Background: Numerous products based on soybean are available and various food technologies are applied for their production. The allergenicity of natural soybean may be modified by these treatments.
Objectives: To compare the allergenicity of native soybean proteins with those of soy milk and texturized protein products. To show additional allergens.
Methods: Three commercial products and two infant formulas were studied: Soybean flour, soy milk, texturized soy proteins, two infant formulas; the first containing total proteins and the second containing a soy protein hydrolysate. Sera from 9 patients allergic to soy protein were tested by immunoblotting (IB). IB inhibition was achieved by incubating sera with protein extract from soybean flour.
Results: The SDS-PAGE profile of soybean flour protein and soy milk showed a difference in the proportions of the various protein fractions, with a higher concentration of 37-kD protein in flour and 33-kD protein in milk. Infant formula 1 contained proteins with a molecular weight below 28 kD. The texturized extract contained high proportions of 31- to 34- and 38-kD proteins. Immunoblotting revealed a lack of allergenicity in infant formula. Sera recognizing the 38- and 50-kD proteins in texturized soy protein also recognized the 37- and 49-kD proteins in soybean flour and in soy milk, suggesting a protein glycation by texturization processes. The 30- to 34-kD band in texturized proteins was devoid of any allergenicity. This study seems to indicate that the 30-kD allergen (Gly m Bd 30) disappears during the production of texturized soy protein.
Conclusion: All technologies applied to soybean-based products induce striking variation in the protein profile and allergenicity. Texturized protein could lack the major allergen Gly m Bd 30. Further studies or texturization might generate modified technologies in order to create hypoallergenic texturized proteins.
Copyright 2002 S. Karger AG, Basel