Enzyme Immunoassay for the quantitative determination of Walnut in food.
Background: Walnut (Juglans regia) belongs to the walnut plants (Juglandaceae). With 15% the fraction of proteins in walnuts is high. Some of these proteins are known for being allergenic, such as rJug r 1 and rJug r 4. Many of them are heat resistant making them stable to different production processes. For this reason walnut represents an important food allergen. For walnut allergic persons hidden walnut allergens in food are a critical problem. Already very low amounts of walnut can cause allergic reactions, which may lead to anaphylactic shock in severe cases. Because of this, walnut allergic persons must strictly avoid the consumption of walnuts or walnut containing food. Cross-contamination, mostly in consequence of the production process, is often noticed. The chocolate production process is a representative example. This explains why in many cases the existence of walnut residues in food cannot be excluded. For this reason sensitive detection systems for walnut residues in foodstuffs are required.
The Walnut ELISA represents a highly sensitive detection system and is particularly cap-able of the quantification of walnut residues in cookies, cereals, ice cream and chocolate.
Description: The Walnut quantitative test is based on the principle of the enzyme linked immunosorbent assay. An antibody directed against walnut proteins is bound on the surface of a microtiter plate. Walnut 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 walnut proteins 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 walnut 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;
- Walnut Standards: 0, 2, 6, 20, 60 ppm;
- ELISA reader at 450 nm;
- Standard range: 2 - 60 ppm;
- Sensitivity analytical: 0.35 ppm.