Lupin analysis for quinolizidine alkaloids – A substitute for soybean?
Lupins (Lupinus spp.) belong to the legume family (Fabaceae) and are herbaceous plants growing up to 4.5 meters high. With up to 50% high-quality protein in dry matter, lupins are more than just an alternative to soybeans. In cultivation, they require little fertilization, little sun, loosen soils and bind atmospheric nitrogen.
For this reason, lupins are not only a popular raw material as animal feed, but are also increasingly used in the food industry. For example, the (ground) seeds of lupins are often used in bread and baked goods, confectionery, ice cream products, fried foods or even as a caffeine-free hot drink.
Despite all these benefits, lupins, like many plants, form toxic secondary metabolites, which include quinolizidine alkaloids (QA) in particular. In total, more than 200 compounds of this type are known, with the structures of lupanine, sparteine, lupinine and 13-hydroxylupanine being the most important QAs in terms of quantity, depending on the species. Original lupin species contain up to 4.5% of QAs and are therefore also called bitter lupins. By breeding or debittering, the contents can be significantly reduced, resulting in sweet lupins containing only 0.01-0.08% of QAs.
The acute toxicity of QAs causes symptoms such as dizziness, nausea, palpitations, dry mouth, and confusion, up to and including loss of motor control. At higher doses, cardiac arrest and respiratory paralysis occur. The lethal dose of QAs is reported to be 20-400 mg/kg body weight, depending on the substance. The BfR warns that in the case of "lupine seeds as a snack or roast" this threshold dose can be quickly exceeded. Therefore, only sweet lupins or sufficiently debittered lupin seeds should be used as food and feed.
GBA offers an adequate analytical LC-MS/MS method, with certified reference standards for the quantification of QAs. The method, accredited according to DIN EN ISO 17025, covers determination limits of 10 mg/kg for lupin seeds and lupin products. Have your lupin products analyzed for quinolizidine alkaloid content to verify that they are below the threshold.
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