Upload
others
View
1
Download
0
Embed Size (px)
Citation preview
Food Science and Technology Research, 20 (2), 283_293, 2014Copyright © 2014, Japanese Society for Food Science and Technologydoi: 10.3136/fstr.20.283
http://www.jsfst.or.jp
*To whom correspondence should be addressed. E-mail: [email protected]
IntroductionThe manufacturing procedures of spirits in the world such as
whisky, brandy, rum, vodka, cachaça, and Chinese spirits are constituted of three consecutive processes: fermentation, distillation and ageing. For these processes, distillation process is closely correlated with the quality and yield of the raw spirit. Alembic stills and column stills are applied to the distillation of brandy, whisky, and cachaça. The former has no trays or appreciable reflux and requires multiple distillation to achieve high-proof raw spirits, while the latter has a reflux column to decreases the concentration
of the congeners in raw spirits (Claus and Berglund, 2005). A distinct device called as Zeng-tong (Li et al., 2012) has been widely applied to the distillation of Chinese spirits for a long history. The Zeng-tong is composed of reboiler, taper barrel, condenser and other attachments, such as stream pipes, lid and tube type heat exchanger (shown in Figure 1A). Similar to fruit brandy (Claus and Berglund, 2005), the operation mode of Chinese spirits belongs to a batch distillation. The main production process of Chinese spirits is as follows (Figure 1B). Prior to the spirit distillation, the fresh grains and grain hull are mixed with the fermented grains to adjust
Short communication
Volatile Compounds of Raw Spirits from Different Distilling Stages of Luzhou-flavor Spirit
Jia Zheng1, Ru Liang
1, Jun Huang1, Rui-Ping Zhou
4, Zhe-Jun Chen4, Chong-De Wu
1, Rong-Qing Zhou1,2,3* and
Xue-Pin Liao1,2
1 Key Laboratory of Leather Chemistry and Engineering, Ministry of Education, and College of Light Industry, Textile & Food Engineering, Sichuan University, Chengdu 610065, China
2 National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University, Chengdu 610065, China3 National Engineering Research Center of Solid-State Brewing, Luzhou 646000, China4 Xufu distillery company, Yibin 644000, China
Received August 6, 2013 ; Accepted November 9, 2013
Distillation process is closely correlated with the quality and yield of the raw spirit. The volatile properties of raw spirits from three distilling stages (head, heart and tail) of Luzhou-flavor spirit were investigated based on GC and GC-MS analyses. A total of 71 compounds were identified and ester derivatives attributed the largest number and concentration of volatile compounds in three raw spirits. The total concentration of raw spirit was decreased from the head raw spirit (5105 mg/L) to the tail raw spirit (1843 mg/L). Many volatile compounds with high concentrations such as acetaldehyde, 1-hexanol, 2-methylbutanoic acid, hexanoic acid, and ethyl hexanoate were found to decrease during distillation. Odor active value (OAV) was used to evaluate the contribution of special compounds to the whole odor of the raw spirit. Ethyl hexanoate followed by ethyl butyrate, ethyl heptanoate, ethyl octanoate, and 3-methylbutanal were found to be the most potent odor-active compounds. The liquid-liquid extraction together with GC-MS and GC analyses could be a useful tool to characterize the volatile composition of different distilling cuts of Chinese spirit. The decreasing of total content of volatile compound was determined by the ester derivate because of its high volatility and content.
Keywords: volatile compound, raw spirit, distilling process, odor active value
J. Zheng et al.284
their titer acidity, moisture and bulk density. Then the mixture is gradually filled into the barrel with the vapor spilling out from the surface of layer and forms a specific packed bed column. The distilling process begins after the mixture fully fills the Zeng-tong. After the distillation completed, the distilled mixture is cooled and mixed with Daqu-starter for fermentation in the pit. At last the fermented grains are sequentially treated with the way described above. Therefore, the distillation process involves not only the condensing of alcohol and fractionating of the congeners, but also the gelatinization and liquification of starch in grains. The quality of raw spirit is generally controlled by dividing the distillates into several appropriate fractions or “cuts” (i.e discarding the head fraction, collecting the heart fraction and redistilling/discarding the tail fraction) (Scanavini et al., 2010). However, the aromatic stability and consistence of the raw spirit completely depend on the operator’s smell and taste. Till now, little information available concerning the effect of distillation process on the quality of raw spirit was reported.
Chinese spirits can be classified into several fragrance types including strong aroma (Luzhou-flavor), light aroma (Fen-flavor), sauce aroma (Maotai-flavor), sweet honey and miscellaneous type
according to their flavor characteristics and brewing technology. The volatile compositions of them have been previously studied, and more than seven hundreds components have been identified (Fan and Qian, 2006b; Zhu et al., 2007). Whereas, few attention was paid on the characteristics of volatile compounds in different distilling stages (head, heart and tail fraction). Furthermore, confirming the fingerprint of flavor compounds in these distillates may contribute to optimize the distillation process and increase the yield and distilling efficiency, and evaluate the influence of distillation process on the formation of harmful compounds. From the latest literatures, Rogelio et al. analyzed the role of batch rectification on the quality of Mexican tequila, and compared the copper and stainless steel alembics on the formation of volatile compounds (Rogelio et al., 2005). Bruno et al. investigated the influence of the configuration of the distilling system and procedure on the level of ethyl carbamate in cachaça (Bruno et al., 2007). Lukić et al. analyzed the change of concentrations of various volatile constitutions during the distillation process of fermented Muscat Blanc and Muškat ruža porečki grape marcs (Lukic et al., 2011). However, till now, little is known about the variation of the volatile compounds and their odor active values (OAV) in the
Fig. 1. (A) Diagram of the distillation system (Zeng-tong) for Luzhou-flavor spirit. (a): reboiler-equipped with a secondary stream distributor; (b): taper barrel-filled with fermented grains; (c): lid; (d): stream pipes; (e): tube type heat exchanger. (B) Brief manufacturing procedure of Chinese spirits.
Volatile Compounds of Luzhou-flavor Raw Spirits 285
distillation process of Luzhou-flavor spirit.The aim of this study was to investigate the volatile compounds
in raw spirits from three distilling stages, and analyze the influence of distillation on the quality of raw spirit. The OAV was used to evaluate the contribution of the volatile compounds to the whole odor.
Methods and MaterialsSamples and chemicals Ethyl acetate (99.9%), ethyl lactate
(99.0%), ethyl butyrate (99.5%), ethyl hexanoate (99.0%), ethyl palmitate (99.0%), ethyl linoeate (99.0%), ethyl phenylacetate (98.0%), ethyl oleate (98.0%), methyl caprylate (99.0%), phenethyl alcohol (99.0%), furfural (98.0%), benzenacetaldehyde (99.0%), 4-ethylphenol (97.0%), 4-ethyl-2-methoxylphenol (98.0%), acetic acid (99.5%), butanoic acid (99.0%), hexanoic acid (98.0%), caprylic acid (98.0%), methanol (99.8%) and acetaldehyde (99.5%) were all purchased from Sigma-Aldrich (St. Louis, MO, USA), and all standards used were of GC purity. Other reagents were of analytical purity.
A total of three raw spirits belong to three distilling stages in the same batch were collected from Xufu distillery Co., Ltd., which is one of the typical Luzhou-flavor spirit manufacturing company in China. The distilling stages and related raw spirits were as follows: (1) head stage: about 1.5 kg raw spirit is collected from the pipe of tube type heat exchanger (e, Fig. 1) at the beginning of distillation, and this spirit is named as “head spirit”; (2) heart stage: along with the distillation, the heart raw spirit is collect within 30 min with special operation parameters (the spirit temperature: more than 30℃, outflow of spirit: approximately 2.5 kg/min), and this part of spirit is named as “heart spirit”; (3) tail stage: when the collection of heart spirit completed, the operators usually increase the steam reaching the maximum level to gelatinize and liquify the starch in grains and this stage will cost 45 min to 1 h, and the spirit collected at this stage is named as “tail spirit”. Before the analyses, a total of 500 mL samples of each distilling stage were putted into reagent bottles with grinding stopper, sealed and stored at room temperature until analysis.
Extraction of volatile compounds The volatile compounds in raw spirits were extracted based on the liquid-liquid extraction (LLE) method reported previously (Qian and Reineccius, 2002) with some modifications. Briefly, 10 mL raw spirit was transferred into roundflask and internal standard (methyl caprylate and capryl-ic acid) was added. Prior to the extraction of volatile compounds, the concentration of ethanol in raw spirit was adjusted to approxi-mately 14% by distilled water. The mixture was saturated with NaCl and adjusted to pH 11 with 10% NaOH. Then 50 mL anhy-drous diethyl ether was added into the pretreated raw spirit mixture to extract volatile compounds. The organic phase was transferred into the clean glass tube and labeled as “neutral fraction”. The aqueous phase was adjusted to pH 1.7 with 2 M H2SO4 and extract-ed by 50 mL anhydrous diethyl ether, and the extracted organic
phase was labeled as “acidic fraction”. All fractions were dried with 5 g of anhydrous Na2SO4, and concentrated the filtrate to 0.5 mL under the soft nitrogen. Each raw spirit was extracted and tested in three duplicate.
GC-MS analysis The neutral and acidic fraction were ana-lyzed on a Trace GC Ultra gas chromatograph-DSQ ΙΙ mass spec-trometer (Thermo Electron Corporation, Waltham, MA, USA) equipped with a HP-5MS capillary column (30.0 m × 0.25 mm i.d., 0.25 μm film thickness, Agilent, Santa Clara, CA, USA), respec-tively. GC analyses were performed under the following condi-tions: an inlet temperature of 250℃, split ratio of 10:1, and Helium (purity: 99.999%) carrier gas flow of 1 mL/min. The oven tempera-ture was kept at 40℃ for 5 min, followed by an increase of 5℃ / min to 200℃, and then programmed to 220℃ at 10℃/min, and held for 5 min. For mass spectrometer, the temperatures of the transfer line, quadruple and ionization source were of 250℃, 150℃, and 230℃, respectively. The mass spectrum was generated in the electron impact (EI) mode at 70 eV. Detection was carried out in the full scan mode in the range of m/z 35 ~ 400.
Each volatile compound was identified by comparison of their mass spectrum with the NIST05 spectrum database. Kováts retention indices (RI) of each compound were calculated by using C8 ~ C20 n-alkanes (Sigma-Aldrich, St. Louis, MO, USA) (Cates and Meloan, 1963). The identification of each volatile compound was additionally confirmed by comparison of their RI with the RI reported in previous literatures (RIL). The relative concentration of volatile compound (mg/L) to the internal standards (methyl octanoate and octanoic acid) was semi-quantified on the basis of comparing their peak areas to that of the internal standard on GC total ion chromatograms.
GC analysis The specific low molecular volatile compounds (methanol and acetaldehyde) were quantified by GC analysis. Concentrations of methanol and acetaldehyde were analyzed using GC-FID (Agilent 6890A, Santa Clara, CA, USA) equipped with DB-WAX (30.0 m × 0.25 mm i.d., 0.25 μm film thickness, Agilent, Santa Clara, CA, USA). The GC analysis procedure was according to the procedure reported in Lukić et al. (2011).
Statistical analysis The content of volatile compound was expressed as mg/L. Analysis of variance (ANOVA) with Turkey’s test was performed to evaluate significant differences in volatile compounds from different distilling stages. Significance of difference was defined at p < 0.05 (n = 3). One-way ANOVA was conducted using SPSS software (version 17.0; SPSS Inc., Chicago, IL, USA).
Results and DiscussionAccuracy of quantitative analysis based on GC-MS The
accuracy and reliability of final analyses results are tightly correlated with the sample preparation procedure. In some previous literatures, numerous sample preparation methods, such as LLE, solid-phase microextraction (SPME) and stir bar sorptive extraction
J. Zheng et al.286
(SBSE), coupled with GC-MS were used to determine volatile compounds in Chinese spirits and wines (Hernandez-Gomez et al.; 2005, Sanchez-Palomo et al., 2009; Fan and Qian, 2006a). LLE represented a better applicability for sample preparation in previous experiments because all volatile compounds (low, medium and high volatility) can be analyzed in one or more extraction steps (Hernanz et al., 2008; Caldeira et al., 2007). Prior to GC-MS detection, the main volatile compounds determined in previous literature (Fan and Qian, 2006a) were used to validate the accuracy of the detection method in the present research. The peak area ratios (neutral fraction/methyl caprylate and acidic fraction/caprylic acid) were used for the quantification of each compound. As shown in Table 1, good linearity of calibration curve (r > 0.9) was obtained, and extraction recoveries were higher than 90% for all compounds tested. It was suggested that methyl caprylate and caprylic acid used as the internal standards was suitable to semi-quantitatively or quantitatively evaluate the relative level of volatile compounds in distillates from different distilling stages.
Volatile compositions of different raw spirits In this study, the volatile compounds from the head, heart and tail raw spirit were extracted by LLE method and then detected using GC-MS and GC analyses. Typical total ion chromatograms of neutral and acidic fraction in GC-MS system are displayed in Figure 2. Figure 3 represents the total concentration of the volatile compounds. It is clear that the total concentration of volatile compounds significantly decreased with the distillation ( p < 0.05). The highest concentration was detected in head raw spirit (5105 mg/L), which was 1.4- and 2.8-fold higher than that in the heart (3611 mg/L) and tail raw spirits (1843 mg/L), respectively. The levels of esters and other compounds were sharply decreased from the head to tail raw spirit, whereas high levels of acids, alcohols, aldehydes and ketones were observed in the heart raw spirit ( p < 0.05).
The compounds identified, quantified and grouped by their affiliation with different chemical classes are revealed in Table 2. A total of 71 compounds composed of 10 alcohols, 34 esters, 10 acids, 5 aldehydes, 4 ketones, 2 phenols, 3 hydrocarbon compounds and 3 oxygen-containing compounds were identified and quantified. The raw spirit exhibited the ethanol contents ranging from 44% in the tail spirit to 75% (v/v) in the head spirit. Besides the ethanol, esters which accounted for 14% _ 61% of the total concentration were the largest group among these volatiles. The most abundant compounds were methanol , 2-pentanol , 3-methylbutanol, 1-hexanol, propanoic acid, hexanoic acid, ethyl butyrate, ethyl pentanoate, ethyl hexanoate, ethyl heptanoate, ethyl octanoate, acetaldehyde, 3-methylbutanal, 1,1-diethoxyethane and 1,1-diethoxyl-3-methylbutane.
Esters: Esters, the most numerous volatiles, are formed mostly through the esterification of alcohols with fatty acids during the fermentation, thermal distillation and maturing processes (Fan and Qian, 2005). A total of 34 esters including 24 ethyl esters and 10 other esters were quantified with the total concentration ranging from 260 mg/L to 3133 mg/L (Table 2). Esters especially ethyl esters represented the largest group in the number and concentration of volatile compounds identified. This result was coincided with the previous study (Fan and Qian, 2006a) which also reported that ethyl ester was the main group in esters. Ethyl hexanoate was considered to be the dominant compound in Luzhou-flavor spirit (Xu et al., 2010). In this study, ethyl hexanoate accounting for 36.7 _ 70.0% of the total esters was the most important ethyl ester and its concentration obviously decreased during the distillation process (P < 0.05). Meanwhile, the concentration of most esters was also significantly decreased from the head to tail raw spirit (P < 0.05), such as ethyl butyrate, pentanoate, hexanoate, nonanoate, palmitate, oleate and butyl
Table 1. Characteristics of calibration curves.
Standard materiala Standard curve R2 Validation rage(mg/L)
Recovery(%)
Detection limit(LOD, μg/L)d
Ethyl butyrate y=0 .0309x + 0 .457b 0 . 9899 10 .96 _ 1096 97 .85 0 .03Ethyl lactate y=0 .093x + 0 .9671b 0 . 9772 5 .40 _ 540 96 .52 0 .04
Ethyl hexanoate y=1 .8196x + 10 .458b 0 . 9874 21 .8 _ 21850 98 .12 0 .01Ethyl phenylacetate y=0 .0286x + 1 .1054b 0 . 8521 1 .29 _ 129 99 .11 0 .02Ethyl hexadecanoate y=0 .0063x + 0 .3924b 0 . 9475 10 .75 _ 1075 90 .42 0 .03
Ethyl oleate y=0 .095x + 0 .9172b 0 . 8827 11 .00 _ 1100 91 .49 0 .01Ethyl phenylacetate y=0 .0711x + 1 .4449b 0 . 9457 5 .85 _ 580 99 .11 0 .01Phenylacetaldehyde y=0 .093x + 0 .9671b 0 . 9772 5 .40 _ 540 96 .52 0 .05
Butanoic acid y=0 .0789x + 0 .4133c 0 . 8791 12 .00 _ 1200 101 .45 0 .04Hexanoic acid y=_0 .001x + 0 .052c 0 . 9815 11 .62 _ 1162 106 .75 0 .03
a Standard materials were all purchased from Sigma-Aldrich (St. Louis, MO, USA), and five levels of concentration for each volatile compound, covering the concentration ranges expected, were tested in triplicate.b Standard curves were fitted with the ratio of volatile compound to methyl caprylate.c Standard curves were fitted with the ratio of volatile compound to caprylic acid.d Detection limit of each compounds was calculated under the condition of the standard signal/noise of base line = 3.
Volatile Compounds of Luzhou-flavor Raw Spirits 287
hexanoate. The similar pattern was also found in Muškat Ruža Porečki grape marcs and melon wine (Lukic et al., 2011; Hernandez-Gomez et al., 2005). Whereas ethyl lactate significantly decreased during the distilling process. It is possible that high flow
rate of vapor in the initial stage of distillation process promote the volatilization of these esters with high boiling point.
Traditionally, the content sequence of ethyl esters in commercial Luzhou-flavor spirit is ethyl hexanoate > acetate ≥
Fig. 2. Total ion chromatogram of volatile compounds in (A) neutral fraction and (B) acidic fraction using GC-MS. Compounds series: internal standard (IS), alcohols (AL), aldehydes (AD), acids (AC), esters (ES), ketones (KT), phenols (PH), hydrocarbon compounds (HC) and oxygen-containing compounds (OC).
Fig. 3. Total concentration and relative abundance of each kind of volatile compounds in the head, heart and tail raw spirits. Error bars indicated standard deviations (n = 3). Different letters indicate significant differences ( p < 0.05, ANOVA, Turkey’s test).
J. Zheng et al.288Ta
ble
2.
Volu
me
frac
tion
of e
than
ol (v
/v) a
nd q
uant
itativ
e co
ncen
tratio
n (m
g/L)
of v
olat
ile c
ompo
unds
in d
iffer
ent r
aw sp
irits
.
Num
ber
Com
poun
dsR
I HP-
5MS
Iden
tifica
tion1
Thre
shol
d2 (mg/
L)C
once
ntra
tion3 (m
g/L)
OAV
Hea
dH
eart
Tail
Hea
dH
eart
Tail
Volu
me
frac
tion
of e
than
ol74
.50
75.8
044
.00
Alc
ohol
s (10
)A
L1M
etha
nol
-St
d13
68a
±8
1214
a±
713
18a
±7
AL2
1-Pr
opan
ol<8
00M
S, R
IL30
64.
4±
0.5
10.4
±1.
23.
3±
0.4
<1<1
<1A
L32-
Met
hylp
ropa
nol
<800
MS,
RIL
16 (Q
ian
and
Wan
g, 2
005)
0.53
a±
0.04
0.83
a±
0.04
37.5
b±
0.94
<1<1
<1A
L42-
Pent
anol
<800
MS,
RIL
8.1
(Qia
n an
d W
ang,
200
5)21
.9c
±0.
816
.2b
±1.
02.
67a
±0.
193
2<1
AL5
3-M
ethy
lbut
anol
<800
MS,
RIL
30 (G
uth,
199
7)11
7b±
613
6a±
112.
63c
±3.
004
5<1
AL6
1-Pe
ntan
ol<8
00M
S, R
IL1.
5 (G
iri e
t al.,
201
0b)
0.10
±0.
04nd
1.58
±0.
14<1
-<1
AL7
1-H
exan
ol87
5M
S, R
IL2.
5 (Q
ian
and
Wan
g, 2
005)
16.9
±0.
832
.3±
2.9
22.1
±0.
97
139
AL8
2-Fu
rald
ehyd
e di
ethy
l ace
tal
1080
MS
0.07
±0.
060.
05±
0.01
ndA
L91-
Non
anol
1106
MS,
RIL
1 (Q
ian
and
Wan
g, 2
005)
1.44
b±
0.08
1.35
b±
0.06
0.22
a±
0.01
11
<1A
L10
Phen
ethy
l alc
ohol
1116
MS,
RIL
, Std
1 (Q
ian
and
Wan
g, 2
005)
1.80
a±
0.15
1.38
a±
0.17
8.71
b±
0.40
21
9A
cids
(10)
AC
1A
cetic
aci
d<8
00M
S, S
td20
0 (G
uth,
199
7)1.
73ab
±0.
042.
31b
±0.
260.
05a
±0.
02<1
<1<1
AC
2Pr
opan
oic
acid
<800
MS
8.1
(Fer
reira
et a
l., 2
000)
44.2
b±
8.1
36.3
b±
1.7
11.7
a±
2.0
54
1A
C3
2-M
ethy
lpro
pano
ic a
cid
<800
MS
200
(Gut
h, 1
997)
0.65
±0.
240.
14±
0.11
0.03
±0.
01<1
<1<1
AC
4B
utan
oic
acid
871
MS,
Std
1 (Q
ian
and
Wan
g, 2
005)
8.03
b±
2.09
7.17
b±
1.18
0.05
a±
0.01
43.
5<1
AC
53-
Met
hylb
utan
oic
acid
839
MS
3 (G
uth,
199
7)5.
65±
0.14
4.88
±1.
135.
41±
0.42
21.
81.
9A
C6
2-M
ethy
lbut
anoi
c ac
id84
1M
S3
(Gut
h, 1
997)
19.9
±4.
68.
18±
1.63
7.71
±0.
146.
72.
72.
6A
C7
Pent
anoi
c ac
id91
6M
S4.
58a
±0.
287.
98b
±2.
0244
.9c
±2.
2A
C8
Hex
anoi
c ac
id10
37M
S, S
td3
(Gut
h, 1
997)
115b
±12
153c
±15
87.2
a±
3.4
1419
11A
C9
Hep
tano
ic a
cid
1115
MS
17.9
b±
1.08
17.2
b±
0.69
9.12
a±
1.19
AC
10H
exad
ecan
oic
cid
1963
MS,
Std
5.22
b±
0.77
2.20
a±
0.49
0.55
a±
0.02
Est
ers (
34)
ES1
Ethy
l ace
tate
<800
MS,
RIL
, Std
7.5
(Gut
h, 1
997)
13.0
b±
4.2
13.8
b±
0.5
2.63
a±
0.12
1.5
1.6
<1ES
2Et
hyl b
utyr
ate
806
MS,
RIL
, Std
0.02
(Gut
h, 1
997)
123c
±9
19.5
b±
4.1
6.34
a±
0.36
6127
975
468
ES3
Ethy
l lac
tate
823
MS,
RIL
, Std
14 (F
erre
ira e
t al.,
200
0)30
.3b
±5.
21.
16a
±0.
267.
00a
±0.
642
<1<1
ES4
Ethy
l 2-m
ethy
lbut
anoa
te85
3M
S, R
IL0.
001
(Gut
h, 1
997)
0.28
b±
0.05
0.41
c±
0.05
0.07
a±
0.00
280
410
70ES
5Et
hyl 3
-met
hylb
utan
oate
857
MS,
RIL
0.00
3 (G
uth,
199
7)0.
81b
±0.
010.
59b
±0.
090.
08a
±0.
0327
019
326
.7ES
6Et
hyl p
enta
noat
e90
4M
S, R
IL0.
005
(Tak
eoka
et a
l., 1
990)
90.8
b±
12.5
44.8
b±
2.5
4.29
a±
0.08
1816
089
5085
8ES
7Et
hyl 3
-met
hylp
enta
noat
e92
9M
S,R
IL1.
07b
±0.
13b
0.49
a±
0.02
0.20
a±
0.02
ES8
Ethy
l 4-m
ethy
lpen
tano
ate
969
MS
1.82
b±
0.81
1.36
ab±
0.05
0.61
a±
0.04
ES9
Ethy
l 2-m
ethy
lpen
tano
ate
972
MS,
RIL
0.07
±0.
010.
59±
0.09
ndES
10Et
hyl h
exan
oate
1005
MS,
RIL
, Std
0.00
5 (G
uth,
199
7)25
78c
±62
1453
b±
319
1a±
251
5766
2907
2438
286
ES11
Ethy
l 2-h
ydro
xy-4
-met
hylp
enta
noat
e10
61M
S3.
07b
±0.
230.
65a
±0.
011.
06a
±0.
17
Volatile Compounds of Luzhou-flavor Raw Spirits 289
Tabl
e 2.
Vo
lum
e fr
actio
n of
eth
anol
(v/v
) and
qua
ntita
tive
conc
entra
tion
(mg/
L) o
f vol
atile
com
poun
ds in
diff
eren
t raw
spiri
ts.
Num
ber
Com
poun
dsR
I HP-
5MS
Iden
tifica
tion1
Thre
shol
d2 (mg/
L)C
once
ntra
tion3 (m
g/L)
OAV
Hea
dH
eart
Tail
Hea
dH
eart
Tail
ES12
Ethy
l 5-m
ethy
lhex
anoa
te10
65M
S0.
63±
0.02
0.47
±0.
020.
89±
0.14
ES13
Ethy
l hep
tano
ate
1100
MS,
RIL
0.00
2 (G
iri e
t al.,
201
0b)
84.3
c±
4.2
57.1
b±
6.1
5.30
a±
0.01
4216
028
535
2650
ES14
Ethy
l ben
zoat
e11
73M
S, R
ILnd
0.15
±0.
01nd
ES15
Ethy
l oct
anoa
te11
99M
S, R
IL0.
002
(Gut
h, 1
997)
81.2
c±
2.2
72.8
b±
5.3
6.63
a±
0.24
4059
036
390
3315
ES16
Ethy
l ben
zene
acet
ate
1248
MS,
RIL
, Std
0.15
5 (G
iri e
t al.,
201
0b)
0.45
±0.
050.
19±
0.00
0.63
±0.
052.
91.
24.
1ES
17Et
hyl n
onan
oate
1297
MS,
RIL
1.61
b±
0.05
1.64
b±
0.10
0.22
a±
0.02
ES18
Ethy
l ben
zenp
ropa
noat
e13
52M
S1.
18±
0.11
0.78
±0.
072.
46±
0.26
ES19
Ethy
l dec
anoa
te13
97M
S, R
IL0.
2 (T
ao a
nd Z
hang
, 201
0)3.
00b
±0.
023.
48b
±0.
320.
28a
±0.
0315
171
ES20
Ethy
l dod
ecan
oate
1597
MS
2.12
b±
0.20
1.83
b±
0.20
0.31
a±
0.01
ES21
Ethy
l tet
rade
cano
ate
1796
MS
4.19
b±
0.49
3.00
a±
0.25
a1.
04a
±0.
25ES
22Et
hyl p
alm
itate
1996
MS,
Std
2 (Q
ian
and
Wan
g, 2
005)
32.8
b±
1.0
22.4
b±
0.4
6.41
a±
0.20
ES23
Ethy
l lin
olea
te>2
000
MS,
Std
17.1
c±
2.7
9.59
b±
1.29
2.79
a±
0.69
ES24
Ethy
l ole
ate
>200
0M
S, S
td9.
67c
±1.
305.
76b
±0.
671.
82a
±0.
48ES
25H
exyl
ace
tate
1018
MS,
RIL
1.5
(Cam
po e
t al.,
200
6)3.
11b
±0.
080.
75a
±0.
010.
59a
±0.
072
<1<1
ES26
3-M
ethy
lbut
yl b
utan
oate
1059
MS
1.71
b±
0.17
1.18
a±
0.03
0.89
a±
0.03
ES27
3-M
ethy
lbut
yl 2
-met
hoxy
acet
ate
1072
MS
0.48
±0.
010.
05±
0.01
0.04
±0.
01ES
28Pr
opyl
hex
anoa
te10
96M
S, R
ILnd
5.75
b±
0.81
b0.
67a
±0.
04ES
29B
utyl
hex
anoa
te11
34M
S0.
7 (T
akeo
ka e
t al.,
199
0)0.
52b
±0.
030.
50b
±0.
030.
09a
±0.
01<1
<1<1
ES30
Isob
utyl
hex
anoa
te11
53M
S2.
97b
±0.
152.
42b
±0.
140.
26a
±0.
04ES
31D
ieth
yl su
ccin
ate
1184
MS
0.70
±0.
040.
29±
0.00
0.55
±0.
01ES
32H
exyl
but
anoa
te11
93M
S20
.2b
±0.
517
.7b
±1.
01.
70a
±0.
41ES
33Is
open
tyl h
exan
oate
1252
MS
1.52
a±
0.06
11.8
b±
1.0
1.15
a±
0.05
ES34
Pent
yl h
exan
oate
1289
MS,
RIL
1.97
b±
0.01
1.94
b±
0.13
0.22
a±
0.02
Ket
ones
(4)
KT1
2-Pe
ntan
one
<800
MS
0.01
(Qia
n an
d W
ang,
200
5)nd
nd0.
21±
0.03
--
26K
T22-
But
anon
e<8
00M
S80
(Qia
n an
d W
ang,
200
5)0.
05b
±0.
010.
04a
±0.
010.
08c
±0.
00<1
<1<1
KT3
2-H
epta
none
894
MS
0.00
1 (Q
ian
and
Wan
g, 2
005)
0.57
c±
0.05
0.51
b±
0.00
0.06
a±
0.01
5750
6K
T44-
Met
hyl-3
-hep
tano
ne93
4M
S0.
02±
0.01
nd0.
03±
0.02
Ald
ehyd
es (5
)A
D1
Ace
tald
ehyd
e-
Std
1.2
54.9
b±
0.3
4.58
a±
0.10
3.83
a±
0.05
454
3A
D2
3-M
ethy
lbut
anal
<800
MS
0.00
035(
Qia
n an
d W
ang,
200
5)37
.9c
±2.
529
.4b
±1.
53.
18a
±0.
0410
8285
8400
090
85A
D3
1,1-
Die
thox
yeth
ane
<800
MS,
RIL
0.05
(Gut
h, 1
997)
48.3
b±
4.7
40.9
b±
1.1
2.97
a±
0.01
965
820
60A
D4
Furf
ural
838
MS,
RIL
,Std
14.1
(Fer
reira
et a
l., 2
000)
4.06
b±
0.21
1.60
a±
0.16
0.02
a±
0.00
<1<1
<1A
D5
Ben
zene
acet
alde
hyde
1044
MS,
RIL
1(C
ampo
et a
l., 2
006)
0.38
a±
0.02
0.30
a±
0.01
1.98
b±
0.21
<1<1
<1
J. Zheng et al.290
lactate (or lactate > acetate) > butanoate > pentanoate, and the appropriate content range of ethyl hexanoate in typical Luzhou-flavor spirit range from 1200 mg/L to 2800 mg/L according to the China National Standard (GB10781.1-2006, Strong flavor Chinese spirit). Result of this study showed that the highest level of ethyl hexanoate was monitored in the head spirit (2578 mg/L), and ethyl pentanoate, butanoate and palmitate also represent higher content in the head raw spirit than these in other samples. Furthermore, the tail spirit represented the lowest content of ethyl esters especially ethyl hexanoate (191 mg/L). In this way, only the heart raw spirit showed the most acceptable content of ethyl hexanoate (1453 mg/L) because the blending process could increase the total content of ethyl hexanoate.
Acids: Acids were the second largest group detected in this study. In the spirit samples, 10 acid derivates were identified (Table 2), and 9 of them were also indentified in previous studies (Fan and Qian, 2006a). The total concentration decreased from 239 mg/L in the heart raw spirit to 167 mg/L in the tail raw spirit. Based upon their concentration percentage, hexanoic acid was the major acid in all spirits (accounting for approximately 50% of total acids). A sharp decrease of the concentration was noted in propanoic acid and palmitic acid from the head to tail raw spirit ( p < 0.05), which was deviated with that obtained by Lukić (Lukic et al., 2011). Li et al., (2012) found that high flow rate of vapor could increase the volatility of hexanoic acid. Combined with the decreasing tendency of ethyl lactate, it assumed that the excessive high flow rate of vapor at the head stage lead to the acids streamed out too early.
Alcohols: Alcohols are major products of fermentation of sugars and amino acid (Silva et al., 1996; Wondra and Berovic, 2001). Among 10 alcohols detected, methanol, 2-methylpropanol, 2-pentanol, 3-methylbutanol and 1-hexanol were considered to be the predominant alcohols on account of their high content. Approximately equal concentrations of methanol were detected from the head raw spirit to tail spirit, which showed a similar pattern in the Muškat ruža porečki grape marc (Lukic et al., 2011). It was reported that methanol is produced by the hydrolysis of pectic substances (Mangas et al., 1995). High level of methanol in raw spirits maybe explained by the intense liquefaction of grains especially the grain hull during the distilling process. The concentration of 2-pentanol significantly decreased from the head to tail spirit ( p < 0.05). High concentrations of 1-propanol, 3-methylbutanol and 1-hexanol were monitored in the head and heart raw spirits, and this was agreement with the previous finding (Leaute, 1989). Probably high volatility of these low boiling point compounds such as 1-hexanol and 1-propanol leaded to high content in the heart raw spirit. As it documented that 1-hexanol is considered to be a positive affection on the aroma of the distillate when the content of which up to 20 mg/L (Apostolopoulou et al., 2005). It suggested that the quality of the heart raw spirit may superior to others. The aromatic higher alcohol-phenethyl alcohol (8.70 mg/L) exhibited an increasing trend from the head to tail raw
Tabl
e 2.
Vo
lum
e fr
actio
n of
eth
anol
(v/v
) and
qua
ntita
tive
conc
entra
tion
(mg/
L) o
f vol
atile
com
poun
ds in
diff
eren
t raw
spiri
ts.
Num
ber
Com
poun
dsR
I HP-
5MS
Iden
tifica
tion1
Thre
shol
d2 (mg/
L)C
once
ntra
tion3 (m
g/L)
OAV
Hea
dH
eart
Tail
Hea
dH
eart
Tail
Phen
ols (
2)PH
14-
Ethy
lphe
nol
1175
MS,
RIL
, Std
1.01
(Giri
et a
l., 2
010b
)0.
52b
±0.
080.
18a
±0.
051.
92c
±0.
174
114
PH2
4-Et
hyl-2
-met
hoxy
phen
ol12
82M
S, R
IL, S
td0.
033(
Ferr
eira
et a
l., 2
000)
1.27
a±
0.06
0.55
a±
0.12
6.51
b±
1.06
5825
256
Hyd
roca
rbon
com
poun
ds (3
)H
C1
n-Pr
opyl
benz
ene
954
MS,
RIL
0.09
±0.
010.
10±
0.04
ndH
C2
2-M
ethy
lnap
htha
lene
1295
MS,
Std
0.30
±0.
040.
32±
0.07
0.33
±0.
07H
C3
1-M
ethy
lnap
htha
lene
1313
MS,
Std
0.18
a±
0.01
0.23
b±
0.08
0.21
ab±
0.10
Oxy
gen-
cont
aini
ng c
ompo
und
(3)
OC
11,
1-D
ieth
oxy-
3-m
ethy
lbut
ane
958
MS,
RIL
47.8
c±
5.3
32.0
b±
1.4
1.19
a±
0.03
OC
2(2
,2-D
ieth
oxye
thyl
)ben
zene
1327
MS
1.02
±0.
160.
90±
0.04
1.16
±0.
09O
C3
Hex
anoi
c ac
id, a
nhyd
ride
1370
MS,
RIL
0.47
b±
0.06
0.07
a±
0.01
0.10
a±
0.01
1 MS,
com
poun
ds w
ere
iden
tified
by
MS
spec
tra; R
IL, c
ompo
unds
wer
e id
entifi
ed b
y a
com
paris
on w
ith th
e re
tent
ion
inde
x fr
om th
e lit
erat
ures
; Std
, com
poun
ds w
ere
iden
tified
by
a co
mpa
rison
with
the
rete
ntio
n in
dex
from
the
pure
stan
dard
.2 T
he re
fere
nce
from
whi
ch th
e od
or th
resh
old
had
been
take
n w
as g
iven
in p
aren
thes
es.
3 The
con
cent
ratio
ns o
f vol
atile
com
poun
ds w
ere
repr
esen
ted
as m
ean
valu
e of
trip
licat
e sa
mpl
es ±
stan
dard
dev
iate
s (m
ean
± SD
). D
iffer
ent l
ette
rs in
dica
te si
gnifi
cant
diff
eren
ces (
p <
0.0
5, A
NO
VA,
Turk
ey’s
test
). ‘n
d’ m
eans
not
det
erm
ined
.
Volatile Compounds of Luzhou-flavor Raw Spirits 291
spirit, which was in accordance with the result of Lukić and Apostolopoulou (Lukic et al., 2011; Apostolopoulou et al., 2005). Additionally, 2-methylpropanol also exhibited the highest concentration of 37.5 mg/L in the tail raw spirit.
Aldehydes and ketones: Most aldehydes are probably metabo-lites of bacteria (Lachenmeier and Sohnius, 2008), and ketones are formed by the autoxidation of fatty acids, especially unsaturated fatty acids (Grosch, 1982). Furfural is formed during the distilla-tion due to dehydration of fermentable sugars (pentoses) caused by heating in acid conditions and/or Maillard reaction (Mangas et al., 1995). A total of 4 ketones and 5 aldehydes were observed, and the highest levels of aldehyde and ketone were determined in the heart raw spirit, followed by the head and the tail raw spirit. However, the previous literature observed a significant decrease in concentra-tion during the distillation (Apostolopoulou et al., 2005). It as-sumed that this was also owing to the high flow rate of vapor. Ac-etaldehyde, 3-methylbutanal and 1,1-diethoxyethane were considered to be dominant aldehydes in raw spirit upon their high concentration, and this agreed with these reported in previous stud-ies (Fan and Qian, 2005; Kim et al., 2009). A significantly de-c r e a s e d p a t t e r n o f a c e t a l d e h y d e , 3 - m e t h y l b u t a n a l , 1,1-diethoxyethane and furfural was represent from the head to tail raw spirit ( p < 0.05), assumedly depending on their relatively low boiling points (103 _ 209℃) and the solubility in alcohol. Acetal-dehyde is originated from the spontaneous or microbially mediated oxidation in distillates (Qian and Wang, 2005). In this study, the acetaldehyde in raw spirits may from the spirit fermentation pro-cess of raw material because the raw spirits were not stored before sampling.
Phenols: Phenols especially 4-ethyl-2-methoxyphenol (4-ethylguaiacol) were the thermal degradation products of lignin-related phenolic carboxylic acid (Zhang and Tao, 2009). The highest concentrations of 4-ethylphenol and 4-ethyl-2-methoxyphenol were monitored in the tail spirit, with the concentration of 1.92 mg/L and 6.51 mg/L, respectively. Similarly, these two phenols were also identified in Yanghe spirit (Fan and Qian, 2006b), Maotai spirit (Zhu et al., 2007) and whisky (Caldeira et al., 2007). High boiling point (217 and 236℃) could determine the concentration of them only emerging in the tail raw spirit because the last stage with higher flow rate and temperature comparing with other stages is always applied to gelatinize and liquefy the starch of grains.
Moreover, a total of 6 volatile compounds were identified. N-propylbenzene, 2-methylnaphthalene, 1-methylnaphthalene be-longs to hydrocarbon compound and (2,2-diethoxyethyl) benzene, 1,1-diethoxyl-3-methylbutane, and hexanoic acid, anhydride be-longs to oxygen-containing compound. The decreased tendency was monitored in 1,1-diethoxyl-3-methylbutane because of its low boiling point (156℃) and which has also been identified in other Chinese Luzhou-flavor liquor (Fan and Qian, 2005), aronia spirit and sparkling wines (Bosch-Fusté et al., 2007; Balcerek, 2010).
Due to their low concentration, the identification and classification of many compounds in these two groups (hydrocarbon and oxy-gen-containing compound) such as n-propylbenzene, 2-methyl-naphthalene, and 1-methylnaphthalene in raw spirit are still re-quired in the further analysis.
OAV of volatiles in different raw spirits The quantification data of volatile compounds in raw spirits from three distilling stages is listed in Table 2. It is obvious that ethyl hexanoate had the highest OAV, and its value decreased from the highest in the head spirit (515766) to the lowest in the tail spirit (38286). Previous studies also reported that ethyl hexanoate was the key volatile compound in most Luzhou-flavor spirits, such as Yanghe (Fan and Qian, 2005), Wuliangye and Jiannanchun (Fan and Qian, 2006a) based on its flavor dilution (FD) value, which contributed to the fruity, anise, apple, sweetish and pear odor (Jiang and Zhang, 2010). It suggested that ethyl hexanoate played the most important role in the whole odor feature of the raw spirit.
Most esters with high OAV detected had a typical “fruit” and “floral” descriptor, and contributed to fruity, sweet, apple, pineapple, and floral odors. For example, ethyl pentanoate (858 _ 18160), ethyl heptanoate (2650 _ 42160), and ethyl octanoate (3315 _ 40590) contributed to the odor of fruity, flora, sweet and pineapple (Fan and Qian, 2006a; Jiang and Zhang, 2010; Zhang et al., 2010). It was worth noting that 3-methylbutanal with low threshold value (0.35 μg/L) (Qian and Wang, 2005) may largely contributed to a characteristic aroma of apple, although the concentration was relatively low (3.18 mg/L-37.9 mg/L).
Meanwhile, the important aroma compounds (OAV ≥ 10) in-cluded 1-hexanol, hexanoic acid, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl benzenacetate, ethyl decanoate, 2-penta-none, 2-heptanone, 1,1-diethxoyethane 4-ethylphenol and 4-eth-yl-2-methoxylphenol. 1-Hexanol, with a floral and fruity odor (Ji-ang and Zhang, 2010), could be the dominant alcohol with the highest OAV. Hexanoic acid, one of main metabolites of Clostridi-um bacteria (Weimer and Stevenson, 2011), was also identified as the dominating volatile component in various raw spirits. Previous-ly, it was reported that 1,1-diethxoyethane was an important aroma compound in Yanghe spirit with the FD value more than 256 (Fan and Qian, 2005). In this study, 1,1-diethxoyethane also showed high OAV, assuming that a tight relationship existed between the raw spirit and commercial spirit. 4-Ethylphenol and 4-ethyl-2-me-thoxyphenol were the odor active compounds in many oriental fer-mentation condiments such as soy sauce and soybean paste, which had the odor of cooked soybean, smokey and phenolic odours (Lee and Ahn, 2009; Giri et al., 2010b; Giri et al., 2010a).
In addition, other volatile compounds such as propanoic acid, 2-methylbutanoic acid, ethyl acetate, ethyl butyrate, hexyl acetate and acetaldehyde with the OAV more than 1 may also contribute to the whole odor of the spirit. Ethyl acetate and ethyl butyrate represented the odor descriptions of green apple, strawberry, pineapple and sweet (Zhang et al., 2010; Vilanova et al., 2012).
J. Zheng et al.292
ConclusionThe volatile compounds of raw spirits collected from three
distilling stages of Luzhou-flavor spirit were detected using GC-MS and GC analyses. Results showed that the total concentration of volatile compounds was obviously decreased from the head spirit to tail spirit ( p < 0.05) without any research purely based on the different boiling points or solubility of the compounds (e.g. esters have higher volatility than alcohols). Ethyl hexanoate with the highest concentration and OAV was the most important odor active compound in each spirit. On the basis of high OAV, ethyl butyrate, ethyl heptanoate, ethyl octanoate, and 3-methylbutanal were also elucidated to be main contributors to the overall flavor of raw spirits. Results presented in this article may benefit to understand the changes and odorant contributions of volatile compounds in the distillation process of Luzhou-flavor spirit.
Acknowledgments This work was financially supported by the National Science Foundation of China (31171742).
ReferencesApostolopoulou, A. A., Flouros, A. I., Demertzis, P. G., and Akrida-
Demertzi, K. (2005). Differences in concentration of principal volatile
constituents in traditional Greek distillates. Food Control, 16, 157-164.
Balcerek, M. (2010). Carbonyl compounds in aronia spirits. Polish J. Food
Nutri. Sci., 60, 243-249.
Bosch-Fusté, J., Riu-Aumatell, M., Guadayol, J. M., Caixach, J., López-
Tamames, E., and Buxaderas, S. (2007). Volatile profiles of sparkling
wines obtained by three extraction methods and gas chromatography–
mass spectrometry (GC-MS) analysis. Food Chem., 105, 428-435.
Bruno, S. N. F., Vaitsman, D. S., Kunigami, C. N., and Brasil, M. G.
(2007). Influence of the distillation processes from Riode Janeiro in the
ethyl carbamate formation in Brazilian sugar cane spirits. Food Chem.,
104, 1345-1352.
Caldeira, M., Rodrigues, F., Perestrelo, R., Marques, J. C., and Câmaraj.S.
(2007). Comparison of two extraction methods for evaluation of volatile
constituents patterns in commercial whiskeys elucidation of the main
odour-active compounds. Talanta, 74, 78-90.
Campo, E., Ferreira, V., Escudero, A., Marqués, J. C., and Cacho, J. (2006).
Quantitative gas chromatography–olfactometry and chemical quantitative
study of the aroma of four Madeira wines. Anal. Chim. Acta, 563, 180-
187.
Claus, M. J. and Berglund, K. A. (2005). Fruit brandy production by batch
column distillation with reflux. J. Food Process Eng., 28, 53-67.
Cates, V. and Meloan, C. (1963). Separation of sulfones by gas
chromatography. J. Chromatogr. A, 11, 472-478.
Fan, W. L. and Qian, M. C. (2005). Headspace solid phase microextraction
and gas chromatography-olfactometry dilution analysis of young and
aged Chinese “Yanghe Daqu” liquors. J. Agric. Food Chem., 53, 7931-
7938.
Fan, W. L. and Qian, M. C. (2006a). Characterization of aroma compounds
of Chinese “Wuliangye” and “Jiannanchun” liquors by aroma extract
dilution analysis. J. Agric. Food Chem., 54, 2695-2704.
Fan, W. L. and Qian, M. C. (2006b). Identification of aroma compounds in
Chinese‘Yanghe Daqu’liquor by normal phase chromatography
fractionation followed by gas chromatography/Olfactometry. Flav. Frag.
J., 21, 333-342.
Ferreira, V., Lpez, R., and Cacho, J. F. (2000). Quantitative determination
of the odorants of young red wines from different grape varieties. J. Sci.
Food Agri., 80, 1659-1667.
Giri, A., Osako, K., and Ohshima, T. (2010a). Identification and
characterisation of headspace volatiles of fish miso, a Japanese fish meat
based fermented paste, with special emphasis on effect of fish species
and meat washing. Food Chem., 120, 621-631.
Giri, A., Osako, K., Okamoto, A., and Ohshima, T. (2010b). Olfactometric
characterization of aroma active compounds in fermented fish paste in
comparison with fish sauce, fermented soy paste and sauce products.
Food Res. Inter., 43, 1027-1040.
Grosch, W. (1982). In Food flavors. Part A. Introduction, 1st ed.; Morton,
I.D., Macleod, A.J., Eds.; Elsevier: Amsterdam, The Netherlands, pp.
325-398.
Guth, H. (1997). Quantitation and sensory studies of character impact
odorants of different white wine varieties. J. Agr. Food Chem., 45, 3027-
3032.
Hernandez-Gomez, L. F., Ubeda-Iranzo, J., Garcia-Romero, E., and
Briones-Perez, A. (2005). Comparative production of different melon
distillates: Chemical and sensory analyses. Food Chem., 90, 115-125.
Hernanz, D., Gallo, V., Recamales, A. F., Melendez-Martinez, A. J., and
Heredia, F. J. (2008). Comparison of the effectiveness of solid-phase and
ultrasound-mediated liquid-liquid extractions to determine the volatile
compounds of wine. Talanta, 76, 929-935.
Jiang, B. and Zhang, Z. (2010). Volatile compounds of young wines from
cabernet sauvignon, cabernet gernischet and chardonnay varieties grown
in the loess plateau region of china. Molecules, 15, 9184-9196.
Kim, J. S., Kam, S. F., and Chung, H. Y. (2009). Comparison of the volatile
components in two Chinese wines, Moutai and Wuliangye. J. Korean
Soc. Appl. Biol. Chem., 52, 275-282.
Lachenmeier, D. W., and Sohnius, E. M. (2008). The role of acetaldehyde
outside ethanol metabolism in the carcinogenicity of alcoholic beverages:
evidence from a large chemical survey. Food Chem. Toxicol., 46, 2903-
2911.
Leaute, R. (1989). Distillation in Alambic. Am. J. Enol. Viticul., 41, 90-103.
Lee, S. J. and Ahn, B. (2009). Comparison of volatile components in
fermented soybean pastes using simultaneous distillation and extraction
(SDE) with sensory characterisation. Food Chem., 114, 600-609.
Li, H. L., Huang, W. X., Shen, C. H., and Yi, B. (2012). Optimization of
the distillation process of Chinese liquor by comprehensive experimental
investigation. Food Bioprod. Process., 90, 392-398.
Lukic, I., Tomas, S., Milicevic, B., Radeka, S., and Persuric, D. (2011).
Behaviour of volatile compounds during traditional alembic distillation
of fermented Muscat Blanc and Muškat Ruža Porečki grape marcs. J.
Inst. Brew., 117, 440-450.
Mangas, J., Rodrıguez, R., Moreno, J., and Blanco, D. (1995). Changes in
Volatile Compounds of Luzhou-flavor Raw Spirits 293
the major volatile compounds of cider distillates during maturation. LWT
- Food Sci. Technol., 29, 357-364.
Qian, M. and Reineccius, G. (2002). Identification of aroma compounds in
Parmigiano-Reggiano cheese by gas chromatography/olfactometry. J.
Dairy Sci., 85, 1362-1369.
Qian, M. C. and Wang, Y. Y. (2005). Seasonal variation of volatile
composition and odor activity value of ‘Marion’ (Rubus spp. hyb) and
‘Thornless Evergreen’ (R. laciniatus L.) blackberries. J. Food Sci., 70,
C13-C20.
Rogelio, P. R., Victor, G. A., Carlos, P. O., Norberto, C., Mirna, E., and
Héctor E, G. H. (2005). The role of distillation on the quality of tequila.
Inter. J. Food Sci. Technol., 40, 701-708.
Sanchez-Palomo, E., Alanon, M. E., Diaz-Maroto, M. C., Gonzalez-Vinas,
M. A., and Perez-Coello, M. S. (2009). Comparison of extraction
methods for volatile compounds of Muscat grape juice. Talanta, 79, 871-
876.
Scanavini, H. F. A., Cheriani,R., Cassini, C. E. B., Souza, E. L. R., Filho,
F. M., and Meirelles, A. J. A. (2010). Cachça production in a lab-scale
alembic modeling and computational simulation. J. Food Process Eng.,
33, 226-252.
Silva, M., Malcata, F., and Revel, G. (1996). Volatile contents of grape
Marcs in Portugal. J. Food Comp. Anal., 9, 72-80.
Takeoka, G. R., Flath, R. A., Man, T. R., Teranishi, R., and Guentert, M.
(1990). Volatile Constituents of Apricot (Prunus armeniaca) J. Agr.
Food Chem., 38, 471-477.
Tao, Y. S. and Zhang, L. (2010). Intensity prediction of typical aroma
characters of cabernet sauvignon wine in Changli County (China). LWT -
Food Sci. Technol., 43, 1550-1556.
Vilanova, M., Siebert, T. E., Varela, C., Pretorius, I. S., and Henschke, P. A.
(2012). Effect of ammonium nitrogen supplementation of grape juice on
wine volatiles and non-volatiles composition of the aromatic grape
variety Albariño. Food Chem., 133, 124-131.
Weimer, P. J. and Stevenson, D. M. (2011). Isolation, characterization, and
quantification of Clostridium kluyveri from the bovine rumen. Appl.
Microbiol. Biotechnol., 94, 461-466.
Wondra, M. and Berovic, M. (2001). Analyses of aroma components of
Chardonnay wine fermented by different yeast strains. Food Technol.
Biotechnol., 39, 141-148.
Xu, Y., Wang, D., Fan, W. L., Mu, X. Q., and Chen, J. (2010). Traditional
chinese biotechnology. Adv. Biochem. Eng. Biotechnol., 122, 189-233.
Zhang, Y., Li, X., Lo, C. K., and Guo, S. T. (2010). Characterization of the
volatile substances and aroma components from traditional soypaste.
Molecules, 15, 3421-3427.
Zhang, Y. F. and Tao, W. Y. (2009). Flavor and taste compounds analysis
in Chinese solid fermented soy sauce. Afr. J. Biotechnol., 8, 673-681.
Zhu, S., Lu, X., Ji, K., Guo, K., Li, Y., Wu, C., and Xu, G. (2007).
Characterization of flavor compounds in Chinese liquor Moutai by
comprehensive two-dimensional gas chromatography/time-of-flight mass
spectrometry. Anal. Chim. Acta., 597, 340-348.