Abstract: The effect of aliphatic aldehydes on Maillard reaction and meaty flavor formation was investigated in cysteine-xylose model systems. The Maillard reaction in the absence and presence of hexanal, (E)-2-heptenal, or (E,E)-2,4-decadienal, was carried out at 90 ℃, pH 5.5 for 5 h. Changes in the concentrations of xylose, cysteine, initial reaction intermediates (2-threityl-4-carboxythiazolidine and Amadori rearrangement product of cysteine (Cys-Amadori)) with reaction time were determined by high performance liquid chromatography with evaporate light scattering detection (HPLC-ELSD). Also, changes in the pH and absorbance values at 294 and 420 nm of the reaction mixtures were monitored. Volatile flavor compounds in the 3 h reaction mixtures were compartaively analyzed by solid phase microextraction coupled with gas chromatography and mass spectrometry (SPME-GC-MS). As indicated by decreased concentrations of Cys-Amadori and 2-threityl-4-carboxythiazolidine in the presence of aliphatic aldehydes, all the three aldehydes showed inhibitory effects on the initial stage of the Maillard reaction, among which (E)-2-heptenal was the stongest inhibitor, followed by (E,E)-2,4-decadienal and hexanal. Additionally, hexanal also showed inhibitory effect on the intermediate and final stages of the Maillard reaction, as indicated by decreased absorbance at 294 and 420 nm. However, (E)-2-heptenal and (E,E)-2,4-decadienal accelerated both the intermediate and final stages, as indicated by increased absorbance values at 294 and 420 nm, with the latter being more effective than the former. On the other hand, the reaction systems in the presence of (E)-2-heptenal and (E,E)-2,4-decadienal produced a relatively greater amount of total volatile sulfur-containing compounds than the blank model system, and additionally produced some new alkyl chain sulfur-containing compounds and furane derivatives such as 2-hexylthiophene and 2-propylfuran as detected by GC-MS analysis, due to participation of the aldehydes in cysteine-xylose reaction and reaction of the aldehydes themselves in the buffered cysteine-xylose solution.

Key words: lipid oxidization, Maillard reaction, meaty flavor, hexanal, (E)-2-heptenal, (E,E)-2,4-decadienal, Amadori compound