Enzyme immunoassay for the quantitative determination of Soy in food.
Background: Soy (Glycine max) belongs to the legumes. With 39% the fraction of proteins in soy beans is very high. Many of these proteins are known for being allergenic, such as Gly m1, Glycinin, Kunitz-Trypsin-Inhibitor and Gly m4 which is known to be cross-reactive to birch pollen allergen Bet v1. For this reason soy represents an important food allergen. For soy allergic persons hidden soy allergens in food are a critical problem. Already very low amounts of soy can cause allergic reactions, which may lead to anaphylactic shock in severe cases. Because of this, soy allergic persons must strictly avoid the consumption of soy or soy containing food. Partly undeclared addition of soy as additive in many foods is of particular importance. Cross-contaminations, mostly in consequence of the production process are representing another problem. The chocolate production process is a representative example. For this reason sensitive detection systems for soy residues in foodstuffs are required. Only a few soy proteins are stable to conventional production processes (for example high temperature). For this reason robust indicator proteins are necessary for detection. Soy trypsin inhibitors (STI) are representing such proteins. Soy ELISA represents a highly sensitive detection system on the base of STI and is particularly capable of the quantification of soy residues in cookies, cereals, ice cream, chocolate, instant soups and sausage.
Description: The soy quantitative test is based on the principle of the enzyme linked immunosorbent assay. An antibody directed against STI is bound on the surface of a microtiter plate. Soy containing samples or standards are given into the wells of the microtiter plate. After 20 minutes incubation at room temperature, the wells are washed with diluted washing solution to remove unbound material. A peroxidase conjugated second antibody directed against STI is given into the wells and after 20 minutes of incubation the plate is washed again. A substrate solution is added and incubated for 20 minutes, resulting in the development of a blue colour. The colour development is inhibited by the addition of a stop solution, and the colour turns yellow. The yellow colour is measured photometrically at 450 nm. The concentration of STI and hence the concentration of soy is directly proportional to the colour intensity of the test sample.
- The kit contains reagents for 96 determinations;
- Microtiter plate consisting of 12 strips with 8 breakable wells;
- STI Standards: 0, 40, 100, 400, 1000 ppb;
- ELISA reader at 450 nm;
- Standard range: 40 - 1000 ppb;
- Sensitivity analytical: 16 ppb.