Table 2 Volatile organic compounds (VOCs) detected via SPME-GC–MS of T. melanosporum fermentation.

From: Aroma improvement by repeated freeze-thaw treatment during Tuber 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

—

—

—

—

—

—

—

—

—

  

Aromatic

           

compounds

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

—

—

—

—

—

—

—

—

—

  1. aCompound number (No.) according to linear retention index (LRI) from low to high.
  2. bLRI: Linear retention index calculated on an HP-5 column.
  3. cCompounds with * exhibited a significant difference, p < 0.05, compounds with **exhibited a highly significant difference, p < 0.001.
  4. dSpecific ion (m/z) selected for relative quantification of each compound.
  5. ePeak area of each compound, with log2-transformed value, calculated as the average of five replicates (n = 5).
  6. fControl: fermentation sample without repeated freeze-thaw treatment.
  7. gRFTT: fermentation sample with repeated freeze-thaw treatment.
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