Preparation and pyrolysis of two Amadori analogues as flavor precursors

Amadori compounds, produced during Maillard reaction, are considered as precursors of flavor compounds. On the basis of Amadori compounds, herein two Amadori analogues, di-O-isopropylidene-2,3:4,5-β-D-fructopyranosyl alanine ester (A-ARP) and di-O-isopropylidene-2,3:4,5-β-D-fructopyranosyl proline ester (P-ARP), were chemically synthesized and their possibility as flavor precursors was evaluated by thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), and pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). TG-DTG analyses indicated that the samples were stable at room temperature, and the largest mass-loss rates (Tp) were at 208 and 278 °C, respectively. Upon thermal pyrolysis, the major flavor substances were butan-2-one, ethyl propionate, furfural, and dl-limonene for A-ARP, while 2,5-dimethylfuran, heptan-2-one, acetophenone, and 1H-pyrrole for P-ARP. The flavor profiles are different from that of corresponding Amadori compounds, and are influenced by pyrolytic temperatures. These results provide one method to regulate the species and amounts of the degraded flavor products. Finally, the possible mechanisms of the pyrolytic processes are proposed.