International journal of food science and technology vol:31 issue:3 pages:223-231
The thermal inactivation of horseradish peroxidase was studied in sodium phosphate buffer solutions and in pure water at pH 7 in the temperature range of 70-95 degrees C. The sodium phosphate ions concentration affected both the thermostability and the kinetic patterns and had a stabilizing effect. The gradual change observed at low concentrations made a series-type mechanism theoretically more coherent with the experimental observations than the conventionally applied two-fraction model. In water the kinetics is apparently first order at high temperatures, while the results obtained at 25 degrees C support the occurrence of a series-type inactivation mechanism. The pH and enzyme concentration also affect the inactivation profile, supporting the conclusion that the thermal inactivation is not a monomolecular process with respect to protein concentration.