Thermostability of soluble and bound peroxidases from artichoke and a mathematical model of its inactivation kinetics.

Soluble peroxidases (SP), and ionically (IBP) and covalently (CBP) bound peroxidases were extracted from leaves and edible part of artichoke heads (heart). The peroxidase (POD) forms showed a characteristic electrophoretic pattern; in particular SP and IBP forms showed nearly the same pattern, while CBP was quite different. Several basic and acid POD isoforms were present in SP and CBP forms, whereas in IBP only basic components were found. The thermal stability of different POD forms was tested at different temperatures (70-80-90-100 °C). The leaf POD forms showed greater heat stability compared to the head ones. The heat sensitivity of three POD forms was different: the bound forms were characterized by a greater heat stability than the soluble form. A series-type mathematical model has been developed to describe the inactivation kinetics of artichoke POD. The activation energies for the three POD forms of artichoke leaves and hearts were estimated by an Arrhenius-type relationship. The second step of the inactivation requires more energy to be carried out in all POD forms, especially in SP and IBP.