there was an electronic tongue reported in Wired back in 1998, which was also in the excellent docu "Beyond Human Senses" which is still on sale for $5.99 :-) -BT

Researchers at University of Warwick, England, have created an electronic tongue able to identify the four basic tastes: sour, sweet, salt and bitter.

"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.

Electronic Taster

Instead of having chemical membranes like human tastebuds, the new tongue doesn't taste at all — it hollers and listens.

Using sound waves crossing the surface of a crystal, the sensor 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.
Each fluid changes the sound wave differently, creating a 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 miniature electronic tongues someday might be used at dairies, in beverage and pharmaceutical industries, to monitor water quality, and in biomedical labs.

Via Discovery Channel.