Carrot (Daucus carota L.) peroxidase inactivation, phenolic content and physical changes kinetics due to blanching

The kinetics of peroxidase thermal inactivation, total phenolic content degradation, and colour (CIE L*a*b*) and texture changes were studied in a temperature range of 70-90 °C for carrots (Daucus carota L.). Peroxidase inactivation, total phenolic content degradation and the lightness colour (L* parameter) change were successfully described by a first-order reaction model. The redness and yellowness colour (a* and b* parameters, respectively) and texture (firmness and energy parameters) changes presented a fractional conversion kinetic model behavior. The temperature effect was well described by the Arrhenius law. All the blanching conditions recommended to reduce peroxidase inactivation to an acceptable level (90% loss of its original activity) ensured good quality retention. However, to obtain a high quality carrot product a balance must be made between colour and total phenolic content losses. Therefore, blanching at 80 °C for 6 min is suggested as a compromise condition to maximize quality. The overall study indicated that colour is a critical parameter to optimize carrot hot water blanching condition.