Assessment of allergenic activity of a heat-coagulated ovalbumin after in vivo digestion

We often eat heat-coagulated (H-C) food proteins, but there have been few studies on the allergenic activity of H-C proteins after digestion and absorption in vivo. To show that H-C protein is not an allergen after digestion, mice were used to investigate the digestion and absorption of the protein through the intestinal epithelium into portal blood employing immunoblotting and competitive inhibition ELISA. Ovalbumin (OVA) was used as the model protein, and H-C OVA was prepared by heating a 5% OVA solution for 15 min in boiling water. Antigenic OVA was not detected in the soluble fraction of gastrointestinal contents or the portal blood of mice administered H-C OVA. Also, voluntary physical activities, as an assessment of anaphylaxis, were monitored for 15 h using OVA sensitized mice. Compared to the voluntary physical activities of sensitized mice without any load, no decrease in activity was observed in the group administered H-C OVA, but a significant decrease in activity was found in the mice administered unheated OVA. These results strongly indicate that H-C OVA does not retain allergenic properties.