In this study (open access) the researchers developed and validated HPLC and LC-MS method for curcumin in turmeric and coumarin in cinnamon . They used the methods to test approximately 150 samples of each; a mix of market samples taken at Rotterdam port and samples sourced from the country of origin. They tested for statistical outliers as a flag for potential fraud.
For turmeric, they report that just under 5% were flagged as significant outliers. These were characterized by curcumin concentrations drastically lower than the population mean. Specifically, their values fell below 15% of the mean value and below 20% of the standard deviation of the entire dataset. All outliers were samples collected at Rotterdam port. The authors conclude that this low curcumin content provides strong evidence of adulteration with non-curcuminoid fillers (such as starch, chalk, or other cheaper turmeic varieties) or, less likely, spice material of exceptionally low quality.
For cinnamon (47 declared C. verum samples) three samples were found to be significant outliers. These outliers had coumarin concentrations which were orders of magnitude higher than the group's mean and are far more consistent with the coumarin profile of cassia varieties. This strongly indicates that these three samples, despite being labeled as C. verum, were adulterated with cheaper, high-coumarin cassia species. This finding translates to a non-compliance rate of 6.4% within the subset of samples declared as authentic Sri Lankan cinnamon.
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