Detection of 7S and 11S soy protein fractions by monoclonal antibody-based immunoassays in food

Abstract

A panel of four monoclonal antibodies (MAbs) recognizing antigenic determinants on soy protein was produced and partially characterized. The protein fractions 7S and 11S were extracted and purified from the soy protein isolate and defatted flour of soy, respectively. To obtain hybridomas, popliteal lymph nodes of BALB/c immunized mice (10,0 μg protein/ footpad) were excised and fused to SP2-0 myeloma cells. The hybridomas were screened by enzyme-linked immunosorbent assay (ELISA) using peroxidase-labelled rat anti-mouse IgG MAb and cloned under limiting dilution conditions. The specificity of these antibodies was evaluated by Western blotting. Three antibodies produced by stable clones (1H4, 2A8 and 1F9) recognized the subunits α, α′ and β of the 7S soy protein fraction and one monoclonal antibody (3F2) recognized the basic subunit of the 11S fraction. ELISA assays with the MAbs anti-7S (IgG2b) and 11S (IgG1) fractions were able to detect the presence of these fractions in soy-containing commercial products as yogurt, milk and juice. The present study showed that these MAbs specifically detect the subunits of the 7S fraction and the basic subunits of the 11S fraction of soy protein and may be used in immunoassays to detect these protein fractions in soy-based products. © 2005 Taylor & Francis Group Ltd.