Table 1.
The volatile aldehydes detected during the processes of soybean oil heating (control), WD frying, and CBM frying a,b
| No. | RT (min) | Compounds (Systematic name) | MQ (%) | RI | Possible precursor | Proposed mechanism |
|---|---|---|---|---|---|---|
| 1 | 6.729 | 3-Methylbutanal | 83 | 917 | Ln | oxidation |
| 2 | 8.180 | Trans-2-pentenal | 86 | 771 | Ln-9-hydroperoxide | further oxidation |
| 3 | 9.289 | Hexanal | 91 | 2203 | L-13-hydroperoxide; L-12-hydroperoxide | β-homolysis; keto-enol tautomerism |
| 4 | 10.941 | Trans-2-hexenal | 96 | 931 | Ln-12-hydroperoxide | keto-enol tautomerism; isomerization |
| 5 | 12.274 | Heptanal | 87 | 16126 | O-11-hydroperoxide | further oxidation |
| 6 | 14.002 | Trans-2-heptenal | 93 | 1023 | L-12-hydroperoxide | β-homolysis |
| 7 | 14.051 | Cis-2-heptenal | 97 | 1031 | trans-2-Heptenal | cis-trans isomerization |
| 8 | 14.456 | Benzaldehyde | 96 | 1131 | L; 2,4-decadienal | oxidation, dehydration; further oxidation |
| 9 | 15.561 | Trans,trans-2,4-Heptadienal | 95 | 1006 | Ln-12-hydroperoxide | β-homolysis |
| 10 | 17.206 | Trans-2-octenal | 82 | 1149 | L-9-hydroperoxide; L-10-hydroperoxide | further oxidation |
| 11 | 18.550 | Nonanal | 86 | 1105 | O-10-hydroperoxide; O-9-hydroperoxide | β-homolysis; keto-enol automerism |
| 12 | 20.196 | Trans-2-nonenal | 93 | 1256 | L-9-hydroperoxide; 2-undecenal | position isomerization; further oxidation |
| 13 | 21.466 | Decanal | 84 | 1205 | O-8-hydroperoxide | keto-enol tautomerism |
| 14 | 21.778 | Trans,trans-2,4-nonadienal | 95 | 1220 | L-9-hydroperoxide; trans-2-nonenal | further oxidation |
| 15 | 22.645 | 4-Oxononanal | 90 | 1298 | L | further oxidation |
| 16 | 23.058 | Trans-2-decenal | 91 | 1387 | O-9-hydroperoxide | β-homolysis |
| 17 | 24.315 | Trans,trans-2,4-decadienal | 96 | 1315 | L-9-hydroperoxide | β-homolysis |
| 18 | 25.663 | Trans-2-tridecenal | 80 | 1476 | trans-2-undecenal | combining reaction |
| 19 | 25.741 | Trans-2-undecenal | 80 | 1500 | O-8-hydroperoxide | β-homolysis; cis-trans isomerization |
| 20 | 25.741 | Trans-2-dodecenal | 82 | 1500 | trans-2-undecenal | combining reaction |
| 21 | 27.260 | Trans,trans-2,4-undecadienal | 88 | 1430 | trans-2-undecenal | further oxidation; desaturation |
| 22 | 27.260 | Trans,trans-2,4-dodecadienal | 84 | 1430 | trans-2-dodecenal | further oxidation; desaturation |
| 23 | 28.127 | Cyclohexanecarboxaldehyde, 4-(hydroxymethyl)- | 80 | 1519 | structure-similar alkanes, alkenes | oxidation |
| 24 | 32.747 | Cis,cis-10,12-hexadecadienal | 93 | 1890 | unsaturated radicals | combination reaction |
| 25 | 32.976 | Trans-14-hexadecenal | 84 | 2191 | unsaturated FAs | decarboxylic reaction; free radical reaction |
a Abbreviations: WD wheat dough, CBM chicken breast meat, RT retention time, MQ matching quality, RI relative retention index, O oleic acid, L linoleic acid, Ln linolenic acid
b MQ was consulted from NIST08.L MS database. RI values calculated in relation to the C5-C20 n-alkanes for a DB-5 MS column