Effect of glyceraldehyde on the kinetics of Maillard browning and inhibition by sulphite species

The kinetics of browning (A(470)) are reported for glyceraldehyde+glycine and glucose+glycine+glyceraldehyde mixtures ([glucose] = 0-1 mol l(-1); [glycine] = 0-1 mol l(-1); [glyceraldehyde] = 0-10 mmol l(-1); pH 5.5, [acetate buffer] = 0.2 mol l(-1) with respect to acetate ion; 55 degrees C). In the absence of glucose the rate of reaction depends only on glyceraldehyde concentration, whereas glycine is required for colour development. The rate of browning when all 3 reactants are present is much greater than calculated as the sum of the individual glyceraldehyde+glycine and glucose+glycine reactions. This synergistic behaviour is accompanied by the removal of the induction phase normally seen for the Maillard reaction, and a browning reaction whose kinetics depend on the concentrations of all 3 reactants. The apparent dissociation constant of the hydroxysulphonate of glyceraldehyde is 6.76x10(-5) mol l(-1) (pH 5.5, 55 degrees C, ionic strength approximate to 0.2 mol l(-1)). Theoretical calculations suggest that the conversion of glyceraldehyde to its hydroxysulphonate could contribute to the mechanism of the inhibition of Maillard browning by sulphite species. (C) 1999 Elsevier Science Ltd. All rights reserved.