Enzyme-linked Immunosorbent Assay and Immunobiotting Using IgY Antibodies Against Soybean Glycinin A

Using IgY antibodies obtained from egg yolk of immunized chickens, an enzyme-linked immunoassay (ELISA) and an immunoblotting procedure has been developed for specific determination of soy protein. The procedure. for antigen preparation provides a rapid method for the isolation of SDS-denatured glycinin A from polyacrylamide gels that could be used directly for immunization. ELISA with SDS-denatured soy protein isolate was linear in the range 0.5-256 mu g/ml and covers the expected levels of soy protein in simulated milk and milk products, Immunostaining of SDS-PAGE blots allowed the detection of glycinin A at nanogram levels. It is claimed that the antigenic status of SDS-denatured glycinin A is independent of food processing conditions and that the specific immunoreaction is controlled by high affinity IgY antibodies against the SDS-denatured protein conformation.