Development and optimization of a LAMP assay for lupin detection in foods

Abstract

Lupin (Lupinus spp.) is increasingly incorporated into processed foods as a gluten-free ingredient and alternative protein source, but it is also a regulated allergen in the European Union due to cross-reactivity with other legumes, especially peanut. Reliable methods for detecting undeclared lupin traces in complex food matrices are therefore essential for consumer protection. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for rapid and sensitive detection of lupin DNA. Several nuclear and chloroplast regions were evaluated for primer design, and gene encoding the Lup a 1 allergen was selected as the optimal target. Amplification was monitored by real-time fluorescence, agarose gel electrophoresis, and visual colorimetry. The selected primer set achieved a detection limit of 25 pg of lupin DNA and consistently detected lupin in binary mixtures down to 10 mg/kg, with no cross-reactivity against closely related legumes or tree nuts. Application to processed foods confirmed detection in products declaring lupin and revealed potential undeclared presence in some commercial samples. Colorimetric detection provided reliable results comparable to real-time monitoring, enabling simple readouts without specialized equipment. Overall, the developed LAMP assay represents a rapid, specific, and sensitive alternative to PCR-based methods for allergen monitoring and food safety management.