Table 3.
Volatile compounds at different fermentation stages of Huyou vinegar analyzed by GC–MS
| Category | Aroma compounds | Retention index | Relative content (%) | |||
|---|---|---|---|---|---|---|
| HP | HW | HV-LS | HV-SS | |||
| Esters | Methyl acetate | 944RI,MS | – | – | 0.91 | 0.87 |
| Ethyl acetate | 956RI,MS | 1.55 | 1.37 | 12.05 | 15.21 | |
| Isobutyl acetate | 917RI,MS | – | – | 0.26 | 0.17 | |
| Butanedioic acid, dipropyl ester | 752RI,MS | – | – | – | 0.62 | |
| 1-Butanol-3-methyl-acetate | 856RI,MS | 1.03 | – | 2.391 | 1.59 | |
| Ethyl hexanoate | 834RI,MS | – | 0.06 | 0.34 | 0.15 | |
| Hexyl acetate | 924RI,MS | – | – | 0.09 | 0.09 | |
| Ethyl lactate | 788RI,MS | – | 0.06 | – | – | |
| Ethyl sorbate | 906RI,MS | – | 0.19 | – | – | |
| Methyl benzoate | 947RI,MS | – | 0.30 | – | – | |
| Ethyl 2-furoate | 724RI,MS | – | 0.14 | – | – | |
| Ethyl decanoate | 896RI,MS | – | 0.11 | – | – | |
| Ethyl benzoate | 933RI,MS | 0.85 | 9.59 | 0.37 | ||
| Diethyl succinate | 914RI,MS | – | 6.42 | – | 0.29 | |
| Phenethyl acetate | 962RI,MS | – | – | 1.86 | 2.21 | |
| 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate | 841RI,MS | 0.36 | – | – | – | |
| γ-Nonalactone | 907RI,MS | – | – | 0.54 | 0.42 | |
| Isopropyl myristate | 862RI,MS | 0.33 | – | – | – | |
| Ethyl palmitoleate | MS | – | 0.09 | – | 0.03 | |
| Methyl dihydrojasmonate | MS | 0.22 | – | – | – | |
| Diethyl phthalate | 932RI,MS | 0.77 | – | – | – | |
| Ethyl oleate | 853RI,MS | – | – | – | 0.05 | |
| Ethyl linoleate | 860RI,MS | – | 0.04 | – | 0.06 | |
| Dibutyl phthalate | 948RI,MS | 4.11 | 0.07 | 0.04 | – | |
| Total number | 8 | 12 | 9 | 14 | ||
| Total relative content (%) | 9.22 | 18.44 | 18.48 | 22.13 | ||
| Acids | Acetic acid | 978RI,MS | 0.67 | 1.52 | 33.24 | 44.52 |
| Isovaleric acid | MS | – | – | 4.30 | 2.54 | |
| Pentanoic acid | 903RI,MS | – | – | 0.22 | 0.07 | |
| Hexanoic acid | 960RI,MS | 1.76 | – | 5.45 | 1.60 | |
| Heptanoic acid | 894RI,MS | – | – | 0.47 | 0.18 | |
| Octanoic acid | 919RI,MS | – | 0.43 | 3.55 | 0.55 | |
| Sorbic Acid | 908RI,MS | – | 0.25 | – | 0.08 | |
| Nonanoic acid | 916RI,MS | 1.34 | 0.09 | 0.34 | 0.16 | |
| 2-Octenoic acid | 869RI,MS | – | – | 0.08 | 0.03 | |
| n-Decanoic acid | 897RI,MS | 0.26 | 0.18 | 0.44 | 0.10 | |
| Benzoic acid | 942RI,MS | – | 0.88 | 0.55 | 0.46 | |
| Dodecanoic acid | 839RI,MS | 0.23 | – | – | – | |
| Phenylacetic acid | 858RI,MS | – | – | 0.09 | 0.05 | |
| n-Hexadecanoic acid | 845RI,MS | – | – | – | 0.15 | |
| Total number | 5 | 6 | 11 | 13 | ||
| Total relative content (%) | 4.26 | 3.35 | 48.73 | 50.49 | ||
| Aldehydes | Acetaldehyde | 969RI,MS | – | – | 0.10 | 0.11 |
| Pentanal | 893RI,MS | 1.30 | – | – | – | |
| Hexanal | 926RI,MS | 25.31 | – | 0.04 | 0.15 | |
| Heptaldehyde | 911RI,MS | 1.15 | – | – | – | |
| Octanal | 935RI,MS | 0.42 | – | – | – | |
| Nonanal | 931RI,MS | 0.95 | – | – | – | |
| Furfural | MS | – | 2.69 | – | – | |
| Benzaldehyde | 904RI,MS | 0.48 | 1.74 | 2.81 | 6.70 | |
| 5-Methyl furfural | MS | – | – | – | 0.10 | |
| 2-Hydroxy-benzaldehyde | 857RI,MS | – | – | – | 0.05 | |
| α-Ethylidene-benzene-acetaldehyde | 874RI,MS | – | – | – | 0.22 | |
| Total number | 6 | 2 | 3 | 6 | ||
| Total relative content (%) | 29.61 | 4.43 | 2.95 | 7.33 | ||
| Alcohols | Ethanol | 957RI,MS | 6.01 | 41.88 | 3.47 | 4.63 |
| 2-Methyl-1-propanol | 943RI,MS | – | 0.64 | 0.28 | 0.19 | |
| 3-Methyl-1-butanol | 968RI,MS | – | 8.26 | 3.93 | 2.34 | |
| 1-Pentanol | 859RI,MS | 1.53 | – | – | – | |
| Cis-2-pentenol | MSRI,MS | 1.17 | – | – | – | |
| 1-Hexanol | 918RI,MS | 10.97 | 0.52 | 0.37 | 0.35 | |
| 3-Hexen-1-ol | 963RI,MS | 13.94 | 0.07 | – | – | |
| Trans-2-hexen-1-ol | 950RI,MS | 3.17 | – | – | – | |
| Oct-1-en-3-ol | 877RI,MS | 0.50 | – | – | – | |
| 2-Ethylhexan-1-ol | 872RI,MS | 0.71 | – | 0.24 | 0.32 | |
| Trans-2-hepten-1-ol | 922RI,MS | 1.78 | – | – | – | |
| Linalool | 887RI,MS | 0.98 | – | – | – | |
| Octan-1-ol | 905RI,MS | 0.73 | – | 0.13 | 0.11 | |
| 4-Terpenol | 920RI,MS | 0.84 | 0.25 | 0.42 | 0.26 | |
| (E)-oct-2-en-1-ol | 934RI,MS | 0.87 | – | – | – | |
| α-Terpineol | 899RI,MS | 1.63 | 0.38 | 0.61 | 0.34 | |
| Benzyl alcohol | 929RI,MS | – | – | 0.17 | – | |
| 2-Phenylethanol | 952RI,MS | – | 10.99 | 12.86 | 3.27 | |
| Cedrol | 925RI,MS | 1.59 | – | – | 0.16 | |
| Total number | 15 | 8 | 10 | 10 | ||
| Total relative content (%) | 46.42 | 62.99 | 22.48 | 11.97 | ||
| Heterocycles | Toluene | 890RI,MS | 0.24 | – | – | – |
| d-limonene | 953RI,MS | 4.21 | – | – | – | |
| 2,4,5-Trimethyl-1,3-oxazole | MS | – | – | 0.10 | 0.09 | |
| 1-Methyl-2-propan-2-benzene | MS | 0.64 | – | – | – | |
| 2,3,5-Trimethylpyrazine | 891RI,MS | – | – | – | 0.08 | |
| 2,4,7,9-Tetramethyl-5-decyne-4,7-diol | 854RI,MS | – | – | 0.14 | – | |
| Total number | 3 | 0 | 2 | 2 | ||
| Total relative content (%) | 5.09 | 0 | 0.24 | 0.17 | ||
| Ketones | Acetone | 949RI,MS | – | – | 0.43 | 0.62 |
| Pentan-3-one | 828RI,MS | 0.96 | – | – | – | |
| 2,3-Butanedione | 939RI,MS | – | – | – | 2.07 | |
| Ethyl vinyl ketone | 866RI,MS | 0.22 | – | – | – | |
| Octan-3-one | 819RI,MS | 0.48 | – | – | – | |
| Acetoin | 855RI,MS | – | 0.06 | 1.57 | 1.09 | |
| Sulcatone | MSRI,MS | 0.28 | – | 0.08 | – | |
| D-Carvone | 889RI,MS | 0.70 | – | – | – | |
| 6,10-Dimethyl-5,9-Undecadien-2-one | 830RI,MS | 0.63 | – | – | – | |
| Total number | 6 | 1 | 3 | 3 | ||
| Total relative content (%) | 3.27 | 0.06 | 2.08 | 3.78 | ||
| Alkanes | 2,4,5-Trimethyl-1,3-dioxolane | 927RI,MS | – | – | 3.04 | 3.90 |
| Hexadecane | 879RI,MS | – | 0.17 | 0.10 | – | |
| 2,6,10-Trimethyl-pentadecane | 865RI,MS | – | 0.55 | – | – | |
| 2,6,10,14-Tetramethyl-pentadecane | 883RI,MS | – | 8.17 | 0.66 | – | |
| Nonadecane | 848RI,MS | 0.53 | – | – | – | |
| Heptadecane | 930RI,MS | – | 0.99 | – | – | |
| 2,6,10-Trimethyl-hexadecane | 863RI,MS | – | 0.12 | – | – | |
| 2,6,10-Trimethyl-dodecane | 831RI,MS | 1.09 | 0.15 | – | – | |
| 4-Methyl-heptadecane | 885RI,MS | – | 0.23 | – | – | |
| 2-Methyl-octadecane | 902RI,MS | – | 0.13 | – | – | |
| Total number | 2 | 8 | 3 | 1 | ||
| Total relative content (%) | 1.62 | 10.51 | 3.80 | 3.90 | ||
RI the volatile aroma compounds were identified by matching retention index (RI) of the measured data matched with RI of standard samples measured by the same method saved in GC–MS system. MS the volatile aroma compounds were identified by the compounds in the database of MS