Kinetics of colour change of kiwifruits during hot air and microwave drying

The kinetics of colour changes of kiwifruits, due to drying by hot air, microwave (MW) and hot air-MW finish drying, were studied. Kinetic parameters for the colour change were determined using Hunter L-, a-, b-values, chroma, Hue, total colour difference and browning index (BI) values. The drying process changed all three colour parameters (L, a, b), causing a colour shift towards the darker region. Parameters L and b decreased and a-value increased during drying. The Hunter parameters were more influenced by MW drying. Zero- and first-order kinetic models were applied to describe colour change. Both models were found to describe the L- and b-data adequately. However, a-values and DeltaE followed zero-order and whole data of hot air-MW drying followed first-order kinetics. (C) 2001 Elsevier Science Ltd. All rights reserved.