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 edible yam (Dioscorea cayenensis-rotundata cv. “Zrèzrou”) polyphenol oxidase activity was studied over a range of 35 to 75°C. Under all conditions investigated, a first-order kinetic model could describe the thermal inactivation data with k-values between 0.004 and 0.108 min-1. The D- and k-values decreased and increased, respectively, with increasing temperature, indicating faster polyphenol oxidase inactivation at higher temperatures. Results suggested that polyphenol oxidase of D. cayenensis-rotundata cv “Zrèzrou” (PPOZ) is a relatively thermostable enzyme with a Z-value of 26.32°C and activation energy (Ea) of 78.93 kJ.mol-1. The average values of enthalpy (ΔH#), entropy (ΔS#) and Gibbs free energy (ΔG#) were respectively 76.20 kJ.mol-1, -36.41 J.mol-1K-1 and 88.15 kJ.mol-1at 308-348 K. The results of the thermodynamic investigations indicated that the oxidation reactions were: 1) not spontaneous (ΔG#>0), 2) slightly endothermic (ΔH#>0) and 3) reversible (ΔS#<0).
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