Detection of soy protein in soy lecithin, margarine and, occasionally, soy oil

Samples of soy lecithin, soy oil and margarine were tested for the presence of soy proteins by an inhibition technique using ELISA. All but one of the soy lecithin samples contained soy protein, as did some of the soy oil and margarine samples. The positive margarines contained only about 25% as much soy protein as the soy lecithin preparations. The presence of soy proteins in these soy products might account for hitherto unrecognized exposure to soy proteins in various foods.