Our sense of taste results from our tongue’s ability to identify sweet, salty, bitter, and sour substances. Different substances stimulate unique combinations of these four characteristics, and our tongue can distinguish subtleties in these combinations with great accuracy. Although our tongues can easily differentiate various flavors of ice cream, for example, they usually can not identify the chemical composition of the ice cream. Nor can they perform complicated medical tests.

To chemically identify substances, scientists around the world are trying to develop artificial taste sensors that mimic the human tongue. Recently researchers at the University of Texas in Austin have developed an electronic sensor that has the potential to detect taste as well as to identify the chemicals of any substances.1 It has uses for food and beverage development as well as medical applications.

Besides the tongue, an electronic nose has also recently been developed to mimic the sense of smell, but it can only detect volatile molecules in the air. Since many chemicals of interest, such as those in food and beverages, are not easily transported into vapor phase, there needs to be a way of detecting a combination of them in solution, such as the electronic tongue.

A team of engineers and chemists in Austin has come up with a prototype of the artificial tongue which resembles the mammalian tongue in some ways. The surface of the human tongue contains cavities which hold chemical receptors known as taste buds. The artificial tongue consists of an array of tiny chemical sensors on a square-centimeter chip. The sensors are actually polymer microbeads placed inside micromachined wells on a silicon wafer which mimics real taste buds on a human tongue. Each bead responds to specific conditions (for example, high acidity or charged ions). A special camera records those colors, which the researchers can then monitor on a computer.

One obvious application of the electronic tongue is in the rapid testing of new foods and beverages; the results could be quickly compared with databases of known popular consumer tastes. When developed further, the electronic tongue should be able to analyze chemical processing streams, biological fluids and other complex mixtures without exposing human beings to possibly harmful substances such as antigens, toxins, and bacteria. For the tasting of ice cream, though, we will likely continue to use our own tongues.

FOOTNOTES:
1. J.J. Lavigne, S. Savoy, M.B. Clevenger, J.E. Ritchic, B. McDoniel, S.J. Yoo, E.V.
Ansyln, J. T. McDevitt, J. B. Shear and D. Neikirk, J. Am. Chem. Soc., 1998, 120,
6429-6430.
See also R. Dagani, Chem. & Eng. News, June 29,
1998, 12.

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