A study that used DNA barcoding to genetically identify the ingredients of 146 tea products suggests that about one third of herbal teas may contain plants or plant parts not listed on the label. The findings, which are reported online in Scientific Reports, highlight the potential of DNA barcoding for providing more accurate ingredient labels to consumers, thereby improving the safety of food and botanical products.

In its strictest definition, tea refers to infusions prepared from the leaves of the tea plant, Camellia sinensis, but infusions prepared using other plants or plant parts are also commonly referred to as tea. Accurate labelling of commercial tea products is important for consumers, marketers and regulators because it is difficult to identify particular plant ingredients to different species based on visual appearance alone.

Mark Stoeckle and colleagues describe the use of DNA barcoding to identify the ingredients of 146 tea products. This technique involves using a short genetic marker in an organism's DNA to identify it as belonging to a particular species. 90% of the teas contained one or both of the standard plant barcodes rbcL and matK (96% of Camellia sinensis teas and 84% of herbal teas). The authors also found that 35% of herbal teas contained one or more barcode that indicated an ingredient not listed on the label. This could have been an inadvertent introduction, during harvesting or in the factory, or involve the adding or substitution of ingredients — to improve the taste or appearance or for economic reasons, perhaps.