Thermal and High-Pressure Inactivation Kinetics of Avidin

Abstract

High-pressure (HP) inactivation of pure avidin as well as avidin in egg were evaluated and compared with conventional thermal inactivation kinetics. Test samples were treated at 500 to 700 MPa and 80 to100C for pure avidin and at 500 to 700 MPa and 30 to 50C for avidin present in egg white and whole liquid egg. Avidin inactivation was well described by the first-order kinetic model. Pure avidin was found to be relatively very resistant as compared with avidin in egg, and thermal inactivation was much slower than HP inactivation. Conventional thermal treatment at 100C gave a D value of 111 min while HP treatment (700 MPa) at the same temperature reduced the D value to 26 min for pure avidin. However, avidin naturally present in egg was sensitive to both thermal and pressure treatments. Avidin in egg had a D100C value of 10.0 to 10.9 min indicating greater heat sensitivity. Conventional thermal treatment at 50C had negligible effect on avidin inactivation in egg while HP treatment at 700 MPa almost completely inactivated it in 5–10 min (D value of 2.2 min). The pressure and temperature sensitivity parameters (z value) were also determined both as a function of pressure at different temperatures and as a function of temperature at different pressure levels. Practical Applications Avidin present in egg white possesses antinutritional properties as it can bind with biotin (vitamin B7) making it inaccessible to the body. Biotin is an important vitamin necessary for cell growth, metabolism of fats and amino acids in the human body. It has been shown that one molecule of avidin has the ability to bind four molecules of biotin. Since avidin is very stable, processing treatments aim at inactivating it so as to make biotin available for digestion and absorption by the body. Avidin is traditionally inactivated by thermal processing. HP processing is a nonthermal alternative to conventional thermal processing aimed at minimizing the thermal damage to quality factors. This research compares thermal and HP techniques for inactivating avidin. HP has been shown to accelerate the inactivation of avidin.