Kinetics of colour change of kiwifruits during hot air and microwave drying Original Research Article

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 ΔE followed zero-order and whole data of hot air–MW drying followed first-order kinetics.