Browning and degradation of dehydroascorbic acid (DHA) and chlorogenic acid (CA) at pH 6, was studied at variable water activities (aw) and temperature in a model food system containing cellulose, DHA and/or CA. Rate of DHA browning followed an apparent zero order reaction and was maximum at intermediate aw. Activation energies for browning ranged from 13-17 Kcal and were independent of aw. Browning and degradation of CA was negligible at aw below 0.6. CA loss in the DHA-CA mixture was apparently delayed by decomposition products of DHA and this was pronounced at high aw.