Kinetics of browning and correlations between browning degree and pyrazine compounds in L-ascorbic acid/acidic amino acid model systems

The kinetics of browning and the correlation between browning products (BPs) and pyrazine compounds were investigated by heating equimolar L-ascorbic acid (ASA)/acidic amino acids under weak alkaline conditions at 120-150 degrees C for 10-120 min. The formations of BPs and pyrazine compounds from the reaction were monitored by UV-vis and SPME-GC-FID, respectively. The formation of BPs in both ASA/Lglutamic acid and ASA/L-aspartic acid model reaction systems followed zero order reaction kinetics with activation energies (Ea) of 90.13 and 93.38 kJ/mol, respectively. ASA/L-aspartic acid browned at a slightly higher rate than ASA/L-glutamic acid. The total concentration of pyrazine compounds was highly and positively correlated with that of BPs. Based on the observed kinetic data, the formation mechanisms of BPs and pyrazine compounds were proposed. (C) 2016 Elsevier Ltd. All rights reserved.