Characterization of odor-active compounds of various Chinese “Wuliangye” liquors by gas chromatography–olfactometry, gas chromatography–mass spectrometry and sensory evaluation

Figures & data

Table 1. Aroma compounds identified in W1, W2, and W3 by GC–O.

Code	Compound identified	Odor descriptors	RIcal^a	Fraction^b	FD factors
					W1	W2	W3
1	Ethyl acetate	Pineapple	909	N + A	64	16	16
2	1,1-Diethoxyethane	Fruit, cream	888	N	16	256	256
3	3-Methylbutanal	Malt	909	N	1	16	16
4	Ethyl isobutyrate	Sweet	963	N	256	16	16
5	2-Pentanone	Fruit	981	N	1
6	2-Butanol	Wine	1003	N + A + W	1	1	4
7	Ethyl butyrate	Apple	1006	N	1024	1024	4096
8	Ethyl 2-methylbutyrate	Apple	1018	N		64	64
9	Ethyl 3-methylbutyrate	Fruit	1030	N		256	1024
10	unknown	Fruit	1042	N + W	16	16	256
11	Isobutyl alcohol	Wine, solvent, bitter	1057	N + A + W	1	4	4
12	2-Pentanol	Green	1071	N + A + W	16	16	16
13	Ethyl pentanoate	Sweet, fruit	1076	N	1024	1024	1024
14	1-Butanol	Medicine, Alcoholic	1085	N + A + W	64	64	64
15	3-Methylbutanol	Malty, burnt	1141	N + A + W	256	256	256
16	1-Pentanol	Balsamic	1192	A + W	1	4	64
17	Ethyl hexanoate	Fruit	1202	N	1024	1024	4096
18	2-n-Butylfuran	Roasted, baked	1234	N		64
19	Hexyl acetate	Fruit, herb	1239	N	4
20	2-Methylbutyl 2-methylbutyrate	Fruit	1260	N	16
21	2-Heptanol	Mushroom	1270	N + W	1	4
22	1,1,3-Triethoxypropane	Fruit, vegetal	1271	N	16
23	Ethyl heptanoate	Fruit	1289	N	4	64	64
24	Propyl hexanoate	Fruit	1285	N	64
25	2-Methylpropyl hexanoate	Fresh	1289	N	16
26	2,6-Dimethylpyrazine	Roasted nut	1292	N			1
27	Ethyl lactate	Fruit	1295	N + W	1024	256	256
28	1-Hexanol	Resin, flower, green	1315	N + W	16	16	64
29	2,3,5-Trimethylpyrazine	Roast, potato	1365	N			64
30	Butyl hexanoate	Fruit	1370	N	256
31	unknown	Flower	1383	N	16
32	Ethyl octanoate	Fruit	1406	N	1024	1024	1024
33	Acetic acid	Sour, vinegar	1404	A	16	256	4
34	Isoamyl hexanoate	Fruit, flower	1417	N	1
35	Furfural	Almond, sweet	1426	N + A		256	16
36	2-Ethyl-1-hexanol	Fose, green	1443	N	16
37	Benzaldehyde	Almond, burnt Sugar	1495	N + A	16	4	4
38	Propionic acid	Pungent, Rancid, soy	1494	A	16	64	4
39	Isobutyric acid	Rancid, butter, cheese	1522	A	16		1
40	5-Methyl-2-furancarboxaldehyde	Almond, caramel	1546	N + A	4	16	1
41	Hexyl hexanoate	Apple peel, peach	1568	N	256	16	16
42	Butyric acid	Rancid, cheese, sweat	1589	N + A + W	1024	1024	1024
43	2-Acetyl-5-methylfuran	Roasted	1582	N	4
44	Ethyl decanoate	Grape, fruit	1593	N	16	16	16
45	2-Phenylacetaldehyde	Floral, rose	1614	N	16	1	1
46	Furfuryl alcohol	Burnt	1622	N + A + W	16	64	16
47	Isovaleric acid	Sweat, acid, Rancid	1632	N + A + W	16	256	64
48	Diethyl succinate	Wine, fruit	1643	N		4
49	Pentanoic acid	Sweat	1705	N + A + W	16	64	64
50	Ethyl phenylacetate	Fruit, sweet	1766	N	64	16	16
51	Isocaproic acid	Sweat, sour	1772	A	16	16
52	Hexanoic acid	Sweat	1820	A	1024	256	4
53	Furfuryl hexanoate	Caramel, fruity	1848	N	1
54	2-Phenylethanol	Honey, spice, rose, lilac	1914	N + A + W	256	256	256
55	Heptanoic acid	Unpleasant	1941	A	16	64	16
56	Phenol	Phenol	1997	N + A	64	64	64
57	Octanoic acid	Sweat, cheese	2073	A	4	4	4
58	4-Methylphenol	phenol, Smoke	2079	N + W		4	16
59	unknown	Smoke	2211	A		16
60	Ethyl hexadecanoate	Wax	2266	N + A		1	1
61	Decanoic acid	Rancid, fat	2263	A		4
62	Ethyl 2-hydroxy-3-phenylpropanoate^c	Smoke	2295	N	4

^aThe linear retention index (LRI) calculated of unknown compounds on a HP-INNOWAX capillary column.

^bThe odorants were detected in the following fractions: A – acidic fraction, N – neutral/basic fraction or W – water-soluble fraction. Each fraction was analyzed by GC–O.

^cTentatively identified. This compound was identified by comparison with the retention index from the literatures and mass spectrum comparison using Wiley or Nist library.

Table 2. Result of recovery (%) and RSD (%) (n = 6) in W1, W2, and W3 for the 13 volatile compounds.

Code	Compound	W1		W2		W3
		Recovery	RSD	Recovery	RSD	Recovery	RSD
1	Ethyl acetate	73.2	8.2	79.7	9.2	83.0	8.5
2	Ethyl butyrate	89.6	8.3	92.1	9.7	92.9	6.8
3	1-Butanol	99.3	10.6	90.7	9.8	98.8	7.3
4	Ethyl hexanoate	91.2	10.2	102.6	11.3	100.4	7.1
5	2-n-Butylfuran	–	–	101.0	9.0	–	–
6	Ethyl heptanoate	98.9	8.8	102.2	10.2	95.6	5.7
7	Ethyl lactate	104.0	9.5	99.7	10.3	99.5	7.9
8	2,3,5-Trimethylpyrazine	–	–	–	–	100.7	5.2
9	Butyric acid	95.5	9.4	90.5	9.0	93.9	8.9
10	Hexyl hexanoate	87.5	6.8	95.8	9.1	89.1	8.2
11	Ethyl phenylacetate	87.0	5.2	88.6	7.9	93.7	8.2
12	Hexanoic acid	79.9	8.6	96.9	7.4	87.3	6.4
13	4-Methylphenol	–	–	75.4	9.0	80.3	9.5

In some cases, recovery was not calculated because concentration data of some compounds were not available in the liquors.

Table 3. Concentrations of the volatile components.

Code	Components	Concentration (g/L)
		W1	W2	W3
1	Ethyl acetate	0.42 ± 0.01^a	0.01 ± 0.00	0.09 ± 0.02
2	1,1-Diethoxyethane	0.82 ± 0.04	4.49 ± 0.23	1.99 ± 1.59
3	3-Methylbutanal	0.30 ± 0.01	3.99 ± 0.12	2.24 ± 0.45
4	Ethyl isobutyrate	0.80 ± 0.03	0.27 ± 0.08	0.35 ± 0.12
5	Ethyl butyrate	3.55 ± 0.47	3.61 ± 0.60	5.25 ± 3.23
6	Ethyl 2-methylbutyrate	n.d.	0.55 ± 0.01	0.69 ± 0.14
7	Ethyl 3-methylbutyrate	n.d.	1.08 ± 0.08	2.34 ± 0.94
8	2-Pentanol	0.10 ± 0.01	0.05 ± 0.00	0.07 ± 0.04
9	Ethyl pentanoate	1.77 ± 0.47	7.69 ± 0.35	5.81 ± 3.16
10	1-Butanol	4.37 ± 0.68	2.15 ± 0.08	2.19 ± 2.32
11	3-Methylbutanol	2.68 ± 0.87	1.92 ± 1.39	1.57 ± 4.56
12	1-Pentanol	0.01 + 0.00	0.02 + 0.00	0.12 ± 0.01
13	Ethyl hexanoate	10.41 ± 8.08	26.07 ± 13.00	34.36 ± 38.71
14	2-n-Butylfuran	n.d.	0.01 ± 0.00	n.d.
15	2-Methylbutyl 2-methylbutyrate	0.01 ± 0.00	n.d.	n.d.
16	1,1,3-Triethoxypropane	0.01 ± 0.00	n.d.	n.d.
17	Ethyl heptanoate	0.24 ± 1.09	2.06 ± 1.68	10.98 ± 2.07
18	Propyl hexanoate	0.02 ± 0.00	n.d.	n.d.
19	2-Methylpropyl hexanoate	0.01 ± 0.00	n.d.	n.d.
20	Ethyl lactate	7.76 ± 0.17	3.57 ± 0.04	3.42 ± 1.37
21	1-Hexanol	1.31 ± 0.01	1.43 ± 0.01	3.64 ± 0.36
22	2,3,5-Trimethylpyrazine	n.d.	n.d.	0.02 ± 0.00
23	Butyl hexanoate	0.02 ± 0.00	n.d.	n.d.
24	Ethyl octanoate	6.62 ± 0.67	9.85 ± 0.20	7.43 ± 0.19
25	Acetic acid	0.58 ± 0.02	3.87 ± 0.19	0.33 ± 0.32
26	Furfural	n.d.	5.65 ± 0.17	1.98 ± 0.90
27	2-Ethyl-1-hexanol	0.01 ± 0.00	n.d.	n.d.
28	Benzaldehyde	0.18 ± 0.00	0.06 ± 0.00	0.08 ± 0.02
29	Propionic acid	0.34 ± 0.00	1.18 ± 0.02	0.12 ± 0.02
30	Isobutyric acid	0.02 ± 0.00	n.d.	0.01 ± 0.00
31	5-Methyl-2-furancarboxaldehyde	0.60 ± 0.01	1.29 ± 0.05	0.33 ± 0.03
32	Hexyl hexanoate	3.87 ± 0.16	0.50 ± 0.03	0.25 ± 0.23
33	Butyric acid	3.15 ± 0.36	1.33 ± 0.11	1.07 ± 0.54
34	Ethyl decanoate	0.70 ± 0.01	0.66 ± 0.01	0.11 ± 0.02
35	2-Phenylacetaldehyde	0.44 ± 0.01	0.10 ± 0.00	0.01 ± 0.07
36	Furfuryl alcohol	1.77 ± 0.02	0.66 ± 0.05	0.45 ± 0.13
37	Isovaleric acid	0.23 ± 0.00	6.95 ± 0.23	2.11 ± 0.04
38	Pentanoic acid	0.11 ± 0.00	0.24 ± 0.00	0.32 ± 0.07
39	Ethyl phenylacetate	2.89 ± 0.12	0.54 ± 0.03	0.88 ± 0.08
40	Isocaproic acid	0.01 ± 0.00	0.01 ± 0.00	n.d.
41	Hexanoic acid	8.42 ± 0.01	6.20 ± 0.12	2.29 ± 0.86
42	2-Phenylethanol	2.82 ± 0.06	1.74 ± 0.07	1.94 ± 0.28
43	Heptanoic acid	3.05 ± 0.52	7.57 ± 0.38	2.74 ± 1.55
44	Phenol	0.18 ± 0.01	0.07 ± 0.00	0.18 ± 0.02
45	4-Methylphenol	n.d.	0.01 ± 0.00	0.01 ± 0.00

^aMean standard deviation (average of triplicate). n.d.: not detected.

Table 4. The mean scores of the seven attributes for the three Chinese liquors in sensory analysis and description of sensory attributes.

Sensory attribute	Mean score			Description
	W1	W2	W3
Aging	2.67 ± 0.82^c	4.31 ± 0.36^b	7.33 ± 0.86^a	The mature aroma characteristics after long-term storage of liquor by solid natural formation
Fruity	7.00 ± 0.49^a	5.76 ± 0.83^b	5.13 ± 0.49^b	Exhilarating scent and smelling strongly of varieties of ripe fruits
Cellar	3.63 ± 0.33^b	7.61 ± 0.22^a	8.81 ± 0.9^c	The aroma characteristics of ethyl hexanoate
Floral	6.75 ± 0.78^a	4.62 ± 0.61^b	3.93 ± 0.47^c	The perfume of fresh flowers
Sweet	3.25 ± 0.43^c	4.80 ± 0.66^b	6.91 ± 0.67^a	The aroma of honeys and fruities
Caramel	2.30 ± 0.51^c	4.85 ± 0.5^b	6.21 ± 0.58^a	The aroma of baking cereals and grains and caramel
Grain	4.15 ± 0.85^c	8.60 ± 1.1^a	5.24 ± 0.46^b	The steamed food aroma from the fermentation and distillation of Sorghum, rice, wheat and other grains

^a,b,cDifferent letters of the same row on the upright side mean significantly differences (p < 0.05) using Duncan’s multiple comparison test (n = 30: 10 panelists with 3 replications).

Table 5. Correlation observed between the volatile compounds and sensory attributes.

Code	Components	Aging	Fruity	Cellar	Floral	Sweet	Caramel	Grain
1	Ethyl acetate	−0.649	0.873	−0.924	0.917	−0.708	−0.868	−0.803
2	1,1-Diethoxyethane	0.146	−0.481	0.579	−0.566	0.226	0.472	0.997
3	3-Methylbutanal	0.376	−0.675	0.756	−0.745	0.450	0.667	0.950
4	Ethyl isobutyrate	−0.769	0.944	−0.976	0.972	−0.819	−0.940	−0.689
5	Ethyl butyrate	0.928	−0.740	0.658	−0.670	0.895	0.747	−0.309
6	Ethyl 2-methylbutyrate	0.844	−0.978	0.995	−0.994	0.884	0.976	0.593
7	Ethyl 3-methylbutyrate	0.992	−0.974	0.941	−0.946	0.999	0.976	0.192
8	2-Pentanol	−0.415	0.705	−0.783	0.772	−0.487	−0.698	−0.936
9	Ethyl pentanoate	0.532	−0.794	0.859	−0.850	0.599	0.787	0.881
10	1-Butanol	−0.973	0.993	−0.972	0.976	−0.988	−0.994	−0.298
11	3-Methylbutanol	0.577	−0.825	0.885	−0.877	0.641	0.819	0.854
12	1-Pentanol	0.954	−0.790	0.714	−0.725	0.926	0.796	−0.235
13	Ethyl hexanoate	0.998	−0.955	0.915	−0.921	1.000	0.958	0.123
14	2-n-Butylfuran	−0.169	−0.185	0.297	−0.282	−0.088	0.175	0.972
15	2-Methylbutyl 2-methylbutyrate	−0.769	0.944	−0.976	0.972	−0.819	−0.940	−0.689
16	1,1,3-Triethoxypropane	−0.769	0.944	−0.976	0.972	−0.819	−0.940	−0.689
17	Ethyl heptanoate	−0.656	0.352	−0.241	0.257	−0.592	−0.362	0.709
18	Propyl hexanoate	−0.769	0.944	−0.976	0.972	−0.819	−0.940	−0.689
19	2-Methylpropyl hexanoate	−0.769	0.944	−0.976	0.972	−0.819	−0.940	−0.689
20	Ethyl lactate	−0.788	0.953	−0.982	0.978	−0.836	−0.950	−0.667
21	1-Hexanol	0.953	−0.789	0.712	−0.724	0.926	0.795	−0.237
22	2,3,5-Trimethylpyrazine	0.938	−0.759	0.678	−0.690	0.907	0.765	−0.283
23	Butyl hexanoate	−0.769	0.944	−0.976	0.972	−0.819	−0.940	−0.689
24	Ethyl octanoate	−0.906	0.997	−0.999	1.000	−0.938	−0.996	−0.483
25	Acetic acid	−0.230	−0.123	0.237	−0.221	−0.150	0.113	0.955
26	Furfural	0.183	−0.513	0.609	−0.596	0.262	0.505	0.993
27	2-Ethyl-1-hexanol	−0.769	0.944	−0.976	0.972	−0.819	−0.940	−0.689
28	Benzaldehyde	−0.680	0.893	−0.939	0.933	−0.737	−0.888	−0.778
29	Propionic acid	−0.362	0.015	0.101	−0.084	−0.285	−0.025	0.905
30	Isobutyric acid	−0.554	0.809	−0.872	0.864	−0.620	−0.803	−0.868
31	5-Methyl-2-furancarboxaldehyde	−0.434	0.093	0.023	−0.006	−0.359	−0.103	0.870
32	Hexyl hexanoate	−0.808	0.962	−0.987	0.985	−0.853	−0.960	−0.643
33	Butyric acid	−0.836	0.975	−0.994	0.992	−0.878	−0.973	−0.604
34	Ethyl decanoate	−0.958	0.797	−0.722	0.733	−0.931	−0.804	0.223
35	2-Phenylacetaldehyde	−0.769	0.944	−0.976	0.972	−0.819	−0.940	−0.689
36	Furfuryl alcohol	−0.857	0.983	−0.998	0.996	−0.896	−0.981	−0.572
37	Isovaleric acid	0.106	−0.445	0.546	−0.532	0.186	0.436	0.999
38	Pentanoic acid	0.948	−0.999	0.989	−0.991	0.971	1.000	0.381
39	Ethyl phenylacetate	−0.678	0.891	−0.938	0.932	−0.735	−0.887	−0.780
40	Isocaproic acid	−0.938	0.759	−0.678	0.690	−0.907	−0.765	0.283
41	Hexanoic acid	0.957	−0.998	0.984	−0.987	0.978	0.999	0.353
42	2-Phenylethanol	−0.651	0.875	−0.925	0.918	−0.711	−0.870	−0.801
43	Heptanoic acid	0.120	0.233	−0.344	0.329	0.039	−0.223	−0.982
44	Phenol	0.207	0.146	−0.260	0.244	0.127	−0.136	−0.962
45	4-Methylphenol	0.947	−1.000	0.989	−0.992	0.970	1.000	0.383

The larger the positive number, the stronger the positive correlation but negative correlation was the opposite.

Figure 1. Graph of the mean sensory scores of three Wuliangye liquors studied. * and *** indicate the significance levels at p < 0.05 and p < 0.001, respectively.