In this paper (open access), researchers have developed and validated a specific qPCR panel to detect 5 common adulterants (cheaper vegetable/plant species) in each of paprika/chili, turmeric, saffron, cumin, oregano and black pepper.
They chose the adulterants to target in each spice from those reported in recent EU-wide surveillance testing and those that have been reported in the scientific literature. The researchers developed primers for each. They then developed methods based on SYBR™ Green qPCR, which is an extraction system particularly suited to dried herbs and spices. Herbs and spices can contain inhibitors, so the inclusion of a reference gene was critical. The specificity of primers and the potential for inhibition of each matrix and adulterant were meticulously investigated to highlight the limits of each method and how to handle them.
The authors conclude that their method is rugged and accessible. It is suitable for widespread roll-out to laboratories involved in spice authenticity testing. It quantifies each adulterant (30 in total – 5 for each of 6 herbs/spices) above the concentrations permitted by ISO standards for adventitious contamination, so can differentiate adulteration from contamination. It is particularly suitable for confirming, estimating or quantifying the presence of botanicals either identified by NGS screenings or suspects flagged by prior knowledge or investigations Full internal validation and interlaboratory validation will establish the limit of quantification, reproducibility and measurement uncertainties associated with the methods, allowing their deployment for official analyses, further supporting quality controls in the field of spices and herbs.
Graphical abstract from the paper.
For an introduction to the principles of qPCR see FAN’s method explainers for DNA-based techniques.
Comments