Serine protease inhibitor. Inhibits trypsin. No decrease in activity observed after incubating at pH 2.5 and pH 7.4 for 1 hour. Retains 20% activity after incubation at pH 12 for 1 hour. No decrease in activity observed after heating for 1 hour at up to 80 degrees Celsius. Retains 20% activity after incubation at 95 degrees Celsius for 1 hour. Avian ovomucoid consists of three homologous, tandem Kazal family inhibitory domains. Causes an allergic reaction in human.