Study of the kinetic behaviour of non-enzymatic browning reaction between L-ascorbic acid and glycine by the excess concentration method

Abstract

The formation kinetics of browning products (BPs) derived from the self-degradation of L-ascorbic acid (AA) and the reaction between AA and glycine (Gly) were investigated at pH 6.8 and various other parameters, such as temperature, time, and molar concentration ratio of AA/Gly. The temperature ranged from 110 to 150°C, the time ranged from 10 to 240 min, and the molar concentration ratios of AA to Gly were 4:1, 2:1, 1:1, 1:2, and 1:4. The results suggested that the formation rate of BPs was promoted by increasing the temperature, prolonging the time, and augmenting the molar ratio of AA. Based on the assumption of a kinetic model and a possible reaction pathway, the formation rate of BPs followed a pseudo-first order, and the rate was primarily dependent on the consumption of AA. The formation activation energies (Ea) for the BPs were 60.76 and 70.16 kJ/mol with AA/Gly ratios of 4:1 and 1:4, respectively.