Identification of the aroma-active compounds in Longjing tea characterized by odor activity value, gas chromatography- olfactometry, and aroma recombination

Figures & data

Table 1. Mean concentration (μg/kg) of volatile compounds detected in three Longjing tea samples.

		RI^b			Mean concentration (μg/kg)
Number	Retention time (min)^a	Calculate	Literature	Aroma compound	Y1	RSD	Y2	RSD	Y3	RSD^d	Standard curves^e	R^2	Linear ranges (μg/kg)^f	Identification basis^g
1	4.200	<600	505^h	Dimethyl sulfide	2583.5a^c	8.9	890.3c	8.4	1256.2b	9.5	y = 0.5563x – 0.0005	0.943	500–5000	MS, RI, Std
2	5.060	<600	602^i	2,3-Butanedione	2448.1a	9.0	2325.7a	9.8	1764.4b	5.6	y = 0.7286x – 0.0007	0.964	500–5000	MS, RI, Std
3	7.163	692	686^j,k	1-Penten-3-ol	798.4b	6.0	1178.9ab	5.8	1412.7a	7.1	y = 0.6464x – 0.0013	0.958	500–5000	MS, RI, Std
4	8.159	702	700^j	2,3-Pentanedione	3094.1a	7.5	953.1b	7.3	931.92b	9.5	y = 0.8987x – 0.0004	0.976	500–5000	MS, RI, Std
5	8.621	726	724^h	3-Hydroxy-2-butanone	9893.5a	9.9	10,310.5a	9.7	6758.8b	7.0	y = 1.5439x – 0.0013	0.929	2000–20,000	MS, RI, Std
6	9.800	759	766^j	1-Pentanol	1509.4b	6.5	2681.1a	6.4	1595.5b	6.6	y = 0.5681x – 0.0003	0.954	500–5000	MS, RI, Std
7	10.033	762	756^i	2-Methyl-2-butenal	343.2	6.8	–	–	141.6	5.9	y = 0.2580x + 0.0032	0.948	50–500	MS, RI, Std
8	10.723	767	767^h	Epoxylinalool	3609.4b	6.7	5776.2ab	6.0	6203.4a	6.0	y = 0.3899x – 0.0001	0.963	1000–10,000	MS, RI, Std
9	12.100	798	798^h	4-Methyl-3-penten-2-one	8984.3b	5.9	11,480.0a	5.8	13408.4a	10.8	y = 1.3147x – 0.0004	0.973	5000–50,000	MS, RI, Std
10	12.280	810	801^j	Hexanal	5784.9a	9.3	1623.2b	9.6	1182.6b	9.0	y = 0.6070x – 0.0011	0.946	500–10,000	MS, RI, Std
11	14.419	828	828^h	2-Methylpyrazine	3768.8b	8.2	6435.5a	9.2	1296.1c	8.6	y = 0.1708x – 0.0030	0.971	500–10,000	MS, RI, Std
12	16.350	853	851^j	1-Hexanol	2509.4ab	9.8	2960.5a	9.5	1192.8b	4.8	y = 1.1967x + 0.0004	0.983	500–5000	MS, RI, Std
13	17.940	897	893^j	2-Acetylfuran	7849.6a	5.2	1127.9c	4.7	2342.3b	7.9	y = 0.9086x – 0.0004	0.972	500–10,000	MS, RI, Std
14	19.430	903	903^j	Heptanal	13,989.4a	7.3	14,760.6a	7.5	7406.1b	8.7	y = 0.3603x + 0.0002	0.973	5000–50,000	MS, RI, Std
15	19.590	905	905^j	2,5-Dimethylpyrazine	8943.5a	8.2	3385.9b	8.6	4588.6b	6.9	y = 1.9065x – 0.0003	0.982	2000–20,000	MS, RI, Std
16	19.740	907	907^h	2-Ethylpyrazine	3209.3a	7.4	1835.8c	7.4	2590.3b	7.8	y = 0.4578x – 0.0008	0.967	1000–5000	MS, RI, Std
17	20.450	913	913^h	2,6-Dimethylpyrazine	1698.7b	7.5	1758.3b	7.0	3209.9a	6.5	y = 1.7225x + 0.0003	0.953	1000–5000	MS, RI, Std
18	22.200	970	960^j	Benzaldehyde	5409.4a	6.1	5591.8a	6.7	2768.1b	6.7	y = 0.9287x + 0.0012	0.926	1000–10,000	MS, RI, Std
19	22.420	976	974^j	6-Methyl-5-hepten-2-one	904.5	7.1	–	–	–	–	y = 0.9074x – 0.0039	0.942	500–5000	MS, RI, Std
20	22.525	978	978^j	5-Methyl-2-furfural	2898.3a	6.5	873.5c	6.3	1523.3b	4.5	y = 0.5248x – 0.0039	0.963	500–5000	MS, RI, Std
21	22.760	980	980^h	Phenol	8739.1	4.7	6059.5	4.6	–	–	y = 0.6328x – 0.0002	0.978	2000–20,000	MS, RI, Std
22	23.235	992	992^h	β-Myrcene	276.8	7.9	–	–	332.6	5.7	y = 0.7410x + 0.0021	0.948	100–1000	MS, RI, Std
23	24.300	1003	1000^j	2,3,5-Trimethylpyrazine	3494.5b	5.8	3107.6b	6.4	4324.6a	7.5	y = 1.1879x – 0.0004	0.978	2000–10,000	MS, RI, Std
24	24.600	1011	1011^j	(E,E)-2,4-heptadienal	908.2b	8.4	1470.0a	7.5	824.8b	6.9	y = 0.9382x + 0.0001	0.945	200–2000	MS, RI, Std
25	24.635	1012	1012^h	2-Acetyl pyridine	890.3a	6.7	494.8b	6.6	235.4c	7.5	y = 0.7237x + 0.0006	0.945	100–1000	MS, RI, Std
26	25.400	1026	1024^j	2-Ethyl hexanol	5181.8b	6.5	7223.9a	6.7	1780.1c	6.4	y = 1.0967x – 0.0038	0.984	1000–10,000	MS, RI, Std
27	26.200	1039	1039^j,k	Benzyl alcohol	26,983.3a	5.8	9070.6c	6.6	12778.3b	5.5	y = 0.4101x – 0.0024	0.959	5000–50,000	MS, RI, Std
28	26.700	1045	1044^h	2-Acetylpyrrole	35,838.9a	6.1	23,874.4b	6.0	15318.2c	5.1	y = 1.1377x – 0.0007	0.949	10,000–50,000	MS, RI, Std
29	26.950	1047	1047^h	2-Ethyl-5-methylpyrazine	4974.4a	5.5	3790.0b	5.0	2329.2c	8.5	y = 0.9332x + 0.0027	0.982	1000–10,000	MS, RI, Std
30	28.400	1075	1075^h	p-Cresol	5243.7a	7.9	1343.6c	8.1	2409.5b	6.3	y = 0.3884x – 0.0005	0.968	500–10,000	MS, RI, Std
31	28.648	1082	1072^j	1-Octanol	3581.9	6.0	5428.4	6.3	–	–	y = 0.6388x – 0.0007	0.937	1000–10,000	MS, RI, Std
32	28.863	1083	1082^h	2-Ethyl-3,5-dimethylpyrazine	3163.5a	6.4	2466.8b	6.4	2514.7b	6.6	y = 0.6820x + 0.0008	0.974	1000–5000	MS, RI, Std
33	28.965	1087	1087^h	Maltol	20,673.3	6.6	–	–	–	5.3	y = 1.3991x – 0.0036	0.967	10,000–50,000	MS, RI, Std
34	29.260	1103	1100^j	Linalool	22,914.0a	5.7	5300.1b	5.5	7352.4b	4.6	y = 0.9274x – 0.0003	0.954	2000–50,000	MS, RI, Std
35	29.400	1106	1104^j,k	Nonanal	13,353.2a	4.9	3591.3b	4.7	3800.7b	7.2	y = 0.6394x – 0.0002	0.968	1000–20,000	MS, RI, Std
36	29.600	1109	1101^j	Hotrienol	10,274.5	7.5	8324.6	7.4	–	–	y = 0.6367x – 0.0004	0.953	5000–20,000	MS, RI, Std
37	30.100	1123	1118^j	Phenylethyl alcohol	30,386.5b	5.6	34,218.1b	5.5	46075.0a	6.3	y = 1.6993x – 0.0004	0.952	10,000–100,000	MS, RI, Std
38	31.400	1195	1185^j	α-Terpineol	10,675.1a	6.4	3405.7b	7.0	4500.4b	5.3	y = 0.372x – 0.0031	0.959	1000–20,000	MS, RI, Std
39	32.100	1212	1212^j	Trans-linalool oxide	14,398.4a	6.0	3152.4b	5.3	5108.4b	6.7	y = 0.8793x – 0.0018	0.985	1000–20,000	MS, RI, Std
40	33.200	1235	1234^j	Methyl salicylate	6860.1	6.5	–	–	2443.4	7.0	y = 0.4859x – 0.0001	0.918	1000–10,000	MS, RI, Std
41	35.200	1276	1276^j	Geraniol	35,012.4a	6.0	29,749.7ab	6.2	16896.7b	4.7	y = 0.5857x – 0.0002	0.948	10,000–50,000	MS, RI, Std
42	37.783	1293	1292^j	Indole	12,768.5a	4.3	2731.6b	4.9	3482.9b	6.7	y = 0.2375x + 0.0001	0.918	1000–20,000	MS, RI, Std
43	38.200	1332	1334^h	2-Methoxy-4-vinylphenol	7222.5	6.8	3876.8	6.6	–	–	y = 0.5792x – 0.0030	0.918	1000–10,000	MS, RI, Std
44	38.500	1340	1337^h	Methyl anthranilate	2758.3a	6.9	3550.3a	7.0	2686.9a	7.2	y = 0.7010x + 0.0004	0.927	1000–10,000	MS, RI, Std
45	39.600	1378	1381^h	(Z)-3-hexenyl hexanoate	13,085.4a	7.7	11,982.1a	7.4	15665.7a	6.5	y = 1.0601x + 0.0002	0.926	5000–50,000	MS, RI, Std
46	39.774	1382	1370^j	(Z)-jasmone	21,284.0a	6.9	23,874.4a	6.7	3954.3b	5.0	y = 0.8195x – 0.0014	0.928	1000–50,000	MS, RI, Std
47	42.134	1493	1493^j,k	β-Ionone	2201.5a	5.2	1594.1b	5.1	2710.7a	6.0	y = 0.2269x + 0.0019	0.938	500–5000	MS, RI, Std
48	42.200	1493	1489^j	Dihydroactinidiolide	3386.5	5.6	3500.5	5.5	–	–	y = 0.3119x – 0.0010	0.972	1000–10,000	MS, RI, Std
49	44.883	1565	1539^j	(Z)-nerolidol	5048.7ab	9.6	8390.9a	10.5	3533.6b	7.1	y = 0.4687x + 0.0024	0.963	1000–10,000	MS, RI, Std
50	45.278	1573	1574^h	(Z)-3-hexenyl benzoate	7717.1a	8.0	7732.0a	7.2	2637.8b	7.1	y = 0.6095x – 0.0004	0.985	1000–10,000	MS, RI, Std
51	46.952	1626	1626^j	Methyl jasmonate	6745.9a	7.0	2378.4b	6.9	3127.6b	6.1	y = 0.2727x + 0.0002	0.938	1000–10,000	MS, RI, Std
52	48.600	1676	1676^h	α-Cadinol	8494.8	5.3	–	–	–	–	y = 0.8677x + 0.0007	0.915	2000–20,000	MS, RI, Std
53	58.300	2079	2079^h	4-Vinylphenol	3673.7	4.5	2802.4	5.1	–	–	y = 0.4838x – 0.0025	0.925	1000–5000	MS, RI, Std

^aThe retention time of aroma compounds in column.

^bRI: retention index on different stationary phases.

^cValues with different roman letters (a–c) in the same row are significantly different according to the Duncan’s test (p < 0.05).

^dRSD: relative standard deviation.

^eStandard curves of aroma compounds.

^fLinear ranges of aroma compounds.

^gMethod of identification: MS, mass spectrum comparison using Wiley library; RI: retention index in agreement with literature value; Std: confirmed by authentic standards.

The RI referred from literatures:

^hhttp://www.flavornet.org/

ⁱReference 28: JianCai Zhu et al., Comparison of Aroma-Active Compounds and Sensory Characteristics of Durian (Durio zibethinus L.) Wines Using Strains of Saccharomyces cerevisiae with Odor Activity Values and Partial Least-Squares Regression, J. Agric. Food Chem. 2015, 63, 1939−1947.

^jReference 8: JianCai Zhu et al., Comparison of Aroma-Active Volatiles in Oolong Tea Infusions Using GC-Olfactometry, GC-FPD, and GC-MS, J. Agric. Food Chem. 2015, 63, 7499−7510.

^kReference 7: JianCai Zhu et al., Characterization of the Key Aroma Volatile Compounds in Cranberry (Vaccinium macrocarpon Ait.) Using Gas Chromatography−Olfactometry (GC-O) and Odor Activity Value (OAV), J. Agric. Food Chem. 2016, 64, 4990−4999.

Figure 1. (a) Five fibers, coated with 65 μm PDMS/DVB, 80 μm PA, 100 μm PDMS, 75 μm CAR/PDMS, and 50/30 μm CAR-PDMS-DVB, were assessed for the extraction of the aroma compounds. (b) Six different extraction times were evaluated in the experiment.

Figure 2. Total ion chromatogram (TIC) of three Longjing tea samples. The numbers (1–53) in the peak refer to the identified aroma compounds in Table 1.

Table 2. GC-O and OAV of identified aroma-active compounds in Longjing tea samples.

				OAV^c			Aroma intensity^d
Number	Descriptor^a	Aroma compound	Odor threshold (μg/kg)^b	Y1	Y2	Y3	Y1	Y2	Y3	Identification basis^e
1	Garlic	Dimethyl sulfide	1100	2.3	<1	1.1	1.6a ± 0.16	0.7b ± 0.06	1.1ab ± 0.1	Odor, Std
2	Butter, sweet	2,3-Butanedione	100	24.5	23.3	17.6	2.8a ± 0.25	2.9a ± 0.32	2.6a ± 0.2	Odor, Std
3	Fruity	1-Penten-3-ol	400	2.0	2.9	3.5	1.7a ± 0.14	1.8a ± 0.15	1.9a ± 0.21	Odor, Std
4	Butter, sweet	2,3-Pentanedione	5500	<1	<1	<1	0.9a ± 0.1	1.1a ± 0.1	1.2a ± 0.1	Odor, Std
5	Butter	3-Hydroxy-2-butanone	800	12.4	12.9	8.4	4.3a ± 0.36	4.5a ± 0.54	3.7b ± 0.34	Odor, Std
6	Balsamic, grassy	1-Pentanol	5000	<1	<1	<1	0.8b ± 0.07	1.3a ± 0.12	1.1ab ± 0.13	Odor, Std
7	Green, floral	2-Methyl-2-butenal	459	<1	–^g	<1	0.9 ± 0.11	NP^h	1.1 ± 0.11	Odor, Std
8	Floral, lemon-like	Epoxylinalool	6	601.6	962.7	1033.9	8.1a ± 0.75	8.3a ± 0.77	8.5a ± 0.7	Odor, Std
9	Floral	4-Methyl-3-penten-2-one	NF^f	–	–	–	4.4a ± 0.37	4.5a ± 0.4	4.7a ± 0.43	Odor, Std
10	Grassy, green	Hexanal	479	12.1	3.4	2.5	2.5a ± 0.23	1.4b ± 0.12	1.1b ± 0.1	Odor, Std
11	Nutty, peanut	2-Methylpyrazine	27,000	<1	<1	<1	1.2a ± 0.11	1.1a ± 0.09	0.9a ± 0.08	Odor, Std
12	Green, plant	1-Hexanol	2500	1.0	1.2	<1	0.9a ± 0.08	1.1a ± 0.11	0.9a ± 0.07	Odor, Std
13	Peanut, sweet	2-Acetylfuran	15025.2	<1	<1	<1	0.8a ± 0.06	0.9a ± 0.09	0.8a ± 0.08	Odor, Std
14	Green	Heptanal	550	25.4	26.8	13.5	4.6a ± 0.47	4.8a ± 0.43	4.6a ± 0.47	Odor, Std
15	Nutty, cooked rice	2,5-Dimethylpyrazine	800	11.2	4.2	5.7	2.6a ± 0.26	1.2b ± 0.11	1.1b ± 0.1	Odor, Std
16	Nutty	2-Ethylpyrazine	6000	<1	<1	<1	1.2a ± 0.11	1.1a ± 0.1	0.9a ± 0.08	Odor, Std
17	Nutty	2,6-Dimethylpyrazine	157.6	10.8	11.2	20.4	2.3b ± 0.21	2.6b ± 0.24	3.2a ± 0.3	Odor, Std
18	Floral, almond	Benzaldehyde	750.9	7.2	7.4	3.7	1.2a ± 0.11	1.2a ± 0.1	0.8b ± 0.08	Odor, Std
19	Floral	6-Methyl-5-hepten-2-one	50	18.1	–	–	2.6 ± 0.24	NP	NP	Odor, Std
20	Burnt sugar	5-Methyl-2-furfural	1110	2.6	0.8	1.4	1.3a ± 0.11	0.8b ± 0.07	1.1ab ± 0.1	Odor, Std
21	Medicinal, phenolic	Phenol	1000	8.7	6.1	–	1.4 ± 0.13	1.6 ± 0.14	NP	Odor, Std
22	Sulfury, mango-like	β-Myrcene	100	2.8	–	3.3	1.4 ± 0.13	NP	1.8 ± 0.16	Odor, Std
23	Nutty	2,3,5-Trimethylpyrazine	297	11.8	10.5	14.6	1.8b ± 0.16	1.7b ± 0.18	2.1a ± 0.16	Odor, Std
24	Green	(E,E)-2,4-heptadienal	94.8	9.6	15.5	8.7	1.2b ± 0.1	2.5a ± 0.25	1.3b ± 0.13	Odor, Std
25	Nutty	2-Acetyl pyridine	19	46.9	26.0	12.4	6.2a ± 0.64	5.9a ± 0.53	5.1b ± 0.52	Odor, Std
26	Floral	2-Ethyl hexanol	300	17.3	24.1	5.9	2.3b ± 0.23	5.4a ± 0.5	2.1b ± 0.19	Odor, Std
27	Floral	Benzyl alcohol	100	269.8	90.7	127.8	8.4a ± 0.75	8.1a ± 0.76	8.3a ± 0.75	Odor, Std
28	Nutty, herbal	2-Acetylpyrrole	170,000	<1	<1	<1	1.1a ± 0.1	0.8b ± 0.07	1.2a ± 0.12	Odor, Std
29	Nutty, peanut	2-Ethyl-5-methylpyrazine	100	49.7	37.9	23.3	5.2a ± 0.49	4.8b ± 0.41	4.6b ± 0.44	Odor, Std
30	Smoky	p-Cresol	100	52.4	13.4	24.1	5.7a ± 0.53	4.4b ± 0.41	4.5b ± 0.37	Odor, Std
31	Fruity	1-Octanol	110	32.6	49.3	–	4.6 ± 0.39	5.3 ± 0.47	NP	Odor, Std
32	Nutty	2-Ethyl-3,5-dimethylpyrazine	7.52	420.7	328.0	334.4	4.8a ± 0.45	4.5a ± 0.39	4.6a ± 0.41	Odor, Std
33	Sweet	Maltol	2500	8.3	–	–	1.5 ± 0.13	NP	NP	Odor, Std
34	Floral, green	Linalool	500	45.8	10.6	14.7	6.5a ± 0.57	5.2b ± 0.54	5.6b ± 0.44	Odor, Std
35	Soapy, aldehydic	Nonanal	2530	5.3	1.4	1.5	0.8a ± 0.06	0.5a ± 0.05	0.7a ± 0.07	Odor, Std
36	Floral, grass	Hotrienol	110	93.4	75.7	–	6.4 ± 0.66	5.3 ± 0.47	NP	Odor, Std
37	Floral	Phenylethyl alcohol	750	40.5	45.6	61.4	6.2b ± 0.63	6.4b ± 0.59	7.5a ± 0.65	Odor, Std
38	Floral	α-Terpineol	330	32.3	10.3	13.6	4.8a ± 0.43	4.2b ± 0.39	4.4ab ± 0.4	Odor, Std
39	Grass, floral	Trans-linalool oxide	320	45.0	9.9	16.0	5.6a ± 0.52	3.7c ± 0.31	4.6b ± 0.39	Odor, Std
40	Sweet	Methyl salicylate	40	171.5	–	61.1	8.1 ± 0.76	NP	6.8 ± 0.66	Odor, Std
41	Green, floral	Geraniol	40	2508.4	743.7	422.4	4.4a ± 0.37	3.9b ± 0.33	3.5b ± 0.32	Odor, Std
42	Animal-like	Indole	500	25.5	5.5	7.0	5.2a ± 0.48	4.4b ± 0.38	4.5b ± 0.41	Odor, Std
43	Spicy, smoky	2-Methoxy-4-vinylphenol	3000	2.4	1.3	–	1.1 ± 0.09	0.9 ± 0.07	NP	Odor, Std
44	Sweet, floral	Methyl anthranilate	300	9.2	11.8	9.0	1.4a ± 0.12	1.4a ± 0.13	1.6a ± 0.17	Odor, Std
45	Sweet, floral	(Z)-3-hexenyl hexanoate	NF	–	–	–	4.3a ± 0.36	4.5a ± 0.44	4.9a ± 0.51	Odor, Std
46	Sweet, burnt	(Z)-Jasmone	NF	–	–	–	4.3b ± 0.4	5.1a ± 0.43	3.9c ± 0.34	Odor, Std
47	Floral, woody	β-Ionone	7	314.5	227.7	387.3	6.7ab ± 0.65	6.3b ± 0.49	7.3a ± 0.66	Odor, Std
48	Roasted	Dihydroactinidiolide	NF	–	–	–	9.2 ± 0.78	9.1 ± 1	NP	Odor, Std
49	Floral, woody	(Z)-nerolidol	15	336.6	559.4	235.6	8.6a ± 0.67	8.8a ± 0.84	8.4a ± 0.74	Odor, Std
50	Fruity, green	(Z)-3-hexenyl benzoate	NF	–	–	–	4.5a ± 0.5	4.3a ± 0.45	4.1a ± 0.37	Odor, Std
51	Floral	Methyl jasmonate	70	96.4	34.0	44.7	4.4a ± 0.42	4.1ab ± 0.34	3.9b ± 0.34	Odor, Std
52	Floral	α-Cadinol	NF	–	–	–	3.6 ± 0.38	NP	NP	Odor, Std
53	Smoky	4-Vinylphenol	100	36.7	28.0	–	4.8 ± 0.4	4.6 ± 0.43	NP	Odor, Std

^aAroma description from penalists.

^bThe odor threshold referred from literature (Van Gemert, L. J. 2003. Complilations of Odour Threshold Values in Air, Water and Other Media; Van Setten Kwadraat: Houten, The Netherlands).

^cOdor activity values were calculated by dividing the concentrations by the respective odor threshold.

^dAroma intensity obtained by GC-O.

^eOdor, compounds were identified by comparing with olfactory description; Std, compounds were identified by pure authentic standards.

^fNot found.

^gNot obtained.

^hNot perceived.

Table 3. Models consisting aroma compounds with AI > 4 and OAV > 10.

		OAV			Aroma intensity
Number	Aroma compound	Y1	Y2	Y3	Y1	Y2	Y3
1	2,3-Butanedione	24.5	23.3	17.6	NA	NA	NA
2	3-Hydroxy-2-butanone	12.4	12.9	NA	4.3	4.5	NA
3	Epoxylinalool	601.6	962.7	1033.9	8.1	8.3	8.5
4	4-Methyl-3-penten-2-one	NA	NA	NA	4.4	4.5	4.7
5	Hexanal	12.1	NA	NA	NA	NA	NA
6	Heptanal	25.4	26.8	13.5	4.6	4.8	4.6
7	2,5-Dimethylpyrazine	11.2	NA	NA	NA	NA	NA
8	2,6-Dimethylpyrazine	10.8	11.2	20.4	NA	NA	NA
9	6-Methyl-5-hepten-2-one	18.1	NA	NA	NA	NA	NA
10	2,3,5-Trimethylpyrazine	11.8	10.5	14.6	NA	NA	NA
11	(E,E)-2,4-heptadienal	NA	15.5	NA	NA	NA	NA
12	2-Acetyl pyridine	46.9	26.0	12.4	6.2	5.9	5.1
13	2-Ethyl hexanol	17.3	24.1	NA	NA	5.4	NA
14	Benzyl alcohol	269.8	90.7	127.8	8.4	8.1	8.3
15	2-Ethyl-5-methylpyrazine	49.7	37.9	23.3	5.2	4.8	4.6
16	p-Cresol	52.4	13.4	24.1	5.7	4.4	4.5
17	1-Octanol	32.6	49.3	NA	4.6	5.3	NA
18	2-Ethyl-3,5-dimethylpyrazine	420.7	328.0	334.4	4.8	4.5	4.6
19	Linalool	45.8	10.6	14.7	6.5	5.2	5.6
20	Hotrienol	93.4	75.7	NA	6.4	5.3	NA
21	Phenylethyl alcohol	40.5	45.6	61.4	6.2	6.4	7.5
22	α-Terpineol	32.3	10.3	13.6	4.8	4.2	4.4
23	Trans-linalool oxide	45.0	9.9	16.0	5.6	NA	4.6
24	Methyl salicylate	171.5	NA	61.1	8.1	NA	6.8
25	Geraniol	2508.4	743.7	422.4	4.4	3.9	3.5
26	Indole	25.5	NA	NA	5.2	4.4	4.5
27	Methyl anthranilate	NA	11.8	NA	NA	NA	NA
28	(Z)-3-hexenyl hexanoate	NA	NA	NA	4.3	4.5	4.9
29	(Z)-jasmone	NA	NA	NA	4.3	5.1	NA
30	β-Ionone	314.5	227.7	387.3	6.7	6.3	7.3
31	Dihydroactinidiolide	NA	NA	NA	9.2	9.1	NA
32	(Z)-Nerolidol	336.6	559.4	235.6	8.6	8.8	8.4
33	(Z)-3-hexenyl benzoate	NA	NA	NA	4.5	4.3	4.1
34	Methyl jasmonate	96.4	34.0	44.7	4.4	4.1	NA
35	4-Vinylphenol	36.7	28.0	NA	4.8	4.6	NA

NA: not added in the model.

Figure 3. Radar plot of electronic nose analysis data for the original odor concentrates of three Longjing tea samples and different aroma synthetic solutions based on data from gas chromatography–olfactometry (GC-O) and odor activity value (OAV) as well as the value corresponding to sensors between each aroma recombination model and the original model.

Figure 4. Aroma profiles of three Longjing tea samples and different aroma synthetic solutions based on data from GC-O (model 1) and OAV (model 2).