh, green, soapy

yellow passion fruit11, pink guava13, jostaberry51, gooseberry52, baked potato14

(E)-3-Heptenal

899

1224

14

3.5 – 14

citrus-like, soapy, fatty,

n.r.

green (E)-3-Octenal

998

1327

12

2.9 – 12

citrus-like, soapy, fatty

roasted chickpeas53

(E)-3-Nonenal

1097

1429

12

6.2 – 25

fatty, fresh, coriander-like

oyster leaf15

(E)-3-Decenal

1199

1530

9.05

4.5 – 36

fatty, soapy, coriander-like

n.r.

(E)-3-Undecenal

1301

1636

11

2.8 – 23

coriander-like, fatty, green

n.r.

(E)-3-Dodecenal

1396

1737

8.33

4.2 – 17

coriander-like, soapy

n.r.

a


b


c


d




Page 26 of 41

Table 2a. Odor thresholds (OT, GC-O) of all five panelists (P 1 to P 5) of (E)-3-alkenoic acids

Entry

Odorant

OT in air (ng/LAir)a Geometric mean

P1

P2

P3

P4

P5

Literatureb

1


21

14

28

56

3.6

56

n.r.

2

(E)-3-Hexenoic acid

3.6

4.1

8.3

4.1

0.27

17

n.r.

3


2.7

3.6

7.2

0.9

0.49

14

n.r.

4

(E)-3-Octenoic acid

29

34

34

17

7.7

138

n.r.

5

(E)-3-Nonenoic acid

40

68

68

8.6

17

137

n.r.

6

(E)-3-Decenoic acid

32

66

132

16

3.9

66

n.r.

7

(E)-3-Undecenoic acid

20

12

24

24

4.6

94

n.r.

8

(E)-3-Dodecenoic acid

18

8.5

34

34

3.3

68

n.r.

a

Odor thresholds in air were determined as described by Ullrich and Grosch (1987).1

b

n.r.: OT (determined like in this study) has not been reported previously, to the best of our knowledge.


Page 27 of 41


Table 2b. Odor thresholds (OT, GC-O) of all five panelists (P 1 to P 5) of (E)-3-alken-1-ols

Entry

a b

Odorant


P1

P2

P3

P4

P5

Literatureb

9

(E)-3-Penten-1-ol

314

827

1655

26

207

414

n.r.

10

(E)-3-Hexen-1-ol

46

69

138

9.0

35

69

n.r.

11

(E)-3-Hepten-1-ol

99

227

57

28

114

227

n.r.

12

(E)-3-Octen-1-ol

47

124

62

8.0

62

62

n.r.

13

(E)-3-Nonen-1-ol

65

459

57

7.0

57

115

n.r.

14

(E)-3-Decen-1-ol

80

484

61

30

30

121

n.r.

15

(E)-3-Undecen-1-ol

34

181

23

11

11

90

n.r.

16

(E)-3-Dodecen-1-ol

90

207

104

52

52

104

n.r.

Odor thresholds in air were determined as described by Ullrich and Grosch (1987).1 n.r.: OT (determined like in this study) has not been reported previously, to the best of our knowledge.



Page 28 of 41

Table 2c. Odor thresholds (OT, GC-O) of all five panelists (P 1 to P 5) of (E)-3-alkenals

Entry

a b

Odorant


P1

P2

P3

P4

P5

Literatureb

17

(E)-3-Pentenal

6.9

48

3.0

12

3.0

3.0

n.r.

18

(E)-3-Hexenal

3.3

5.0

5.0

0.62

10

2.5

n.r.

19

(E)-3-Heptenal

9.3

14

14

3.5

14

7.0

n.r.

20

(E)-3-Octenal

7.8

12

12

5.9

12

2.9

n.r.

21

(E)-3-Nonenal

14

12

25

25

6.2

12

n.r.

22

(E)-3-Decenal

12

36

9.1

4.5

9.1

18

n.r.

23

(E)-3-Undecenal

7.4

23

11

2.8

2.8

11

n.r.

24

(E)-3-Dodecenal

9.6

17

17

4.2

8.3

8.3

n.r.

Odor thresholds in air were determined as described by Ullrich and Grosch (1987).1 n.r.: OT (determined like in this study) has not been reported previously, to the best of our knowledge.


Page 29 of 41


Table 3a. Odor qualities (GC-O) of all five panelists (P 1 to P 5) of (E)-3-alkenoic acids Entry

Odorant

1


Odor qualities P1

P2

P3

P4

P5

sweet,

sweaty

sweaty

pungent,

sweaty, moldy

flowery 2

(E)-3-Hexenoic acid

plastic-like

sweet,

sweaty

flowery 3


pungent,

sweaty

musty, cheesy 4

5

6

7

8

(E)-3-Octenoic acid

(E)-3-Nonenoic acid

(E)-3-Decenoic acid

(E)-3-Undecenoic acid

(E)-3-Dodecenoic acid

sweaty,

pungent,

sweaty, moldy,

cheesy

plastic-like, sweaty

musty

plastic-like,

pungent,

waxy, moldy

green

plastic-like

plastic-like

pungent,

waxy,

plastic-like

paraffin-like Waxy

cheesy,

plastic-like,

plastic-like

waxy

pungent,

plastic-like,

plastic-like,

plastic-like,

sweaty

waxy

sweaty

burned rubber

pungent,

sweaty, waxy,

plastic-like

plastic-like,

cheesy, musty

plastic-like,

acidic,

sweaty, waxy,

sweaty,

sweaty, cheesy,

pungent, waxy,

vomit-like

plastic-like,

waxy

plastic-like

old wood-like,

vomit-like

plastic-like,

waxy

burned rubber,

waxy, burned

waxy, black tea

burned rubber

waxy


pungent


Page 30 of 41

Table 3b. Odor qualities (GC-O) of all five panelists (P 1 to P 5) of (E)-3-alken-1-ols Entry

Odorant

9

(E)-3-Penten-1-ol

Odor qualities P1

P2

P3

P4

P5

fresh, green,

green, grassy

grassy, green

green, grassy

soapy, green

green, fresh,

musty, green,

green, grassy,

grassy, musty

musty, putrid

flowery

sweaty

musty

green,

musty, green,

citrus-like,

musty,

citrus-like,

plastic-like

cleanser-like

cleanser-like

citrus-like

soapy

green, sweet,

musty, cleanser-

citrus-like,

citrus-like,

citrus-like, fresh,

fatty

like

cleanser-like

sweet

cleanser-like

fatty, fresh

musty, citrus-like,

citrus-like,

citrus-like,

citrus-like,

cleanser-like

cleanser-like

cleanser-like

cleanser-like

sweet, green,

musty, cleanser-

citrus-like,

cleanser-like

soapy

flowery

like, green,

cleanser-like,

citrus-like

pungent

cleanser-like

cleanser-like,

cleanser-like,

cleanser-like,

citrus-like

sebum-like

musty

sweet 10

11

12

13

14

15

16

(E)-3-Hexen-1-ol

(E)-3-Hepten-1-ol

(E)-3-Octen-1-ol

(E)-3-Nonen-1-ol

(E)-3-Decen-1-ol

(E)-3-Undecen-1-ol

(E)-3-Dodecen-1-ol

sweet

citrus-like,

musty,

cleanser-like,

cleanser-like,

herb-like,

fresh, green

cleanser-like

green

sebum-like

citrus-like


Page 31 of 41


Table 3c. Odor qualities (GC-O) of all five panelists (P 1 to P 5) of (E)-3-alkenals Entry

Odorant

17

(E)-3-Pentenal

18

(E)-3-Hexenal

19

(E)-3-Heptenal

Odor qualities P1

P2

P3

P4

P5

flowery, cheesy green, grassy

green

green

musty

fresh, green,

green, musty,

green, soapy

green,

grassy, fatty,

cabbage-like

sweaty

honey-like

metallic

sweet, flowery,

green,

soapy, green

citrus-like, fatty,

musty

cleanser-like,

soapy, green

soapy

citrus-like 20

21

22

23

(E)-3-Octenal

(E)-3-Nonenal

(E)-3-Decenal

(E)-3-Undecenal

fresh,

green, fatty,

citrus-like

citrus-like

fatty, fresh,

fatty, green,

cucumber-like

soapy, fatty

soapy,

citrus-like, soapy,

citrus-like

fresh

coriander-like,

fatty,

fatty, green,

soapy

soapy, fatty

coriander-like

fresh

fresh,

coriander-like,

coriander-like,

coriander-like,

citrus-like, balmy,

citrus-like, fatty

soapy

soapy

fatty

woody

sweet, flowery

coriander-like

green, fatty

coriander-like

citrus-like, eucalyptus, ethereous, balmy

24

(E)-3-Dodecenal

citrus-like,

soapy,

coriander-like,

coriander-like,

ethereous, fresh,

fresh

coriander-like,

soapy

soapy

rancid, cedar-like

cucumber-like



Page 32 of 41

Table 4a. Odor thresholds in air (OT in air) of (E)-3-alkenoic acids compared to odor thresholds of (Z)-3-alkenoic acids and saturated carboxylic acids obtained from literature

Number carbon atoms

a

OT in air (ng/LAir)a (E)-3-alkenoic acidsa,b

(Z)-3-alkenoic acidsc

saturated carboxylic acidsc

5

28

n.r.

4.654

6

4.13

n.r.

n.r.

7

3.60

n.r.

n.r.

8

34

n.r.

n.r.

9

68

n.r.

n.r.

10

66

n.r.

n.r.

11

24

n.r.

n.r.

12

34

n.r.

n.r.


b

In this study determined median odor threshold values.

c



Page 33 of 41


Table 4b. Odor thresholds in air (OT in air) of (E)-3-alken-1-ols compared to odor thresholds of (Z)-3-alken-1-ols and 1alkanols obtained from literature

Number carbon atoms

a

OT in air (ng/LAir)a (E)-3-alken-1-olsa,b

(Z)-3-alken-1-olsc

1-alkanolsc

5

414

n.r.

15055

6

69

4-1656

n.r.

7

114

n.r.

n.r.

8

62

n.r.

n.r.

9

57

n.r.

2255

10

61

n.r.

1855

11

23

n.r.

n.r.

12

104

n.r.

n.r.


b


c




Page 34 of 41

Table 4c. Odor thresholds in air (OT in air) of (E)-3-alkelals compared to odor thresholds of (Z)-3-alkenals and 1-alkanals obtained from literature

Number carbon atoms

a

OT in air (ng/LAir)a (E)-3-alkenalsa,b

(Z)-3-alkenals

1-alkanals

5

414

n.r.

n.r.

6

69

0.09-0.3656

1.155

7

114

n.r.

0.955

8

62

n.r.

0.455

9

57

n.r.

2.655

10

61

n.r.

2.655

11

23

n.r.

n.r.

12

104

n.r.

n.r.


b


c



Page 35 of 41


Figure 1a: Synthetic route leading to the (E)-3-alkenoic acids



Figure 1b: Synthetic route leading to the (E)-3-alken-1-ols


Page 36 of 41

Page 37 of 41


Figure 1c: Synthetic route leading to the (E)-3-alkenals



Figure 2a: Influence of the chain length on the odor thresholds of (E)-3-alkenoic acids. Mean value (± SD), markers at minimum and maximum OT, box perc. 25-75%.


Page 38 of 41

Page 39 of 41


Figure 2b: Influence of the chain length on the odor thresholds of (E)-3-alken-1-ols. Mean value (± SD), markers at minimum and maximum OT, box perc. 25-75%.



Figure 2c: Influence of the chain length on the odor thresholds of (E)-3-alkenals. Mean value (± SD), markers at minimum and maximum OT, box perc. 25-75%.


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TOC graphic


3-Alkenoic Acids, (E)-3-Alken-1-ols, and (E)-3 ... - ACS Publications

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