Enzyme-linked immunosorbent assay kit for the determination of soybean protein in processed foods: interlaboratory evaluation.

The labeling of foods containing ingredients derived from soybean is recommended in Japan because of an increasing number of patients who are allergic to soybeans. To ensure proper labeling, a novel sandwich ELISA kit for the determination of soybean protein in processed foods (FASTKIT Ver. II, "Soybean", Nippon Meat Packers, Inc.; "soy kit") has been developed. Five types of incurred samples (model processed foods: rice gruel, sausage, sweet adzuki bean soup, sweet potato cake, and tomato sauce) containing 10 microg soybean soluble protein/g food were prepared for use in interlaboratory evaluations of the soy kit. The soy kit displayed a sufficient RSD(R) value (interlaboratory precision: 9.3-13.4% RSD(R)) and a high level of recovery (97-114%) for all the incurred samples. The RSD(R) value for the incurred samples was mostly < 4.8%. The results of this interlaboratory evaluation suggest that the soy kit can be used as a precise and reliable tool for the determination of soybean proteins in processed foods.