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Herbs and spices are one of the food commodities most susceptible to adulteration and fraud. In this study, 5 fingerprinting techniques - Near Infrared (NIR), Mid-Infrared (MIR), Hyper Spectral Imaging (HSI), Gas Chromatography coupled to Mass Spectrometry (GC–MS), and Proton-transfer Reaction Time-of-Flight Mass spectrometry (PTR-TOF-MS), combined with chemometrics, are examined to evaluate their potential to authenticate oregano. In total, 102 oregano samples from one harvest season were analysed for origin and variety assessment, 159 samples for adulteration assessment, and 72 samples for batch-to-batch control. Different chemometric models were applied for adulteration, origin and variety assessment. The best results were for origin assessment, which gave prediction rates of more than 89%. A level of 10% adulteration of oregano with myrtle, sumac, olive and cistus could be detected using HSI, NIR and PTR-TOF-MS.

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Recent cases show that herbs and spices are susceptible to adulteration. Italian researchers have utilised AMS (ambient mass pectrometry) coupled to mid-level data fusion as a rapid non-targeted method for oregano authentication for the first time. Authentic and adulterated oregano samples were extracted using two procedures and analysed in positive and negative ion modes by direct analysis in real time-high resolution mass spectrometry (DART-HRMS). The four blocs of data were combined into a unique dataset and analysed chemometrically to distinguish authentic from adulterated oregano.  Fourteen most informative signals of authenticity were chosen and validated. The final model gave an accuracy, sensitivity and specificity of >90%.  

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The use of hand-held infrared spectrometers combined with chemometrics to authenticate different foods has increased in popularity especially for screening samples in-situ. This study is the first interlaboratory trial to compare the performance of low-cost portable NIR devices coupled to chemometrics to detect adulterated food. In the study, there were 27 participants from 22 countries across five continents using 34 unique devices. The food chosen for this study was oregano, which already had a history of vulnerability to adulteration by different leaves of olive, myrtle, sumac, cistus and phlomis. Participants were sent authentic samples of oregano, and of olive and cistus leaves, as well as a calibration set of oregano and adulterated samples and a validation set of authentic and adulterated samples in order to build models for oregano adulteration. Participants correctly predicted >98% genuine oregano after device standardisation, and predicted 100% adulterated samples after standardisation. The devices native setup shows limited ability to perform a true screening of oregano using the setup offered. However modifications to the setup could in the future offer a solution that facilitates fit-for-purpose real time detection of adulterated samples within the supply chain.

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FSAI has worked with a commercial laboratory (Identigen) over the past two years to adapt NGS (next generation sequencing), so that it can be used as a DNA screening tool to check that the composition of the food matches what is stated on the product’s labelling or descripion. FSAI screened 45 plant-based foods and food supplements from Irish health food shops and supermarkets. It looked for the presence of all plant species in the selected products and identified 14 food products for further investigation that may contain undeclared plant species. Of these 14 products, one was confirmed to contain undeclared mustard at significant levels, which is an allergen that should be declared. Another product (oregano) was found to contain DNA from two undeclared plant species, one at significant levels. A third product was found to have no DNA from the plant species declared on the label, but instead rice DNA was identified. All three products are under further investigation. FSAI will apply the same technology for the screening of meat, poultry and fish products.

 Read the FSAI Press Release and the full report

 In this study, more than 400 pesticides were screened in a representative set of 42 genuine and 34 adulterated dried oregano samples collected from various locations across Europe. The results obtained by advanced mass spectrometry-based methods, showed, that some pesticide residues could be detected in virtually all tested samples, nevertheless, on average, higher contamination was found in the adulterated oregano samples. Increased incidence of insecticides such as cyfluthrin, permethrin and cyhalothrin was typical for these samples, moreover, pyriproxyfen was detected exclusively in adulterated samples. As pyriproxyfen was absent in genuine oregano, it could be used as a screen for adulterated oregano. 

    Read the abstract here