Quantitative analysis of Gly m Bd 28K in soybean products by a sandwich enzyme-linked immunosorbent assay

A sandwich enzyme-linked immunosorbent assay for the soybean allergen, which consists of a monoclonal antibody (D4) as the fixing (first) antibody and another peroxidase-conjugated monoclonal antibody (C5) as the second, has been developed. Both D4 and C5 monoclonal antibodies strongly bound to the guanidine/HCl-denatured allergen, Gly m Bd 28K. Therefore the samples used in the present experiment were extracted with sodium phosphate buffer (pH 8.0) containing 6 M guanidine and 10 mM 2-mercaptoethanol, then completely dialyzed against phosphate-buffered saline (PBS). The dialyzed samples were subjected to the assay. Various soybean products were observed to contain the allergen at high concentrations, such as soybean protein isolate (SPI), tofu, kori-dofu, and yuba, but its content in soy milk and abura-age were found to be low. In fermented products such as natto, soy sauce, and miso, and even in the processed foods with soybean protein isolate (SPI), the allergen was not detected. These results were also confirmed by an immunoblotting technique with D4.