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 a nd glucose+glycine+glyceraldehyde mixtures ([glucose] = 0-1 mol l(-1); [gly cine] = 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 con centration, 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 rea ctions. This synergistic behaviour is accompanied by the removal of the ind uction phase normally seen for the Maillard reaction, and a browning reacti on whose kinetics depend on the concentrations of all 3 reactants. The appa rent 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 glyce raldehyde to its hydroxysulphonate could contribute to the mechanism of the inhibition of Maillard browning by sulphite species. (C) 1999 Elsevier Sci ence Ltd. All rights reserved.