Modelling kinetics of thermal degradation of colour in peach puree

Optimisation of thermal processes relies on adequate degradation kinetic models for food safety and quality. In order to use peach puree as a model food to further validate calculated optimal conditions, isothermal experiments, using peach puree, were performed between 110 degrees C and 135 degrees C. Colour was quantified using the L, a, b system. Two combinations of these parameters, La/b and Total Colour Difference (TCD), were used to evaluate the total colour change. A one-step non-linear regression was performed on all data using the Arrhenius model. The changes in the L and b values followed a first-order reaction with activation energies of 107+/-7 and 109+/-8 kJ/mol, respectively. The fractional conversion model was applied to a, La/b and TCD resulting in activation energies of 106+/-3, 106+/-10 and 119+/-9 kJ/mol, respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.