Table 2.
Identification of flavor compounds in fermented grain samples at different stages of fermentation based on gas chromatography–ion mobility spectrometry.
| Number | Compound | Formula | Molecular weight (MW) | Retention index (Ri) | Retention time (Rt/s) | Mobility time (Dt) | Peak area | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| GA | GB | GC | GD | MA | MB | MC | MD | |||||||
| A1 | 1-methylethyl acetate | C5H10O2 | 102.1 | 870.3 | 272.4 | 1.05694 | 131.6 ± 9.9 b | 89.9 ± 8.1 c | 86.2 ± 8.0 cd | 65.4 ± 8.9 d | 293.2 ± 24.7 a | 123.9 ± 2.5 b | 74.3 ± 1.6 cd | 75.1 ± 12.1 cd |
| A2 | tert-butyl acetate | C6H12O2 | 116.2 | 732.3 | 300.5 | 1.28766 | 161.0 ± 4.9 b | 112.5 ± 5.0 c | 113.7 ± 8.1 c | 110.1 ± 7.2 c | 581.5 ± 38.5 a | 172.5 ± 1.6 b | 158.3 ± 4.6 b | 129.4 ± 2.4 c |
| A3 | Propyl formate | C4H8O2 | 88.1 | 642.4 | 310.0 | 1.3704 | 898.9 ± 19.0 a | 635.7 ± 21.2 d | 718.4 ± 23.7 c | 732.1 ± 17.0 bc | 741.8 ± 19.4 bc | 563.6 ± 9.0 e | 764.8 ± 17.0 b | 743.7 ± 9.9 bc |
| A4 | Propyl propanoate | C6H12O2 | 116.2 | 830.2 | 394.2 | 1.22838 | 208.4 ± 18.6 e | 356.1 ± 4.6 d | 466.3 ± 23.8 c | 444.3 ± 44.2 d | 594.1 ± 13.1 b | 656.4 ± 2.7 a | 583.4 ± 8.5 b | 687.3 ± 17.3 a |
| A5 | 2-Methylpropyl propionate | C7H14O2 | 130.2 | 1070.6 | 439.7 | 1.27413 | 57.8 ± 9.9 b | 23.5 ± 2.9 d | 20.7 ± 2.1 d | 25.2 ± 7.1 cd | 24.9 ± 2.2 cd | 31.9 ± 5.2 cd | 39.4 ± 1.5 c | 105.5 ± 17.1 a |
| A6 | Butyl acetate | C6H12O2 | 116.2 | 1,070 | 439.1 | 1.23993 | 236.5 ± 56.0 a | 29.0 ± 4.0 c | 34.3 ± 1.9 bc | 34.3 ± 5.4 bc | 40.9 ± 2.3 bc | 43.5 ± 3.4 bc | 41.0 ± 4.9 bc | 70.6 ± 6.3 b |
| A7 | Ethyl 3-methylbutanoate monomer | C7H14O2 | 130.2 | 1057.4 | 424.8 | 1.64903 | 163.9 ± 19.7 f | 421.5 ± 7.0 de | 489.9 ± 31.2 cd | 546.8 ± 66.0 c | 368.0 ± 16.0 e | 706.7 ± 16.0 b | 773.3 ± 41.7 b | 1121.7 ± 77.2 a |
| A8 | Ethyl 3-methylbutanoate dimer | C7H14O2 | 130.2 | 1058.3 | 425.8 | 1.2513 | 28.7 ± 4.2 e | 62.9 ± 4.1 de | 85.4 ± 5.8 d | 136.9 ± 21.4 c | 53.1 ± 5.1 de | 209.8 ± 4.6 b | 244.6 ± 3.3 b | 755.3 ± 80.2 a |
| A9 | Ethyl acetate | C4H8O2 | 88.1 | 910.2 | 299.1 | 1.33593 | 23535.4 ± 411.4 d | 33202.4 ± 55.8 a | 33147.4 ± 154.3 a | 33269.6 ± 239.9 a | 28010.6 ± 208.9 c | 32327.3 ± 76.1 b | 32943.5 ± 179.6 a | 33305.2 ± 44.2 a |
| A10 | Ethyl butanoate monomer | C6H12O2 | 116.2 | 1044.5 | 410.3 | 1.55569 | 2989.8 ± 12.7 c | 3240.4 ± 20.4 a | 3153.6 ± 50.6 b | 2999.5 ± 65.5 c | 2955.9 ± 21.8 cd | 3027.9 ± 7.4 c | 2968.3 ± 40.4 cd | 2902.6 ± 51.1 d |
| A11 | Ethyl butanoate dimer | C6H12O2 | 116.2 | 1043.6 | 409.3 | 1.20181 | 681.6 ± 94.9 c | 1658.2 ± 66.6 b | 2231.5 ± 41.0 a | 2061.9 ± 294.9 a | 905.8 ± 55.1 c | 1734.0 ± 26.8 b | 1996.6 ± 58.6 a | 2213.0 ± 209.3 a |
| A12 | Ethyl hexanoate monomer | C8H16O2 | 144.2 | 1239.3 | 706.4 | 1.80055 | 1314.1 ± 57.5 b | 1556.5 ± 35.9 a | 1632.6 ± 49.1 a | 1408.2 ± 174.7 b | 1028.9 ± 72.6 c | 1068.3 ± 11.9 c | 1115.8 ± 58.5 c | 972.0 ± 77.3 c |
| A13 | Ethyl hexanoate dimer | C8H16O2 | 144.2 | 1,243 | 711.8 | 1.34374 | 871.8 ± 93.6 cd | 2156.1 ± 81.7 b | 2551.2 ± 215.0 a | 1891.9 ± 377.1 b | 609.9 ± 48.1 d | 831.3 ± 42.9 cd | 1086.0 ± 49.8 c | 804.8 ± 111.9 cd |
| A14 | Ethyl lactate monomer | C5H10O3 | 118.1 | 1359.7 | 899.3 | 1.53874 | 8342.5 ± 3177.4 c | 17552.0 ± 635.0 a | 18296.3 ± 95.9 a | 18008.4 ± 411.8 a | 11173.3 ± 4026.6 bc | 12413.7 ± 587.7 b | 16830.3 ± 352.5 a | 17220.5 ± 200.4 a |
| A15 | Ethyl lactate dimer | C5H10O3 | 118.1 | 1,361 | 901.7 | 1.14697 | 3033.7 ± 2363.7 c | 27066.4 ± 5344.0 b | 42081.4 ± 4162.4 a | 43065.2 ± 5043.2 a | 7613.0 ± 7419.6 c | 6602.1 ± 1007.3 c | 23390.3 ± 4347.6 b | 24622.7 ± 2386.7 b |
| A16 | Ethyl propanoate | C5H10O2 | 102.1 | 965.4 | 336.7 | 1.45341 | 526.9 ± 76.9 g | 1469.4 ± 35.4 e | 1709.2 ± 17.4 d | 1829.9 ± 109.1 c | 672.1 ± 13.9 f | 1535.3 ± 29.0 e | 2480.9 ± 39.5 a | 2290.3 ± 74.5 b |
| A17 | Hexyl butanoate | C10H20O2 | 172.3 | 1468.1 | 1087.9 | 1.48649 | 446.4 ± 27.2 cd | 690.6 ± 24.7 a | 722.2 ± 24.0 a | 648.3 ± 20.8 b | 438.0 ± 11.1 cd | 474.6 ± 15.8 c | 469.2 ± 22.1 c | 412.2 ± 7.5 d |
| A18 | Isoamyl acetate monomer | C7H14O2 | 130.2 | 1130.9 | 529.6 | 1.74269 | 2106.9 ± 56.4 b | 1722.8 ± 34.1 de | 1711.7 ± 49.8 e | 1760.4 ± 70.3 de | 2207.9 ± 27.9 a | 1871.3 ± 24.8 c | 1790.5 ± 9.7 d | 1727.8 ± 13.1 de |
| A19 | Isoamyl acetate dimer | C7H14O2 | 130.2 | 1131.5 | 530.7 | 1.30775 | 5303.5 ± 386.3 e | 8538.7 ± 205.3 abc | 9207.5 ± 382.8 a | 8708.8 ± 662.4 abc | 7131.5 ± 256.4 d | 8085.5 ± 58.8 b | 8282.5 ± 156.9 bc | 8960.8 ± 524.2 ab |
| A20 | Isobutyl acetate monomer | C6H12O2 | 116.2 | 1022.3 | 385.4 | 1.61121 | 450.2 ± 25.6 c | 363.0 ± 15.8 de | 343.7 ± 25.9 e | 335.1 ± 30.4 e | 584.5 ± 19.6 a | 506.4 ± 22.7 b | 461.3 ± 4.5 bc | 402.1 ± 45.5 d |
| A21 | Isobutyl acetate dimer | C6H12O2 | 116.2 | 1020.8 | 383.7 | 1.28805 | 1193.6 ± 97.9 e | 3158.8 ± 46.9 bc | 2975.6 ± 100.5 c | 3179.5 ± 186.1 b | 1956.6 ± 20.6 d | 3073.8 ± 52.0 bc | 2970.9 ± 51.8 c | 3952.7 ± 140.6 a |
| A22 | Propyl acetate | C5H10O2 | 102.1 | 987.7 | 351.0 | 1.48043 | 666.8 ± 51.5 f | 1477.2 ± 20.5 c | 1606.6 ± 44.5 b | 1476.5 ± 70.2 c | 1129.7 ± 28.9 e | 1553.7 ± 23.6 b | 1307.7 ± 15.6 d | 1677.9 ± 26.0 a |
| B1 | 2-butanol | C4H10O | 74.1 | 614.1 | 343.9 | 1.56275 | 285.1 ± 36.9 g | 787.7 ± 21.9 e | 963.8 ± 10.6 d | 1392.1 ± 113.8 c | 472.7 ± 9.3 f | 1019.7 ± 30.5 d | 1794.0 ± 31.9 b | 2621.9 ± 99.9 a |
| B2 | 1-propanethiol | C3H8S | 76.2 | 603.5 | 228.1 | 1.13359 | 269.9 ± 9.8 f | 418.4 ± 11.0 d | 352.3 ± 9.0 e | 474.5 ± 18.6 c | 354.9 ± 22.8 e | 652.3 ± 41.2 a | 636.6 ± 37.8 ab | 600.3 ± 43.3 b |
| B3 | 2-Methyl-1-propanol monomer | C4H10O | 74.1 | 1100.9 | 476.1 | 1.3687 | 1626.4 ± 40.7 a | 966.0 ± 15.7 d | 990.3 ± 70.1 cd | 966.0 ± 43.0 d | 1494.6 ± 28.0 b | 1056.2 ± 18.7 c | 1000.3 ± 43.9 cd | 956.8 ± 42.1 d |
| B4 | 2-Methyl-1-propanol dimer | C4H10O | 74.1 | 1100.9 | 476.1 | 1.17201 | 10231.5 ± 180.4 ab | 10184.5 ± 177.0 ab | 9723.4 ± 274.6 cd | 9269.4 ± 378.4 d | 9555.2 ± 72.5 de | 9946.2 ± 46.3 bc | 9320.1 ± 45.4 d | 10318.7 ± 139.8 a |
| B5 | 3-Methyl-1-butanol monomer | C5H12O | 88.1 | 1216.3 | 673.4 | 1.49626 | 3307.2 ± 104.4 a | 2678.8 ± 25.7 c | 2614.8 ± 70.7 c | 2594.4 ± 43.7 c | 3067.1 ± 34.3 b | 2679.7 ± 17.6 c | 2611.6 ± 7.2 c | 2625.7 ± 19.5 c |
| B6 | 3-Methyl-1-butanol dimer | C5H12O | 88.1 | 1217.3 | 674.9 | 1.24711 | 12573.4 ± 219.6 d | 14259.6 ± 21.9 a | 14051.7 ± 286.7 ab | 13265.2 ± 838.6 c | 12624.5 ± 48.0 d | 13202.4 ± 57.8 cd | 13446.7 ± 226.1 bc | 13585.5 ± 295.8 bc |
| B7 | Butanol monomer | C4H10O | 74.1 | 1148.8 | 561.5 | 1.38429 | 611.1 ± 26.3 a | 306.5 ± 9.7 b | 300.5 ± 5.9 bc | 285.3 ± 47.5 bcd | 259.1 ± 4.4 cde | 245.9 ± 8.0 de | 226.7 ± 9.1 e | 245.6 ± 40.5 de |
| B8 | Butanol dimer | C4H10O | 74.1 | 1150.6 | 564.7 | 1.18309 | 327.3 ± 7.0 a | 188.6 ± 4.9 bc | 220.6 ± 23.9 b | 155.3 ± 55.3 c | 49.3 ± 2.7 d | 72.5 ± 5.1 d | 63.8 ± 2.1 d | 83.8 ± 7.9 d |
| B9 | Ethanol | C2H6O | 46.1 | 945.3 | 322.6 | 1.14763 | 21165.5 ± 105.7 cd | 22572.7 ± 24.9 a | 22591.0 ± 210.8 a | 21670.0 ± 480.7 b | 20839.5 ± 134.7 d | 21546.1 ± 111.3 bc | 21498.0 ± 59.7 bc | 21863.5 ± 255.6 b |
| C1 | 2-methyloctane | C9H20 | 128.3 | 858 | 264.2 | 1.0634 | 1216.1 ± 42.9 g | 2547.4 ± 38.4 e | 2573.2 ± 76.9 de | 2669.6 ± 49.8 c | 2130.4 ± 40.3 f | 2646.5 ± 31.5 cd | 2753.6 ± 27.3 b | 3081.7 ± 22.8 a |
| C2 | Oct-2-ene | C8H16 | 112.2 | 821.3 | 239.6 | 1.08438 | 278.2 ± 13.0 d | 152.9 ± 9.5 e | 140.2 ± 5.8 e | 134.3 ± 12.3 e | 507.9 ± 13.2 a | 291.3 ± 12.5 cd | 373.0 ± 4.8 b | 341.2 ± 78.7 bc |
| C3 | 1,1,1-Trichloroethane | C2H3Cl3 | 133.4 | 658 | 264.2 | 1.0634 | 278.5 ± 14.9 d | 265.6 ± 2.2 de | 241.9 ± 2.9 f | 254.7 ± 19.7 ef | 315.5 ± 12.1 c | 367.2 ± 4.6 b | 440.8 ± 7.7 a | 315.3 ± 22.2 c |
| C4 | 2-Pentenal | C5H8O | 84.1 | 746.8 | 393.7 | 1.32854 | 203.9 ± 4.6 f | 580.6 ± 15.6 d | 667.7 ± 30.3 c | 620.8 ± 39.4 d | 482.0 ± 6.3 e | 751.2 ± 12.8 b | 703.8 ± 8.0 c | 827.2 ± 52.3 a |
| D1 | 2-methylfuran | C5H6O | 82.1 | 612.3 | 251.0 | 1.06259 | 1583.7 ± 126.8 a | 165.6 ± 11.9 c | 183.4 ± 5.2 c | 228.8 ± 8.6 c | 1531.4 ± 47.4 a | 242.6 ± 5.4 c | 350.6 ± 7.5 b | 230.4 ± 45.5 c |
| D2 | Tetrahydrofuran | C4H8O | 72.1 | 629.3 | 239.6 | 1.08438 | 1451.3 ± 89.6 a | 255.8 ± 58.9 c | 286.8 ± 18.0 c | 325.2 ± 12.5 c | 1250.4 ± 14.9 b | 272.7 ± 40.3 c | 331.2 ± 15.4 c | 267.7 ± 105.9 c |
| D3 | Thiophene | C4H4S | 84.1 | 686.8 | 350.5 | 1.27262 | 91.6 ± 12.8e | 289.3 ± 10.5 d | 350.7 ± 8.1 bc | 389.6 ± 55.3 b | 135.1 ± 2.3 e | 336.1 ± 7.1 c | 559.2 ± 16.1 a | 577.4 ± 41.7 a |
| E1 | 4-methylpentanal | C6H12O | 100.2 | 1030.2 | 391.8 | 1.45233 | 38.4 ± 7.4 f | 171.4 ± 1.8 e | 217.3 ± 11.7 d | 204.9 ± 32.3 d | 201.3 ± 5.3 d | 339.6 ± 6.9 b | 289.3 ± 9.2 c | 386.8 ± 14.1 a |
| E2 | Butanal monomer | C4H8O | 72.1 | 849.8 | 258.7 | 1.27998 | 1115.7 ± 30.6 c | 940.7 ± 16.7 d | 822.2 ± 16.9 e | 812.3 ± 17.4 e | 1111.5 ± 8.6 c | 1234.5 ± 13.8 b | 1533.9 ± 18.7 a | 1135.2 ± 66.2 c |
| E3 | Butanal dimer | C4H8O | 72.1 | 852 | 260.2 | 1.10766 | 1172.8 ± 113.8 cd | 1120.3 ± 52.1 de | 1264.9 ± 32.0 bc | 1279.2 ± 15.2 bc | 1873.7 ± 87.1 a | 738.1 ± 37.3 e | 1035.0 ± 42.6 d | 1366.5 ± 50.5 b |
| F1 | 3-hydroxy-2-butanone dimer | C4H8O2 | 88.1 | 1294.9 | 786.8 | 1.07149 | 12871.4 ± 1184.7 a | 2996.5 ± 2714.6 b | 386.1 ± 61.6 c | 269.1 ± 49.c8 | 3188.9 ± 508.9 a | 519.4 ± 273. 6 c | 321.5 ± 43.5 c | 263.4 ± 20.8 c |
| F2 | 3-Hydroxy-2-butanone monomer | C4H8O2 | 88.1 | 1295.6 | 787.9 | 1.33247 | 5490.7 ± 240. 3 a | 2401.5 ± 913.0 c | 1059.7 ± 136.5 d | 881.0 ± 31.3d | 3170.9 ± 283.7 b | 1242.5 ± 286.6 d | 980.8 ± 23.6 d | 822.3 ± 6.4 d |
| G1 | Acetic acid monomer | C2H4O2 | 60.1 | 1,524 | 1185.2 | 1.15805 | 11809.5 ± 318.2 c | 12005.7 ± 446.5 bc | 12339.4 ± 132.1 ab | 12245.5 ± 143.1 abc | 12657.1 ± 125.8 a | 12293.4 ± 245.4 abc | 12091.3 ± 370.7 bc | 11948.2 ± 179.0 bc |
| G2 | Acetic acid dimer | C2H4O2 | 60.1 | 1525.3 | 1187.3 | 1.05271 | 4621.6 ± 364.1 e | 7557.9 ± 2100.9 cd | 10501.9 ± 1146.4 a | 8592.5 ± 1152.8 b | 5219.5 ± 198.5 de | 5608.8 ± 543.5 cde | 6692.4 ± 1167.4 bcd | 6855.3 ± 597.3 bcd |
All data are presented as mean ± standard deviation (n = 3). Values with different letters in a row indicate significant differences at p < 0.05 as determined by one-way ANOVA Duncan’s test.