National Academy of Agricultural Sciences (NAAS)
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PRINT ISSN : 2319-7692
Online ISSN : 2319-7706 Issues : 12 per year Publisher : Excellent Publishers Email : editorijcmas@gmail.com / submit@ijcmas.com Editor-in-chief: Dr.M.Prakash Index Copernicus ICV 2018: 95.39 NAAS RATING 2020: 5.38 |
The effect of heat treatment on polyphenoloxidases and peroxidase activities in three tissues (cambium, central cylinder and internal bark) of the varietie of cassava roots (Manihot esculenta CRANTZ) Bonoua 2 were studied over a range of 30 to 70 °C, using pyrogallol, 4-methylcatechol, dopamine and pyrocatechol as a substrates for polyphenol oxydase and guaiacol as a substrate for peroxidase. Optimal conditions for enzymatic studies were determined to between pH 8.6 and 9.6 for polyphenoloxydases and pH 6.6 and 7.6 for peroxidase and 25-45 °C. T1/2-values of enzymatic activities are between 2.22 and 4.27 min at 70 °C, they decreased with increasing temperature, indicating a difference thermostability of each enzyme. D- and k-values decreased and increased, respectively, with increasing temperature, indicating faster of these enzymes inactivation at higher temperatures. Results suggested that polyphenoloxydases and peroxidase were relatively thermostable enzymes with a Z-value which vary from 21.49 at 37.76 °C and Ea of 75.84 at 139.17 kJmol-1. Thermodynamic parameters were also calculated. The Gibbs free energy ΔG values range from 47.33 to 265.85 kJ/mol. These kinetic data can be used to predict prevention of browning in the cassava roots (Manihot esculenta CRANTZ) by thermal inactivation of enzymes.
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