Reference Gene-Assisted LAMP–LFD for Sensitive and Specific Detection of Soy DNA as a Marker for Allergen Presence in Complex Food Products

Sensitive, selective screening for allergenic ingredients with internal control is crucial to identify food adulteration and remove allergens from the food chain. Here, loop-mediated isothermal amplification combined with a lateral flow device (LAMP–LFD) was developed for the fast and easy detection of soy DNA. The integrated quality controls included a regular control line to ensure proper implementation (extraction and amplification control) and a second LAMP–LFD assay for the cytochrome oxidase gene, which is a housekeeping gene in plants. The developed LAMP assay showed a limit of detection of only 5 pg DNA input per reaction, for both pure soy and spiked food samples. The test was subsequently implemented for the examination of 32 real food products with different compositions and declared soy contents, and benchmarked against qPCR. Then, this system was combined with a digital cube reader, allowing direct interpretation of the test results, facilitating the point-of-need applicability.