The effect of various proteins on the loss of lysine and rate of nonenzymatic browning was studied in an intermediate moisture food system containing glucose as 10% of the solids. The system was prepared to a water activity range of 0.6–0.8 and the samples were held at 35 °C to accelerate the reaction. It was found that proteins which showed long induction times before color development also had lower browning rates. The proteins also showed over 50% loss of available lysine soon after initial color development occurred. Free lysine added to the formulation caused very rapid browning. No pattern of browning rate and lysine loss existed with the total lysine availability.