Enzyme immunoassay for the quantitative determination of Lupine in food.
Background: Lupin belongs to the legume family. With about 35-45% the fraction of proteins in lupin seed is very high. Some of these proteins, predominantly those in the a-, β- and g-Conglutin fractions are known for being allergenic, due to cross-reaction to allergens of soy and peanut. Because of its convenient nutritional properties the use of lupin flour as a food ingredient is highly increasing. Lupin is often used in dietary products, especially for milk allergic people, vegetarians and patients with celiac disease. In food production three (sweet) lupin species are commonly used: Lupinus albus, Lupinus angustifolius and Lupinus luteus. For lupin allergic persons hidden lupin allergens in food are a critical problem. Already very low amounts of lupin can cause allergic reactions, which may lead to anaphylactic shock in severe cases. Because of this, lupin allergic persons must strictly avoid the consumption of lupin containing food. Cross-contamination, mostly in consequence of the production process, is often noticed. This explains why in many cases the existence of lupin residues in food cannot be excluded. For this reason sensitive detection systems for lupin residues in foodstuffs are required.
The Lupin ELISA represents a highly sensitive detection system for lupin and is particularly capable of the quantification of residues in sausage, bakery products, potato products, ketchup and juices. Due to high cross-reactivity the test is suitable for the detection of all commonly used lupin species.
Description: The Lupin quantitative test is based on the principle of the enzyme linked immunosorbent assay. An antibody directed against lupin proteins is bound on the surface of a microtiter plate. Lupin 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 lupin 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 lupin 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;
- Lupin Standards: 0, 2, 5, 15, 30 ppm;
- ELISA reader at 450 nm;
- Standard range: 2 - 30 ppm;
- Sensitivity analytical: 0.2 ppm.