Chemistry of non-enzymic browning. III. Effect of Bisulphite, Phosphate, and Malate on the reaction of Glycine and glucose

Abstract

1-Deoxy-1-glycino-D-fructose was obtained in good yield from the reaction of glycine and glucose in the presence of sodium bisulphite and 10 per cent. of water. Small quantities of by-products with similar properties were formed. The results were not affected qualitatively by the reaction temperature or the presence of salts of phosphoric or malic acids. For quantitative studies deoxyglycinofructose was separated from neutral reducing compounds on a cation-exchange resin and determined with alkaline ferricyanide. The yield of deoxyglycinofructose was dependent on the proportion of glucose and bisulphite to glycine and decreased as the water content of the mixture was increased above 10 per cent. The rate of reaction of glycine and glucose in the presence of bisulphite was studied over the pH range 3.5-5.6 and the temperature range 25 to 100 °C. Pseudo first-order rate constants obtained for pH 3.6 and 4.7 fitted the Arrhenius equation. The addition of phosphate at pH 3.6 and malate at pH 3.5 increased the rate of reaction of glycine and glucose ; the increase was proportional to the square root of the concentration of dihydrogen phosphate or hydrogen malate ion. The implications of these results in the non-enzymic browning of dried fruit are discussed.