A robust set of qPCR methods to evaluate adulteration in major spices and herbs

Consumers and companies associated with food or pharmaceuticals rely on spices and herbs in various forms. Their intricate supply chains, elevated prices, and low-volume production render them vulnerable to fraudulent practices. However, comprehensive methodologies to detect adulterants remain scarce, impeding national control laboratories from enforcing European and national legislation. In this study, we present quantitative realtime PCR (qPCR) methods designed to identify the top five adulterants of each of six commonly consumed spices and herbs: paprika/chili, turmeric, saffron, cumin, oregano and black pepper. The specificity of each method was confirmed by qPCR analysis of a large collection of relevant plant species. Each authentic sample was combined with its respective top five adulterants as identified in the European Union-wide coordinated control plan on herbs and spices in 2021 or in the existing literature. These binary mixtures were used to evaluate the method's performance with respect to sensitivity, linearity and trueness at four levels of adulterants concentration. Detection was also investigated in multi-adulterated samples. These SYBRTM Green-based qPCR methods enable the specific detection of adulterants, and their sensitivity allows for the distinction between inadvertent contamination and deliberate adulteration. Altogether, these methods contribute to safeguard the authenticity of these high-value commodities.