Thermal and high‐pressure treatment stability of egg‐white avidin in aqueous solution

The combined pressure (0.1 and 600 MPa) and thermal (30, 65, 75, 90, and 105°C) treatment effects on the binding properties of egg‐white avidin were investigated using fluorescence spectroscopy titrations with fluorescein‐labeled biotin for various holding times (up to 45 min). Pressure treatment was carried out in a high‐pressure kinetic tester whereas heat treatment was conducted using metal tubes in a temperature‐controlled oil bath. Avidin binding activity and strength decreased by approximately three orders of magnitude with increases in temperature and holding time, while the binding free energy (−52.3 ± 0.47 kJ/mol) remained unaffected by high‐pressure (600 MPa at 30°C) treatment. The thermal inactivation rate constant ranged from 0.009 to 0.793 per min at 65–105°C, 0.1 MPa. Combined pressure (600 MPa)–thermal (65–105°C) treatment reduced the corresponding values by a factor of two to nine, resulting in inactivation rates that ranged from 0.001 to 0.422 per min. Activation energies for avidin inactivation were 120 ± 10 and 149 ± 8 kJ/mol for thermal and combined pressure–thermal treatment, respectively. In conclusion, while heat treatment alone destroyed biotin binding strength of avidin, combined pressure, and heat exhibited antagonistic effects on avidin–biotin binding energies. PRACTICAL APPLICATIONS: Heat and pressure can have synergistic, additive, or antagonistic effects on food components. The synergistic effect is important from food safety aspect whereas antagonistic effect is desirable to retain food quality attributes during food processing. The parameters of reaction kinetic models, more specifically rate constant and activation energy can be used to evaluate the interactions of heat and pressure during food processing. Egg‐white avidin has been selected in this study to evaluate the interaction between heat and pressure. Information obtained from this study can be used to preserve egg‐white avidin binding activity for various applications including food formulations, biochemical assays and preservation, due to its enormously high binding ability with biotin.