J Food Bioact

Journal of Food Bioactives, ISSN 2637-8752 print, 2637-8779 online

Journal website www.isnff-jfb.com

Original Research

Volume 21, March 2023, pages 44-54

Quantitation of key odorants in arginine/cysteine-glucose maillard reactions

Figure 1. The chemical structure of (a) L-arginine and (b) L-cysteine.

Figure 2. Proposed formation of (a) 2-(pyrazin-2-yl)ethan-1-ol; (b) 2-(5-methylpyrazin-2-yl)ethan-1-ol; and (c) 2-(6-methylpyrazin-2-yl)ethan-1-ol.

Figure 3. Proposed formation of (a) 2-vinylpyrazine; (b) 2-methyl-6-vinylpyrazine; and (c) 2-methyl-5-vinylpyrazine by water elimination of the respective hydroxyethyl pyrazine.

Figure 4. The structures of (a) 2,5-dimethyl-4-hydroxy-3(2H)-thiophenone (DMHT) and (b) 2,5-dimethyl-2,4-dihydroxy-3(2H)-thiophenone (DMDHT).

**Table 1.** The volatile compounds from the Arg-Glu reactions
Compound	OV1 (Kovats)	Arg-Glu (100 °C) SAFE pH 7.4*	Arg-Glu (130 °C) SAFE pH 7.4*	Arg-Glu (160 °C) SAFE pH 7.4*	Arg-Glu (160 °C) SAFE pH 10.4*
nd: not detected; *Data reported in mg/mol.
pyrazines
pyrazine	716	0.06	0.15	4.79	24.18
methylpyrazine	804	nd	0.01	0.42	105.40
2,6- + 2,5-dimethylpyrazine	891	nd	nd	0.21	50.10
ethylpyrazine	898	nd	nd	0.25	6.00
2,3-dimethylpyrazine	898	nd	nd	0.08	4.08
vinylpyrazine	928	nd	0.01	0.56	3.32
2-ethyl-6-methylpyrazine	978	nd	nd	nd	3.73
2-ethyl-5-methylpyrazine	981	nd	nd	nd	2.02
trimethylpyrazine	988	nd	nd	nd	6.21
2-methyl-5-vinylpyrazine	998	nd	nd	nd	2.12
quinoxaline	1,173	nd	nd	0.78	0.76
total pyrazines		0.06	0.17	7.09	207.92
Furans/pyrans
2-furfural	809	nd	0.49	2.96	0.63
2-furfuryl alcohol	828	nd	0.10	1.57	34.65
2-acetylfuran	890	0.06	0.01	0.52	nd
5-methyl-2-furfural	939	nd	nd	0.57	nd
5-methyl-2-furanmethanol	947	nd	nd	nd	2.43
furaneol	1,030	nd	nd	0.53	8.30
5-hydroxy-5,6-dihydromaltol	1,116	0.01	0.13	3.39	5.25
5-hydroxymethyl-2-furfural	1,177	nd	0.04	18.58	nd
total furans/pyrans		0.07	0.78	28.12	51.26
Misc.
1-hydroxypropan-2-one	622	nd	nd	0.84	16.08
acetoin	680	nd	nd	0.18	2.06
cyclohexan-1,2-dione	974	nd	0.39	nd	nd
cyclotene	997	nd	nd	1.05	8.58
2-aminophenol	1,177	nd	nd	8.11	2.70
benzene-1,2-diol	1,168	nd	nd	nd	7.74
acetaldehyde	485	0.30	0.44	0.14	0.26

Table 1. The volatile compounds from the Arg-Glu reactions

Compound

OV1 (Kovats)

Arg-Glu (100 °C) SAFE pH 7.4*

Arg-Glu (130 °C) SAFE pH 7.4*

Arg-Glu (160 °C) SAFE pH 7.4*

Arg-Glu (160 °C) SAFE pH 10.4*

nd: not detected; *Data reported in mg/mol.

pyrazines

pyrazine

716

0.06

0.15

4.79

24.18

methylpyrazine

804

0.01

0.42

105.40

2,6- + 2,5-dimethylpyrazine

891

0.21

50.10

ethylpyrazine

898

0.25

6.00

2,3-dimethylpyrazine

898

0.08

4.08

vinylpyrazine

928

0.01

0.56

3.32

2-ethyl-6-methylpyrazine

978

3.73

2-ethyl-5-methylpyrazine

981

2.02

trimethylpyrazine

988

6.21

2-methyl-5-vinylpyrazine

998

2.12

quinoxaline

1,173

0.78

0.76

total pyrazines

0.06

0.17

7.09

207.92

Furans/pyrans

2-furfural

809

0.49

2.96

0.63

2-furfuryl alcohol

828

0.10

1.57

34.65

2-acetylfuran

890

0.06

0.01

0.52

5-methyl-2-furfural

939

0.57

5-methyl-2-furanmethanol

947

2.43

furaneol

1,030

0.53

8.30

5-hydroxy-5,6-dihydromaltol

1,116

0.01

0.13

3.39

5.25

5-hydroxymethyl-2-furfural

1,177

0.04

18.58

total furans/pyrans

0.07

0.78

28.12

51.26

Misc.

1-hydroxypropan-2-one

622

0.84

16.08

acetoin

680

0.18

2.06

cyclohexan-1,2-dione

974

0.39

cyclotene

997

1.05

8.58

2-aminophenol

1,177

8.11

2.70

benzene-1,2-diol

1,168

7.74

acetaldehyde

485

0.30

0.44

0.14

0.26

**Table 2.** Three hydroxyethyl pyrazines identified in the Arg-Glu reactions.
Compound	RI (apol)^a	RI (pol)^b	Odor Description^c
^aRI on an apolar column. ^bRI on a polar column. ^cOdor descriptors from blotter evaluation of 2-(pyrazin-2-yl)ethan-1-ol diluted 1% in ethanol.
2-(pyrazin-2-yl)ethan-1-ol	1,127	1,891	nutty, pyrazinic, stale, chocolate
2-(5-methylpyrazin-2-yl)ethan-1-ol	1,211	1,928	nutty, chocolate, pyrazinic, burnt
2-(6-methylpyrazin-2-yl)ethan-1-ol	1,205	1,917	nutty, burnt, chocolate, pyrazinic

Table 2. Three hydroxyethyl pyrazines identified in the Arg-Glu reactions.

Compound

RI (apol)^a

RI (pol)^b

Odor Description^c

^aRI on an apolar column. ^bRI on a polar column. ^cOdor descriptors from blotter evaluation of 2-(pyrazin-2-yl)ethan-1-ol diluted 1% in ethanol.

2-(pyrazin-2-yl)ethan-1-ol

1,127

1,891

nutty, pyrazinic, stale, chocolate

2-(5-methylpyrazin-2-yl)ethan-1-ol

1,211

1,928

nutty, chocolate, pyrazinic, burnt

2-(6-methylpyrazin-2-yl)ethan-1-ol

1,205

1,917

nutty, burnt, chocolate, pyrazinic

**Table 3.** The volatile compounds from the Cys-Glu reactions at two different reaction temperatures
Compound	OV1 (Kovats)	Cys-Glu (130 °C) SAFE pH 7.4*	Cys-Glu (160 °C) SAFE pH 7.4*
nd: not detected; * Data reported in mg/mol of cysteine.
pyrazines
pyrazine	716	nd	0.07
methylpyrazine	804	nd	0.94
2,6- + 2,5-dimethylpyrazine	891	nd	0.12
ethylpyrazine	898	nd	0.33
2,3-dimethylpyrazine	898	nd	0.16
total pyrazines		0.00	1.62
furans/pyrans
2-furfural	809	nd	nd
2-furfuryl alcohol	828	nd	7.14
2-acetylfuran	890	nd	1.74
5-methyl-2-furfural	939	nd	0.91
5-methyl-2-furanmethanol	947	nd	0.66
furaneol	1,030	nd	2.63
5-hydroxy-5,6-dihydromaltol	1,116	0.14	5.20
total furans/pyrans		0.14	18.28
thiophenes
thiophene	647	nd	0.50
2-methylthiophene	757	nd	0.16
2,5-dimethylthiophene	861	nd	0.18
2-formylthiophene	975	nd	1.79
2-acetylthiophene	1,074	nd	0.33
2-formyl-4-methylthiophene	1,091	nd	4.92
tetrahydrothiophen-3-one	920	nd	1.90
3-thiophenethiol	950	0.01	5.89
2-methyltetrahydrothiophen-3-one	958	nd	1.02
3-mercapto-2-methylthiophene	1,054	0.02	2.04
2,5-dimethyl-4-hydroxy-3(2H)-thiophenone	1,134	0.07	7.53
thieno[3.2.b]thiophene	1,176	nd	1.39
2,5-dimethyl-2,4-dihydroxy-3(2H)-thiophenone	1,223	0.07	5.72
total thiophenes		0.16	33.37
misc. sulfur compounds
methyl mercaptan	484	nd	0.00
1,1-ethanedithiol	715	nd	0.14
2-mercaptoethanol	769	nd	0.12
1-mercaptopropan-2-one	749	0.04	3.97
3-mercaptobutan-2-one	791	0.02	9.21
1,2-ethanedithiol	801	nd	0.41
1-mercaptobutan-3-one	850	nd	0.36
1-mercaptobutan-2-one	852	nd	0.76
2-methylfuran-3-thiol	853	nd	0.43
3-mercaptopentan-2-one	881	nd	0.80
2-mercaptopentan-3-one	886	nd	1.00
furfuryl mercaptan	895	nd	0.33
2-(1-mercaptoethyl)-furan	932	nd	0.47
5-methyl-2-furanmethanethiol	994	nd	1.21
2-mercaptopropionic acid	985	nd	185.24
3-mercaptopropionic acid	998	0.01	97.38
3,5-dimethyl-1,2,4-trithiolane isomer i	1,112	nd	1.31
3,5-dimethyl-1,2,4-trithiolane isomer ii	1,119	nd	0.60
1,2-dithian-4-one	1,124	nd	2.21
total misc sulfur compounds		0.07	305.95
misc.
1-hydroxypropan-2-one	622	nd	0.29
acetoin	680	nd	0.95
cyclopentanone	763	nd	0.71
acetaldehyde	485	0.08	0.06

Table 3. The volatile compounds from the Cys-Glu reactions at two different reaction temperatures

Compound

OV1 (Kovats)

Cys-Glu (130 °C) SAFE pH 7.4*

Cys-Glu (160 °C) SAFE pH 7.4*

nd: not detected; * Data reported in mg/mol of cysteine.

pyrazines

pyrazine

716

0.07

methylpyrazine

804

0.94

2,6- + 2,5-dimethylpyrazine

891

0.12

ethylpyrazine

898

0.33

2,3-dimethylpyrazine

898

0.16

total pyrazines

0.00

1.62

furans/pyrans

2-furfural

809

2-furfuryl alcohol

828

7.14

2-acetylfuran

890

1.74

5-methyl-2-furfural

939

0.91

5-methyl-2-furanmethanol

947

0.66

furaneol

1,030

2.63

5-hydroxy-5,6-dihydromaltol

1,116

0.14

5.20

total furans/pyrans

0.14

18.28

thiophenes

thiophene

647

0.50

2-methylthiophene

757

0.16

2,5-dimethylthiophene

861

0.18

2-formylthiophene

975

1.79

2-acetylthiophene

1,074

0.33

2-formyl-4-methylthiophene

1,091

4.92

tetrahydrothiophen-3-one

920

1.90

3-thiophenethiol

950

0.01

5.89

2-methyltetrahydrothiophen-3-one

958

1.02

3-mercapto-2-methylthiophene

1,054

0.02

2.04

2,5-dimethyl-4-hydroxy-3(2H)-thiophenone

1,134

0.07

7.53

thieno[3.2.b]thiophene

1,176

1.39

2,5-dimethyl-2,4-dihydroxy-3(2H)-thiophenone

1,223

0.07

5.72

total thiophenes

0.16

33.37

misc. sulfur compounds

methyl mercaptan

484

0.00

1,1-ethanedithiol

715

0.14

2-mercaptoethanol

769

0.12

1-mercaptopropan-2-one

749

0.04

3.97

3-mercaptobutan-2-one

791

0.02

9.21

1,2-ethanedithiol

801

0.41

1-mercaptobutan-3-one

850

0.36

1-mercaptobutan-2-one

852

0.76

2-methylfuran-3-thiol

853

0.43

3-mercaptopentan-2-one

881

0.80

2-mercaptopentan-3-one

886

1.00

furfuryl mercaptan

895

0.33

2-(1-mercaptoethyl)-furan

932

0.47

5-methyl-2-furanmethanethiol

994

1.21

2-mercaptopropionic acid

985

185.24

3-mercaptopropionic acid

998

0.01

97.38

3,5-dimethyl-1,2,4-trithiolane isomer i

1,112

1.31

3,5-dimethyl-1,2,4-trithiolane isomer ii

1,119

0.60

1,2-dithian-4-one

1,124

2.21

total misc sulfur compounds

0.07

305.95

misc.

1-hydroxypropan-2-one

622

0.29

acetoin

680

0.95

cyclopentanone

763

0.71

acetaldehyde

485

0.08

0.06

**Table 4.** The volatile compounds from the Arg/Cys-Glu reactions
Compound	OV1 (Kovats)	Arg/Cys-Glu (100 °C) SAFE pH 7.4*	Arg/Cys-Glu (130 °C) SAFE pH 7.4*	Arg/Cys-Glu (160 °C) SAFE pH 7.4*
nd: not detected; * Data reported in mg/mol of arginine.
pyrazines
pyrazine	716	0.02	0.02	0.06
methylpyrazine	804	nd	nd	0.47
total pyrazines		0.02	0.02	0.53
furans/pyrans
2-furfuryl alcohol	828	nd	nd	5.11
2-acetylfuran	890	nd	nd	1.85
5-methyl-2-furfural	939	nd	nd	1.70
5-methyl-2-furanmethanol	947	nd	nd	0.48
furaneol	1,030	nd	0.13	1.36
5-hydroxy-5,6-dihydromaltol	1,116	nd	1.15	3.52
total furans/pyrans		0.00	1.28	14.03
thiophenes
thiophene	647	nd	nd	0.67
2-methylthiophene	757	nd	nd	0.38
2-ethylthiophene	852	nd	nd	0.81
2-formylthiophene	975	nd	nd	2.51
2-acetylthiophene	1,074	nd	nd	2.01
2-formyl-4-methylthiophene	1,091	nd	nd	4.51
tetrahydrothiophen-3-one	920	nd	nd	3.22
3-thiophenethiol	950	nd	nd	3.98
2-methyltetrahydrothiophen-3-one	958	nd	nd	1.86
3-mercapto-2-methylthiophene	1,054	nd	nd	1.74
2,5-dimethyl-4-hydroxy-3(2H)-thiophenone	1,134	nd	nd	13.57
thieno[3.2.b]thiophene	1,176	nd	nd	1.56
2,5-dimethyl-2,4-dihydroxy-3(2H)-thiophenone	1,223	0.00	0.00	36.82
total thiophenes		0.00	0.00	73.64
misc. sulfur compounds
1-mercaptopropan-2-one	749	nd	0.15	3.40
3-mercaptobutan-2-one	791	nd	0.14	4.99
furfuryl mercaptan	895	nd	nd	0.30
2-mercaptopropionic acid	985	nd	nd	216.46
3-mercaptopropionic acid	998	nd	nd	42.39
5-acetyl-2,3-dihydro-1,4-thiazine	1,322	nd	0.07	nd
total misc sulfur compounds		0.00	0.36	267.53
misc.
acetoin	680	nd	nd	0.32
acetaldehyde	485	0.00	0.00	0.32

Table 4. The volatile compounds from the Arg/Cys-Glu reactions

Compound

OV1 (Kovats)

Arg/Cys-Glu (100 °C) SAFE pH 7.4*

Arg/Cys-Glu (130 °C) SAFE pH 7.4*

Arg/Cys-Glu (160 °C) SAFE pH 7.4*

nd: not detected; * Data reported in mg/mol of arginine.

pyrazines

pyrazine

716

0.02

0.06

methylpyrazine

804

0.47

total pyrazines

0.02

0.53

furans/pyrans

2-furfuryl alcohol

828

5.11

2-acetylfuran

890

1.85

5-methyl-2-furfural

939

1.70

5-methyl-2-furanmethanol

947

0.48

furaneol

1,030

0.13

1.36

5-hydroxy-5,6-dihydromaltol

1,116

1.15

3.52

total furans/pyrans

0.00

1.28

14.03

thiophenes

thiophene

647

0.67

2-methylthiophene

757

0.38

2-ethylthiophene

852

0.81

2-formylthiophene

975

2.51

2-acetylthiophene

1,074

2.01

2-formyl-4-methylthiophene

1,091

4.51

tetrahydrothiophen-3-one

920

3.22

3-thiophenethiol

950

3.98

2-methyltetrahydrothiophen-3-one

958

1.86

3-mercapto-2-methylthiophene

1,054

1.74

2,5-dimethyl-4-hydroxy-3(2H)-thiophenone

1,134

13.57

thieno[3.2.b]thiophene

1,176

1.56

2,5-dimethyl-2,4-dihydroxy-3(2H)-thiophenone

1,223

0.00

36.82

total thiophenes

0.00

73.64

misc. sulfur compounds

1-mercaptopropan-2-one

749

0.15

3.40

3-mercaptobutan-2-one

791

0.14

4.99

furfuryl mercaptan

895

0.30

2-mercaptopropionic acid

985

216.46

3-mercaptopropionic acid

998

42.39

5-acetyl-2,3-dihydro-1,4-thiazine

1,322

0.07

total misc sulfur compounds

0.00

0.36

267.53

misc.

acetoin

680

0.32

acetaldehyde

485

0.00

0.32