Thermal degradation studies of glucose/glycine melanoidins.

Nondialyzable and water-insoluble melanoidins, isolated from a glucose/glycine model reaction mixture, which was prepared in a standardized way according to the guidelines of the COST Action 919, were heated at different temperatures ranging from 100 to 300 degrees C. Among the volatile compounds, which were analyzed by SPME and GC-MS, pyrazines, pyridines, pyrroles, and furans were detected. In general, total amounts of volatile compounds increased with the temperature. When water-insoluble melanoidins were heated, especially at higher temperatures, this resulted in a higher diversity of isolated compounds. For furans, pyrroles, pyrazines, and carbonyl compounds a maximum was observed in the case of high molecular weight melanoidins around 200-220 degrees C. Pyridines and total oxazoles, however, were generated in higher yields with increasing temperatures. These results demonstrate the possibility of producing some flavor-significant volatiles from heated standard melanoidins at temperatures relevant to food preparation and contribute to the flavor aspects originating from melanoidins.