Avidin - Inactivation of Biotin Binding Activity

Inactivation of Biotin Binding Activity

The thermal stability and biotin binding activity of avidin are of both practical and theoretical interest to researchers, as avidin's stability is unusually high and avidin is an antinutrient in human food. A 1966 study published in Biochemical and Biophysical Research Communications found that the structure of avidin remains stable at temperatures below 70 °C (158 °F). Above 70 °C (158 °F), avidin's structure is rapidly disrupted and by 85 °C (185 °F), extensive loss of structure and ability to bind biotin is found. A 1991 assay for the Journal of Food Science detected substantial avidin activity in cooked egg white: "mean residual avidin activity in fried, poached and boiled (2 min) egg white was 33, 71 and 40% of the activity in raw egg white." The assay surmised that cooking times were not sufficient to adequately heat all cold spot areas within the egg white. Complete inactivation of avidin's biotin binding capacity required boiling for over 4 minutes.

A 1992 study found that thermal inactivation of the biotin binding activity of avidin was described by D_121°C = 25 min and z = 33°C. The study disagreed with prior assumptions "that the binding site of avidin is destroyed on heat denaturation".