Kinetics of non-enzymatic browning reaction from the l-ascorbic acid/l-cysteine model system

Abstract

The kinetics of the non-enzymatic browning reaction from l-ascorbic acid/l-cysteine model systems was investigated at 125–155°C for 10–120 min by measuring the loss of reactants and monitoring the brown colour development. The result showed that the browning products were produced at the first order reaction kinetics requirement, with the E_a being 114.33 kJ/mol. The mechanism for the browning development was proposed. The correlation coefficient between browning products and uncoloured intermediate products increased with the rising temperature. At temperatures below 110°C, the non-enzymatic browning reaction did not occur at all or the reaction was slow. Browning products could not be produced solely by self-degradation of l-cysteine. The amount of browning products negatively correlated with the l-ascorbic acid concentration.