Determination of beta-conglycinin in soybean and soybean products using a sandwich enzyme-linked immunosorbent assay

Soybean protein has long been recognized as a source of dietary allergens for humans and animals with beta-conglycinin being the major allergen. This paper presents a sandwich enzyme-linked immunosorbent assay (ELISA) that allows for the detection of trace amount of beta-conglycinin in soybean and soybean products. In the sandwich ELISA, mouse anti-beta-conglycinin monoclonal antibody (Mab 5C5) was used as coating antibody, and rabbit anti-beta-conglycinin polyclonal antibody (Pab) was used as secondary antibody. The assay showed high specificity for beta-conglycinin with minimum cross-reactions with other soy proteins. The practical working range for the determination of beta-conglycinin using the developed assay was 3-100 ng m L-1 and the limit of determination (LOD) was 1.63 ng mL(-1). The recoveries of beta-conglycinin in spiked soybean samples were between 88.1% and 106.6% with relative standard deviation less than 8.9% (intra-day) and 13.1% (inter-day). The developed method was used to analyze 469 soybean seed samples from different sources as well as five soybean products treated with different processing techniques. The data showed that the concentration of beta-conglycinin decreased significantly after processing, especially for soybean protein isolation, where the concentration of beta-conglycinin dropped to nearly zero. The assay provides a specific and sensitive method for the screening of beta-conglycinin and allows for further investigation into hypersensitive mechanisms of soybean proteins and development of soybean processing techniques to reduce their negative effects. (c) 2012 Elsevier B.V. All rights reserved.