Development of Sandwich and Competitive ELISA Formats to Determine Soybean Allergen: Evaluation of Their Performance to Detect Soy in Processed Food

Taking soybean mixed allergens as the target, a sandwich-enzyme linked immunosorbent assay and an indirect competitive enzyme-linked immunosorbent assay for the rapid and convenient detection of soybean allergens were established. The two methods were compared through the recovery experiment of actual processed samples, the recovery experiment of spiked food and the detection of real food samples, and their respective application scopes were determined. Sandwich ELISA method, the standard concentration was in the range of 0.0078~30 μg/mL, showing a good linear relationship, the curve equation was y=0.2333x+0.0692 with coefficient of determination R²=0.995. The detection range of the competitive ELISA method was 10~100000 ng/mL, and the lowest detection limit was 10 ng/mL. The recovery rate of orange juice after sandwich ELISA was higher than that after competitive ELISA, reaching more than 100%. For chocolate, beef sauce, bread and cake with complex ingredients and processing methods, the recovery rate after competitive ELISA was higher than that after double-antibody sandwich ELISA. In the detection of soybean allergens in fermented foods, the concentration detected by competitive ELISA was higher than that detected by sandwich ELISA, while in the detection of simple ingredients such as sesame paste and soy milk, the concentration detected by sandwich ELISA was slightly higher than that detected by competitive ELISA. In general, the competitive ELISA method was more suitable for the food with complex food matrix and deeply processed, while the sandwich ELISA method was more suitable for the food with simple food ingredients and lightly processed food, both of the two methods can achieve more accurate detection in their respective application scope.