Oct. 11, 2004 — British researchers have created an electronic tongue that could someday help keep people safe from spoiled or contaminated food, water and drugs.

Designed at the University of Warwick, England, the high-tech taster is capable of detecting the four basic tastes: sour, sweet, salt and bitter.

The new tongue is reported in the Sept. 29 issue of the journal Sensors and Actuators B: Chemical.

"Electronic tongues are likely to find use in food and clinical labs especially for testing of bitter or obnoxious substances such as urine," said electric sensor researcher Anil Deisingh of the University of the West Indies in Trinidad & Tobago.

So far, however, they are being tested on slightly less repulsive substances. "We have used it to test freshness of milk," said Marina Cole, one of the electric tongue's developers.

Unlike other electronic tongues being developed, the new tongue has no taste buds. Instead of having chemical membranes to detect sweet, sour, salty or bitter chemicals, like human tastebuds, the new tongue doesn't taste at all — it hollers and listens.

Using sound waves crossing the surface of a tiny crystal, the sensor physically rattles whatever liquid is being tasted and observes how the fluids respond. It turns out that different-tasting fluids respond to the rattling in signature ways.

To prove its tasting prowess, the Warwick electronic tongue was subjected to swigs of four fluids, each with one of the basic four tastes: sour, salty, bitter and sweet. A common acid was used for the sour taste, table salt for salty, quinine for bitter and sucrose for sweet.

Each fluid changed the sound wave differently, Cole explained, creating a separate and distinguishable taste signal.

The device is unique among experimental electrical tongues because it uses physical, rather than electrical or chemical, features of substances to detect taste. The big advantage this offers, said Cole, is that the new tongue doesn't need special coatings for specific tastes, as do other electronic tongues.

It is more versatile, said the researchers, and less specialized than using separate membranes for every taste. So without any specialized membranes or layers, it can detect all four basic tastes, something other tongues can't do.

"Unlike electronic tongue devices reported so far, our devices are miniature, low-cost, robust, durable, micropower devices," said Cole. "This increases the lifetime and durability of the resultant devices."

The Warwick electronic tongue is also tiny: just 8 millimeters by 10.5 millimeters. That's small enough for one to fit on the average adult index fingernail.

Cole envisions miniature electronic tongues someday being put to use almost everywhere — at dairies, in beverage and pharmaceutical industries, to monitor water quality, and in biomedical labs.

Imagine, for instance, a spoon that tells you the sauce needs more salt.

"Development (of electric tongues) is still in its infancy," said Deisingh.