At its simplest, authentication refers to a process for verifying that a product conforms to the description on its label in terms of quality, origin or consumer safety. Authentication testing is well-established for products such as Olive Oil and wine where consumer demand backed by legislation supports rigorous testing regimes, especially in Europe. However research on authentication methods for tea has lagged behind these other industries, and there is no universally accepted technique currently available.
This slow uptake of authentication testing may arise because consumers perceive tea to be a low value product coupled with widespread misconceptions about the difference between tea blends and single origin teas that is further confused by the current use of geographic indicators on labels. Pervasive examples in the UK are the established brands “Scottish Breakfast Tea” and “Yorkshire Tea”, which do not contain any Scottish or Yorkshire grown tea, despite the indications on their labels.
Genuine Scottish-grown tea is an artisanal product that is currently produced by about 30 growers across the country and as yet many have not started to produce tea since the plants are still immature. Growers that are producing tea either process the plucked leaves independently or send it to the newly opened . Scottish-grown tea has a quality profile that is highly valued by consumers and the sector has potential to expand both nationally and internationally. A labelling system backed by authenticity testing would differentiate these genuine single-origin teas from imported blended teas and help to offset the confusion associated with current labelling practices.
Similar benefits might arise for tea growers in other parts of the world where there are doubts about the authenticity of the provenance and evidence of fraudulent labelling, such as persistent claims that the quantity of Darjeeling tea marketed internationally far exceeds the amount of tea actually produced in the Indian State of Darjeeling.
Many methods have been developed for testing the authenticity of claims about geographical origins of food and drink products. Most of these methods achieve this by creating a chemical fingerprint from a sample of the product, and matching that to records in a database of samples of known origin. The available methods differ in terms of the chemical component that is examined, the detection limit of the instruments used and the required specificity of the results, which means that different methods are appropriate for different products. For tea, a spate of recent studies from China shows that the geographical origin of tea can be authenticated using techniques that analyse multiple micronutrients and trace elements within samples, which identify differences in elemental concentrations between teas sourced from locations with varying soil conditions. In other contexts this approach has become known as “ionomics”, which refers to the unique elemental profile in any organism and the emerging understanding of the ways in which this profile is determined by the external environment and sources of nutrition.
A recent study implemented by the University of Aberdeen in conjunction with the Scottish Tea Factory, which processed a variety of teas from different gardens under controlled conditions and the collective of growers has tested the feasibility of this approach for authenticating Scottish-grown tea. We compared the concentrations of 10 trace elements in tea sourced from Scottish growers with those in samples of imported teas of known geographical origin. The results show a promising differentiation of the chemical signature of teas of authentic Scottish origin, possibly reflecting the distinctive background composition of soils in Scotland compared to the traditional tea-growing regions of Africa and Asia.
Although these methods require further development, the studies from China coupled with our own suggest that chemical finger-printing of tea using multi-elemental analyses such as ionomics holds promise as a method for low-cost authentication of the geographical origin of single-estate tea, both in Scotland and across the world. This exciting discovery paves the way for the development of more precise labelling of tea and greater reassurance to consumers, with resulting benefits across the industry and with wider potential uses across the food and drinks industry.
David Burslem is a professor at the School of Biological Sciences, University of Aberdeen; [email protected]
Beverly Wainwright is the founder of The Scottish Tea Factory; [email protected]