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.
ABSTRACT
The maximum acid phosphatasic activity was detected in peanut seed at the 5th day of germination. At least, two acid phosphatases were purified by successive chromatography separations on DEAE-Sepharose CL-6B, CM-Sepharose CL-6B, Sephacryl S-100 HR, and Phenyl-Sepharose HP to apparent homogeneity from five days old cotyledon of peanut after germination. These isoenzymes, designated peanut cotyledon acid phosphatase 1 and 2 [PCAP 1 and PCAP 2], had native molecular weights of approximately 27.5 and 24 kDa by gel permeation, respectively. SDS-PAGE [Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis] of PCAP 1 and PCAP 2 resolved a single protein band [each] that migrated to approximately 27 and 29 kDa, respectively. Thus, these acid phosphatases likely function as a monomer. The two isoenzymes had a similar optimum temperature [55°C], two closely optima pH [5.6 and 5.0], and appeared to be stable in the presence of some detergents such as Triton X-100, Nonidet P-40, Taurocholic acid sodium salt, Polyoxyethylene-9-lauryl ether as well as Mg2[+], Sr2[+], Fe3[+] and Ba2[+]. Substrate specificity indicated that PCAP 1 and PCAP 2 hydrolyzed a broad range of phosphorylated substrates. However, natural substrates such as ADP, ATP and phenylphosphate had the highest rate of hydrolysis for the two isoenzymes