Characterization of the Key Aroma Compounds in Aged Chinese Rice

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Chemistry and Biology of Aroma and Taste

Characterization of the Key Aroma Compounds in Aged Chinese Rice Wine by Comparative Aroma Extract Dilution Analysis, Quantitative Measurements, Aroma Recombination, and Omission Studies Shuang Chen, Wang cheng Cheng, Michael C. Qian, Zhou Li, and Yan Xu J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.9b01420 • Publication Date (Web): 28 Mar 2019 Downloaded from http://pubs.acs.org on March 29, 2019

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Journal of Agricultural and Food Chemistry

Characterization of the Key Aroma Compounds in Aged Chinese Rice Wine by Comparative Aroma Extract Dilution Analysis, Quantitative Measurements, Aroma Recombination, and Omission Studies Shuang Chen1†, Chengcheng Wang1, 3†, Michael Qian2, Li Zhou1, and Yan Xu1*

1State

Key Laboratory of Food Science & Technology, Key Laboratory of Industrial

Biotechnology of Ministry of Education & School of Biotechnology, Jiangnan University Wuxi, Jiangsu, China, 214122 2Department

of Food Science & Technology, Oregon State University, Corvallis, Oregon 97331, United States

3

Institute of Renhuai Jiang-Flavor Liquor, Renhuai, Guizhou, China, 564500

*Correspondence to: Jiangnan University 1800 Lihu Ave., Wuxi, Jiangsu, China 214122 Phone: +86-510-85964112 Fax: +86-510-85918201 E-mail: [email protected] †Both

authors contributed equally to this work.

1

ACS Paragon Plus Environment


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ABSTRACT

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The aroma compounds in young and aged Chinese rice wines (rice wines) with clear

3

difference in their overall aroma profiles were analyzed by comparative aroma extract

4

dilution analysis (cAEDA). In AEDA, more aroma-active regions with flavor dilution

5

(FD) factors of ≥ 64 were detected in the aged rice wine than in the young rice wine.

6

A total of 43 odorants were further identified and quantitated. The odor activity values

7

(OAVs) revealed 33 aroma compounds with OAV ≥ 1 in young or aged rice wines.

8

Among these aroma compounds with relatively higher OAVs, 3-methylbutanoic acid,

9

1,1-diethoxyethane, vanillin, 3-methylbutanal, sotolon, benzaldehyde, 4-

10

vinylguaiacol, methional, and 2,3-butanedione showed significant differences

11

between young and aged rice wines. This difference was confirmed through a

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quantitative analysis of 34 rice wine samples with ages for 0-15 years. Then, the

13

aroma profile of the aged rice wine was successfully simulated through an aroma

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recombination model. Omission models suggested that sotolon, vanillin, 3-

15

methylbutanal, and benzaldehyde played key roles in the overall aroma of aged rice

16

wine.

17 18

KEYWORDS: aged Chinese rice wine, cAEDA, OAV, aroma recombination and

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omission

2


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INTRODUCTION Chinese rice wine (rice wine) is a very popular alcoholic beverage in China and

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East Asia due to its unique flavor, with an annual consumption exceeding 2 million

23

kiloliters in China.1, 2 As in other alcoholic beverages, such as wine, beer, and

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Japanese sake, aroma is one of the most important quality attributes that contribute to

25

rice wine quality and consumer acceptance. The aroma of rice wine can be developed

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by a complex balance of aroma compounds derived from raw materials, fermentation

27

and the aging process.3, 4

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Rice wine is typically fermented from glutinous rice with “Wheat Qu” as a

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saccharifying agent and cultured yeast as a fermenting agent.3 In general, newly

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produced (young) rice wine has undesirable aroma characteristics, e.g., “harsh”,

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“flavorless”, and “uncoordinated”.5 Long-term aging (maturation) is usually used to

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generate the typical and characteristic aroma profile of rice wine. After fermentation,

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sterilized young rice wine is maturated in a sealed pottery jar at ambient temperature

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for 3 years or even longer before blending and bottling.6, 7 During this process, many

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chemical and physical reactions, such as oxidation, hydrolysis, esterification, and

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alcohol-water hydrogen bond association can occur.7 Due to the permeability of

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pottery jars, air can slowly penetrate into the pottery jars and accelerate the oxidation

38

reactions.8, 9 Generally speaking, the economic value of rice wine highly depends on

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its age.

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Lots of studies have been carried out on the aging process of rice wine. Several

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different techniques have been used for discriminating rice wine age, including near-

42

infrared (NIR) spectroscopy,10 electronic tongue,11 electronic nose12. Additionally,

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major volatile compounds presenting different aging times for rice wines have been

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analyzed by gas chromatography-mass spectrometry (GC-MS).13 Zheng et al. studied 3



45

the key volatile aroma compounds changes in sweet Hongqu glutinous rice wine (a

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special type of rice wine) by headspace solid-phase microextraction (HS-SPME) and

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GC-Olfactometry (GC-O).14 However, the key aroma compounds, which are

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responsible for the aroma profile of aged rice wines, have not yet been clearly

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elucidated.

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It is well accepted that only a small subset of volatiles (key aroma compounds) is

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involved in aroma perception in food.15 Combining gas chromatography and

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human“sniffing” detection, the birth of GC-O provides a powerful tool for screening

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aroma odorants from the bulk of sensorially inactive volatiles in food and alcoholic

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beverages.16-18 Commercial Huadiao Chinese rice wine and Sweet-type Chinese rice

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wine have been submitted to GC-O and GC-MS analyses in our previous study, and

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more than 70 aroma compounds has been identified.2, 19 By repeated GC-O analysis of

57

serially diluted aroma distillates, aroma extract dilution analysis (AEDA) is one of the

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most frequently used methods for the screening of potentially important aroma

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compounds in food.20 Combined with the calculation of odor activity values (OAVs),

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aroma recombination and omission tests, this systematic study method (also called a

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sensomics approach) is an efficient approach for decoding the chemical odor codes of

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a given food.15, 21-23 AEDA has also been widely used to analyze the potential key

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aroma compounds present in many aged alcoholic beverages, including Madeira

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wine,24 sherry wine,25 rum,26 and sake.27 Through application of AEDA, Chen et al.

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identified sotolon as the potentially key contributor to the caramel-like descriptor of in

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commercial sweet-type rice wine.2 However, this method has not yet been applied to

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determine the aromatic composition of young and aged rice wines.

68 69

Therefore, the main objectives of the study were (1) to clearly explain the difference in odor compositions between young and aged rice wines using 4


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comparative AEDA; (2) to assess the contribution of aroma compounds to young and

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aged rice wines through further quantifying of odor compounds in multiple

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quantitative methods and the calculation of OAVs; and (3) to verify the key aroma

73

compounds of aged rice wine via aroma recombination and an omission test. On the

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basis of these results, the study may improve our understanding of the essence of the

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aroma difference between young and aged rice wines and can provide a substantial

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basis for further research into the control of flavor during the aging process for rice

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wine.

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MATERIALS AND METHODS

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Materials. Thirty-four samples of rice wine with ages between 0 and 15 years (4-6

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batches of each year) were used in this study. All samples were manufactured by

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Guyuelongshan Chinese Rice Wine Co. Ltd. (Shaoxing, Zhejiang Province, China)

83

following the standard traditional Chinese rice wine making procedures and matured

84

in pottery jar (except 0 years old samples). Each batch of rice wines were sampled,

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sealed in sample vials and kept at −20 °C until analysis. The profiles of rice wine

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samples were showed in Table 1. One batch of 0 years old (young, 17.0% v/v) and

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one batch of 15 years old (aged, 15.7% v/v) rice wine samples were used for sensory

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and GC-O analysis. The representative of these samples were confirmed by sensory

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evaluation with a sensory panel composed of seven nationally certified Chinese rice

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wine tasters.

91

Reagents and Chemicals. Chemical standards and all internal standards (Is) were

92

supplied commercially with high-purity grade (GC grade). Among them, ethyl acetate

93

(≥99.5%), 1,1-diethoxyethane (≥98%), 3-methylbutanal (97%), ethyl 2-

94

methylpropanoate (99%), 2,3-butanedione (97%), ethyl 3-methylbutanoate (98.0%), 5



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2-methylpropanol (99.5%), 3-methylbutyl acetate (≥99%), 3-methylbutanol (99%),

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ethyl hexanoate (≥99%), 1-octen-3-one (≥99.0%), 3-hydroxy-2-butanone (≥97%),

97

ethyl lactate (99%), dimethyl trisulfide (≥98%), ethyl octanoate (≥99%), acetic acid

98

(≥99.7%), methional, furfural (≥99%), benzaldehyde (≥99%), 2-methylpropanoic acid

99

(99%), phenylacetaldehyde (≥95%), butanoic acid (≥99%), 3-methylbutanoic acid

100

(99%), acetophenone (≥99.0%), ethyl 2-phenylacetate (≥98%), β-damascenone

101

(≥99%), guaiacol (98.0%), 2-phenylethyl acetate (≥99.0%), hexanoic acid (99%),

102

benzyl alcohol (≥99%), β-phenylethyl alcohol (≥99.0%), phenol (≥98%), 4-

103

ethylguaiacol (≥98%), octanoic acid (≥99%), γ-nonalactone (≥98%), ethyl cinnamate

104

(≥98%), 4-ethylphenol (≥99.0%), 4-vinylguaiacol(≥98%), sotolon (≥98%), vanillin

105

(≥99%), acetovanillone (≥98%), ethyl vanillate (≥98%), O-(2,3,4,5,6-

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pentafluorobenzyl) hydroxylamine hydrochloride (≥99.0%, PFBHA, derivatization

107

reagents), 2-octanol (≥99%, Is1), 4-(4-methoxyphenyl)-2-butanone (≥99%, Is2),

108

pentyl acetate (≥98%, Is3), menthol (99%, Is4) and p-fluorobenzaldehyde (98%, Is5)

109

were purchased from Sigma-Aldrich Co., Ltd. (Shanghai, China). Ethyl butanoate

110

(99%) was supplied by J&K Scientific Co., Ltd. (Beijing, China). Sodium chloride

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(NaCl), anhydrous sodium sulfate (Na2SO4), sodium bicarbonate (NaHCO3) and

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sulfuric acid (H2SO4) were purchased from China National Pharmaceutical Group

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Corp. (Shanghai, China). Ethanol (HPLC grade) was supplied by J&K Scientific Co.,

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Ltd. (Beijing, China). Dichloromethane (HPLC grade, ANPEL Scientific Instrument

115

Co., Ltd. China) was distilled prior to use. Pure water was obtained from a Milli-Q

116

purification system (Millipore, Bedford, MA, USA).

117

Sensory analysis. Aroma profiling was performed by trained panelists (10 males and

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14 females, 23 years old on average) from the Laboratory of Brewing Microbiology

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and Applied Enzymology at Jiangnan University, who were well trained according to 6


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the previous report.2, 28 These panelists showed a good ability in terms of aroma

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memory and score accuracy for each aroma descriptor after 3 months of trainings and

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tests. The rice wine samples were evaluated by the trained panelists. According to

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Chen et al,28 the assessors were asked to score 0 (not perceivable) to 3 (strongly

124

perceivable) for 7 aroma descriptions of rice wine through aroma intensity: alcoholic,

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caramel-like, fruity, smoky, Qu aroma (the extract for Qu aroma note), honey and

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herb. The rice wine samples (20 mL) were poured into a glass cup at 20 °C and

127

presented in a coded form, and the processed data were an average of the scores from

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all trained panelists.

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Comparative Aroma Extract Dilution Analysis of Young and Aged Rice Wines.

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Aroma Compound Isolation by Solid Phase Extraction (SPE). Young and aged rice

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wine sample were extracted according to the method described by Chen et al.28

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Briefly, a rice wine sample (100 mL) was diluted with a saturated NaCl solution at a

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1:1 ratio (by volume) in a 500-mL flask. One gram of LiChrolut-EN resin (Merck

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KGaA) and a magnetic stirrer bar were added to the flask. The sample was stirred for

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5 h on a magnetic stirrer (800 rpm) at room temperature. After extraction, the content

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was poured into an empty tube with a filter to recover the resins. The resins were

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washed with 30 mL of Milli-Q water and dried in a vacuum (−50 KPa, 20 min).

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Dichloromethane (30 mL) was used to elute the volatile fractions. The

139

dichloromethane eluent was washed with 3 × 3 mL of aqueous NaHCO3 (0.1 M). The

140

organic phase was dried with anhydrous Na2SO4 overnight and concentrated to 500

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μL, and this concentrate (labeled “neutral/basic fraction”) was stored at −20 °C prior

142

to GC-O analysis. The remaining aqueous fraction was adjusted to pH 2 with H2SO4

143

(1.0 M), saturated with NaCl, and extracted with dichloromethane (3 × 2 mL). All

144

extracts were combined and dried with anhydrous Na2SO4, and this fraction was 7



145

concentrated to 500 μL (labeled “acidic fraction”). These fractions were kept at

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−20 °C until GC-O analysis.

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Gas Chromatography−Mass Spectrometry (GC-MS). An Agilent 6890N gas

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chromatograph (Agilent Technologies, Folsom, CA, USA) with a 5975 mass selective

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detector (MSD) was employed. Both a DB-FFAP column (60 m × 0.25 mm i.d., 0.25

150

μm film thickness, Agilent Technologies Inc.) and a DB-5 column (30 m × 0.25 mm

151

i.d., 0.25 μm film thickness, Agilent Technologies Inc.) were used to analyze the

152

samples. Helium was used as the carrier gas at a rate of 2 mL/min. The initial oven

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temperature was 45 °C, held for 2 min, ramped to 230 °C at a rate of 5 °C/min, and

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held for 15 min at this final temperature. The sample (1 μL) was injected at 250 °C in

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splitless mode. The electron ionization (EI) mass spectra mode was used at 70 eV

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ionization energy. The time of solvent delay was 8 min, and the temperature of the ion

157

source was 230 °C. The mass range was set from 35 to 350 amu in full scan mode.

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Gas Chromatography−Olfactometry (GC-O). An Agilent 6890N gas

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chromatograph coupled to an olfactometer system (ODP 2, Gerstel, Mülheim, Ruhr,

160

Germany) was employed to analyze samples. Four panelists (two females and two

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males) from the Laboratory of Brewing Microbiology and Applied Enzymology at

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Jiangnan University were employed for the GC-O study. The panelists were trained

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for three months using at least 30 aroma reference compounds, and they were familiar

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with the sensory descriptors of each aroma compound. During a GC run, the panelist

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placed his/her nose close to the top of the sniffing port and recorded the retention

166

time, as well as the aroma descriptor.

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Comparative Aroma Extract Dilution Analysis (cAEDA). First, cAEDA was

168

applied to further analyze the contribution of all aroma compounds identified by GC-

169

O, and then the aroma differences between young and aged rice wines were 8


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compared. Aroma extracts were stepwise diluted with dichloromethane in a 1:1 ratio.

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AEDA was performed on the DB-FFAP column as previously described. The original

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distillate and each diluted sample were analyzed consecutively at least twice by every

173

panelist. The FD factor of each compound was defined as the maximum dilution at

174

which the aroma compound could be detected. Aroma compounds were identified by

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comparing the odors, mass spectra, and retention indices (RIs) with those authentic

176

standards. The RIs were calculated based on the linear retention times of the n-alkanes

177

(C5−C30) in both the DB-FFAP and DB-5 columns under the same chromatographic

178

conditions.

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Quantitative Analysis of Aroma Compounds. Liquid−Liquid Microextraction−GC-

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MS (LLME-GC-MS). Acids, phenols, and odorants with high polarity were quantitated

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by LLME-GC-MS. The sample (20 mL) was diluted with 20 mL of saturated NaCl

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solution. The mixture was spiked with two internal standards (Is1: 2-octanol, 100

183

mg/L, 80 μL; Is2: 4-(4-methoxyphenyl)-2-butanone, 100 mg/L, 40 μL) and

184

dichloromethane (5 mL), and then mixed with a vortex (500 rpm) for 5 min. The

185

organic phase was separated through a Pasteur pipette (SGCR-4-100-230-250.

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ANPEL Scientific Instrument Co., Ltd, Shanghai, China) and dried overnight by

187

adding anhydrous Na2SO4. Then, the extract was concentrated to 1 mL and stored at

188

−20 °C until analysis. Each sample was analyzed in triplicate. The GC-MS condition

189

was the same as GC-O analysis, as described previously on a DB-FFAP column (60

190

m × 0.25 mm i.d., 0.25 μm film thickness, Agilent Technologies Inc.). The standard

191

solution was prepared to construct a standard curve in the alcohol aqueous solution

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(15% water/ethanol solution, with 5.0 g/L lactic acid, pH 4.0). The extraction of each

193

standard solution was the same as described previously for the wine samples. The

9



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Agilent Chemstation software was used to construct the standard curve and calculate

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the concentrations of each compound in the samples.

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Headspace Solid−Phase Microextraction−GC-MS (HS-SPME-GC-MS). Most

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volatile alcohols, esters, and other minor compounds were quantitated by HS-SPME-

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GC-MS. Rice wine samples (3 mL) spiked with internal standards (Is1: 2-octanol, 100

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mg/L, 10 μL; Is3: pentyl acetate, 100 mg/L, 10 μL; Is4: menthol, 100 mg/L, 20 μL)

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were mixed with 6 mL of pure water and saturated with 3 g NaCl in a 20 mL screw-

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capped vial. An automatic headspace sampling system (MultiPurpose Sample MPS2

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with a SPME adapter, from Gerstel) with a 50/30 μm divinybenzene/carboxen/poly

203

(dimethylsiloxane) (DVB/CAR/PDMS) fiber (2 cm, Supelco, Inc., Bellefonte, PA,

204

U.S.A.) was provided for the extraction of volatile compounds. The sample was

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equilibrated at 50 °C for 5 min and extracted for 45 min at 50 °C under stirring (250

206

rpm). After extraction, the fiber was inserted into the GC injection port (250 °C) to

207

desorb volatile compounds for 5 min. Sample analysis was conducted in triplicate.

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The standard curve was developed to calculate the concentrations of volatile

209

compounds as described previously.

210

Derivatization combined with HS-SPME-GC-MS in selective ion monitoring

211

(SIM) mode. In this study, 1-octen-3-one and 2,3-butanedione were quantitated after

212

derivatization with PFBHA according to the method reported previously.29 Rice wine

213

samples (3 mL) were diluted with 6 mL of pure water. The diluted solution saturated

214

with NaCl (3 g) was spiked with an internal standard (Is5: p-fluorobenzaldehyde, 2.39

215

mg/L, 20 μL) and PFBHA solution (15 mg/mL in water, 500 μL) in a 20-mL screw-

216

capped vial. The GC condition was the same as the method of HS-SPME-GC-MS

217

described previously but in SIM mode. The ions m/z 279 and 140 were selected for

218

the quantitation of 1-octen-3-one and 2,3-butanedione, respectively. 10


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Aroma Recombination. The aged rice wine was deodorized by solid phase extraction

220

according to the method described previously for the extraction of aroma compounds.

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Aged wine samples (100 mL) with a magnetic stir bar and one gram of LiChrolut-EN

222

resins (Merck KGaA) were mixed in a 500-mL flask. The mixture was stirred for 5 h

223

on a magnetic stirrer (800 rpm) at room temperature. After extraction, an empty solid

224

phase extraction column was applied to filter the resins, and the deodorized rice wine

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was collected. The aroma compounds (31 odor compounds, OAVs ≥ 1) in aged rice

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wine were mixed at their actual concentrations (Table 3) in deodorized rice wine and

227

equilibrated for 10 min at room temperature. The reconstituted sample was subjected

228

to a sensory test by 24 trained panelists. The assessors were asked to score from 0 to 3

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(“0” is not perceivable, “3” is strongly perceivable) for 7 aroma descriptions in a

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recombination model and an aged rice wine through aroma intensity, as previously

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described in the sensory analysis. The similarity in the recombination model and aged

232

rice wine was analyzed by scoring from 0 (not similar) to 3 (very similar).

233

Omission Experiments. Five key aroma compounds were selected to reconstruct an

234

omission model, which has obvious aroma differences in OAVs between young and

235

aged rice wines. A triangle test was applied to test the significant differences in the

236

compounds. Three samples, including two reconstituted samples and one omission

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sample, were coded randomly in three digits for the triangle test. Panelists (24

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members) perceived the aroma of three samples and recorded the code of the sample

239

with significant differences compared to two other samples.

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Statistical analysis. Statistical analyses were performed using the SPSS version 15.0

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statistical package for Windows (SPSS Inc., Chicago, Illinois, USA). One-way

242

analysis of variance (ANOVA) test was applied to the data obtained from aroma

243

profiling analysis and omission experiments. 11



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RESULTS AND DISCUSSION

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Sensory Analysis of Rice Wine Samples. To determine the overall aroma profiles

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difference between young and aged rice wine, aroma profiling was performed by a

247

well-trained panelists. The results showed distinct differences in the young and aged

248

rice wine samples (Figure 1). The overall aroma intensity was higher in the aged rice

249

wine than in young samples. Statistical analysis showed that caramel-like, herb, fruity,

250

and smoky aroma attributes were significantly different (p < 0.05) in the two rice

251

wine samples. Among them, caramel-like, herb, and smoky aroma attribute intensities

252

were higher in aged rice wine, and fruity aroma attribute intensities were higher in

253

young rice wine. In addition, the overall aroma profile of the young rice wine was

254

relatively simple compared to aged rice wine, and this might be the reason for the

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higher intensity of fruity aroma attribute in young rice wine. To further analyze the

256

odorants responsible for the aroma differences of the two rice wines, cAEDA was

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applied to study the aroma differences in young and aged rice wines.

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Identification of Odor−Active Compounds in Young and Aged Rice Wines. The

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aroma extracts isolated by SPE revealed the typical aroma profiles of the original rice

260

wines when evaluated using filter paper. Subsequently, the aroma extracts of young

261

and aged rice wines were compared by AEDA. The flavor dilution chromatogram

262

obtained from AEDA in young and aged rice wines was shown in Figure 2. Greater

263

numbers of odorants (FD ≥ 64) were detected in aged rice wine (Table 2). A total of

264

33 odorants were detected with higher FD factors in the aged rice wine than in the

265

young rice wine. In contrast, only 9 odorants were detected with higher FD factors in

266

the young rice wine. Forty-three odorants were further identified based on comparison

267

of their RIs, odor characteristics, and mass spectra with reference substances. These

268

compounds included 11 esters, 2 lactones, 6 acid compounds, 2 sulfur-containing 12


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compounds, 5 aldehyde compounds, 5 ketones, 4 alcohols, and 8 phenols (Table 2).

270

Among these aroma compounds, the FD factors of 3-methylbutanal, ethyl 2-

271

methylpropanoate, benzaldehyde, butanoic acid, acetophenone, benzyl alcohol,

272

sotolon, vanillin, acetovanillone, and ethyl vanillate were 16−32 times higher in the

273

aged rice wine than in the young rice wine (Figure 2, Table 2). On the contrary, the

274

FD factors of 2-methylpropanoic acid, 4-vinylguaiacol, and methional were 8−16

275

times higher in the young rice wine than in the aged rice wine. These aroma

276

compounds might be explained by the FD factor, as the overall aroma showed

277

significant differences between young and aged rice wines. In aged rice wine, the

278

highest FD factor (≥ 1024) was obtained for 1,1-diethoxyethane (2; fruity), 3-

279

methylbutanal (3; malty), ethyl butanoate (6; sweet, fruity, pineapple), ethyl 3-

280

methylbutanoate (7; sweet, fruity), 1-octen-3-one (14; mushroom), butanoic acid (24;

281

acidic, cheese), 3-methylbutanoic acid (25; acidic, smelly), γ-nonalactone (37;

282

coconut), sotolon (41; caramel) and vanillin (42; sweet, vanilla). Therefore, these

283

aroma compounds might be the major contributors to the characteristic aroma of aged

284

rice wine.

285

Quantitation of Aroma Compounds and OAV Analysis. AEDA, as a screening

286

method, indicated the potential key odorants from rice wine with the bulk of odorless

287

volatiles. To confirm the aroma contributions of these odorants, the concentrations

288

were further quantitated for these aroma compounds. A total of 43 aroma compounds

289

in young or aged rice wine exhibiting high FD factors (≥ 64) were quantitated using

290

multiple quantitation approaches. The calibration curves, linearity ranges, and

291

recoveries of these methods were presented in Table S1. Quantitative results showed

292

that acetic acid, ethyl acetate, β-phenylethyl alcohol, 1,1-diethoxyethane and 3-

293

methylbutanol showed relatively high concentrations in both rice wines. The 13



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concentration of 1,1-diethoxyethane was quantitated in rice wine for the first time

295

herein. Lower concentrations were obtained for 1-octen-3-one, dimethyl trisulfide, β-

296

damascenone, and guaiacol, which were present in concentrations below 10 μg/L.

297

To evaluate the contributions of these odorants to the overall aroma in both rice

298

wines, OAV (the ratio of concentration to its odor threshold) was calculated based on

299

threshold data from the literature. As seen from Table 3, a total of 27 and 31 aroma

300

compounds with OAVs higher than 1 in young and aged rice wine, respectively.

301

Among them, 3-methylbutanoic acid (OAV 379), 1,1-diethoxyethane (OAV 134),

302

ethyl butanoate (OAV 70), vanillin (OAV 56), butanoic acid (OAV 51), 1-octen-3-

303

one (OAV 50), ethyl 3-methylbutanoate (OAV 47), ethyl 2-methylpropanoate (OAV

304

44), dimethyl trisulfide (OAV 28) 3-methylbutanal (OAV 26), and sotolon (OAV 23)

305

were presented with relatively high OAVs and might be important contributor to the

306

aroma of aged rice wine. However, 4-vinylguaiacol (OAV 68), methional (OAV 35),

307

1-octen-3-one (OAV 33), dimethyl trisulfide (OAV 18), and 1,1-diethoxyethane

308

(OAV 16) had the highest OAVs in the young rice wine. The quantitative results,

309

together with OAVs could supplement the results of AEDA. Among these aroma

310

compounds with relatively high OAVs, the concentrations of 3-methylbutanoic acid,

311

1,1-diethoxyethane, ethyl butanoate, vanillin, butanoic acid, 3-methylbutanal, sotolon,

312

3-methylbutyl acetate, hexanoic acid, and benzaldehyde were 5-56 times higher in the

313

aged rice wine than in the young rice wine. However, in young rice wine, only 4-

314

vinylguaiacol, methional, and 2,3-butanedione were quantitated with concentrations

315

over 5 times higher than in the aged rice wine. These aroma compounds might be to

316

explain the aroma differences between young and aged rice wines.

317

Changes in the Concentrations of Aroma Compounds in Rice Wine during

318

Aging. To conform the changes of aroma compounds during rice wine aging, a total 14


Page 15 of 37


319

of 34 rice wine samples with ages from 0-15 years were further quantitated (the detail

320

data was showed in Table S2). Figure 3 showed the changes of some aroma

321

compounds which OAVs were significant different between young and aged rice wine

322

in above study. Figure 3A showed the concentrations of vanillin and 4-vinylguaiacol,

323

which clearly increased and decreased during aging, respectively. 4-Vinylguaiacol

324

was mostly produced from the decarboxylation of ferulic acid in rice wine

325

fermentation.30 Young rice wine usually contain relatively high concentration of 4-

326

vinylguaiacol.30, 31 The conversion of 4-vinylguaiacol into vanillin was reported

327

during beer aging.32 The increase of vanillin during rice wine aging indicated that 4-

328

vinylguaiacol might be the precursor of vanillin in rice wine. Figure 3B showed the

329

concentrations of aldehydes and acetal, such as 3-methylbutanal, benzaldehyde, and

330

1,1-diethoxyethane, all of which increased clearly during rice wine aging. 1,1-

331

Diethoxyethane could be formed via the reaction of ethanol and acetaldehyde,33 and

332

was regarded as aging marker in different alcoholic beverages, such as sherry wine,34

333

Chinese baijiu.35 In this study, the concentration of 1,1-diethoxyethane tended to

334

increase during aging, which suggested that 1,1-diethoxyethane might be an aging

335

marker for rice wine. Figure 3C showed the concentration of methional and 2,3-

336

butanedione. They tended to decrease during the aging. Methional was quantitated

337

with the second highest OAV in young rice wine (17.6 μg/L, OAV 35) in the young

338

rice wine sample. But its concentration decreased below 1 μg/L in 10 and 15 years old

339

rice wine samples. It was suggested that dimethyl disulfide was formed from

340

methional during the storage of beer.36 However, the concentration of dimethyl

341

disulfide was relatively constant during rice wine aging in this study (Table S2).

342

Figure 3D showed the concentration of sotolon clearly increased with the aging time.

343

Sotolon was confirmed as a key aroma compound in aged Japanese sake,37 Madeira 15



Page 16 of 37

344

wine,38 and Port wine.39 The formation of sotolon by aldol condensation between

345

acetaldehyde and 2-ketobutyric acid during aging was well-studied in wines and

346

sake.37, 40 And its formation was closely related with aging time, temperature, and

347

oxygen.41 Figure 3E showed the concentrations of organic acids, such as 3-

348

methylbutanoic acid, butanoic acid, and hexanoic acid. The concentration of 3-

349

methylbutanoic acid was tended to increase with the aging period. However, the

350

concentrations of butanoic acid and hexanoic acid varied between different aging

351

years.

352

Aroma Simulation and Omission of Aged Rice wine. Compared to young rice wine,

353

the flavor of aged rice wine was more abundant. To verify the aroma contributions of

354

aromatic compounds with OAV ≥ 1 to the aged rice wine, an aroma recombination

355

study was performed by trained panelists, as described previously. The intensities of

356

seven aroma descriptors for the recombined wine and authentic aged rice wine were

357

scored very similar by 24 trained panelists, and the data was presented in the spider

358

web diagram (Figure 4). The panelists rated 2.7 for the overall aroma similarities of

359

the recombined model wine compared with the aged rice wine, indicating that the

360

odor of aged rice wine was successfully simulated by the recombination model.

361

A triangle test was performed to test the aroma contributions of five key aroma

362

compounds to aged rice wine, including 1,1-diethoxyethane, vanillin, 3-

363

methylbutanal, sotolon and benzaldehyde, and these aroma compounds with higher

364

OAVs in aged rice wine had obvious differences in OAVs between the wines. The

365

results (Table 4) showed that 20 of 24 panelists could recognize the omission model

366

lacking sotolon, which showed very highly significant differences (p ≤ 0.001)

367

compared with the complete recombination, pinpointing that the caramel aroma

368

played a key role in the overall aroma of aged rice wines. In addition, the omission 16


Page 17 of 37


369

models lacking vanillin, 3-methylbutanal and benzaldehyde showed significant

370

differences compared with the complete sample (p ≤ 0.001). However, no siginificant

371

difference was found when 1,1-diethoxyethane was missed in the recombination

372

model. 1,1-Diethoxyethane was described as fruity note by GC-O analysis. However,

373

there were a number of aroma compounds (ethyl butanoate, ethyl 3-methylbutanoate,

374

ethyl 2-methylpropanoate, etc.) in rice wine with high OAV values showed fruity

375

note. This could be a reason why 1,1-diethoxyethane didn’t show significant

376

differences by Omission test. Consequently, sotolon, vanillin, 3-methylbutanal and

377

benzaldehyde could be regarded as the key aroma compounds in aged rice wine,

378

which might play indispensable roles in the overall aroma profiles during the aging of

379

rice wine.

380 381

ABBREVIATIONS AND NOMENCLATURE

382

cAEDA – comparative aroma extract dilution analysis

383

GC−MS – gas chromatography−mass spectrometry

384

OAV – odor activity value

385

GC-O – gas chromatography-olfactometry

386

FD – flavor dilution

387

SPE – solid phase extraction

388

RI – retention index

389

LLME – liquid−liquid microextraction

390

HS-SPME – headspace solid−phase microextraction

391 392

ACKNOWLEDGMENTS

393

Funding 17



Page 18 of 37

394

The authors gratefully acknowledge the National Natural Science Foundation of

395

China (NO. 21506074, 31530055), National Key R&D Program of China (NO.

396

2018YFC1604100), Project funded by China Postdoctoral Science Foundation (NO.

397

2018M631971), the Jiangsu Province “Collaborative Innovation Center for Advanced

398

Industrial Fermentation” industry development program and 111 Program of

399

Introducing Talents for their financial supports (NO.111-2-06), Key Laboratory of

400

Wuliangye-flavor Liquor Solid-state Fermentation, China National Light Industry

401

(NO. 2017JJ18).

402

Notes

403

The authors declare no competitive financial interest.

18


Page 19 of 37


404

REFERENCES

405

1.

406

biotechnology. In Biotechnology in china, Springer: 2009; pp 189-233.

407

2.

408

type Chinese rice wine by aroma extract dilution analysis with special emphasis on

409

sotolon. J. Agric. Food Chem. 2013, 61, 9712-9718.

410

3.

411

1996.

412

4.

413

compounds in Chinese rice wines by headspace solid phase microextraction followed

414

by gas chromatography-mass spectrometry. J. Inst. Brew. 2008, 114, 172-179.

415

5.

416

storage of yellow rice wine by high-capacity stainless steel tanks. Liquor-Making Sci.

417

Technol. 2014, 239, 67-70.

418

6.

419

gas chromatography–olfactometry and gas chromatography–mass spectrometry. Acs

420

Symposium 2012, 1104, 277-301.

421

7.

422

Liquor-Making Sci. Technol. 1999, 93, 66-67.

423

8.

424

blended Chinese rice wine ages based on near-infrared spectroscopy. Int. J. Food

425

Prop. 2012, 15, 1262-1275.

Xu, Y.; Wang, D.; Fan, W. L.; Mu, X. Q.; Chen, J., Traditional chinese

Chen, S.; Wang, D.; Xu, Y., Characterization of odor-active compounds in sweet-

Zhou, J., Chinese rice wine brewing process. China Light Industry Press: Beijing,

Luo, T.; Fan, W. L.; Xu, Y., Characterization of volatile and semi-volatile

Fan, W. G.; Zhang, Y. M.; Qiao, X. J.; Niu, J. B.; Pang, X. G., Research on the

Fan, W. L.; Xu, Y., Characteristic aroma compounds of Chinese dry rice wine by

Wang, Y. X., Elementary introduction of store maturity of yellow rice wine

Shen, F.; Ying, Y. B.; Li, B. B.; Zheng, Y. F.; Liu, X. Q., Discrimination of

19



Page 20 of 37

426

9.

Xu, R. N.; Bao, Z. D.; Pan, X. X.; Hu, P. X., Maturization of Chinese rice wine.

427

Liquor Making 2003, 30, 50-52.

428

10. Shen, F.; Niu, X. Y.; Yang, D. T.; Ying, Y. Y.; Li, B. B.; Zhu, G. Q.; Wu, J. A.,

429

Determination of amino acids in Chinese rice wine by Fourier transform near-infrared

430

spectroscopy. J. Agric. Food Chem. 2010, 58, 9809-9816.

431

11. Ouyang, Q.; Zhao, J. W.; Chen, Q. S., Classification of rice wine according to

432

different marked ages using a portable multi-electrode electronic tongue coupled with

433

multivariate analysis. Food Res. Technol. 2013, 51, 633-640.

434

12. Yu, H. Y.; Dai, X.; Yao, G. Y.; Xiao, Z. B., Application of gas chromatography-

435

based electronic nose for classification of Chinese rice wine by wine age. Food Anal.

436

Method. 2013, 7, 1489-1497.

437

13. Wang, L.; Zeng, Q. M., Comprasion of aroma component in Chinese rice wine of

438

different vintages. J. Anhui Agric. Sci. 2016, 44, 93-96.

439

14. Zheng, C. Y.; Gong, L. T.; Huang, Z. Q.; Liu, Z. B.; Zhang, W.; Ni, L., Analysis

440

of key volatile aroma compounds in sweet Hongqu glutious rice wine. J. Chinese Inst.

441

Food Sci. Technol. 2014, 14, 209-217.

442

15. Dunkel, A.; Steinhaus, M.; Kotthoff, M.; Nowak, B.; Krautwurst, D.; Schieberle,

443

P.; Hofmann, T., Nature's chemical signatures in human olfaction: a foodborne

444

perspective for future biotechnology. Angew. Chem., Int. Ed. 2014, 53, 7124-7143.

445

16. Acree, T. E., GC/olfactometry. Anal. Chem. 1997, 69, 170A.

446

17. Plutowska, B.; Wardencki, W., Application of gas chromatography–olfactometry

447

(GC–O) in analysis and quality assessment of alcoholic beverages – A review. Food 20


Page 21 of 37


448

Chem. 2008, 107, 449-463.

449

18. d’Acampora Zellner, B.; Dugo, P.; Dugo, G.; Mondello, L., Gas

450

chromatography–olfactometry in food flavour analysis. J. Chromatogr. A 2008, 1186,

451

123-143.

452

19. Chen, S.; Xu, Y.; Qian, M. C., Aroma Characterization of Chinese Rice Wine by

453

Gas Chromatography-Olfactometry, Chemical Quantitative Analysis, and Aroma

454

Reconstitution. J. Agric. Food Chem. 2013, 61, 11295-11302.

455

20. Grosch, W., Detection of potent odorants in foods by aroma extract dilution

456

analysis. Trends Food Sci. Technol 1993, 4, 68-73.

457

21. Frauendorfer, F.; Schieberle, P., Identification of the key aroma compounds in

458

cocoa powder based on molecular sensory correlations. J. Agric. Food Chem. 2006,

459

54, 5521-5529.

460

22. Langos, D.; Granvogl, M.; Schieberle, P., Characterization of the key aroma

461

compounds in two Bavarian wheat beers by means of the sensomics approach. J.

462

Agric. Food Chem. 2013, 61, 11303-11311.

463

23. Hofmann, T.; Krautwurst, D.; Schieberle, P., Current status and future

464

perspectives in flavor research: highlights of the 11th Wartburg symposium on flavor

465

chemistry & biology. J. Agric. Food Chem. 2018, 66, 2197-2203.

466

24. Silva, H. O.; de Pinho, P. G.; Machado, B. P.; Hogg, T.; Marques, J. C.; Camara,

467

J. S.; Albuquerque, F.; Ferreira, A. C. S., Impact of forced-aging process on Madeira

468

wine flavor. J. Agric. Food Chem. 2008, 56, 11989-11996.

469

25. Zea, L.; Moyano, L.; Medina, M., Changes in aroma profile of sherry wines 21



Page 22 of 37

470

during the oxidative ageing. Int. J. Food Sci. Technol. 2010, 45, 2425-2432.

471

26. Pino, J. A.; Tolle, S.; Gok, R.; Winterhalter, P., Characterisation of odour-active

472

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

473

27. Isogai, A.; Utsunomiya, H.; Kanda, R.; Iwata, H., Changes in the aroma

474

compounds of sake during aging. J. Agric. Food Chem. 2005, 53, 4118-4123.

475

28. Chen, S.; Xu, Y.; Qian, M., Aroma Characterization of Chinese Rice Wine by

476

Gas Chromatography-Olfactometry, Chemical Quantitative Analysis, and Aroma

477

Reconstitution. J. Agric. Food Chem. 2013, 61, 11295-11302.

478

29. Ma, Y.; Tang, K.; Xu, Y.; Li, J. M., Characterization of the key aroma

479

compounds in Chinese Vidal icewine by gas chromatography-olfactometry,

480

quantitative measurements, aroma recombination, and omission tests. J. Agric. Food

481

Chem. 2017, 65, 394-401.

482

30. Mo, X. L.; Xu, Y., Ferulic acid release and 4-vinylguaiacol formation during

483

Chinese rice wine brewing and fermentation. J. Inst. Brew. 2010, 116, 304-311.

484

31. Chen, S.; Xu, Y., Effect of 'wheat Qu' on the fermentation processes and volatile

485

flavour-active compounds of Chinese rice wine (Huangjiu). J. Inst. Brew. 2013, 119,

486

71-77.

487

32. Vanbeneden, N.; Saison, D.; Delvaux, F.; Delvaux, F. R., Decrease of 4-

488

vinylguaiacol during beer aging and formation of apocynol and vanillin in beer. J.

489

Agric. Food Chem. 2008, 56, 11983-11988.

490

33. Capeletti, M. R.; Balzano, L.; de la Puente, G.; Laborde, M.; Sedran, U.,

491

Synthesis of acetal (1,1-diethoxyethane) from ethanol and acetaldehyde over acidic 22


Page 23 of 37


492

catalysts. Appl. Catal. A-Gen. 2000, 198, L1-L4.

493

34. Moreno, J. A.; Zea, L.; Moyano, L.; Medina, M., Aroma compounds as markers

494

of the changes in sherry wines subjected to biological ageing. Food Control 2005, 16,

495

333-338.

496

35. Zhu, M. X.; Fan, W. L.; Xu, Y.; Zhou, Q. Y., 1,1-Diethoxymethane and

497

methanethiol as age markers in Chinese roasted-sesame-like aroma and flavour type

498

liquor. Eur. Food Res. Technol. 2016, 242, 1985-1992.

499

36. Gijs, L.; Perpète, P.; Timmermans, A.; Collin, S., 3-Methylthiopropionaldehyde

500

as precursor of dimethyl trisulfide in aged beers. J. Agric. Food Chem. 2000, 48,

501

6196-6199.

502

37. Takahashi, K.; Tadenuma, M.; Sato, S., 3-hydroxy-4,5-dimethyl-2(5H)-furanone,

503

a burnt flavoring compound from aged sake. Agric. Biol. Chem. 1976, 40, 325-330.

504

38. Câmara, J. S.; Marques, J. C.; Alves, M. A.; Silva Ferreira, A. C., 3-Hydroxy-4,

505

5-dimethyl-2 (5 H)-furanone levels in fortified Madeira wines: Relationship to sugar

506

content. J. Agric. Food Chem. 2004, 52, 6765-6769.

507

39. Ferreira, A. C. S.; Barbe, J. C.; Bertrand, A., 3-Hydroxy-4,5-dimethyl-2(5H)-

508

furanone: a key odorant of the typical aroma of oxidative aged Port wine. J. Agric.

509

Food Chem. 2003, 51, 4356-4363.

510

40. Pons, A.; Lavigne, V.; Landais, Y.; Darriet, P.; Dubourdieu, D., Identification of

511

a sotolon pathway in dry white wines. J. Agric. Food Chem. 2010, 58, 7273-7279.

512

41. Martins, R. C.; Monforte, A. R.; Ferreira, A. S., Port wine oxidation

513

management: a multiparametric kinetic approach. J. Agric. Food Chem. 2013, 61, 23



Page 24 of 37

514

5371-5379.

515

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

516

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

517

1667.

518

43. Peinado, R. A.; Moreno, J.; Bueno, J. E.; Moreno, J. A.; Mauricio, J. C.,

519

Comparative study of aromatic compounds in two young white wines subjected to

520

pre-fermentative cryomaceration. Food Chem. 2004, 84, 585-590.

521

44. Guth, H., Quantitation and sensory studies of character impact odorants of

522

different white wine varieties. J. Agric. Food Chem. 1997, 45, 3027-3032.

523

45. Jin, B.; Wang, D.; Xu, Y.; Zhao, G., Study on olfactory thresholds for several

524

aroma components in Chinese rice wine. Sci. Technol. Food Ind. 2012, 33, 35-138.

525

46. La Guerche, S.; Dauphin, B.; Pons, M.; Blancard, D.; Darriet, P., Characterization

526

of some mushroom and earthy off-odors microbially induced by the development of

527

rot on grapes. J. Agric. Food Chem. 2006, 54, 9193-9200.

528

47. Campo, E.; Ferreira, V.; Escudero, A.; Marques, J. C.; Cacho, J., Quantitative gas

529

chromatography-olfactometry and chemical quantitative study of the aroma of four

530

Madeira wines. Anal. Chim. Acta 2006, 563, 180-187.

531

48. Etievant, P., Volatile compounds in food and beverages. In Dekker: New York,

532

NY, USA: 1991.

533

49. Nakamura, S.; Crowell, E.; Ough, C.; Totsuka, A., Quantitative analysis of γ‐

534

nonalactone in wines and its threshold determination. J. Food Sci 1988, 53, 1243-

535

1244. 24


Page 25 of 37


536

50. Silva Ferreira, A. C.; Guedes de Pinho, P.; Rodrigues, P.; Hogg, T., Kinetics of

537

oxidative degradation of white wines and how they are affected by selected

538

technological parameters. J. Agric. Food Chem. 2002, 50, 5919-5924.

539

51. Pino, J. A.; Queris, O., Analysis of volatile compounds of mango wine. Food

540

Chem. 2011, 125, 1141-1146.

541

52. Escudero, A.; Hernandez-Orte, P.; Cacho, J.; Ferreira, V., Clues about the role of

542

methional as character impact odorant of some oxidized wines. J. Agric. Food Chem.

543

2000, 48, 4268-4272.

544 545

25



Page 26 of 37

546

Figure captions:

547

Figure 1. Aroma profiles of young and aged rice wine. The scores of selected

548

descriptors were evaluated by 24 panelists on average. Significance was indicated at *p

549

< 0.05, and **p < 0.01.

550

Figure 2. Comparison of the flavor factor (FD) for the most important aroma

551

compounds in young and aged rice wine. Aroma compounds with big changes in the

552

FD values between young and aged rice wine were labeled, corresponding to the

553

compounds listed in Table 2.

554

Figure 3. Changes in the concentrations of some aroma compounds during rice wine

555

aging.

556

Figure 4. Aroma profiles of aged rice wine and aroma-reconstituted models

557

containing aroma compounds with OAVs ≥ 1.

26


Page 27 of 37


Table 1. Profiles of Chinese Rice Wine Samples. production

ages

alcohol in average

pH in

year

(years)

(%, v/v)

average

2015

0

4

17.2 ± 0.3

4.2 ± 0.2

2014

1

5

17.0 ± 0.5

4.4 ± 0.3

2013

2

6

16.6 ± 0.2

4.3 ± 0.1

2012

3

4

15.6 ± 0.4

4.2 ± 0.2

2010

5

5

16.1 ± 0.6

4.1 ± 0.4

2005

10

5

15.7 ± 0.5

4.3 ± 0.5

2000

15

5

15.5 ± 0.4

4.1 ± 0.2

batch

27



Page 28 of 37

Table 2. Key Aroma Compounds (FD ≥ 64) in Young and Aged Rice Wines RI a

FD factor c

no.

compounds FFAP

DB-5

1

920

605

ethyl acetate

2

926

742

3

931

4

odor

descriptors b

identification young

aged

solvent, fruity

256

512

MS, RI, odor, Stdd

1,1-diethoxyethane

fruity

256

1024

MS, RI, odor, Std

nd e

3-methylbutanal

malty

64

1024

MS, RI, odor, Std

942

768

ethyl 2-methylpropanoate

floral, fruity

32

512

MS, RI, odor, Std

5

971

nd

2,3-butanedione

buttery

2048

512

MS, RI, odor, Std

6

1035

800

ethyl butanoate

sweet, pineapple, fruity

128

1024

MS, RI, odor, Std

7

1076

849

ethyl 3-methylbutanoate

sweet, fruity

128

1024

MS, RI, odor, Std

8

1090

nd

2methylpropanol

nail polish

128

32

MS, RI, odor, Std

9

1132

860

3-methylbutyl acetate

sweet, banana

64

512

MS, RI, odor, Std

10

1157

nd

unknown

phenolic, medicinal

nd

128

11

1221

791

3-methylbutanol

alcoholic, nail polish

256

64

MS, RI, odor, Std

12

1244

980

ethyl hexanoate

fruity, sweet

128

128

MS, RI, odor, Std

13

1276

755

3-hydroxy-2-butanone

buttery

128

256

MS, RI, odor, Std

14

1305

nd

1-octen-3-one

mushroom

1024

2048

MS, RI, odor, Std

15

1357

812

ethyl lactate

fruity

64

64

MS, RI, odor, Std

16

1388

nd

dimethyl trisulfide

cabbage

32

256

MS, RI, odor, Std

17

1431

1189

ethyl octanoate

fruity

256

64

MS, RI, odor, Std

18

1455

nd

acetic acid

vinegar

128

256

MS, RI, odor, Std

19

1463

nd

methional

pungent, potato

512

32

MS, RI, odor, Std

20

1482

825

furfural

almond, burnt sugar

16

64

MS, RI, odor, Std

21

1543

957

benzaldehyde

almond

16

512

MS, RI, odor, Std

22

1559

nd

2-methylpropanoic acid

acidic

128

16

MS, RI, odor, Std

23

1608

1054

phenylacetaldehyde

floral, rose

256

512

MS, RI, odor, Std

24

1631

834

butanoic acid

acidic, cheese

64

1024

MS, RI, odor, Std

25

1688

900

3-methylbutanoic acid

acidic, smelly

1024

4096

MS, RI, odor, Std

26

1717

nd

acetophenone

floral

8

128

MS, RI, odor, Std 28


Page 29 of 37


27

1777

1265

ethyl 2-phenylacetate

rosy, honey

32

128

MS, RI, Odor, Std

28

1822

nd

β-damascenone

floral

64

16

MS, RI, Odor, Std

29

1832

1102

guaiacol

spicy, clove

128

64

MS, RI, Odor, Std

30

1847

1300

2-phenylethyl acetate

rose, floral

64

512

MS, RI, Odor, Std

31

1888

988

hexanoic acid

cheese, acidic

16

128

MS, RI, Odor, Std

32

1908

1031

benzyl alcohol

floral

16

256

MS, RI, Odor, Std

33

1949

1114

β-phenylethyl alcohol

floral, rose

256

256

MS, RI, Odor, Std

34

2014

1008

phenol

phenolic, medicinal

128

256

MS, RI, Odor, Std

35

2026

1297

4-ethylguaiacol

smoky

8

64

MS, RI, Odor, Std

36

2064

1004

octanoic acid

sweat, cheese

64

128

MS, RI, Odor, Std

37

2071

1376

γ-nonalactone

coconut

256

1024

MS, RI, Odor, Std

38

2140

1470

ethyl cinnamate

cinnamon

16

128

MS, RI, Odor, Std

39

2193

1190

4-ethylphenol

smoky

32

64

MS, RI, Odor, Std

40

2206

1333

4-vinylguaiacol

spicy, clove

1024

128

MS, RI, Odor, Std

41

2227

1101

sotolon

caramel

64

1024

MS, RI, Odor, Std

42

2606

1399

vanillin

sweet, vanilla

32

1024

MS, RI, Odor, Std

43

2686

nd

acetovanillone

vanilla

4

128

MS, RI, Odor, Std

44

2713

nd

unknown

caramel

4

128

45

2818

nd

ethyl vanillate

vanilla

8

128

a Retention

MS, RI, Odor, Std

indexes (RIs) of volatile compounds for polar and nonpolar columns. b Odor

descriptors were sniffed during GC-O at the sniffing port. c FD (flavor dilution) was defined as the maximum dilute degree of perception for the flavor in young and aged rice wine by SPE-GC-O-AEDA. d Identification of aroma compound was based on comparison of its odor description (Odor), retention indices (RI) on capillaries DB-FFAP and DB-5 as well as mass spectra (MS) with data of authentic standard compounds (Std). e Compound was not detected in the corresponding column. Table only shows aroma compounds with FD ≥ 64 in young or aged rice wine. 29



Page 30 of 37

Table 3. Odor Thresholds,a Quantitative Data,b and OAVsc of Major Aroma Compounds (OAV

≥ 1) in Young and Aged Rice Wines. RI

compound

odor threshold

concentration (μg/L)

OAV

(μg/L)

young

aged

young

aged

1688

3-methylbutanoic acid

33.442

337 ± 34

12600 ± 270

10

379

926

1,1-diethoxyethane

100043

15800 ± 576

134000 ± 2100

16

134

1035

ethyl butanoate

2044

47.0 ± 1.4

1400 ± 75

2

70

2606

vanillin

2645

33.4 ± 0.1

1460 ± 45

1

56

1631

butanoic acid

17342

686 ± 40

8860 ± 83

4

51

1305

1-octen-3-one

0.0346

1.00 ± 0.03

1.50±0.02

33

50

1076

ethyl 3-methylbutanoate

344

28.9 ± 0.2

142 ± 4.0

10

47

942

ethyl 2-methylpropanoate

1542

143 ± 1

660 ± 17

10

44

1388

dimethyl trisulfide

0.1827

3.32 ± 0.06

5.11 ± 0.02

18

28

931

3-methylbutanal

12027

139 ± 12

3090 ± 190

1

26

2227

sotolon

947

27.9 ± 1.2

207 ± 2.0

3

23

1132

3-methylbutyl acetate

3044

10.3 ± 0.2

437 ± 8.0

Characterization of the Key Aroma Compounds in Aged Chinese Rice

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