Detection of soya proteins in heated meat products by "blotting" and "dot blot"

Soy proteins (isolates, concentrates and texturates) as well as meat products containing soya isolate were analysed by SDS-electrophoresis. The separated proteins were blotted on nitrocellulose and stained with a selective immunoperoxidase system with the following sequence: primary (anti-soya) serum, goat anti-rabbit IgG serum and peroxidase-antiperoxidase complex (rabbit allotype). By developing the blot with a peroxidase substrate the antigenic soya fractions were visualised while the meat proteins did not stain. All major (reduced) soya fractions alpha, alpha', beta conglycinin, the acid and basic subunits of glycinin as well as some minor fractions became visible with a commercially available anti-soya serum as primary antiserum. The pattern thus obtained provides a high evidence for the presence of soya protein in meat products. Detection level is about 0.02% of soya protein. During a 24-h incubation at room temp. (before heat processing) of a meat product containing soya product and raw liver a remarkable loss of antigenic material was observed.