Table 1.
Volatile compounds identified by five extraction methods in combination with GC-O-MS and GC×GC-O-MS.
| No. | Component | CAS | Odor | RI a | Method of Identification b | Relative Content (ng/g) c | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SPME | SAFE | DHS | SBSE | LLE | |||||||||||||
| GC | GC × GC | GC | GC × GC | GC | GC × GC | GC | GC × GC | GC | GC × GC | GC | GC × GC | GC | GC × GC | ||||
| Alcohols | |||||||||||||||||
| 1 | 1-Pentanol | 71-41-0 | balsam | 1247 | 1239 | MS/RI | MS/RI | 50.54 ± 4.37 | 53.99 ± 6.18 | ND | 41.27 ± 12.73 | ND | ND | ND | ND | ND | ND |
| 2 | 2-Furanmethanol | 98-00-0 | musty | 1702 | 1697 | MS/RI | MS/RI | 229.61 ± 16.49 | 288.19 ± 23.04 | 165.24 ± 26.33 | ND | ND | 203.15 ± 35.86 | ND | ND | ND | 75.09 ± 8.39 |
| 3 | 2-Thiophenemethanol | 636-72-6 | roasted | 1885 | ND | MS/RI | ND | 23.83 ± 1.83 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 4 | 1-Octen-3-ol | 3391-86-4 | mushroom | 1430 | 1418 | MS/RI | MS/RI/O | 6.08 ± 1.08 | 7.07 ± 0.98 | ND | 5.49 ± 2.04 | ND | 6.57 ± 4.19 | ND | ND | ND | ND |
| 5 | 1-Butanol | 71-36-3 | oil | ND | 1126 | ND | MS/RI | ND | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 6 | Linalool | 78-70-6 | floral | ND | 1509 | ND | MS/RI | ND | ND | ND | 12.48 ± 1.06 | ND | ND | ND | ND | ND | ND |
| 7 | α-Cumyl alcohol | 617-94-7 | green | 1743 | ND | MS/RI | ND | ND | ND | 2.05 ± 0.16 | ND | ND | ND | ND | ND | 0.16 ± 0.11 | ND |
| 8 | 2-Ethyl-1-hexanol | 104-76-7 | citrus | ND | 1492 | ND | MS/RI | ND | ND | ND | ND | ND | ND | ND | 0.96 ± 0.06 | ND | ND |
| Aldehydes | |||||||||||||||||
| 9 | Furfural | 98-01-1 | sweet woody | 1493 | ND | MS/RI/O | ND | 117.6 1± 5.40 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 10 | 5-Methyl-2-thiophenecarboxaldehyde | 13679-70-4 | almond | 1764 | ND | MS/RI/O | ND | 33.50 ± 1.57 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 11 | (E,Z)-2,6-Nonadienal | 557-48-2 | green fatty | 1590 | ND | MS/RI/O | ND | 3.06 ± 0.05 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 12 | 2-Methylbutyraldehyde | 96-17-3 | musty cocoa | 987 | ND | MS/RI | ND | 25.10 ± 3.72 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 13 | 3-Methylbutanal | 590-86-3 | chocolate | 924 | 935 | MS/RI | MS/RI | 110.01 ± 7.46 | 134.51 ± 11.36 | ND | ND | 58.19 ± 2.63 | 108.32 ± 4.27 | ND | ND | ND | ND |
| 14 | Pentanal | 110-62-3 | fermented | 956 | 944 | MS/RI | MS/RI | 159.20 ± 4.02 | 201.26 ± 18.43 | ND | ND | ND | ND | ND | ND | ND | ND |
| 15 | Hexanal | 66-25-1 | grass | 1062 | 1058 | MS/RI/O | MS/RI/O | 92.66 ± 1.17 | 118.80 ± 7.34 | ND | 88.63 ± 9.33 | 66.04 ± 8.39 | 74.68 ± 6.62 | 26.59 ± 1.95 | 29.27 ± 2.29 | ND | 32.64 ± 5.15 |
| 16 | Octanal | 124-13-0 | waxy citrus | 1279 | 1265 | MS/RI | MS/RI | 2.49 ± 0.36 | 23.31 ± 1.26 | ND | 3.91 ± 0.73 | ND | ND | 0.27±0.06 | 3.08 ± 0.74 | ND | ND |
| 17 | Nonanal | 124-19-6 | orange | 1384 | 1391 | MS/RI | MS/RI | 235.93 ± 12.73 | 304.04 ± 25.62 | 175.56 ± 14.76 | 209.37 ± 12.94 | 104.27 ± 9.26 | ND | ND | 52.60 ± 2.46 | ND | 17.40 ± 0.95 |
| 18 | (E)-2-Octenal | 2548-87-0 | cucumber | 1437 | 1426 | MS/RI | MS/RI/O | 8.71 ± 0.76 | 9.56 ± 0.38 | ND | ND | ND | ND | ND | ND | ND | ND |
| 19 | Benzaldehyde | 100-52-7 | sweet | 1503 | 1509 | MS/RI | MS/RI | 103.81 ± 8.25 | 144.38 ± 12.34 | ND | 73.29 ± 8.37 | 68.53 ± 10.55 | 71.27 ± 9.27 | 34.17 ± 2.91 | 63.26 ± 5.72 | ND | 9.63 ± 0.94 |
| 20 | 5-Methyl-2-furancarboxaldehyde | 620-02-0 | spice caramel | 1578 | 1554 | MS/RI | MS/RI | 352.37 ± 18.45 | 329.13 ± 18.23 | ND | 164.24 ± 24.53 | 228.72 ± 13.66 | 303.24 ± 36.81 | 73.02 ± 10.95 | 142.88 ± 11.91 | ND | ND |
| 21 | Phenylacetaldehyde | 122-78-1 | green | 1662 | ND | MS/RI | ND | 13.68 ± 2.33 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 22 | Pentadecanal | 2765-11-9 | fresh waxy | 2019 | ND | MS/RI | ND | 10.82 ± 0.12 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 23 | (Z)-4-Heptenal | 6728-31-0 | oily fatty | ND | 1287 | ND | MS/RI | ND | 8.46 ± 1.04 | ND | ND | ND | ND | ND | ND | ND | ND |
| 24 | Methional | 3268-49-3 | musty | ND | 1439 | ND | MS/RI | ND | 41.43 ± 6.12 | ND | ND | ND | ND | ND | ND | ND | ND |
| 25 | Decanal | 112-31-2 | sweet waxy | ND | 1538 | ND | MS/RI/O | ND | 25.18 ± 2.25 | ND | 9.73 ± 0.92 | ND | 11.04 ± 1.52 | 3.16 ± 0.06 | 3.95 ± 0.31 | ND | ND |
| 26 | 5-Methyl-2-thiophenecarboxaldehyde | 13679-70-4 | woody | ND | 1783 | ND | MS/RI/O | ND | 20.34 ± 1.59 | ND | ND | ND | ND | ND | ND | ND | ND |
| 27 | Dodecyl aldehyde | 112-54-9 | soapy waxy | 1745 | ND | MS/RI | ND | ND | ND | 18.77 ± 0.35 | ND | ND | ND | ND | ND | ND | ND |
| 28 | (E,E)-2,4-Heptadienal | 4313-03-5 | green | ND | 1497 | ND | MS/RI | ND | ND | ND | 6.38 ± 0.74 | ND | ND | ND | ND | ND | ND |
| 29 | Heptaldehyde | 111-71-7 | fresh | 1174 | 1165 | MS/RI | MS/RI | ND | 221.07 ± 14.28 | ND | ND | 84.93 ± 5.27 | 164.29 ± 12.63 | 43.28 ± 13.75 | 53.22 ± 2.76 | ND | 64.01 ± 6.37 |
| 30 | 3-Methylhexanal | 19269-28-4 | sweet green | 1102 | 1116 | MS/RI | MS/RI | ND | ND | ND | ND | 5.37 ± 1.10 | 12.84 ± 2.12 | ND | ND | ND | ND |
| 31 | 2-Undecenal | 2463-77-6 | fruity | 1793 | 1794 | MS/RI | MS/RI | ND | ND | ND | ND | ND | ND | 16.38 ± 0.97 | 9.96 ± 0.72 | ND | ND |
| Ketones | |||||||||||||||||
| 32 | Hydroxyacetone | 116-09-6 | caramel | 1272 | ND | MS/RI | ND | 522.52 ± 48.29 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 33 | 4-Hydroxy-2,5-dimethyl-3(2H)furanone | 3658-77-3 | sweet | 2037 | ND | MS/RI/O | ND | 35.25 ± 1.45 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 34 | 6-Methyl-5-hepten-2-one | 110-93-0 | citrus | 1342 | 1332 | MS/RI/O | MS/RI/O | 4.34 ± 0.03 | 8.06 ± 1.24 | ND | 2.96 ± 0.91 | 7.47 ± 0.26 | 9.26 ± 0.27 | 0.38 ± 0.05 | 5.67 ± 0.11 | ND | ND |
| 35 | 2-Butanone | 78-93-3 | camphor | 901 | 914 | MS/RI | MS/RI | 22.05 ± 9.25 | 29.37 ± 1.96 | ND | 19.62 ± 2.28 | ND | ND | ND | ND | ND | ND |
| 36 | 2,3-Pentanedione | 600-14-6 | pungent | 1047 | 1058 | MS/RI | MS/RI | 7.17 ± 0.45 | 16.54 ± 0.52 | ND | ND | ND | ND | ND | ND | ND | ND |
| 37 | Acetoin | 513-86-0 | sweet | 1284 | 1273 | MS/RI | MS/RI | 31.42 ± 3.72 | 35.21 ± 0.74 | ND | 17.82 ± 3.32 | 27.37 ± 3.56 | 29.52 ± 2.17 | ND | ND | ND | 5.83 ± 0.64 |
| 38 | 2-Dodecanone | 6175-49-1 | fruity | 1669 | ND | MS/RI | ND | 0.42 ± 0.07 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 39 | 5-Ethyl-2(5H)-furanone | 2407-43-4 | spice | 1756 | ND | MS/RI | ND | 5.69 ± 1.65 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 40 | 2,3-Butanedione | 431-03-8 | butter | ND | 961 | ND | MS/RI | ND | 46.93 ± 4.38 | ND | ND | ND | ND | ND | ND | ND | ND |
| 41 | 1-Penten-3-one | 1629-58-9 | peppery | ND | 1018 | ND | MS/RI | ND | 6.14 ± 0.47 | ND | ND | ND | ND | ND | ND | ND | ND |
| 42 | 2-Heptanone | 110-43-0 | fruity | ND | 1165 | ND | MS/RI | ND | 2.17 ± 0.02 | ND | ND | ND | ND | ND | ND | ND | ND |
| 43 | 1-Hydroxy-2-propanone | 116-09-6 | pungent | 1310 | 1307 | MS/RI/O | MS/RI | ND | 492.86 ± 42.74 | ND | 318.74 ± 41.17 | 148.02 ± 16.14 | 358.60 ± 22.61 | ND | ND | 74.26 ± 12.37 | 169.60 ± 19.95 |
| 44 | 1-Octen-3-one | 4312-99-6 | mushroom | ND | 1208 | O | MS/RI/O | ND | 0.12 ± 0.01 | ND | ND | ND | ND | ND | ND | ND | ND |
| 45 | Acetophenone | 98-86-2 | sweet | 1643 | 1637 | MS/RI | MS/RI | ND | ND | 0.97 ± 0.13 | 3.02 ± 1.05 | ND | ND | ND | ND | ND | ND |
| 46 | 2-Decanone | 693-54-9 | orange | ND | 1498 | ND | MS/RI | ND | ND | ND | 1.34 ± 0.07 | ND | ND | ND | ND | ND | ND |
| 47 | 1-Hydroxy-2-butanone | 5077-67-8 | coffee | ND | 1397 | ND | MS/RI | ND | ND | ND | 0.94 ± 0.19 | ND | ND | ND | ND | ND | ND |
| 48 | 2-Tridecanone | 593-08-8 | fatty | ND | 1809 | ND | MS/RI | ND | ND | ND | 9.48 ± 0.17 | ND | ND | ND | ND | ND | ND |
| 49 | Geranylacetone | 3796-70-1 | green | ND | 1853 | ND | MS/RI | ND | ND | ND | ND | ND | 7.47 ± 0.65 | ND | ND | ND | ND |
| 50 | 4-Hexen-3-one | 2497-21-4 | metallic | 1187 | 1164 | MS/RI/O | MS/RI/0 | ND | ND | ND | ND | ND | ND | 16.33 ± 3.61 | 15.27 ± 4.21 | ND | ND |
| 51 | 5-Ethyldihydro-2(3H)-furanone | 695-06-7 | herbal | 1692 | 1687 | MS/RI | MS/RI | ND | 9.11 ± 1.03 | ND | ND | ND | ND | 2.09 ± 0.95 | 7.14 ± 1.27 | ND | ND |
| Esters | |||||||||||||||||
| 52 | Triethyl phosphate | 78-40-0 | cider | ND | 1674 | ND | MS/RI | ND | ND | ND | 0.14 ± 0.03 | ND | ND | ND | ND | ND | ND |
| 53 | Allyl 2-ethylbutyrate | 7493-69-8 | nut | 1252 | 1246 | MS/RI/O | MS/RI/O | ND | ND | ND | ND | 9.27 ± 1.15 | 9.83 ± 1.63 | ND | ND | ND | ND |
| 54 | geranyl isovalerate | 109-20-6 | green | 1934 | 1948 | MS/RI/O | MS/RI/O | ND | ND | ND | ND | 14.38 ± 1.91 | 47.26 ± 3.25 | 21.22 ± 1.57 | 27.81 ± 4.38 | ND | ND |
| 55 | Nitrous acid, ethyl ester | 109-95-5 | sweet | ND | 1417 | ND | MS/RI | ND | ND | ND | ND | ND | ND | ND | ND | ND | 0.56 ± 0.27 |
| 56 | Acetic acid, butyl ester | 123-86-4 | banana | ND | 1049 | ND | MS/RI | ND | ND | ND | ND | ND | ND | ND | ND | ND | 19.47 ± 3.26 |
| 57 | Butyrolactone | 96-48-0 | oily | ND | 1634 | ND | MS/RI | ND | ND | ND | ND | ND | ND | ND | ND | ND | 5.22 ± 0.84 |
| Acids | |||||||||||||||||
| 58 | Propionic acid | 79-09-4 | pungent | 1509 | 1528 | MS/RI/O | MS/RI | 20.387 ± 2.65 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 59 | 3-Methylpentanoic Acid | 105-43-1 | sweaty | 1761 | ND | MS/RI/O | ND | 49.50 ± 2.73 | ND | ND | 15.63 ± 3.68 | ND | ND | ND | ND | ND | ND |
| 60 | Acetic acid | 64-19-7 | sour | 1452 | 1433 | MS/RI/O | MS/RI/O | 487.86 ± 36.94 | 461.79 ± 54.27 | ND | ND | 268.38 ± 34.76 | 322.47 ± 29.81 | 173.28 ± 14.25 | 236.73 ± 25.77 | ND | ND |
| 61 | Butyric acid | 107-92-6 | cheese | 1631 | 1642 | MS/RI | MS/RI | 38.72 ± 6.28 | 41.76 ± 3.14 | ND | ND | ND | ND | ND | ND | ND | ND |
| 62 | Hexanoic acid | 142-62-1 | fatty | 1859 | 1846 | MS/RI | MS/RI | 69.13 ± 4.92 | ND | ND | ND | 27.48 ± 3.25 | 36.91 ± 2.44 | ND | ND | ND | ND |
| 63 | Octanoic acid | 124-07-2 | waxy | 2056 | ND | MS/RI | ND | 27.44 ± 1.74 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 64 | 3-Methylbutanoic acid | 503-74-2 | sweaty | 1646 | ND | MS/RI/O | ND | ND | ND | ND | 7.30 ± 1.93 | ND | ND | ND | ND | ND | ND |
| 65 | Valeric acid | 109-52-4 | sickening | ND | 1850 | ND | MS/RI | ND | ND | ND | ND | ND | 0.78 ± 0.16 | ND | ND | ND | ND |
| Others | |||||||||||||||||
| 66 | Styrene | 100-42-5 | sweet | 1264 | 1239 | MS/RI | MS/RI | 9.00 ± 0.37 | ND | 5.46 ± 1.58 | 17.29 ± 2.73 | ND | ND | ND | ND | ND | ND |
| 67 | 2-Ethenyl-6-methylpyrazine | 13925-09-2 | hazelnut | 1486 | 1502 | MS/RI | MS/RI | 21.00 ± 1.25 | 28.09 ± 3.38 | ND | 8.63 ± 1.35 | ND | ND | ND | ND | ND | ND |
| 68 | 2-Pentylfuran | 3777-69-3 | fruity | 1231 | 1226 | MS/RI/O | MS/RI/O | 19.93 ± 0.05 | 19.46 ± 2.77 | ND | ND | ND | ND | ND | ND | ND | ND |
| 69 | 2,6-Di-tert-butyl-4-methylphenol | 128-37-0 | camphor | 1905 | ND | MS/RI | ND | 6.33 ± 0.42 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 70 | 2,6-Dimethylpyrazine | 108-50-9 | cocoa | 1309 | ND | MS/RI | ND | 51.84 ± 10.47 | ND | ND | ND | ND | ND | ND | ND | ND | ND |
| 71 | Pyrrole | 109-97-7 | sweet | ND | 1528 | ND | MS/RI | ND | 11.89 ± 0.99 | ND | ND | ND | ND | ND | ND | ND | ND |
| 72 | Dimethyl disulfide | 624-92-0 | vegetable | ND | 1082 | ND | MS/RI | ND | 33.50 ± 1.16 | ND | 18.43 ± 2.55 | ND | ND | ND | ND | ND | ND |
| 73 | Dimethyl trisulfide | 3658-80-8 | sulfurous | ND | 1365 | ND | MS/RI/O | ND | 6.04 ± 0.53 | ND | 0.58 ± 0.17 | ND | ND | ND | ND | ND | ND |
| 74 | Benzene | 71-43-2 | aromatic | ND | 955 | ND | MS/RI | ND | 7.39 ± 0.56 | ND | 7.73 ± 0.36 | ND | ND | ND | ND | ND | ND |
| 75 | 2-Ethylfuran | 3208-16-0 | burnt | ND | 945 | ND | MS/RI | ND | 11.25 ± 0.97 | ND | ND | ND | ND | ND | ND | ND | ND |
| 76 | 2,5-Dimethylpyrazine | 123-32-0 | roasted | ND | 1329 | ND | MS/RI/O | ND | 63.21 ± 3.24 | ND | ND | ND | ND | ND | ND | ND | ND |
| 77 | 2,6-Dimethylpyrazine | 108-50-9 | cocoa | 1352 | 1351 | MS/RI | MS/RI | ND | 1.36 ± 0.17 | ND | 0.06 ± 0.02 | 1.63 ± 0.16 | 5.37 ± 0.68 | ND | ND | ND | ND |
| 78 | 3-Ethyl-2,5-dimethylpyrazine | 13360-65-1 | potato | ND | 1430 | ND | MS/RI/O | ND | 34.18 ± 1.25 | ND | ND | ND | ND | ND | ND | ND | ND |
| 80 | Toluene | 108-88-3 | sweet | 1039 | 1034 | MS/RI | MS/RI | ND | ND | 3.28 ± 0.53 | 7.58 ± 0.95 | ND | ND | ND | ND | ND | ND |
| 81 | 1,2-Xylene | 95-47-6 | geranium | 1171 | 1164 | MS/RI | ND | ND | ND | 7.94 ± 1.27 | ND | ND | ND | ND | ND | ND | ND |
| 82 | Pyridine | 110-86-1 | sour | ND | 1169 | ND | MS/RI | ND | ND | ND | 0.93 ± 0.03 | ND | ND | ND | ND | ND | ND |
| 84 | Naphthalene | 91-20-3 | pungent | ND | 1701 | ND | MS/RI | ND | ND | ND | 16.39 ± 1.55 | ND | ND | ND | ND | ND | ND |
| 85 | Benzothiazole | 95-16-9 | sulfury | 1933 | 1930 | MS/RI | MS/RI | ND | ND | ND | ND | 0.27 ± 0.06 | 3.05 ± 0.74 | ND | ND | ND | ND |
| 86 | Dimethyl trisulfide | 624-92-0 | onion | ND | 1365 | ND | MS/RI/O | ND | 1.69 ± 0.03 | ND | ND | ND | ND | ND | ND | ND | ND |
a: RI, The Retention index on capillaries DB-WAX and DB-5. b: The different identification methods, including MS, RI, and O. In particular, for those compounds which were not able to identify by all three methods, they would be regarded as temporarily identified. ND, not detected. c: Relative concentration stated as the mean ± SD and the unit is ppt (part per trillion, ng/g).