Kinetics of ascorbic acid degradation in dried kiwifruits during storage

Retention of ascorbic acid (AA) in dried kiwifruit in storage is studied. The effects of storage temperature (30 degreesC-50 degreesC) and water activity (a,: 0.51-0.82) are investigated. The degradation of AA follows a first order reaction. A decrease of approximately one order of magnitude in AA is observed when a(w) is increased from 0.51 to 0.82 with the activation energy in the range of (38.0-62.3) kJ/mole. The effect of temperature on the rate constant followed the Arrhenius relationship. An empirical equation combining temperature, water activity rate constant has been developed.