The effect of
heat treatment on the activities of three quality related enzymes peroxidase
(POD), polyphenol oxidase (PPO), and lipoxygenase (LOX), from edible white yam
(Dioscorea rotundata) was studied over a temperature range of 50 to 80°C using
mathematical analysis of the kinetic
and thermodynamic parameters for the thermoinactivation of the enzymes.
Denaturation of
these enzymes, measured by loss in activity, could be described by a simple
first-order reaction that was resolved into biphasic inactivation curves.
This indicates
the existence of two isoforms of different thermal stabilities with k-values
between 0.032 and 0.525. D-values decreased with increasing temperature,
indicating faster inactivation of the enzymes at higher temperatures.
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