Establishment of a Lateral Flow Colloidal Gold Immunoassay Strip for the Rapid Detection of Soybean Allergen β-Conglycinin

A rapid lateral flow colloidal gold immunoassay strip was established in a sandwich format with the colloidal gold-labelled mouse anti-beta-conglycinin monoclonal antibody (mAb) and the rabbit anti-beta-conglycinin polyclonal antibody (pAb) in order to specifically identify a soybean allergen, beta-conglycinin. Soybean and soy derivatives have become ubiquitous in many vegetarian and meat-based food products, and as a result, dietary avoidance has become difficult. Therefore, soybean avoidance is challenging for individuals with soybean allergy. In our study, the selected mAb showed high affinity to the target and no cross-reactivity with other soybean allergens. Based on the sandwich immunoassay principle, the rabbit pAb was applied in the test line with high titre. The assay could be accomplished within 10 min without sophisticated procedures. The limit of detection of the test strip was calculated at 1.66 mg/kg in powdered milk using an optical density scanner that measures relative optical density. The assay showed high specificity for beta-conglycinin, with no cross-reactions with other food allergens. The efficacy of the lateral flow test strip to detect beta-conglycinin in powdered milk samples ranged between 80.8 and 89.2% with relative standard deviations of less than 7.2%. Therefore, the test strip is useful as a rapid and reliable detection method for beta-conglycinin in powdered milk. In addition, this assay is suitable for monitoring beta-conglycinin in other processed foods when samples are appropriately extracted.