Browning of Dehydroascorbic Acid and Chlorogenic Acid as a Function of Water Activity

Browning and degradation of dehydroascorbic acid (DHA) and chlorogenic acid (CA) at pH 6, was studied at variable water activities (a w ) 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 a w . Activation energies for browning ranged from 13‐17 Kcal and were independent of a w . Browning and degradation of CA was negligible at a w below 0.6. CA loss in the DHA‐CA mixture was apparently delayed by decomposition products of DHA and this was pronounced at high a w .