The influence of water and pH on the reaction between amino compounds and carbohydrates.

The mechanisms involved in browning and in the Maillard reaction (1)) together with their effect on the nutritive value of proteins, have been investigated extensively, yet much of the evidence is of a contradictory nature. These experimental results are to be expected if one considers the variety of conditions of temperature, pH, and reactant concentrations employed by the various investigators. In most cases the studies published have been concerned with the secondary changes induced in either the amino compounds or the reducing sugars by heat processing. This has led investigators to view the reaction of amino compounds and reducing sugars (Maillard reaction) largely in its relation to browning, with the consequent tendency to attribute browning to the Maillard reaction. In 1953, Schroeder, Iacobellis, Lees, and Smith (a), continuing a previous investigation (3) on the effect of heat on milk products, presented data secured by the nitrogen balance method on intact animals and by digestion experiments with crystalline enzymes in vitro, showing that the decrease in nutritive value suffered by the contained proteins when dried skim milk is autoclaved was prevented by prior reconstitution with water to protein levels as high as 24.5 per cent. It appeared that water prevented the deleterious effect of heat upon proteins. On the basis of these observations, it was postulated that browning and the Maillard reaction might not bear a causative relation to each other, but rather might be viewed as two separate and independent reactions. The purpose of the present investigation was to determine the influence of both water and pH on the interaction of amino compounds and reducing sugars.