Researchers in Germany have developed “artificial tongues” which can reliably identify different types of whisky. This technique could be used to detect counterfeit whiskies and may have many other applications in the future.
Being able to reliably identify complex substances such as beverages, foodstuffs and prescription drugs is important for both health safety and economic reasons. Whisky is a popular beverage and the target of counterfeit producers of both luxury and mass-market brands. Current methods for checking its authenticity involve expensive and complicated equipment, so a simple testing method would be a useful tool. Researchers in Germany have developed a novel method based on a similar principle to the human tongue, which has a distinct pattern of response to different substances. They recently published their findings in the journal Chem.
Whiskies have complex chemical compositions which are broadly similar, so it is difficult for most test methods to tell the difference between samples. Currently, the most common way to identify whiskies is to use a mass spectrometer, which breaks down and measures the component chemicals in a given sample. Researchers at the University of Heidelberg have used a different approach. They developed a testing technique which responds to the overall whisky mixture rather than identifying the individual components. Their “artificial tongue” is in fact a range of special fluorescent dyes each placed in a small well on a plastic tray. When a drop of test whisky is added to the wells, there is a change (or “quenching”) of the fluorescence. This is caused by the interaction of the complex mixture of substances in the test whisky with the dyes. The trays are then placed on a plate reader which can detect the changes in fluorescence in each of the wells.
When the collected “quenching data” from different whisky samples was analysed, the researchers found that a distinct response pattern appeared for each whisky. A single fluorescent polymer’s response to the whisky would not be particularly useful, but the combination of responses from a small number of different polymers forms a very unique pattern. This principle is similar to the human tongue which has 6 or 7 different receptors types – sweet, salty, bitter, sour, umami and hotness – and can identify different foods based on the reaction pattern of those receptors.
One “artificial tongue” used three fluorescent polyelectrolyte dyes (PAE tongue) and another used three green fluorescent protein dyes (GPA tongue). Using the PAE and GPA tongues individually and in combination, the researchers were able to reliably identify over 30 different types of whisky according to country of origin, brand, blend status (blend or single malt), age and taste (rich or light – although surprisingly the “tongues” were unable to distinguish whiskies according to their “peatiness”)
Although the “tongues” can check similarities between whiskies, they cannot identify a completely unknown sample. However the technique could be used to check the authenticity of a whisky against a verified sample in order to spot counterfeit products.
The “artificial tongue” is equal or superior to using a mass spectrometer with respect to speed and discrimination, and requires no special preparation of the sample. It is also much cheaper than mass spectrometry as it does not require investment in specialized equipment.
The investigators hope that in the future this technique can be used to check the authenticity of other products which are the target of counterfeit producers, such as fine wines, perfumes and prescription drugs.
Written By: Julie McShane, Medical Writer