Is fungal alpha-amylase in bread an allergen?

Abstract

The enzyme alpha-amylase from Aspergillus oryzae used in bakeries to improve the bread quality has been identified as an inhalative allergen in baker's asthma. It is doubtful whether this enzyme can induce allergic sensitization in regular bread consumers. To find out whether fungal alpha-amylase in bread and rolls retains its antibody-binding capacity and allergenicity after the baking procedure. Rabbit antibodies directed to fungal alpha-amylase were used for the development of a two-site enzyme-linked immunosorbent assay (ELISA). This assay was used to analyse different fractions of bread and rolls baked with the usual amounts of alpha-amylase in comparison with control products without 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. With the highly specific two-site ELISA for native alpha-amylase in the crust of bread bottom and sides, 2.3-7 ng antigenic alpha-amylase per gram crust were measured. No alpha-amylase could be detected in the crumb fractions. Rabbit antibodies to native alpha-amylase completely inhibited human IgE binding to alpha-amylase allergen disks. The results prove residual antibody-binding capacity of alpha-amylase in bread crusts and in the crust of some rolls. In comparison with the content of alpha-amylase in dough, between 0.1 and 20% of the antibody-binding capacity remained.