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 esculentaCrantz) root cv. Bocou 2 in order to preventenzymatic 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 Biocatalysisand 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) ofyellow-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 (?G > 0), slightly endothermic (?H > 0) and reversible (?S < 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.