Is fungal alpha-amylase in bread an allergen?

Background The enzyme alpha-amylase from Aspergillus oryzae used in bakerie s to improve the bread quality has been identified as an inhalative allerge n in baker's asthma. It is doubtful whether this enzyme can induce allergic sensitization in regular bread consumers. Objective To find out whether fungal alpha-amylase in bread and rolls retai ns its antibody-binding capacity and allergenicity after the baking procedu re. Methods Rabbit antibodies directed to fungal alpha-amylase were used for th e development of a two-site enzyme-linked immunosorbent assay (ELISA). This assay was used to analyse different fractions of bread and rolls baked wit h the usual amounts of alpha-amylase in comparison with control products wi thout added enzyme. Competitive experiments between bakers' sera containing specific immunoglobulin (Ig) E to alpha-amylase and the rabbit antibodies were performed. Additionally, specific IgE binding to fungal alpha-amylase was inhibited by native or heated alpha-amylase. Results With the highly specific two-site ELISA for native alpha-amylase in the crust of bread bottom and sides, 2.3-7ng antigenic alpha-amylase per g ram crust were measured. No alpha-amylase could be detected in the crumb fr actions. Rabbit antibodies to native alpha-amylase completely inhibited hum an IgE binding to alpha-amylase allergen disks. Conclusion The results prove residual antibody-binding capacity of alpha-am ylase in bread crusts and in the crust of some rolls. In comparison with th e content of alpha-amylase in dough, between 0.1 and 20% of the antibody-bi nding capacity remained.