Thermal Inactivation of Crude Polyphenol Oxidases and Peroxidase from Three Tissues of Yellow-fleshed Cassava (Manihot esculenta Crantz) Root cv. Bocou 2

Abstract

Aims: The objective of this work was to study the thermal inactivation of the polyphenol oxidase (PPO) and peroxidase (POD) activities of cassava (Manihot esculenta Crantz) root cv. Bocou 2 in order to prevent enzymatic browning. Study Design: Crude PPO and POD from yellow-fleshed cassava root were subjected to heat treatment and their thermal inactivation characteristics were examined. Place and Duration of the Study: The study was conducted at Biocatalysis and Bioprocesses Laboratory, Food Science and Technology Unit, Nangui Abrogoua University Abidjan, Côte d’Ivoire, between January and December 2015. Methodology: The crude PPO and POD were extracted from three tissues (cortex, cambium and central pith) of yellow-fleshed cassava root cv. Bocou 2. The thermal inactivation of these enzymatic activities was evaluated between 50 and 70 °C. The kinetic data of thermal inactivation and thermodynamics were analysed. Results: The t1/2- and D-values decreased with increasing temperature, indicating a faster inactivation of PPO and POD at higher temperatures. Z-values ranged from 16.10 to 27.70 °C and activation energy (Ea) from 73.37 to 129.66 kJ mol-1. Thermodynamic investigations indicated that the oxidation reactions involving these enzyme activities were: not spontaneous (ΔG > 0), slightly endothermic (ΔH > 0) and reversible (ΔS < 0). Conclusion: The PPO and POD activities from yellow-fleshed cassava root decreased due to heat denaturation with increasing temperature from 60 to 70 °C. These kinetic data can be used to prevent enzymatic browning in cassava roots.