Uncovering a challenging case of adulterated commercial saffron

- A multi-step workflow uncovered a “tailor-made” case of saffron fraud.
- HPLC, UV-Vis, FT-IR and NMR analyses revealed the type of fraud.
- Derivative UV-Vis and FT-IR data exposed the used artificial colorants.
- Untargeted metabolic fingerprinting by NMR disclosed unforeseen components.

The analytical approach presented uncovers the type of adulteration of a commercial product labeled as “saffron”, sold packed in powder form in a major consuming country. Simple colorimetric and spectrometric tests included in the ISO 3632 trade standard indicated only that it was not “pure saffron”. The TLC and HPLC methods recommended in the same standard for the detection of artificial colorants were not applicable due to limited sample amount available. Since it could not be precluded that substances other than artificial colorants have been used, deeper investigation through metabolic fingerprinting was necessary to uncover chemical composition of the sample. The multistep workflow that exploited chromatographic (HPLC) and spectroscopic (UV-Vis, mid-infrared (FT-IR), and nuclear magnetic resonance (NMR)) data from in-house databases uncovered a “tailor-made” case of 100% substitution of saffron by a mixture of exogenous chemical compounds in such a way that the commercial product would approximately mimic not only the appearance of saffron but also its UV-Vis spectrum and specific absorbance values. The findings indicated a sophisticated practice, including total substitution of saffron constituents by tartrazine and sunset yellow along with propane-1,2-diol, propan-2-ol and acylglycerols, probably as emulsifier agents. Interestingly, the perpetrators avoided the use of toxic compounds. To our knowledge such a type of fraud has not been elucidated so far.

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