An optimized extraction method for gluten analysis in cacao-containing products using an extraction buffer with polyvinylpyrrolidone

Enzyme-linked immunosorbent assay (ELISA) is commonly used to detect trace gluten in foods; however, ELISA for the determination of gluten is affected by matrices from various ingredients, such as plant proanthocyanidins (PACs). In the case of chocolate and other foods containing cacao, we found ELISA methods to be unsuitable for the determination of gluten contamination. The aim of this study was to improve methods for the determination of gluten in foods containing cacao by combining the extraction solution with polyvinylpyrrolidone (PVP), which binds PACs. We optimized the method for gluten determination in cacao-containing foods using PVP solution, and found that the best extraction method for the detection of gluten in cocoa powder was extraction with 1% PVP K15. This new extraction method can be applied to chocolate contaminated with wheat proteins during the manufacturing process, as well as cacao-containing products spiked with gliadin.