Quantity and chemical composition of essential oil of peppermint (Mentha × piperita L.) leaves under different drying methods

Figures & data

Table 1. Considered drying methods and conditions to dry peppermint leaves.

Drying method	Drying conditions
Hot air	Air temperatures: 50°C, 60°C, and 70°C Air velocity: 0.4 m/s Samples lot thickness: 10 mm
Microwave power	Power levels: 200, 400, and 800 W Samples lot thickness: 10 mm
Shade	Ambient temperature: 22°C ± 4°C Samples lot thickness: 10 mm

Figure 1. Influence of the drying methods on essential oil yield (g/kg _{dry matter}) of the peppermint leaves.

Significant different at p < 0.05 have been indicated with different letters.

Table 2. Volatile compound (%) of the essential oils of the fresh and dried peppermint leaves.

				Hot air dried			Microwave dried
No.	RI^a	Composition	Fresh	50°C	60°C	70°C	800 W	400 W	200 W	Shade dried	ANOVA
1	925	α-Thujene	0.02 ± 0.02	0.07 ± 0.00	0.15 ± 0.18	0.04 ± 0.00	-	-	-	0.05 ± 0.02
2	933	α-Pinene	0.37 ± 0.28	1.15 ± 0.12	0.70 ± 0.17	0.74 ± 0.04	0.09 ± 0.05	0.08 ± 0.03	0.05 ± 0.01	0.82 ± 0.05
3	948	Camphene	-	0.03 ± 0.00	0.01 ± 0.01	0.01 ± 0.01	-	-	-	0.01 ± 0.01
4	973	Sabinene	0.41 ± 0.15	0.85 ± 0.10	0.49 ± 0.05	0.60 ± 0.02	0.07 ± 0.03	0.04 ± 0.03	0.02 ± 0.02	0.67 ± 0.03
5	977	β-Pinene	0.70 ± 0.28	1.58 ± 0.09	1.03 ± 0.21	1.16 ± 0.10	0.32 ± 0.16	0.16 ± 0.23	-	1.21 ± 0.06
6	989	Myrcene	0.10 ± 0.07	0.29 ± 0.02	0.14 ± 0.11	0.17 ± 0.01	0.04 ± 0.03	0.12 ± 0.11	0.12 ± 0.16	0.20 ± 0.02
7	994	3-Octanol	0.08 ± 0.07	0.24 ± 0.09	0.11 ± 0.08	0.17 ± 0.03	0.22 ± 0.07	0.29 ± 0.04	0.28 ± 0.01	0.20 ± 0.04
8	1017	α-Terpinene	0.11 ± 0.08	0.36 ± 0.03	0.27 ± 0.08	0.30 ± 0.04	0.16 ± 0.09	0.22 ± 0.03	0.14 ± 0.04	0.31 ± 0.02
9	1024	p-Cymene	0.06 ± 0.04	0.14 ± 0.01	0.04 ± 0.06	0.11 ± 0.02	0.04 ± 0.01	0.03 ± 0.02	0.02 ± 0.01	0.11 ± 0.01
10	1028	Limonene	1.87 ± 0.66	2.56 ± 0.85	2.62 ± 0.60	2.63 ± 0.31	0.76 ± 0.28	0.51 ± 0.14	0.31 ± 0.09	2.74 ± 0.20
11	1031	1,8-Cineole	5.81 ± 1.50	8.20 ± 2.46	6.08 ± 0.37	7.36 ± 0.52	2.06 ± 0.81	0.51 ± 0.11	0.29 ± 0.11	7.96 ± 0.98	p < 0.01
12	1035	cis-β-Ocimene	0.08 ± 0.06	0.20 ± 0.03	0.12 ± 0.09	0.12 ± 0.01	0.04 ± 0.03	0.02 ± 0.01	-	0.14 ± 0.02
13	1058	γ-Terpinene	0.21 ± 0.15	0.58 ± 0.09	0.50 ± 0.16	0.51 ± 0.09	0.34 ± 0.13	0.40 ± 0.05	0.28 ± 0.08	0.50 ± 0.04
14	1067	cis-Sabinene hydrate	1.00 ± 0.17	0.79 ± 0.35	0.65 ± 0.20	0.56 ± 0.12	0.28 ± 0.09	0.11 ± 0.02	0.09 ± 0.07	0.58 ± 0.04
15	1088	α-Terpinolene	0.06 ± 0.05	0.17 ± 0.02	0.11 ± 0.08	0.15 ± 0.03	0.10 ± 0.03	0.11 ± 0.01	0.08 ± 0.02	0.13 ± 0.01
16	1100	Linalool	0.25 ± 0.03	0.25 ± 0.08	0.22 ± 0.04	0.28 ± 0.02	0.22 ± 0.05	0.07 ± 0.05	0.04 ± 0.06	0.25 ± 0.01
17	1146	iso-Pulegol	0.09 ± 0.07	0.13 ± 0.01	0.09 ± 0.06	0.14 ± 0.00	0.13 ± 0.00	0.11 ± 0.00	0.07 ± 0.05	0.14 ± 0.01
18	1156	Menthone	15.36 ± 1.89	12.98 ± 1.99	13.80 ± 2.24	14.25 ± 0.54	9.15 ± 2.91	5.28 ± 0.51	3.66 ± 0.37	14.99 ± 0.98	p < 0.01
19	1165	Menthofuran	10.27 ± 3.43	11.82 ± 2.09	6.95 ± 0.72	2.19 ± 1.09	1.06 ± 0.50	0.92 ± 0.31	1.28 ± 0.94	9.56 ± 0.58	p < 0.01
20	1166	Neoisomenthol	2.37 ± 0.36	3.64 ± 1.58	3.58 ± 2.79	10.43 ± 2.32	8.14 ± 2.55	5.43 ± 1.21	4.14 ± 0.64	0.01 ± 0.00	p < 0.01
21	1178	Menthol	44.39 ± 4.50	35.01 ± 2.05	39.73 ± 6.25	42.32 ± 0.62	46.22 ± 4.07	47.50 ± 2.53	42.97 ± 3.30	39.07 ± 1.84	p < 0.05
22	1180	Terpinen-4-ol	0.92 ± 0.11	0.60 ± 0.43	1.12 ± 0.18	1.27 ± 0.10	1.26 ± 0.15	0.97 ± 0.08	0.90 ± 0.02	1.16 ± 0.04
23	1185	neo-Menthol	0.72 ± 0.53	1.11 ± 0.20	0.66 ± 0.49	1.19 ± 0.04	1.22 ± 0.13	1.14 ± 0.11	0.62 ± 0.45	1.12 ± 0.04
24	1192	α-Terpinoel	0.17 ± 0.13	0.26 ± 0.02	0.26 ± 0.03	0.51 ± 0.12	0.73 ± 0.21	0.43 ± 0.02	0.45 ± 0.02	0.26 ± 0.02
25	1240	Pulegone	0.45 ± 0.03	0.55 ± 0.07	0.42 ± 0.08	0.58 ± 0.04	0.52 ± 0.03	0.49 ± 0.01	0.43 ± 0.04	0.56 ± 0.02
26	1255	Piperitone	0.42 ± 0.19	0.44 ± 0.06	0.47 ± 0.11	0.44 ± 0.06	0.74 ± 0.09	0.76 ± 0.06	0.97 ± 0.04	0.42 ± 0.05
27	1275	Menthol acetate	0.17 ± 0.25	0.35 ± 0.25	0.26 ± 0.21	0.26 ± 0.19	-	0.21 ± 0.29	0.47 ± 0.33	0.21 ± 0.15
28	1295	Menthyl acetate	4.78 ± 2.28	8.66 ± 2.23	7.77 ± 1.81	5.20 ± 3.76	9.76 ± 3.93	16.26 ± 0.37	16.05 ± 0.38	6.10 ± 0.91	p < 0.05
29	1387	β-Bourbonene	0.08 ± 0.08	0.22 ± 0.09	0.28 ± 0.25	0.11 ± 0.03	0.28 ± 0.08	0.38 ± 0.04	0.45 ± 0.08	0.15 ± 0.04
30	1393	β-Elemene	0.03 ± 0.04	0.10 ± 0.04	0.12 ± 0.10	0.04 ± 0.03	0.17 ± 0.07	0.26 ± 0.04	0.26 ± 0.08	0.06 ± 0.02
31	1422	β-Caryophyllene	0.85 ± 0.54	1.54 ± 0.73	2.37 ± 1.61	0.84 ± 0.24	2.22 ± 0.75	3.02 ± 0.30	3.52 ± 0.55	1.10 ± 0.30	p < 0.05
32	1457	trans-β-Farnesene	0.13 ± 0.14	0.31 ± 0.14	0.46 ± 0.42	0.11 ± 0.08	0.45 ± 0.17	0.65 ± 0.07	0.80 ± 0.12	0.20 ± 0.06
33	1484	Germacrene-D	0.98 ± 0.72	1.65 ± 0.85	2.66 ± 1.84	0.86 ± 0.27	2.53 ± 0.97	3.78 ± 0.29	4.61 ± 0.68	1.24 ± 0.35	p < 0.01
34	1499	Bicyclogermacrene	0.11 ± 0.12	0.21 ± 0.11	0.33 ± 0.31	0.11 ± 0.04	0.40 ± 0.19	0.61 ± 0.06	1.81 ± 0.19	0.16 ± 0.04
35	1526	Δ-Cadinene	0.02 ± 0.02	0.05 ± 0.03	0.08 ± 0.07	0.01 ± 0.01	0.09 ± 0.07	0.21 ± 0.03	0.26 ± 0.05	0.03 ± 0.02
36	1581	Spathulenol	-	0.01 ± 0.02	0.02 ± 0.03	-	0.08 ± 0.06	0.17 ± 0.02	0.23 ± 0.02	0.01 ± 0.01
37	1587	Caryophyllene oxide	0.03 ± 0.04	0.07 ± 0.04	0.07 ± 0.05	0.02 ± 0.03	0.20 ± 0.11	0.36 ± 0.02	0.48 ± 0.03	0.04 ± 0.03
38	1595	Viridiflorol	0.33 ± 0.39	0.50 ± 0.33	0.63 ± 0.53	0.27 ± 0.13	1.88 ± 0.17	3.47 ± 0.24	4.77 ± 0.45	0.47 ± 0.19	p < 0.01
			93.84	97.67	95.36	96.04	91.97	93.06	90.91	92.90

^aRetention indices (RI) determined on HP-5MS capillary column.

Figure 2. Comparison of the main chemical groups (%) in the fresh dried peppermint leaves.