Determination of Soy Proteins in Food Products by Enzyme Immunoassay
Jupiter M. Yeung* and Peter G. Collins
Food Research Division, Food Directorate, Bureau of Chemical Safety, Health Protection Branch, Health Canada, PL 2203D, Ottawa, Ontario, Canada, KlA 0L2
Article history:
Received June 23, 1997
Accepted October 15, 1997
Key words:
Soy, food allergen, immunoassay, ELISA, foods, HVP
Summary:
Soy allergy is a common food allergy in North America and it can be fatal. Once it is diagnosed, dietary avoidance is ihe only sure method of management. Until recently, no analytical method was available to detect trace amounts of unintentional allergen contamination in our food supply. We have now developed polyclonal antibodies specific to soy proteins that do not cross-react with any of the 31 nuts, legumes or other common food ingredients tested. The antiserum was used to develop a sensitive immunoassay for the determination of soy proteins in foods. The concentration of soy proteins that inhibits 50% of antibody-antigen binding, IC50 was 35 ng/mL and the linear range was 3 to 117 ng/mL. The detection limit was 2 ppm for the various pods tested. Recoveries ranged from 79-90%. The intra- and inter-assay coefficients of variation in this procedure were <8% for both canned fish and hamburger spiked at three levels between 13.5 to 54.0 ppm. The ELISA procedure was applied to a limited number of samples of hydrolysed vegetable protein (HVP), canned fish, hamburger and infant formula products. Soy proteins were identified in some HVP and soy-containing formulae, but not in the 29 fish, 14 hamburger and 20 infant formula products.
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*Corresponding author: 
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