Determining the chemical composition of coffee flavor is not easy, a new technology should change that. Photo: Mark Sweep, wikipedia, public domain
Read aloud US researchers have a nose for good coffee? more precisely, a novel artificial nose: they have developed a simple sensor system that can distinguish different types of coffee. All you have to do is direct the coffee's steam over a small plate soaked in various colors to create a color pattern that is typical of each variety. The device is not only there to tell skeptical coffee lovers, if they actually have the ordered expensive Guatemala variant in the cup. On the contrary, it should help traders and producers to judge the quality of the harvest as well as the quality of the roast quickly and easily on site. Despite its typical fragrance, is it anything but easy to determine the chemical composition of the coffee flavor? after all, according to current knowledge about 1, 000 different substances contribute to this fragrance. Which ones are depends, among other things, on the roasting temperature, the roasting time and, of course, the coffee bean itself. The biggest problem for classical analysis methods such as mass spectroscopy or gas chromatography: many of the substances are chemically very similar but not quite identical.

Chemist Kenneth Suslick of the University of Illinois at Urbana-Champaign and his colleagues have at least partially avoided this problem. Their idea: They did not try to determine every single component, but searched for a kind of fingerprint, which can be clearly assigned to each type of coffee. For this they developed their novel artificial nose. Its centerpiece is a polymer film, just the size of a small coin, on which the researchers placed dropwise 36 different dyes. The trick: Each of these dyes reacts to a different chemical property. For example, some of them change color depending on the pH level, others react only with certain substances, and yet others are similar to the red blood pigment hemoglobin and discolor only in the presence of a specific charged or uncharged particle.

The principle works, the scientists have already been able to show in ten commercially available coffee variants: When the plate came into contact with the coffee aroma, a different color pattern formed in each variety. Even if the individual device can not be determined with the new device? "The important thing is that we can easily see the differences between different roasts and coffees, " says Suslick. The potential of the new artificial nose could, according to "Science", go far beyond the recognition of coffees: It is conceivable to use practically everywhere, from the detection of explosives to the identification of impurities in toothpaste.

Science, online service Original research by researchers: Kenneth Suslick (University of Illinois, Urbana-Champaign) et al.: Analytical Chemistry, online pre-publication, doi: 10.1021 / ac902823w ddp / science.de - Ilka Lehnen-Beyel advertisement

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