Kinetics of the oligosaccharide-glycine-sulphite reaction: relationship to the browning of oligosaccharide mixtures

The kinetics of the reaction of sulphite species in mixtures of glucose + glycine, maltose + glycine and oligosaccharide mixtures + glycine are modelled in terms of a mechanism which involves two consecutive rate-determining steps. The rate constant for the first step depends on the dextrose equivalent value of the mixture (range 12–100). The value of the rate constant for the second step is similar for maltose and the oligosaccharides, but slightly greater for glucose. In experiments involving oligosaccharide mixtures, the contribution of oligosaccharides with three or more glucose residues, to the overall rate of reaction, was in the range 60–90%. The rate of browning at 420–490 nm is proportional to the value of the rate constant for the first step except for reaction mixtures containing maltose alone; this disaccharide appears to brown more slowly than expected from the correlation which applies to glucose and the oligosaccharide mixtures.