Thermal inactivation of lactoperoxidase in goat, sheep and bovine milk – A comparative kinetic and thermodynamic study

Abstract

Using isothermal heating, inactivation of lactoperoxidase (LPO) in goat, sheep and cow milk was studied in the temperature range of 70–77°C. Kinetic and thermodynamics studies were carried out at different time–temperature combination in order to evaluate the suitability of LPO as marker for the heat-treatment of milk and dairy products from different species. The thermal inactivation of LPO followed the first-order kinetics. D- and k-values decreased and increased, respectively with increasing temperature, indicating a more rapid LPO inactivation at higher temperatures. The influence of temperature on the inactivation rate constant was quantified using the Arrhenius and thermal death time models. The corresponding z-values were 3.38±0.013, 4.11±0.24 and 3.58±0.004°C in goat, sheep and cow milk, respectively. Activation energy values varied between milk species with 678.96±21.43kJmol−1 in goat milk, 560.87±28.18kJmol−1 in sheep milk and 641.56±13.12kJmol−1 in cow milk, respectively.