Identification and Comparison of Differences in Antigens in Two Commercially Available Soybean Protein Isolates

Two commercially available soybean protein isolates were compared with regard to their allergenicity and their subcomponent differences. Isolate (A) is used in commercially prepared liquid infant formulas and isolate (B) in powdered infant formulas. Sera from four children with soy protein hypersensitivity and from five infants with soy protein‐induced enterocolitis were used for in vitro testing. ELISA results show that specific IgE and IgG antibodies to isolate (A) were significantly higher than to isolate (B) in all groups. In SDS polyacrylamide gel electrophoresis, isolate (A) has bands representing the subunits of 7S (B‐conglycinin) and the acidic and basic subunits of 11S; isolate (B) had only much smaller molecular weight compounds. Thus, there may be a difference in the allergenicity of liquid and powdered infant formulas.