November 2003

Banishing Bad Beans

By Erico Guizzo

Coffee merchants rely on  human tasters to ensure that the $70 billion worth of coffee sold every year has consistent flavor. Now, this job is being given to automated technology, and it's happening in the country that produces more coffee than any other.

An "electronic tongue" perfected by Brazil's agricultural research agency Embrapa is poised to begin the mass tasting. Based on technology developed at the University of Pennsylvania, it consists of 10 gold electrodes covered by thin films of an electrically conducting polymer. Each film contains a different mix of organic and inorganic compounds that are sensitive to molecules responsible for characteristics like bitterness, sourness, and acidity-and even levels of caffeine. Various molecules in liquid samples of coffee are absorbed by these thin films, changing the electrical properties of the electrodes and providing taste signatures.

Beginning next year, labs throughout Brazil will use the device to test coffee sold domestically. Later, coffee manufacturers could select a flavor benchmark for subsequent real-time evaluation on the production line. "The electronic tongue is an invaluable tool to improve the quality of coffee sold to consumers," says Nathan Herszkowicz, executive director of the Brazilian Coffee Roasters Association.

Other electronic sensors can distinguish among basic tastes-for example, the sourness of milk or the bitterness of medicine-but they cannot always detect the subtle variations in coffee and other beverages. "Our electronic tongue will cost half of the price and will be about 1,000 times more sensitive than others available," says Luiz Henrique Mattoso, a materials scientist who led the Embrapa project. With any luck, bad beans won't make it into your mug.