30 August 2011

Reverse engineering chocolate yields flavor surprise

by Kate Melville

The aroma of roasted cocoa beans - the key ingredient of chocolate - comes from substances that individually smell like potato chips, cooked meat, peaches, raw beef fat, cooked cabbage, human sweat, dirt and an improbable palate of other distinctly un-cocoa-like aromas. That's among the discoveries emerging from an effort to reverse engineer the essential aroma and taste ingredients in the world's favorite treat, described yesterday at the 242nd National Meeting & Exposition of the American Chemical Society.

Cocoa production has developed largely by trial and error, rather than by scientific analysis, so the substances that give chocolate its subtle flavors are largely unknown, researcher Peter Schieberle told the conference. Over the past 20 years, Schieberle and his team at the Institute for Food Chemistry at the Technical University of Munich have uncovered an increasing number of the secrets behind chocolate's allure. He believes his research could lead to a new genre of "designer chocolates" with never-before-experienced tastes and aromas.

Chocolate is made from cacao (cocoa) beans, the seeds of cacao trees. Raw cocoa beans have an intense, bitter taste and must be processed to bring out their characteristic flavor. Processing starts with fermentation, in which the moist seeds sit for days in baskets covered with banana leaves while yeasts and bacteria grow on the beans. The beans are then dried in the sun and then roasted.

Odorless, tasteless precursors form during fermentation, and these precursors react during roasting to form taste and aroma compounds. The flavors of chocolate and other foods come not just from taste buds in the mouth but also the odor receptors in the nose.

Schieberle identified various substances present in cocoa for aromas that bind to human odor receptors in the nose. He then mimicked the overall chocolate flavor in so-called recombinates containing those ingredients, and taste testers couldn't tell the difference when they sampled some of these artificial chocolates. Individually, those substances had aromas of potato chips, peaches, cooked meat and other un-chocolatey foods.

Because no individual compound was identified bearing the typical aroma of cocoa, the researchers had to pick apart individual aromas and put them back together for the taste testers. Interestingly, Schieberle said that to make a very good cocoa aroma, only 25 of the nearly 600 volatile compounds identified in the beans were necessary.

Schieberle said the data could help manufacturers control and improve the flavor of cocoa products by assessing the key components in their mixtures. "To develop better chocolate, you need to know the chemistry behind the aroma and taste substances in cocoa and other ingredients. That understanding must begin with the flavor substances in the raw cocoa bean, extend through all the processing steps and continue as the consumer eats the chocolate."

Savoring The Flavoring
Aphrodisiac plants put under the microscope

Source: American Chemical Society