A laboratory sensor reported in 2017 distinguished patterns from 25 commercial fruit juices using fluorescence from a single positively charged polymer. It does not taste as a person does: the system measures how juice samples affect light emitted by the polymer, then uses statistical analysis to sort the resulting signals.
What the “polymer tongue” actually does
The phrase “tongue” is a metaphor for a chemical sensing system. The reported device used a fluorescent conjugated polymer called P2, a poly(para-phenyleneethynylene). Constituents in a sample interact with the polymer and quench, or reduce, its fluorescence. Different samples produce different response patterns, which can serve as fingerprints for classification.
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Instead of relying on one measurement, the researchers recorded responses under three pH conditions—3, 7 and 13—and analyzed the fluorescence data with linear discriminant analysis, a statistical method for separating groups based on measured features. The combination of the polymer’s responses and the analysis let the team distinguish the tested juice samples.
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The 2017 paper reported results for 25 commercial products: 14 apple juices, six grape juices and five blackcurrant juices. That is the study’s test set, not evidence that the method can identify every juice brand or variety.
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The system also did not classify every mixture perfectly. Some mixtures of blackcurrant and red-grape juice were classified as red grape. A mixture of red and green grape juice was classified as red grape when it contained more than 70% red grape. These examples show that “distinguish” describes performance on the reported samples and conditions, not an error-free ability to identify any blend.
Why one polymer mattered
The researchers also tested a related negatively charged fluorescent polymer, P1. It could discriminate samples too, but required 50 times the analyte concentration needed by P2 in the reported comparison. That result supports P2’s usefulness for this experiment; it does not establish that P1 is worse in every application or under all conditions.
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What the result does—and does not—show
The work, published in the journal Analyst in 2017, is a laboratory proof of concept for identifying tested juice samples through fluorescence patterns. It is not a biological tongue, a consumer appliance, or evidence of universal juice recognition. The cited paper does not establish routine commercial quality control or a deployed system for detecting counterfeit drinks.
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Corresponding author Uwe H. F. Bunz described possible future uses as a hope: “We hope our sensor will be used for quality control of high value targets such as very expensive white wines. It could also be used for detecting counterfeit alcoholic beverages.” Those are proposed applications, not evidence that the sensor was adopted for them.
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Sources
- Royal Society of Chemistry: “Poly(p-phenyleneethynylene)-based tongues discriminate fruit juices” (2017).
- Chemistry World: “Simple polymer tongue can taste the difference” (2017).
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