Herb and spice adulteration: new tools in an old war
Food authenticity is a crucial concern for consumers, regulators, producers and processors, given the impact adulterated food can have on health, and herbs and spices are no exception. With a complex global supply chain of multiple touch points, from growers to processors and brokers, and high-value products – saffron is worth more per gram than gold, and vanilla more than silver – spices and herbs are in fact particularly susceptible to potential food fraud.
Some of the most common spice adulterations include adding a lower value ingredient to bulk up the volume of product or accentuate one of its characteristics, or extracting the aromatic oil and blending the spent spice material into quality spices. Recent attention has focused on lead additives, which can increase the risk of heart and brain disease and impair cognitive development. Turmeric in particular has been in the news, after a Stanford study found processors in Bangladesh using industrial lead chromate to exaggerate the spice’s yellow hue; lead concentrations were up to 500 times the permitted limit in seven of nine districts’ turmeric.
Herbs are often mixed or substituted with worthless leaves: a study published in late 2019 analysing 6,000 herbal consumer products found that 27% globally were adulterated, rising to 47% in Europe and an astonishing 79% in Australia.
Regulation and testing, therefore, is key. Primary authentication methods include classical microscopy or validated non-targeted chemical/physical procedures including NMR, NIR/MIR spectroscopy and mass spectroscopy. However, these molecular methods have limitations; when working with a complex matrix, for instance, such as a herb blend, identification of all components can be demanding. Here advances in DNA sequencing technology, which have already revolutionised fields of science from biology to plant and animal genomics, are beginning to have an impact.
While next generation sequencing (NGS) is not authorised yet for direct authentication of herbs and spices nor for detection or quantification of them as ingredients in mixtures, according to the ESA, it can be used as a secondary tool to confirm and identify additions of exogenous plant materials containing DNA, when detected by reference methods. The application of NGS procedures to food authenticity depends on obtaining sufficiently good quality DNA, crucial to ensure that all DNA sequences of interest present in a food sample can be amplified and identified (plant, fungal, animal and bacterial).
Despite several caveats, for example around effective extraction and amplification of DNA, NGS is a strong candidate to become a valuable aid or even the technology of choice to achieve regulatory compliance and reputation protection in a number of food fraud situations, particularly for highly complex food matrices. As Haynes et al point out in ‘The future of NGS (Next Generation Sequencing) analysis in testing food authenticity’ (Food Control, July 2019), NGS can scan for thousands of species simultaneously, which opens the door to the “identification of virtually any possible species present in a complex matrix of unlimited ingredients”.
As demand for more complex delineation and recognition of food adulterants and sources grows, and NGS becomes a well-established technique, it may become a key tool for regulatory compliance and reputational protection. In this case methodologies and analysis pipelines should be harmonised among testing laboratories (Endrullat et al., 2016, Gargis et al., 2016).
Our latest herbs and spices proficiency testing sample is therefore designed specifically to be used with NGS, alongside more traditional methods of testing. As a participant in the scheme, you will be able to compare your NGS results to other methods used, and assess the procedure’s suitability and usefulness to your herbs and spices testing program.