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
In this study, the physicochemical properties and fatty acids composition of four varieties of Citrullus lanatus seed oils cultivated in Côte d’Ivoire were investigated. There was one variety (Bebu cultivar) with oval flat seeds and thick edges (COS), and three varieties (wlêwlê cultivars) with flat seeds disentangled and sharp extremity of various size (big seed (CBS), average seed (CAS) and small seed (CSS)). The pH at 30ºC was ranged from 5.85±0.003-6.03±0.001. The results for density (g/ml), refractive index, unsaponifiable matter (% of oil) and impurity (%) were 0.876±0.005-0.924±0.001; 1.4595±0.004-1.4739±0.001; 0.89±0.450-2.07±0.160; 0.05±0.002- 0.1±0.001; respectively. The free fatty acid (%), acid value (mgKOH/g oil), peroxide index (meq O2/kg oil), saponification value (mgKOH/g oil), iodine value (mg of g I2/100 g oil), Total polyphénolics content (mg gallic acid/kg oil) values of the oils were obtained in the range; 0.80±0.050-2.03±0.010; 6.03±0.350-7.93±0.100; 10.93±0.470-13.80±0.100; 228.43±0.040- 244.76±0.010; 84.07±11.250-93.38±1.090; 0.125±0.050-0.291±0.010; respectively. The most abundant fatty acid detected in the four oils was oleic acid ranged from 46.56-59.97. This acid constituted with the aldaic acid, the monounsaturated fatty acids in these oils and accounted for 64.82-73.07. This study showed the presence of others main saturated fatty acids as stearic acid and palmitic acid. The properties of these oils were quite comparable to those of previously reported cucurbitaceaes seeds oils, suggesting their potential use as good table and cooking oils. With a high yield of oil and physicochemical characteristics similar to those of the other commercial edible oils, the Citrullus lanatus seed oil can be considered as a new and valuable source of edible oil. This study also showed potential for Citrullus lanatus seeds oils to ave relatively high oxidative stability that would be suitable for food and industrial applications.