Volatile components of essential oils extracted from Pu-erh ripe tea by different extraction methods

Figures & data

Table 1. Time consumption and extraction rate for extracting the essential oil by different methods.

Extraction method	Raw material quantity (g)	Time consumption (h)	Extraction rate (g/kg)
Soxhlet	30	8	0.81 ± 0.01
UAE	30	4	0.36 ± 0.01
SDE	30	6	0.11 ± 0.01
SD	30	5	0.59 ± 0.01

Extraction rate (g/kg) = Oil quantity/tea powder (mean value ± standard deviation, n = 3).

Table 2. GC-MS analysis results of the tea essential oils from different extraction methods.

No	RI^a	Compound^b	Relative percentage content [%(range)]^c					Odour note
			Soxhlet	UAE	SDE	SD	HS-SPME
1	803	2,3-Butanediol	-	15.92	16.73	-	0.11
2	805	1-Pentanol	-	-	-	0.05	-
3	843	(Z)-3-Hexen-1-ol	-	0.05	0.09	-	0.12	Mushroom^d
4	861	Hexyl alcohol	-	0.12	-	0.09	-
5	884	2-Heptanone	0.08	-	-	0.04	1.20
6	957	Benzaldehyde	5.36	0.07	-	-	-
7	979	1-Octen-3-ol	1.24	2.39	7.34	4.12	0.18	Mushroom^d
8	985	6-Methyl-5-hepten-2-one	-	2.65	-	0.09	1.77	Fat^d, orange^d
9	989	2-Pentylfuran	-	-	10.85	0.04	0.29	Fruit, earthy^d
10	997	α-Phellandrene	0.08			0.08
11	998	Cis-2-(2-pentenyl)furan	-	-	-	0.04	-
12	1018	1,2,3-Trimethylbenzene	-	-	2.02	0.03	0.16
13	1026	Limonene	-	-	-	0.07	0.13
14	1034	Benzyl alcohol	3.84	-	-	0.10	-	Fruit^d, smoke^d
15	1037	(E)-3,7-Dimethyl-1,3,6-octatriene	0.20	0.12	1.49	0.60	0.50
16	1042	Phenyl acetaldehyde	0.36	-	-	-	0.30
17	1048	Ocimene	-	0.06	0.04	-	-	Sweet^d
18	1056	γ-Terpinene	-	-	-	0.04	-
19	1064	Acetophenone	0.08	-	-	-	-
20	1068	(E)-2-Octen-1-ol	-	-	1.72	0.05	0.13
21	1072	Linalool oxide I	-	-	-	-	0.34	Flower^d, wood^e
22	1087	Linalool oxide II	-	-	-	-	2.85	Flower^d, wood^e
23	1092	(E,E)-3,5-octadien-2-one	0.12	0.04	-	0.04	1.04
24	1098	Linalool	-	1.34	-	0.76	0.15	Flower, lavender^d, wood^d
25	1100	Hotrienol	1.43	-	-	0.97
26	1104	Nonanal	-	-	0.05	-	-
27	1110	Phenylethyl alcohol	0.45	-	3.43	0.37	0.31	Rose^e
28	1135	Benzene acetonitrile	0.09	0.02	-	0.07	3.61
29	1137	2,5-Pyrrolidinedione, 1-ethyl-	-	0.06	0.06	-	-
30	1149	1,2-Dimethoxybenzene	-	0.06	-	0.68	0.39
31	1169	Linalool oxide III	-	-	-	-	0.35	Flower^d, wood^e
32	1175	Linalool oxide IV	-	-	-	-	2.89	Flower^d, wood^e
33	1178	Naphthalene	0.28	0.06	2.93	-	0.20
34	1188	α-Terpineol	-	0.04	0.35	0.06	1.24	Flower, clove^e
35	1190	Methyl salicylate	0.15	0.03	0.20	0.22	1.38	Green, fat, herb^e
36	1200	Dodecane	-	0.15	-	-	-
37	1205	Decanal	-	-	1.02	-	-
38	1218	β-Cyclocitral	-	-	0.30	-	0.88
39	1228	Nerol	-	-	1.66	0.15	0.69	Sweet, rose^d
40	1241	3,4-Dimethoxytoluene	0.34	0.09	-	-	1.96	Mouldy^d
41	1256	Geraniol	-	0.02	0.36	-	1.06	Rose^d
42	1260	2-Methoxybenzylalcohol	-	-	0.31	-	0.98
43	1265	3,5-Dimethoxytoluene	-	0.09	-	0.04	2.02
44	1287	2-Methylnaphthalene	1.41	0.15	-	-	-
45	1289	Indole	-	-	0.08	0.05	0.57	Mothball, burnt^d
46	1302	1-Methylnaphthalene	-	0.06	-	-	-
47	1304	Isopropyl salicylate	-	0.03	-	-	-
48	1316	1,2,3-Trimethoxybenzene	4.29	2.35	-	-	27.43	Wood, herb^e
49	1325	4-Ethyl-1,2-dimethoxybenzene	1.33	-	-	0.08	0.24
50	1334	2,6,6-Trimethyl-1-cyclohexene-1-ethanol	-	-	0.05	-	-
51	1351	2,6-Dimethoxyphenol	2.66	12.12	-	-	0.87	Medicine, phenol, smoke^d
52	1362	γ-Nonanolactone	0.09
53	1369	Butanoic acid butyl ester	0.18	0.17		0.07
54	1375	1,2,4-Trimethoxybenzene	3.14	1.19	-	0.15	0.87	Wood, herb^e
55	1387	β-Guaiene	-	0.11	0.76	-	1.27	Wood, spice^d
56	1397	Cis-jasmone	-	-	-	0.07	-
57	1400	Tetradecane	-	0.17	-	0.10	0.54
58	1406	1,2,3-Trimethoxy-5-methylbenzene	0.74	0.18	-	-	2.98
59	1409	α-Cedrene	-	-	0.99	-	-	Wood^e
60	1417	β-Caryophyllene	0.69	0.28	-	-	8.25	Mint^e, spice^d, wood^d
61	1428	α-Ionone	0.29	-	-	-		Wood^d,violet^d
62	1433	1,2-Benzopyrone			0.64	0.33
63	1438	Dihydro-β-ionone	-	-	0.09	-	0.69
64	1442	1-Methoxynaphthalene	-	-	0.07	-	-
65	1447	2-Methoxynaphthalene	-	0.72	9.09	-	1.88	Orange, sweet^d
66	1449	1,2,3,4-Tetramethoxybenzene	-	-	1.18	-	1.06	Herb^e
67	1455	Geranyl acetone	-	-	-	-	0.88	Magnolia, green^d, fruit^e
68	1468	5-Methoxy-6,7-dimethylbenzofuran	0.07			0.17	0.98
69	1487	β-Ionone	-	-	1.02	-	0.65	Seaweed, violet, flower^d
70	1492	2-Tridecanone	-	-	-	0.05	-
71	1497	Methyl isoeugenol	-	-	-	0.09	-
72	1500	Pentadecane	0.36	-	-	0.05	-
73	1506	Dibenzofuran	-	-	-	0.13	-
74	1508	α-Farnesene	-	-	0.09	-	-	Flower, herb^e, green^d
75	1528	Dihydroactinidiolide	0.11	-	-	0.27	-	Musk^d, coumarin^d
76	1543	α-Calacorene				0.50
77	1554	Nerolidol	13.13	6.61	-	17.10	-	Apple, rose, green^d
78	1572	Fluorene	-	2.70	-	6.63	-
79	1598	Cedrol	1.29	-	-	-	0.27	Wood^e, sweet^d
80	1600	Hexadecane	11.18	-	-	-	1.57	Alkane^d
81	1649	Methyl jasmonate	0.14	1.24			8.01
82	1653	α-Cadinol	-	-	-	-	1.09
83	1659	2,2’,5,5’-Tetramethyl-1,1’-biphenyl	6.26	-	1.70	0.88	-
84	1664	2-Methylhexadecane	0.50	-	-	-	0.36
85	1700	Heptadecane	1.43			0.87		Alkane^d
86	1828	Isopropyl myristate	-	0.06	0.10	-	-
87	1840	Caffeine	15.02	19.74	23.85	33.27	2.98
88	1846	Phytone	-	-	-	0.51	-
89	1918	Farnesyl acetone	-	-	-	0.15	0.64	Sweet^d, rose^d
90	1927	Hexadecanoic acid methyl ester	-	-	1.34	-	-
91	1949	Isophytol	2.59	-	-	2.23	1.36	Flower^d, herbs^e
92	1975	Hexadecanoic acid	0.16	18.47	-	-	0.19
93	2000	Eicosane	0.01	-	-	-	-
94	2093	Methyl linoleate	-	-	-	0.05	-
95	2095	Linolenic acid	0.12	-	-	-	0.38
96	2122	Phytol	-	-	-	12.97	3.22	Flower^d, balsam^e

^aRI, retention indices as determined on an HP-5MS column using a homologous series of n-alkanes.

^bCompounds are listed in order of retention time.

^cRelative content, percent normalised peak areas; ‘-’ not detected.

^dhttp://www.flavornet.org/flavornet.html.

^eLiu Shuwen. Synthetic spices manual [M]. China light industry press. 2010.

Table 3. Sensory evaluation on the different essential oils samples from the four extraction methods.

Extraction method	Colour	Persistence	Transparency	Degree of flavour	Taste
Soxhlet	Yellow	Short	General transparency	Can sniff out	Miscellaneous taste
UAE	Yellow	Long	General transparency	Can identify	Commonly
SDE	Light yellow	Medium	More transparent	Slightly stronger	Fragrant
SD	Brown	Longer	Turbid	Very strong	Very fragrant

Figure 1. TICs of Pu-erh tea essential oil by different extraction processes. (A) — headspace-solid phase microextraction (HS-SPME); (B) — ultrasonic-assisted extraction (UAE); (C) — simultaneous distillation extraction (SDE); (D) — Soxhlet extraction; (E) — steam distillation extraction (SD).

Figure 2. The number of the types of aroma compounds in different methods.

Figure 3. Composition comparison of Pu-erh ripe tea essential oils extracted by five different methods.

Figure 4. The appearance and aroma characteristics of the tea essential oils obtained by four extraction methods.