Table 2. Volatile organic compounds (VOCs) detected via SPME-GC–MS of T. melanosporum fermentation.
| NO.a | LRIb | Compoundc | Detected mass m/zd | Log2(peak area)e |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Day 2 |
Day 3 |
Day 4 |
Day 5 |
Day 7 |
|||||||||
| Controlf | RFTTg | Control | RFTT | Control | RFTT | Control | RFTT | Control | RFTT | ||||
| Alcohols | |||||||||||||
| 1 | <600 | Ethanol** | 31.1 | 24.93 ± 0.61 | 18.26 ± 1.09 | 26.98 ± 1.10 | 25.43 ± 1.79 | 27.38 ± 0.70 | 27.25 ± 1.29 | 27.62 ± 0.76 | 27.16 ± 1.11 | 27.31 ± 1.62 | 29.07 ± 1.32 |
| 2 | 623 | 2-Methyl-1-propanol** | 43.1 | — | 18.23 ± 0.93 | 24.30 ± 0.71 | 23.63 ± 1.07 | 25.61 ± 0.80 | 25.72 ± 1.43 | 24.15 ± 0.78 | 25.10 ± 0.51 | 26.70 ± 1.29 | 26.78 ± 1.06 |
| 3 | 730 | 3-Methyl-1-butanol* | 55.1 | 26.98 ± 0.93 | 23.07 ± 1.83 | 27.70 ± 2.00 | 26.81 ± 1.76 | 29.29 ± 1.47 | 27.60 ± 1.73 | 26.20 ± 2.23 | 27.99 ± 1.13 | 28.28 ± 1.41 | 27.41 ± 1.23 |
| 4 | 866 | (E)-4-Hexen-1-ol** | 67.1 | — | — | 21.71 ± 1.08 | — | — | — | — | 22.95 ±1.46 | — | — |
| 5 | 973 | 1-Octen-3-ol** | 57.1 | 21.99 ± 1.07 | 20.37 ± 0.81 | 21.41 ± 1.08 | 24.52 ± 0.92 | 21.93 ± 1.25 | 24.35 ± 0.65 | 21.49 ± 0.79 | 23.39 ± 0.75 | — | — |
| 6 | 989 | 3-Octanol** | 59.1 | — | 19.21 ± 1.19 | — | — | — | 21.58 ± 0.88 | — | 23.48 ± 0.64 | — | — |
| 7 | 1555 | [S-(Z)]-3,7,11- Trimethyl-1,6,10- dodecatrien-3-ol** | 69.1 | 21.04 ± 0.96 | — | — | — | — | — | — | — | — | — |
| Aldehyde | |||||||||||||
| 8 | 654 | 3-Methyl-butanal** | 41.1 | 24.92 ± 1.18 | 19.20 ± 1.30 | 25.33 ± 1.60 | 24.82 ± 0.46 | — | 22.71 ± 0.90 | 25.38 ± 1.49 | 24.53 ± ± 0.96 | — | — |
| Ketone | |||||||||||||
| 9 | 982 | 3-Octanone | 57.1 | 21.13 ± 0.72 | 16.18 ± 0.58 | — | — | 19.74 ± 0.89 | 21.32 ± 0.80 | 20.51 ± 0.66 | 21.16 ± 0.54 | 19.74 ± 1.43 | 24.52 ± 1.78 |
| Esters and acid | |||||||||||||
| 10 | 1239 | Benzeneacetic acid, ethyl ester** | 91.1 | — | — | — | — | 19.86 ± 1.02 | 19.56 ± 1.46 | 20.08 ± 0.59 | — | — | — |
| 11 | 1754 | Tetradecanoic acid** | 73.1 | — | 12.11 ± 0.72 | — | — | — | — | — | — | — | — |
| 12 | 1914 | Hexadecanoic acid, methyl ester** | 74 | 20.26 ± 0.74 | — | — | — | — | 18.74 ± 0.57 | 18.74 ± 0.43 | — | — | — |
| 13 | 1950 | n-Hexadecanoic acid** | 73 | 18.43 ± 0.93 | — | — | — | — | — | — | — | — | — |
| Aromaticcompounds | |||||||||||||
| 14 | 859 | Ethylbenzene** | 91 | — | 15.29 ± 0.81 | 21.13 ± 0.72 | 19.72 ± 0.71 | 21.36 ± 0.78 | 20.97 ± 0.54 | 21.18 ± 0.54 | — | — | — |
| 15 | 865 | p-Xylene** | 91.1 | 21.21 ± 0.86 | 15.69 ± 0.72 | 21.41 ± 0.84 | 19.85 ± 0.87 | 22.36 ± 0.70 | 22.10 ± 1.36 | 23.18 ± 0.30 | — | — | 19.99 ± 1.12 |
| 16 | 887 | Styrene** | 104.1 | 21.28 ± 0.72 | 18.27 ± 0.81 | 21.33 ± 0.82 | 22.66 ± 0.99 | 22.54 ± 0.83 | 22.53 ± 1.57 | 25.14 ± 1.62 | 19.24 ± 1.00 | 22.67 ± 1.03 | 20.89 ± 0.87 |
| 17 | 1036 | Benzeneaceta-ldehyde** | 91.1 | 20.53 ± 0.71 | — | 18.70 ± 0.70 | 18.66 ± 0.66 | 18.77 ± 0.76 | 18.87 ± 0.83 | 20.74 ± 1.14 | 21.07 ± 0.71 | 19.33 ± 1.27 | 18.42 ± 0.98 |
| 18 | 1112 | Phenylethyl alcohol* | 91.1 | 27.14 ± 1.87 | 21.00 ± 1.60 | 28.87 ± 1.09 | 31.28 ± 2.13 | 28.85 ± 1.64 | 29.97 ± 1.51 | 29.43 ± 1.76 | 28.90 ± 1.29 | 29.16 ± 1.83 | 30.46 ± 2.76 |
| 19 | 1159 | 4-Ethyl-phenol* | 107.1 | — | — | — | — | — | — | 19.46 ± 1.47 | 18.31 ± 1.05 | — | — |
| 20 | 1219 | Benzothiazole** | 135 | 17.58 ± 0.79 | — | — | — | — | — | — | 18.17 ± 1.06 | — | — |
| Nitrogen | |||||||||||||
| 21 | <600 | 2-Hydroxy-propanamide** | 45.1 | — | 15.02 ± 1.23 | — | — | — | — | — | 22.28 ± 0.78 | — | — |
| 22 | 906 | 2,5-Dimethyl-pyrazine** | 108.1 | 22.19 ± 0.92 | 18.09 ± 1.04 | 23.83 ± 1.19 | 24.92 ± 0.98 | 24.21 ± 1.30 | 23.07 ± 0.99 | 22.96 ± 0.63 | — | 25.62 ± 1.38 | 24.10 ± 0.45 |
| 23 | 997 | Trimethyl-pyrazine** | 42.1 | 22.98 ± 1.23 | 20.20 ± 1.30 | 21.60 ± 1.35 | 24.36 ± 0.68 | 21.26 ± 0.82 | — | — | — | 25.38 ± 1.38 | 23.75 ± 0.87 |
| 24 | 1069 | 3-Ethyl-2,5-dimethyl- pyrazine** | 135.1 | 20.92 ± 0.78 | 16.45 ± 0.74 | 21.20 ± 0.96 | 22.69 ± 0.79 | 22.15 ± 1.05 | — | 20.92 ± 0.90 | 23.30 ± 1.43 | 20.48 ± 1.06 | 21.16 ± 0.52 |
| 25 | 1308 | 2,5-Dimethyl-3- (3-methylbutyl)- pyrazine** | 122.1 | 18.55 ± 1.08 | 14.61 ± 1.02 | 18.31 ± 0.83 | 20.72 ± 0.97 | 19.27 ± 1.09 | 21.28 ± 0.91 | — | — | 18.39 ± 0.85 | 21.30 ± 1.79 |
| Sulfur | |||||||||||||
| 26 | 976 | 3-(Methylthio)-1- propanol** | 106.1 | 22.70 ± 1.01 | — | — | — | — | — | — | — | — | — |
| Alkene | |||||||||||||
| 27 | 1021 | Limonene** | 68.1 | 19.67 ± 0.82 | — | 19.12 ± 0.91 | — | — | — | 19.58 ± 0.80 | — | — | — |
| 28 | 1310 | 2,3,4-Trimethyl-1,4- pentadiene** | 95.1 | — | — | — | — | — | 23.19 ± 1.87 | 25.31 ± 0.79 | 26.67 ± 1.71 | 21.56 ± 0.93 | — |
| 29 | 1449 | (E)-7,11-Dimethyl-3- methylene-1,6,10- dodecatriene** | 41.1 | 20.31 ± 1.02 | — | — | — | — | — | — | — | — | — |
aCompound number (No.) according to linear retention index (LRI) from low to high.
bLRI: Linear retention index calculated on an HP-5 column.
cCompounds with * exhibited a significant difference, p < 0.05, compounds with **exhibited a highly significant difference, p < 0.001.
dSpecific ion (m/z) selected for relative quantification of each compound.
ePeak area of each compound, with log2-transformed value, calculated as the average of five replicates (n = 5).
fControl: fermentation sample without repeated freeze-thaw treatment.
gRFTT: fermentation sample with repeated freeze-thaw treatment.