Aroma Constituents in Shanxi Aged Vinegar before and after Aging

Subscriber access provided by Northern Illinois University

Article

Aroma Constituents in Shanxi Aged Vinegar before and after Aging Jingjing Liang, Jianchun Xie, Li Hou, Mengyao Zhao, Jian Zhao, Jie Cheng, Shi Wang, and Bao-Guo Sun J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.6b03019 • Publication Date (Web): 17 Sep 2016 Downloaded from http://pubs.acs.org on September 19, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 34

Journal of Agricultural and Food Chemistry

Aroma Constituents in Shanxi Aged Vinegar before and after Aging 1

Jingjing Liang, *1Jianchun Xie, 1Li Hou, 1Mengyao, Zhao, 1Jian Zhao, 2Jie Cheng, 2Shi

Wang, and 1Bao-Guo Sun 1

Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Key

Laboratory of Flavor Chemistry, Beijing Technology and Business University (BTBU), Beijing 100048, China.

2

Institute of Quality Standard and Testing Technology for

Agro-products of CAAS, Beijing 100081, China.

*

Corresponding author: Jianchun Xie, School of Food Science and Chemical Engineering, Beijing Technology and Business

University, No. 33 Fucheng Road, Haidian District, Beijing 100048, China. Phone and Fax: (+86) -10-68984859.

[email protected].

1

ACS Paragon Plus Environment

E-mail:


1

ABSTRACT: Shanxi aged vinegar is one of the most famous China traditional cereal

2

vinegars produced by spontaneous solid-state fermentation. However, aroma composition of

3

Shanxi aged vinegar was still ambiguous. The Shanxi vinegars before and after aging were

4

both analyzed by solvent-assisted flavor evaporation (SAFE) combined with GC-MS as well

5

as GC-O in aroma extract dilution analysis (AEDA). Total of eighty-seven odor-active

6

regions were found by GC-O, among which eighty odor-active compounds were identified.

7

By GC-MS/MS in selected reaction monitoring (SRM) mode, thirty important identifications

8

were quantitated using authentic standards. In comparison, the aroma molecules for the

9

vinegars before and after aging were almost the same, only their levels were altered with

10

mostly the esters and some compounds of pungent smells lost and those from the maillard

11

reaction especially the pyrazines (e.g. tetramethylpyrazine) greatly increased. As for the aged

12

vinegar, the compounds found in high FD factors (> 128) were 3-(methylthio)propanal,

13

vanillin, 2,3-butanedione, tetramethylpyrazine, 3-methylbutanoic acid, γ-nonalactone, guaiacol,

14

3-(methylthio)propyl acetate, dimethyl trisulfide, phenylacetaldehyde, 2-ethyl-6-methylpyrazine,

15

2-acetylpyrazine, 2,3-dimethylpyrazine, furfural, and 3-hydroxy-2-butanone. However, the

16

aroma compounds found in high concentrations (> 25 µg/L) in the aged vinegar were acetic

17

acid, followed by 2,3-butanedione, furfural, 3-hydroxy-2-butanone, tetramethylpyrazine,

18

furfuryl alcohol, and 3-methylbutanoic acid.

19

KEYWORDS: Shanxi aged vinegar, solvent-assisted flavor evaporation, GC-O, quantitation,

20

aroma extract dilution analysis, selected reaction monitoring

2


Page 2 of 34

Page 3 of 34


21

22

Vinegar is one of the most favorite acidic seasonings. In most Asian and European

23

countries, it is the necessary seasoning in every dinner. Traditional Chinese vinegars, also

24

called cereal vinegars, are important seasonings in Chinese daily life, which have a long

25

history of more than 3000 years. There are four famous China-style cereal vinegars,

26

Shanxi aged vinegar, Zhenjiang aromatic vinegar, Sichuan bran vinegar and Fujian

27

Monascus vinegar in China. Different from most European countries, in China the

28

spontaneous solid-state fermentation rather than the submerged fermentation is used

29

during acetic acid fermentation.1-3

30

INTRODUCTION

Up to now, there have been many studies on flavor composition of China-style

31

cereal vinegars. 1, 3-6 For example, 2,3-butanediol, 2,3-butanedione,3-hydroxy-2-butanone,

32

furfural, acetic acid, and butanedioic acid diethyl ester had been found as volatiles from

33

Zhenjiang aromatic vinegar by headspace solid phase micro extraction (HS-SPME) and

34

gas chromatography-mass spectrometry (GC-MS).4 However, most of the studies on

35

China-style cereal vinegars had been focused on the volatile compounds by GC-MS

36

rather than the odor-active compounds, which in fact are only a small fraction of the

37

volatile compounds that actually contribute to overall aroma. GC-O is an effective

38

approach to screen the compounds of aroma-activities in foods. The time-intensity

39

analysis, aroma extract dilution analysis (AEDA), Charm analysis, and frequency

40

detection are the usual techniques utilized in GC-O analysis to detect and evaluate the

41

odorants sniffed.7-10 As for AEDA, the highest dilution, in which the odor of a compound 3



42

can no longer be detected, is defined as its flavor dilution (FD) factor. The greater the FD

43

factor of a compound, the greater the compound is thought to contribute to overall aroma.

44

Thus by AEDA not only those of odor-activities but also those of potent odor-activities,

45

also called key aroma compounds, can be acknowledged. 10

46

Flavor of the China-style cereal vinegars is highly related to their types, fermentation

47

raw materials, and production areas.1 Shanxi aged vinegar is one of the most important

48

traditional Chinese cereal vinegars in China. It originated from Shanxi province in

49

northern China. Now Shanxi still is the main manufacturing location for Shanxi aged

50

vinegar. Different from Zhenjiang aromatic vinegar whose primary raw material is

51

sticky rice mainly planted in southern China, the primary raw material for Shanxi aged

52

vinegar is sorghum mainly planted in northern China. Shanxi aged vinegar tastes thicker

53

and tarter than Zhenjiang aromatic vinegar. The production of Shanxi aged vinegar

54

mainly goes through four manufacturing processes, that is, alcoholic fermentation, acetic

55

fermentation, thermal processing, and aging. The aroma of Shanxi aged vinegar formed

56

during the fermentation process consists of a large number of esters, aldehydes, ketones,

57

alcohols, and heterocyclic compounds.11-12 Thermal processing can produce lots of

58

pyrazines, aldehydes, ketones, and other aroma compounds, resulting from the associated

59

chemical reactions such as hydrolysis and Maillard reaction.13-14 Aging processing, where

60

water is evaporated or frozen, is also rich in chemical reactions and chemical changes.

61

Through aging processing, the flavor of Shanxi aged vinegar is to be soft, round,

62

continuous, and of no precipitation.2 4


Page 4 of 34

Page 5 of 34


The key aroma compounds in Shanxi aged vinegar made from tartary buckwheat

63

14

64

had been characterized by Wang et al

in dynamic headspace sampling and

65

AEDA/GC-O analysis. Yet, for the aforementioned common sorghum Shanxi aged

66

vinegar, how about its aroma composition and which compounds are of significance to

67

overall aroma is still ambiguous. At present, headspace techniques in particular

68

HS-SPME have been primarily used in the analysis of volatile flavor compounds of

69

China cereal vinegars.1,3,4,6,14 In comparison with the HS-SPME,6 solvent-assisted flavor

70

evaporation (SAFE) is not only a mild treatment but also in the nature of no matrix effect

71

from acetic acid and other components such as sugars, organic acids, amino acids,

72

phenolic acids, proteins, and inorganic ions. 15-17 However, as far as we know, the SAFE

73

technique had never been adopted in the analysis of China cereal vinegars. Therefore, the aims of the present work were (1) to

74

analyze the odor-active

75

compounds in Shanxi aged vinegar before and after aging by SAFE and AEDA/GC-O; (2)

76

to quantify the odorants by GC-MS/MS in selected reaction monitoring mode (SRM)

77

using the authentic standards; (3) to expose the aroma composition of the Shanxi aged

78

vinegar and know how it was changed through aging, since the aging process is so long a

79

period and critical to flavor and output of Shanxi aged vinegar. The research results may

80

provide guidance to improve the technology and flavor quality of Shanxi aged vinegar.

81

MATERIALS and METHODS

82

Materials. The Shanxi vinegars before or after aging, were obtained from Dingzhou

83

Branch of Shanxi Aged Vinegar Group Co. Ltd., Baoding City, Hebei Province, China. 5



Page 6 of 34

84

For the sake of representativeness, the samples of different batches well mixed were used

85

in the study. The main raw materials of the vinegars were sorghum, wheat bran, and

86

water. The preparation procedures were as described in the literatures,2,3,14,18 including

87

steaming of raw materials for about 1 h, addition of Da Qu, alcoholic fermentation for 18

88

days, acetic acid fermentation for 15 days, thermal processing at 85°C for 3 days, and

89

finally aging for about 1 year. The Da Qu was made from barley and pea, which was used

90

as starter culture. The aging of the vinegars was conducted spontaneously in 500-L

91

open-top ceramic jars under ambient temperatures placed in a big glass house with a

92

curtain type door, which is just the traditional folk technology called as “insolating in

93

summer and taking out ice in winter.”

94

Reagents and Chemicals. Total of fifty-eight authentic chemicals were used in the

95

identification or quantitation of the odor-active compounds. They were all in a high

96

purity ≥ 95% (GC), purchased from J&K Chemical Ltd. (Beijing, China): dimethyl

97

disulfide (98%), 3-(methylthio)propanal (98%), dimethyl trisulfide (98%), 3-(methylthio)

98

propyl acetate (98%), methylpyrazine (98%), trimethylpyrazine (98%), ethylpyrazine

99

(99%), 2,3-dimethylpyrazine (98%), 2-ethyl-6-methylpyrazine (98%), 2-acetylpyrazine

100

(99%),

2-acetylpyrrole

(98%),

tetramethylpyrazine

101

2,3,5-trimethyl-6-ethylpyrazine (98%), 2-acetyl-3,5-dimethylpyrazine (98%); furfuryl

102

alcohol (98%); furfural (98%), 2-acetylfuran (98%), 5-methylfurfural (98%), 2-furfuryl

103

acetate (98%), 2-acetyl-5-methylfuran (98%), 3-methylbutanal (98%), heptanal (95%),

104

benzaldehyde (98%), phenylacetaldehyde (98%), (Z)-2-nonenal (95%), vanillin (99%), 6


(98%),

Page 7 of 34


105

2,3-butanedione

(98%),

3-hydroxy-2-butanone

106

β-damascenone

(98%),

107

3-methylbutanoic acid (98%), pentanoic acid (98%), hexanoic acid (98%), octanoic acid

108

(98%), benzoic acid (98%), propanoic acid, ethyl ester (98%), isoamyl formate (98%),

109

lactic acid, ethyl ester (98%),γ-pentalactone (98%), succinic acid, diethyl ester (98%),

110

acetic acid, 2-phenylethyl ester (98%), γ-octalactone (98%), γ-nonalactone (98%),

111

ethyl caprate (98%),γ-decalactone (98%), methyl tetradecanoate (98%), hexadecanoic

112

acid, ethyl ester (98%), p-cresol (99%) guaiacol (98%), 4-ethylphenol (98%),

113

4-methylguaiacol (98%), 4-ethylguaiacol (98%), acetic acid (98%), propanoic acid (98%),

114

butanoic acid (98%), and ethyl acetate (98%). Serial n-alkanes (C6~C23) were purchased

115

from Beijing Chemical Reagents Co. Ltd. (Beijing, China). The internal standard,

116

1,2-dichlorobenzene (99%), was purchased from Sigma-Aldrich Co. Ltd (Shanghai,

117

China).

benzophenone

(95%),

(99%),

acetophenone

phenylethylalcohol

(98.5%), (98%),

118

Solvent-Assisted Flavor Evaporation (SAFE). The head and the legs of the SAFE

119

unit (Deutsche Forschungsanstalt für Lebensmittelchemie, Freising, Germany) were

120

thermostated at 25 °C. Two 500 mL flasks were carefully fixed onto the two legs of the

121

unit, where one was called sample flask to receive the dropping sample and the

122

distillation residue, another was called distillate flask to receive the distillate. The

123

vacuum system in a range of 10-4~10-5 mbar was achieved by an Edwards EXT 75DX

124

vacuum pump (China Edwards Technologies Trading (Shanghai) Co Ltd ). Liquid

125

nitrogen was poured into the cooling trap and also into a beaker surrounding the 500 mL

126

distillate flask. A sample of 100 mL vinegar was handled in one run for about 1 h. The 7



127

distillate was extracted by freshly redistilled dichloromethane (3×50 mL). The combined

128

extracts were dried over anhydrous sodium sulphate and concentrated to 0.5 mL using a

129

Vigreux column (50 cm×1 cm i.d.). Two replicates were performed and subjected to the

130

following analyses.

131

Gas Chromatography and Mass Spectrometry (GC-MS). An Agilent 7890B gas

132

chromatograph coupled with a 5977C mass spectrometer (Agilent Technologies, USA)

133

was used. The carrier gas was helium in 1 mL/min. The separation was on both a HP-5

134

MS (30 m × 0.25 mm × 0.25 µm) and a DB-Wax (30 m × 0.25 mm × 0.25 µm) columns

135

(Agilent Technologies, USA). For the HP-5 column, the initial oven temperature was

136

35 °C, holding for 2 min; then ramped to 170 °C at 3 °C /min; and finally ramped to

137

250 °C at 5 °C /min, holding for 2 min.

138

temperature was 35 °C, then ramped to 170 °C at 3 °C /min; and finally ramped to 230 °C

139

at 5 °C /min, holding for 1 min. The sample injected was 1 µL at 250 °C in split mode.

140

The split ratio was 20 : 1.

For the DB-Wax column, the initial oven

141

The mass detector was operated at 150 °C in electron impact mode at 70 eV. The

142

solvent delay was 3 min. The ion source was at 230 °C. The transfer was at 250 °C. The

143

chromatograms were recorded by full scan in the 40~450 mass range.

144

Gas Chromatography and Olfactometry (GC-O). An Agilent 7890A gas

145

chromatograph

(Agilent Technologies, USA) equipped with a FID detector and a

146

DATU 2000 high-resolution olfactometer system (DATU Inc. USA.) was used.8 The

147

column was HP-5 30 m × 0.25 mm × 0.25 µm. The carrier gas was nitrogen at 1.0

148

mL/min. The initial oven temperature was 40 °C, then ramped to 250 °C at 5 °C /min. 1

149

µL of sample was injected in splitless mode at 250 °C. The GC effluent to the odor port

8


Page 8 of 34

Page 9 of 34


150

was enclosed with a stream of humidified air of 16 L/min and transferred by one length

151

of stainless steel tube (10 mm i.d) to the Teflon detection cone.

152

The samples of the concentrates were stepwise diluted using dichloromethane to

153

obtain dilutions (1:1, 1:2,

1:4,

1:8,

1:16,. . . , 1: 1024, and so on) of the original

154

solutions. Each dilution was submitted to GC-O analysis. The time to effuse

155

dichloromethane was figured out in advance to avoid harm. The odor characteristics

156

sniffed were recorded and each odorant was finally assigned a FD factor representing the

157

highest dilution. Three trained sniffers performed the AEDA/GC-O analyses. Retention

158

times of the odor responses were converted into retention index (RI) values relative to the

159

series of n-alkanes (C6-C23).

160

Identification of Compounds. The identification of the odor-active compounds was

161

based on mass spectra in GC-MS, retention indices (RI) relative to C6-C23 n-alkanes in

162

both GC-MS and GC-O analyses, odor characteristics sniffed in GC-O, and the

163

comparison of the above parameters with those of the available authentic chemicals. In

164

GC-MS analyses, both a polar column (DB-Wax) and a weak polar column (HP-5) were

165

employed to separate and identify the compounds as far as possible. The mass spectra of

166

the peaks and the corresponding RIs on both the columns were used for the identification.

167

For mass spectra, compounds were identified according to NIST 2011 mass spectra

168

libraries installed in the GC-MS equipment together with manual interpretation.

169

Quantitative Determination of the Odorants. The Trace 1310-TSR-8000

170

GC-MS/MS with a TG-5 MS 30 m × 0.25 mm × 0.25 µm column (Thermo Fisher

9



171

Scientific, USA) was used. The programmed oven temperatures were identical to those in

172

the above HP-5 column GC-MS analysis. The mass spectrometry was detected in selected

173

reaction monitoring (SRM) mode. The sample injected was 1 µL at 250 °C in splitless

174

mode.

175

The odor-active compounds which were authentic chemicals available and in high

176

concentrations in the vinegars or of high FD factors were mainly quantitated. The

177

analytes were the concentrates mentioned above by the SAFE treatment. Calibration for

178

each compound was performed using the relative area to internal standard. The internal

179

standard used was 1, 2-dichlorobenzene (200 µg/mL in dichloromethane). The parent

180

ions to the daughter ions, the collision energies, the concentrations of the standard

181

solutions prepared in dichloromethane, and the calibration curves obtained for each of

182

the odorants were presented in Table 1. The quantity of an odor-active compound in a

183

concentrate was calculated by the calibration equation, and then taking into account the

184

extraction yield of the concentrate converted to micrograms in per liter vinegar (µg/L).

185

The results were the averages of two replicates.

186

RESULTS and DISCUSSION.

187

The odor descriptors, the flavor dilution factors, the identified compounds, and the

188

concentrations of the quantitated compounds for the vinegars before and after aging were

189

presented in Table 2. Total of eighty-seven odor-active regions were found, of which

190

eighty were identified but seven remained unknown. For the eighty compounds, fifty-four

191

were positively identified by RI, MS, odor descriptors, and authentic compounds;

192

whereas nineteen were identified without authentic compounds, four were identified

193

without MS, and three were identified without MS as well as authentic compounds. The

10


Page 10 of 34

Page 11 of 34


194

seven identifications without using MS were because they were undetected in GC-MS on

195

either the HP or the DB-Wax column. Total of thirty odor-active compounds were

196

quantitated, which mostly showed a high FD factor or a high concentration in the

197

vinegars. Otherwise, a couple of compounds though of a low concentration or a small FD

198

factor e.g. methyl pyrazine also were quantitated as the authentic chemicals were

199

obtainable in our laboratory. For the quantative determination, rather than GC-MS, SRM

200

detection in tandem mass spectrometry (GC-MS/MS) was adopted, since the latter is

201

advantageous in specifity, sensitivity, and detection limit. As could be seen in Table 2,

202

γ-decalactone which was undetectable in the GC-MS analysis was also quantitively

203

determined.

204

(1)The Odor-active Compounds before Aging. In Table 2, before aging, total of

205

eighty odor-active regions were detected in the GC-O analysis. The typical odor

206

characteristics sniffed were sour, fruity, floral, nutty, roasted, cheesy, buttery, grassy, spicy,

207

ect. Among them seventy-five compounds were identified, including four sulfur-containing

208

compounds, eight nitrogen-containing heterocyclic compounds, twelve oxygen-containing

209

heterocyclic compounds, nine aldehydes, nine ketones, one alcohol, eight acids, sixteen

210

esters, six phenols, and two ethers. The compounds (eleven) 3-(methylthio)propanal,

211

vanillin, 2,3-butanedione, 3-methylbutanoic acid, acetic acid, tetramethylpyrazine, guaiacol,

212

γ-nonalactone, 3-(methylthio)propyl acetate, butanoic acid and 2,3-dimethylpyrazine were

213

of high FD factors (log2FD﹥5), suggesting they were of importance to overall aroma of

214

the Shanxi vinegar before aging. The compounds in high concentrations (>25 µg/L) were

215

acetic acid, followed by 2,3-butanedione, furfural, 3-hydroxy-2-butanone, octanoic acid, 11



216

tetramethylpyrazine, furfuryl alcohol, and 3-methylbutanoic acid. The compounds in both

217

high concentrations and high FD values were acetic acid, followed by 2,3-butanedione,

218

tetramethylpyrazine, and 3-methylbutanoic acid.

219

The sulfur-containing compounds sniffed were with onion, meaty, fruity, and cooked

220

potato odors. They can be formed during the thermal processing via Maillard reaction. The

221

Strecker degradation of sulfur amino acids such as cysteine and methionine in Maillard

222

reaction can produce the sulfur compounds. However, sulfur compounds can also be

223

released during the fermentation process. 3-(methylthio)propanal, also called methional,

224

with boiled potato odors, can be synthesized by Saccharomyces cerevisiae in different

225

fermented foods.

226

fermentation, which subsequently remained in the vinegars. 20 So did 3-(methylthio) propyl

227

acetate. Due to the nature of low odor thresholds, the four sulfur compounds discovered

228

were all of a high FD factor ( log2FD ) ranging from 4 to 14, but in a rather low

229

concentration. Among them, 3-(methylthio)propanal (0.19 µg/L, log2FD=14) was of the

230

highest FD factor, followed by 3-(methylthio) propyl acetate, dimethyl trisulfide, and

231

dimethyl disulfide. Noticeably, so far, the presence of sulfur flavor compounds in the

232

common sorghum Shanxi vinegar had been rarely reported. 3-(methylthio)propanal and

233

3-(methylthio) propyl acetate were found for the first time in Shanxi vinegar.

234

3-(methylthio)propanal had been found in red wine vinegar 21 and other fermented foods. 19

235

Otherwise, the occurrences of dimethyl trisulfide in Shanxi aged tartary buckwheat vinegar

236

14

19

3-(methylthio)propanal here probably arose from the alcoholic

and Sherry vinegar, 22 and dimethyl disulfide in Zhenjiang vinegar, Beijing rice vinegar, 12


Page 12 of 34

Page 13 of 34

237


and Shanxi aged vinegar 23 , had been revealed.

238

The number of nitrogen-containing heterocyclic compounds found was more than that

239

of the sulfur-containing compounds. The FD values (log2FD) of the nitrogen-containing

240

heterocyclic compounds ranging from 1 to 10, lower than those of the sulfur-containing

241

compounds. Except for trimethyl oxazole and 2-acetylpyrrole, the nitrogen-containing

242

heterocyclic compounds all were attributed to pyrazine and its derivatives, whose typical

243

odor characteristics were nutty and roasted. Among them, tetramethylpyrazine showed both

244

a high concentration and a high FD factor, followed by 2,3-dimethylpyrazine,

245

trimethylpyrazine, and ethylpyrazine. Pyrazine and its derivatives in Shanxi vinegar are

246

mainly formed by the maillard reaction during thermal processing, as there is an abundance

247

of sugar and nitrogen source in the solid fermentation substrate of the vinegar. 13-14

248

The oxygen-containing heterocyclic compounds in Table 2 all belonged to the furan

249

derivatives. They had FD factors (log2FD) from 1 to 4. Most of them gave sweet and

250

caramel odors. Overall, the concentrations of the oxygen-containing heterocyclic

251

compounds were higher than those of the nitrogen-containing heterocyclic compounds.

252

Among them, furfural (248.01 µg/L) was the richest, followed by furfuryl alcohol (35.08

253

µg/L) and 5-methylfurfural (16.81 µg/L). Also, the furan derivatives were mainly generated

254

by the maillard reaction in thermal processing. It is well known that furfural can be yielded

255

from pentose while 5-methylfurfural can be yielded from hexose.24 The presence of furfural

256

had been reported in a wide variety of vinegars e.g. Zhenjiang aromatic vinegar,4 and

257

Balsamic vinegar. 25 Worth mentioning, furfural had a high concentration but was of a low 13



Page 14 of 34

258

FD factor (log2FD=4) in the vinegar, probably due to its nature of high odor threshold. As

259

was reported, the odor threshold of furfural in the young red wines was found to be as

260

high as 14100 µg/L. 26 The structures of the aldehydes in Table 2 were miscellaneous with FD values

261 262

(log2FD) ranging from 0 to 14. They were typically of green, herbal, sweet, and floral odors.

263

Benzaldehyde, 3,5-dihydroxybenzaldehyde, vanillin, 5-methyl-2-phenyl-2-hexenal, and

264

piperonal, which belong to aromatic aldehydes, can originate from the plant-based raw

265

materials of sorghum, barley and so on. Benzaldehyde was proved to increase during the

266

thermal processing.13-14 Phenylacetaldehyde and 3-methylbutanal can produce from the

267

degradation of phenylalanine and isoleucine, respectively. Heptanal and (Z)-2-nonenal can

268

produce from the degradation of fatty acids. Among the aldehydes, vanillin with sweet and

269

chocolate odors was of a high FD factor (log2FD=14) and in the highest concentration

270

(20.29 µg/L), followed by phenylacetaldehyde, 5-methyl-2-phenyl-2-hexenal and

271

benzaldehyde. The other aldehydes were all in both low concentrations and small FD

272

values (log2FD < 4). Vanillin is present in the Sherry vinegars10, 27 and the strawberry

273

vinegar. 20 It was found for the first time as an odorant in Shanxi vinegar.

274

The ketones were mostly with fruity, buttery, and floral odors. Among the ketones

275

found, 2,3-butanedione (328.29 µg/L, log2FD =13) was in the highest concentration and of

276

a

277

3-Hydroxy-2-butanone and 2,3-butanedione usually are present in fermented foods and

278

beverages such as wine , which can be produced in alcoholic fermentation by the action of

high

FD

factor,

followed

by


14


or

β-damascenone.

Page 15 of 34


279

microorganisms. 21 They can also be formed from sugar degradation via Maillard reaction,

280

and are the precursors of tetramethylpyrazine in Shanxi vinegars in the maillard reaction. 5

281

β-Damascenone and the aromatic ketones e.g. benzophenone should come from the

282

plant-based raw materials used in the fermentation process. Here, β-damascenone

283

(log2FD=5) was for the first time found in Shanxi vinegar, but it proved in too low a level

284

in the vinegars to exactly quantitate in the present study. β-damascenone had been found in

285

Sherry vinegar by HS-SPME and gas chromatography-olfactometry. 22

286

Only one alcohol of 2-phenylethanol (16.51 µg/L) was found. It was in a low FD

287

value (log2FD =3) with fruity and floral notes. It might derive from the reduction of

288

phenylacetaldehyde in alcoholic fermentation or origin from the raw materials used.

289

The acids mainly contribute to the tart and sour flavor of vinegars. They generated in

290

the acetic fermentation process. The acids identified from the vinegar before aging

291

included seven aliphatic acids of two to eight carbon atoms, and benzoic acid. Among

292

them, 3-methylbutanoic acid showed the highest FD factor (log2FD =13), followed by

293

acetic acid (log2FD =10) and butanoic acid (log2FD =6); while in view of concentration

294

acetic acid (581 µg/L) was the highest, followed by octanoic acid, and 3-methylbutanoic

295

acid.

296

The esters usually are considered most important to flavor of vinegars. A lot of esters

297

have been found from Zhenjiang aromatic vinegar 4 and Balsamic vinegar. 25 The esters are

298

of typical fruity aroma characteristics. They can be formed by the reaction of alcohols with

299

organic acids under the effect of the esterase, yeast or mold. From this un-aged Shanxi 15



Page 16 of 34

300

vinegar, total of sixteen esters were identified, with FD values from 1 to 9, including six

301

lactones (e.g. γ-hexalactone and γ-decalactone) and ten aliphatic esters. Lactic acid, ethyl

302

ester (23.77 µg/L) was in the highest concentration, followed by succinic acid diethyl ester

303

(7.75 µg/L), and γ-decalactone (6.99 µg/L). While for the FD values, γ-nonalactone

304

(log2FD =9) ranked the highest, followed by lactic acid ethyl ester (log2FD =4) and

305

γ-hexalactone (log2FD =4). The other esters shown in Table 2 were in quite a low FD value

306

(log2FD 25 ug/L) was reduced

346

from eight to seven. However, conversely the concentrations of some compounds e.g

347

dimethyl trisulfide, trimethylpyrazine, and phenylacetaldehyde were increased. Especially,

348

tetramethylpyrazine was increased markedly from 35.7 to 82.36 µg/L, while there were

349

five new pyrazine compounds found after aging. It could be seen from Table 2 that the

350

new attendees 2-ethyl-6-methylpyrazine and 2-acetylpyrazine each had a high FD value

351

(log 2 FD ) of 8, indicating they were of importance to overall aroma. Besides, similar to

352

tetramethylpyrazine, its precursor 2,3-butanedione again remained in both a high

353

concentration and a high FD value.

354

As shown in Figure. 1, after aging, the top fifteen compounds of high FD factors

355

(log2FD﹥7) were 3-(methylthio)propanal, vanillin, 2,3-butanedione, tetramethylpyrazine,

356

3-methylbutanoic acid, γ-nonalactone, guaiacol, 3-(methylthio)propyl acetate, dimethyl

357

trisulfide,

358

2,3-dimethylpyrazine, furfural, and 3-hydroxy-2-butanone. The compounds in high

359

concentrations ( > 25 µg/L) were acetic acid, followed by 2,3-butanedione, furfural,

360

3-hydroxy-2-butanone, tetramethylpyrazine, furfuryl alcohol, and 3-methylbutanoic acid.

361

The compounds in both high concentrations and high FD values were 2,3-butanedione,

362

followed by tetramethylpyrazine, and 3-methylbutanoic acid. Compared to before aging,

phenylacetaldehyde,

2-ethyl-6-methylpyrazine,

18


2-acetylpyrazine,

Page 19 of 34


363

the most obvious changes were that more pyrazine compounds in a high FD value were

364

found and acetic acid was not so potent to overall aroma of the vinegar as before. However,

365

after aging the Shanxi vinegar often tastes more acidic, as the non-volatile acids such as

366

lactic acid and succinic acid in the vinegar tend to be concentrated with aging time. 3

367

During the aging processing, water in the vinegar is evaporated or frozen in an open

368

top jar, where volatile compounds are liable to be lost. In the meantime, there are various

369

complex chemical reactions taking place. However, the level increase of the aroma

370

compounds e.g. dimethyl trisulfide, tetramethylpyrazine, and phenylacetaldehyde, and the

371

emergence of five new pyrazine compounds indicated that the maillard reaction was of

372

significance in the aging process due to the fermented cereal vinegars rich in proteins,

373

amino acids, and reducing sugars. In addition, during the aging, the contents of amino

374

acids and reducing sugars in the vinegar would increase with time.3 It could be seen from

375

Figure. 2, even for the same compounds in the Shanxi vinegars, after the aging process,

376

the changes of their levels within the composition formula would lead to the alteration of

377

aroma profile of the vinegar. Anyway, the increase in the pyrazine compounds, and the

378

decrease in acetic acid and some other compounds of pungent smells contributed greater

379

to the development of the unique flavor of Shanxi aged vinegar, which was thicker, round,

380

and gentle compared to that before aging.

381

In summary, total of eighty odor-active compounds were identified from the Shanxi

382

vinegars before and after aging, where 3-(methylthio)propanal, 3-(methylthio)propyl

383

acetate, vanillin, and β-damascenone were found for the first time as odorants in Shanxi 19



384

vinegar. The aroma compounds of high FD values before aging mainly were attributed to

385

sulfur-containing compounds, nitrogen-containing heterocyclic compounds, fatty acids,

386

lactones, ketones, aromatic aldehydes, and phenols, which originated from alcoholic

387

fermentation, the mailard reaction, acetic acid fermentation, or the raw materials used.

388

After aging process the aroma molecules were mostly unchanged but their concentrations

389

were being modified. The obvious changes after the aging process were that the

390

compounds with pungent smells e.g. acetic acid and p-cresol were partly or entirely

391

evaporated with water. Instead, the sulfur compounds and especially the pyrazine

392

compounds that give nutty, and roasted notes to the vinegar were further highlighted.

393

These demonstrated during the aging processing, Maillard reaction again played

394

important roles in the development of the unique flavor of Shanxi aged vinegar. The

395

results would be helpful to improve the flavor quality and processing technology of

396

Shanxi aged vinegar.

397

398

Corresponding Author

399

*Jianchun Xie, School of Food Science and Chemical Engineering, Beijing Technology

400

and Business University, No. 33 Fucheng Road, Haidian District, Beijing 100048, China.

401

Phone and Fax: (+86) -10-68984859. E-mail: [email protected]

402

Funding

403

The present work was supported by National Natural Science Foundation of China.

404

(NSFC. 31371838, 31671895 )

AUTHOR INFORMATION

20


Page 20 of 34

Page 21 of 34


405

Notes

406

The authors declare no competing financial interest.

21



407

408

(1) Xiao, Z. B.; Dai, S. P.; Niu, Y.W.; Yu, H. Y.; Zhu, J. C.; Tian, H. X.; Gu, Y. B.

409

Discrimination of Chinese vinegars based on headspace solid-phase microextraction-gas

410

chromatography mass spectrometry of volatile compounds and multivariate analysis. J.

411

Food Sci. 2011, 76, 1125-1135.

412

(2) Chen, H.Y.; Zhou, Y. X.; Shao, Y. C.; Chen, F. S. Free phenolic acids in Shanxi aged

413

vinegar: changes during aging and synergistic antioxidant activities. Int. J. Food Prop.

414

2016, 19, 1183-1193.

415

(3) Chen, T.; Gui, Q.; Shi, J. J.; Zhang, X. Y.; Chen, F.S. Analysis of variation of main

416

components during aging process of Shanxi aged vinegar. Acetic Acid Bacteria. 2013, 2,

417

31-38.

418

(4) Yu, Y. J.; Lu, Z. M.; Yu, N. H.; Xu, W.; Li, G. Q.; Shi J. S.; Xu, Z. H.

419

HS-SPME/GC-MS and chemometrics for volatile composition of Chinese traditional

420

aromatic vinegar in the Zhenjiang region. J. Inst. Brew. 2012, 118, 133-141.

421

(5) Lu, Z. M.; Xu, W.; Yu, N. H.; Zhou, T.; Li, G. Q.; Shi, J. S.; Xu, Z. H. Recovery of

422

aroma compounds from Zhenjiang aromatic vinegar by supercritical fluid extraction. Int.

423

J. Food Sci. Tech. 2011, 46, 1508-1514.

424

(6) Zhu, H.; Zhu, J.; Wang, L. L.; Li, Z. G. Development of a SPME-GC-MS method for

425

the determination of volatile compounds in Shanxi aged vinegar and its analytical

426

characterization by aroma wheel. J. Food Sci. Technol. 2016, 53, 171-183.

427

(7) Su, M. S.; Chien, P. J. Aroma impact components of rabbiteye blueberry ( Vaccinium

REFERENCES

22


Page 22 of 34

Page 23 of 34


428

ashei ) vinegars. Food Chem. 2010, 119, 923-928.

429

(8) De Souza, M. D.; Vásquez, P.; Del Mastro, N. L.; Acree, T. E.; Lavin, E. H.

430

Characterization of cachaça and rum aroma. J. Agric. Food Chem. 2006, 54, 485-488.

431

(9) Xie, J. C.; Sun, B. G.; Zheng, F. P.; Wang, S. B. Volatile flavor constituents in roasted

432

pork of Mini-pig. Food Chem. 2008, 109, 506-514.

433

(10) Callejón, R. M.; Morales, M. L.; Troncoso, A. M.; Ferreira, A. C. S. Targeting key

434

aromatic substances on the typical aroma of Sherry Vinegar. J. Agric. Food Chem. 2008,

435

56, 6631-6639.

436

(11) Zhu, H.; Wang, A. L.; Qiu, J.; Li, Z. G. Changes of aroma compounds in Shanxi

437

aged vinegar during its fermentation determined by dynamic headspace-gas

438

chromatography. Journal of Chinese Institute of Food Science and Technology

439

（Zhongguo Shipin Xuebao）. 2016, 16, 264-271. (In Chinese)

440

(12) Lee, S. W. ; Yoon, S. R. ; Kim, G. R. ; Woo, S. M. ; Jeong, Y. J. ; Yeo, S. H. ; Kim,

441

K. S. ; Kwon, J. H. Effect of nuruk and fermentation method on organic acid and volatile

442

compounds in brown rice vinegar. Food Sci. Biotechnol. 2012, 21, 453-460.

443

(13) Li, H. W.; Wang, X. P.; Yang, X. L. Influence of different fumigation processes on

444

aroma compounds of Shanxi aged vinegar. Food Science (Shipin Kexue). 2015, 36, 90-94.

445

(In Chinese)

446

(14) Wang, A. L.; Song, H. L.; Ren, C. Z.; Li, Z. G. Key aroma compounds in Shanxi

447

aged tartary buckwheat vinegar and changes during its thermal processing. Flavour Fragr.

448

J. 2012, 27, 47-53. 23



449

(15) Pino, J. A.; Tolle, S.; Gök, R.; Winterhalter, P. Characterisation of odour-active

450

compounds in aged rum. Food Chem. 2012, 132, 1436-1441.

451

(16) Wang, J. M.; Gambetta, J. M.; Jeffery, D. W. Comprehensive study of volatile

452

compounds in two australian rosé wines: aroma extract dilution analysis (AEDA) of

453

extracts prepared using solvent-assisted flavor evaporation (SAFE) or headspace

454

solid-phase extraction (HS-SPE). J. Agric. Food Chem. 2016, 64, 3838-3848.

455

(17) Marcq, P.; Schieberle, P. Characterization of the key aroma compounds in a

456

commercial amontillado sherry wine by means of the sensomics approach. J. Agric. Food

457

Chem. 2015, 63, 4761-4770.

458

(18) Wu, J. J.; Ma, Y. K.; Zhang, F. F.; Chen, F. S. Biodiversity of yeasts, lactic acid

459

bacteria and acetic acid bacteria in the fermentation of “Shanxi aged vinegar”, a

460

traditional Chinese vinegar. Food Microbiol. 2012, 30, 289-297.

461

(19) Landaud, S.; Helinck, S.; Bonnarme, P. Formation of volatile sulfur compounds and

462

metabolism of methionine and other sulfur compounds in fermented food. Appl.

463

Microbiol. Biotechnol. 2008, 77, 1191-1205.

464

(20) Ubeda, C.; Callejón, R. M.; Troncoso, A. M.; Moreno-Rojas, J. M.; Peña, F.;

465

Morales, M. L. Characterization of odour active compounds in strawberry vinegars.

466

Flavour Fragr. J. 2012, 27, 313-321.

467

(21) Charles, M.; Martin, B.; Ginies, C.; Etievant, P.; Coste, G.; Guichard, E. Potent

468

aroma compounds of two red wine vinegars. J. Agric. Food Chem. 2000, 48, 70-77.

469

(22) Aceña, L.; Vera, L.; Guasch, J.; Busto, O.; Mestres, M. Chemical characterization of 24


Page 24 of 34

Page 25 of 34


470

commercial Sherry vinegar aroma by headspace solid-phase microextraction and gas

471

chromatography-olfactometry. J. Agric. Food Chem. 2011, 59, 4062-4070.

472

(23) Zhou, Y. X.; Zhang, J. X.; Xu, Y. T. The flavor analysis of five kinds of solid-state

473

fermentation vinegar by GC -MS. Acta Agriculturae Boreali-Occidentalis Sinica (Xibei

474

Nongye Xuebao). 2014, 23, 143-149. (In Chinese)

475

(24) Giordano, L.; Calabrese, R.; Davoli, E.; Rotilio, D. Quantitative analysis of

476

2-furfural and 5-methylfurfural in different Italian vinegars by headspace solid-phase

477

microextraction coupled to gas chromatography–mass spectrometry using isotope

478

dilution. J. Chromatogr. A. 2003, 1017,141-149．

479

(25) Cirlini, M.; Caligiani, A.; Palla, L.; Palla, G. HS-SPME/GC–MS and chemometrics

480

for the classification of Balsamic vinegars of Modena of different maturation and aging.

481

Food Chem. 2011, 124, 1678-1683.

482

(26) Ferreira, V.; López, R.; Cacho, J. F. Quantitative determination of the odorants of

483

young red wines from different grape varieties. J. Sci. Food Agric. 2000, 80, 1659-1667.

484

(27) Callejón, R. M.; Morales, M. L.; Ferreira, A. C. S.; Troncoso, A. M. Defining the

485

typical aroma of Sherry vinegar: sensory and chemical approach. J. Agric. Food Chem.

486

2008, 56, 8086-8095.

25



Page 26 of 34

Table 1 The analysis conditions, the standard solutions, and the calibration equations for the thirty odor-active compounds in the Shanxi vinegars before and after aging determined quantitatively by GC-MS/MS in selected ion monitoring (SRM) mode Compounds 2,3-butanedione acetic acid

Retention indices 617 687

1

SRM (m/z)

86>43(15) ;43>15(5) 60>45(10)

2

Calibration

equations

y=7.3378x+0.0963;R2=0.9979

3

Concentrations (mg/L)

5, 10, 20, 40, 80, 160

2

5, 10, 20, 40, 80, 160

2

y=9.7240x-0.0416; R =0.9983


710

88>45(5);45>27(15)

y=6.2881x+0.0119;R =0.9972

5, 10, 20, 40, 80, 160

methylpyrazine

812

94>67(10) ; 67>26(10)

y=4.9176x-0.0549;R2=0.9983

0.5, 1, 2, 4, 8, 16

lactic acid, ethyl ester

825

75>45(5);45>15(15)

2

y=4.4224x+0.0269;R =0.9968 2

0.5, 1, 2, 4, 8, 16

3-methylbutanoic acid

847

60>42(10);60>45(15)

y=5.5701 x+0.0271;R =0.9981

0.5, 1, 2, 4, 8, 16

furfural

856

96>39(15);67>39(10)

y=7.2172x-0.0581;R2=0.9985

5, 10, 20, 40, 80, 160

furfuryl alcohol

860

2

98>42(10)

y=3.6339x+0.0209;R =0.9982 2

0.5, 1, 2, 4, 8, 16

heptanal

887

70>55(5);57>29(10)

y=3.2869x+0.0188;r =0.9983

0.5, 1, 2, 4, 8, 16

3-(methylthio)propanal

904

104>48(10);76>61(5)

y=1.2669x-0.0558;R2=0.9980

0.025, 0.05, 0.1, 0.2, 0.4, 0.8

ethylpyrazine

907

108>80(10)

2

0.5, 1, 2, 4, 8, 16

2

y=5.9747x+0.0693;R =0.9987

2,3-dimethylpyrazine

915

108>67(10)

y=8.2647x+0.0106;R =0.9988

0.5, 1, 2, 4, 8, 16

benzaldehyde

952

105>77(10)

y=0.8833x+0.0082;R2=0.9992

0.5, 1, 2, 4, 8, 16

5-methylfurfural

957

109>53(10)

2

0.5, 1, 2, 4, 8, 16

2

y=5.5419x+0.0104;R =0.9989

dimethyl trisulfide

960

126>79(15) ;79>64(15)

y=0.2719x+0.0065;R =0.9984

0.05, 0.1, 0.2, 0.4, 0.8, 1.6

trimethylpyrazine

997

122>81(10) ; 122>42(15)

y=1.4940x-0.0184;R2=0.9990

0.5, 1, 2, 4, 8, 16

phenylacetaldehyde

1038

2

120>91(10)

y=2.1670x+0.0324;R =0.9984

26


0.5, 1, 2, 4, 8, 16

Page 27 of 34


2-acetylpyrrole

109>94(10);94>66(10)

y=1.6197x+0.0252;R2=0.9983 2

0.5, 1, 2, 4, 8, 16

guaiacol

1084

124>109(10) ;109>81(10)

y=0.9122x-0.0029;R =0.9981

0.5, 1, 2, 4, 8, 16

tetramethylpyrazine

1085

136>54(15) ;54>39(5)

y=3.3813x+0.0341;R2=0.9985

1, 2, 4, 8, 16, 32

(Z)-2-nonenal

1142

70>55(5) ;57>29(10)

2

0.5, 1, 2, 4, 8, 16

2

y=1.1257x-0.0191;R =0.9866

2-phenylethanol

1118

122>91(15) ; 91>65(15)

y=3.7422x-0.0171;R =0.9981

0.5, 1, 2, 4, 8, 16

3-(methylthio)propyl acetate

1123

73>43(10)

y=0.1623x+0.0045;R2=0.9982

0.05, 0.1, 0.2, 0.4, 0.8, 1.6

4-methylguaiacol

1188

138>123(10);123>95(5)

2

0.05, 0.1, 0.2, 0.4, 0.8, 1.6

2

y=0.6450x+0.0065;R =0.9992

succinic acid, diethyl ester

1189

129>101(5) ;101>73(5)

y=5.0559x+0.0633;R =0.9986

0.5, 1, 2, 4, 8, 16

octanoic acid

1197

73>55(10) ;60>42(10)

y=3.5916x+0.0797;R2=0.9980

0.5, 1, 2, 4, 8, 16

4-ethylguaiacol

1

1061

1273

152>137(10) ;137>122(10)

2

0.05, 0.1, 0.2, 0.4, 0.8, 1.6

2

y=0.2319x+0.0023;R =0.9970

γ-nonalactone

1377

85>57(5);85>29(10)

y=1.8042x+0.0987;R =0.9983

0.5, 1, 2, 4, 8, 16

vanillin

1420

151>123(10)

y=1.3211x+0.0955;R2=0.9965

0.5, 1, 2, 4, 8,16

γ-decalactone

1468

85>29(10); 57>29(10)

1,2-dichlorobenzene

1024

146>111(15) ; 111>75(10)

2

y=1.9583x+0.0123;R =0.9989 -

0.5, 1, 2, 4, 8,16 2

parent ion > daughter ion (collision energy) (eV) used for the calibration. 2 x was the peak area relative to that of the internal standard

1,2-dichlorobenzene, y was the concentration in the extract of a vinegar by solvent assisted flavor distillation (SAFE). the standard solutions prepared in dichloromethane.

27


3

The concentrations of


Page 28 of 34

Table 2 The retention indices, odor descriptors, and flavor dilution factors ( log2FD) in GC-O analysis and the compounds identified with some of their concentrations determined in the Shanxi vinegars before and after aging 2 1

RI

1

Odor descriptors

Compounds

log2FD

a

b

3

Concentrations (µg/L)

4

Identification

a

b

Methods

547

spicy, sweet

unknown

-

1

598

fruity, sweet

2-butanone

0

-

-

-

MS/RI/Odor

608

buttery, sweet

2,3-butanedione

13

14

328.29 ± 2.11

322.64 ± 1.82

MS/RI/Odor/S

621

fruity

ethyl acetate

3

-

-

-

MS/RI/Odor/S

668

pungent, fruity

3-methylbutanal

1

2

-

-

MS/RI/Odor/S

680

pungent, sour

acetic acid

10

6

581 ± 2.83

440.66 ± 1.92

MS/RI/Odor/S

684

fruity

propanoic acid, ethyl ester

2

-

-

-

MS/RI/Odor/S

699

buttery


4

8

96.62 ± 0.45

93.06 ± 0.37

MS/RI/Odor/S

707

onion, cabbage

dimethyl disulfide

4

7

-

-

MS/RI/Odor/S

730

sour, fruity

propanoic acid

2

7

-

-

MS/RI/Odor/S

736

nutty, roasted

pyrazine

-

1

-

-

MS/RI/Odor

787

roasted, nutty

methyl pyrazine

1

1

5.87 ± 0.10

5.74 ± 0.09

MS/RI/Odor/S

788

fruity

isoamyl formate

2

-

-

-

MS/RI/Odor/S

791

rancid, cheesy

butanoic acid

6

5

-

-

MS/RI/Odor/S

801

caramel

dihydro-2-methyl-3(2H)-furanone

1

0

-

-

MS/RI/Odor

822

yogurt

lactic acid, ethyl ester

4

2

23.77 ± 0.17

-

MS/RI/Odor/S

842

rancid, cheesy

3-methylbutanoic acid

13

12

29.23 ± 0.18

27.23 ± 0.16

MS/RI/Odor/S

855

caramel

furfuryl alcohol

4

6

35.08 ± 0.18

40.40 ± 0.14

MS/RI/Odor/S

861

roasted, earthy

trimethyl oxazole

2

3

-

-

MS/RI/Odor

868

caramel

furfural

4

8

248.01 ± 1.15

225.53 ± 0.72

MS/RI/Odor/S

881

green, sweet

heptanal

2

1

1.28 ± 0.03

-

MS/RI/Odor/S

28


Page 29 of 34


891

sweet

2-acetoxy-3-butanone

2

4

-

-

MS/RI/Odor

897

sour, cheesy

pentanoic acid

3

1

-

-

MS/RI/Odor/S

906

nutty, sweet

2-acetylfuran

1

0

-

-

MS/RI/Odor/S

909

boiled potato

3-(methylthio)propanal

14

15

0.19 ± 0.01

0.23 ± 0.01

MS/RI/Odor/S

917

nutty

ethyl pyrazine

3

3

7.61 ± 0.04

7.74 ± 0.03

MS/RI/Odor/S

921

roasted, popcorn

2,3-dimethyl pyrazine

6

8

8.66 ± 0.14

8.79 ± 0.10

MS/RI/Odor/S

954

fruity

γ-pentalactone

1

-

-

-

MS/RI/Odor/S

959

almond

benzaldehyde

3

7

12.36 ± 0.09

9.76 ± 0.06

MS/RI/Odor/S

964

caramel

5-methylfurfural

3

0

16.81 ± 0.16

10.82 ± 0.10

MS/RI/Odor/S

972

roasted meat

dimethyl trisulfide

5

9

0.61 ± 0.01

1.01 ± 0.02

MS/RI/Odor/S

986

earthy, musty

trimethyl pyrazine

3

3

9.9 ± 0.21

13.04 ± 0.27

MS/RI/Odor/S

990

earthy, green

2-pentylfuran

3

-

-

-

MS/RI/Odor

1005

nutty, musty

2-ethyl-6-methyl pyrazine

-

8

-

-

MS/RI/Odor/S

1008

fruity, caramel

2-furfuryl acetate

2

3

-

-

MS/RI/Odor/S

1012

fruity, sweet

3

-

-

-

MS/RI/Odor

1026

nutty, roasted

2-acetylpyrazine

-

8

-

-

MS/RI/Odor/S

1026

rancid, creamy

hexanoic acid

3

3

-

-

MS/RI/Odor/S

1040

sweet, burnt sugar

2-acetyl-5-methylfuran

3

-

-

-

MS/RI/Odor/S

1044

herbal, sweet

γ-hexalactone

4

-

-

-

MS/RI/Odor

1047

rose

phenylacetaldehyde

5

9

6.27 ± 0.04

20.46 ± 0.13

MS/RI/Odor/S

1060

sweet, fruity

acetophenone

2

-

-

-

MS/RI/Odor/S

1064

licorice

2-acetylpyrrole

2

0

8.89 ± 0.13

8.28 ± 0.11

MS/RI/Odor/S

1077

phenol, smoke

p-cresol

1

-

-

-

MS/RI/Odor/S

butanedioic acid, monomethyl ester

1085

spicy, sweet

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

3

-

-

-

MS/RI/Odor

1085

woody

guaiacol

9

11

11.34 ± 0.06

10.81 ± 0.04

MS/RI/Odor/S

1090

nutty, roasted

tetramethyl pyrazine

10

13

35.7 ± 0.28

82.36 ± 0.44

MS/RI/Odor/S

29



Page 30 of 34

1098

fruity, floral

2-phenylethanol

3

0

16.51 ± 0.13

2.28 ± 0.01

MS/RI/Odor/S

1102

cinnamon, caramel

3-(2-furanyl)-2-propenal

4

5

-

-

MS/RI/Odor

1120

fruity

3-(methylthio)propyl acetate

6

9

1.25 ± 0.03

1.40 ± 0.03

MS/RI/Odor/S

1125

fruity, sweet

benzyl methyl ketone

2

-

-

-

MS/RI/Odor

1126

nutty, musty

2,5-dimethyl-3-isopropylpyrazine

-

1

-

-

MS/RI/Odor

1145

fruity, sweet

pantolactone

2

-

-

-

MS/RI/Odor

1152

green, fatty

(Z)-2-nonenal

1

2

10.66 ± 0.09

9.69 ± 0.06

MS/RI/Odor/S

1159

musty

2,3,5-trimethyl-6-ethylpyrazine

1

0

-

-

MS/RI/Odor/S

1169

woody, sweet

4-ethylphenol

2

5

-

-

MS/RI/Odor/S

1175

rancid

octanoic acid

3

1

44.82 ± 0.81

-

MS/RI/Odor/S

1181

sweet, fruity

succinic acid, diethyl ester

3

0

7.75 ± 0.07

6.26 ± 0.04

MS/RI/Odor/S

1192

balsam

benzoic acid

3

-

-

-

MS/RI/Odor/S

1195

woody, herbal

4-methylguaiacol

3

4

0.53 ± 0.01

0.51 ± 0.01

MS/RI/Odor/S

1201

licorice, anise

estragole

0

0

-

-

RI/Odor

1206

nutty, roasted

2-acetyl-3,5-dimethylpyrazine

-

2

-

-

MS/RI/Odor/S

1222

sweet, burnt sugar

5-hydroxymethylfurfural

3

-

-

-

MS/RI/Odor

1237

rancid, spicy

1-phenyl-1,2-propanedione

0

-

-

-

MS/RI/Odor

1246

spicy, green

unknown

3

4

1250

fruity, floral

acetic acid, 2-phenylethyl ester

1

-

-

-

MS/RI/Odor/S

1260

coconut, sweet

γ-octalactone

2

-

-

-

MS/RI/Odor/S

1271

sweet, spicy

4-ethylguaiacol

3

4

0.84 ± 0.02

0.50 ±0 .01

MS/RI/Odor/S

1292

spicy, herbal

unknown

2

1

1294

fennel, herbal

anethole

1

1

-

-

RI/Odor

1320

earthy

unknown

3

-

1338

herbal, sweet

piperonal

2

3

-

-

RI/Odor

1363

coconut

γ-nonalactone

9

11

3.06 ± 0.06

3.57 ± 0.06

MS/RI/Odor/S

1380

fruity

ethyl caprate

2

5

-

-

RI/Odor/S

30


Page 31 of 34


1382

smoky, woody

4-propylguaiacol

0

-

-

-

MS/RI/Odor

1390

fruity, apple

β-damascenone

5

7

-

-

RI/Odor/S

1398

herbal, sweet

3,5-dihydroxybenzaldehyde

0

-

-

-

MS/RI/Odor

1402

sweet, chocolate

vanillin

14

14

20.29 ± 0.13

16.51 ± 0.10

MS/RI/Odor/S

1466

fruity

γ-decalactone

3

1

6.99 ± 0.07

-

RI/Odor/S

1485

green, rancid

5-methyl-2-phenyl-2-hexenal

4

-

-

-

MS/RI/Odor

1514

spicy

unknown

0

-

1520

earthy

unknown

-

1

1616

sweet, floral

benzophenone

2

2

-

-

MS/RI/Odor/S

1626

musty, herbal

unknown

1

1

1675

herbal, rancid

2-phenyl-3-(2-furyl)- propenal

2

-

-

-

MS/RI/Odor

1720

fruity

methyl tetradecanoate

1

2

-

-

RI/Odor/S

1988

fruity

hexadecanoic acid, ethyl ester

2

-

-

-

MS/RI/Odor/S

1

Kovats retention indices, and odor characteristics sniffed in GC-O analysis. 2 the Shanxi vinegars before aging (a) and after aging (b);

“-”, undetected in GC-O analysis. 3 the concentrations were expressed as means ± standard deviations (two replicates) (µg) in per liter of vinegar; “-”，not quantitated. 4 MS, identified by NIST 11 mass spectral database; RI, agreed with the published retention indices; Odor, agreed with the published odor descriptions; S, the analytical parameters of MS, RI, and Odors all agreed with those of the authentic standards used.

31



3-(Methylthio)propanal 2,3-Dimethyl pyrazine Dimethyl trisulfide 2-ethyl-6-methylpyrazine 2-acetylpyrazine

Page 32 of 34

γ-Nonalactone Vanillin

（Retention index））

3-(Methylthio)propyl acetate

Benzaldehyde

Tetramethyl pyrazine Guaiacol Furfural Furfuryl alcohol

Phenylacetaldehyde

3-Methylbutanoic acid 3-Hydroxy-2-butanone Acetic acid 2,3-Butanedione

Figure 1. The comparison of flavor dilution factors (Log2FD) and concentrations (µg/L) for the odor-active compounds in the Shanxi vinegars before and after aging. The retention indices were corresponding to the compounds listed in Table 2, among which the quantitated or the new pyrazines found in the aged vinegar of potent odor-activities were shown. The compounds of log2FD≥ 6 in the vinegar either before or after aging were labeled.

32


Page 33 of 34


Figure 2. Spider-web for the odorants of high flavor dilution factors (log2FD≥ 5), the full distance on the scale was defined to be 5, distance from the origin for a compound is 5 times the ratio of its log2FD value divided by the highest log2FD value among the presented compounds of the vinegar.

33



Graph for table of contents

34


Page 34 of 34

Aroma Constituents in Shanxi Aged Vinegar before and after Aging

Recommend Documents