Non enzymic browning (NEB) was studied in aqueous model systems that consisted of glucose and glycine at three different solid concentrations (20, 30 and 40% by weight), each one at three glucose/glycine molar ratios (1:1, 2:1 and 5:1), heat treated for different times at three temperatures (70, 80 and 90°C). Three different "indicators" of the NEB reaction were used: optical density at 294 nm, carbon dioxide formed via Strecker degradation and volatile compounds formed during the various steps of Maillard reaction.
Spectrophotometric and gaschromatographic data were used in order to calculate kinetic constants and activation energy values of NEB reaction. Each indicator showed that the kinetic constant values increased with increasing solid concentration of the solution and heattreatment temperature and with the decreasing of glucose/glycine molar ratios. The activation energy, which causes carbon dioxide formation, was found to be approximately 100 kjx mol-1, while for Amadoi compound formation the value of activation energy was about 160kjx mol-1 without an evident dependance from the solid concentration of the solution or glucose/glycine molar ratio. In our experimental and analytical conditions, thw measurement of optical density at 294 nm and carbon dioxide detection in the headspace were earlier indicators of the NEB reaction than the volatile compounds detection.
