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Dr. Chocolate

With Halloween upon us, youngsters and adults alike will enjoy a night of regret-free linkurl:chocolate;http://www.the-scientist.com/article/display/20546/ bingeing. But how much do you really know about the sweet substance? If you're Stefan Bernhard, you can safely say you've made a lifetime study of the elixir of the gods. At a recent meeting of the linkurl:Experimental Cuisine Collective(ECC);http://experimentalcuisine.googlepages.com/ at New York University, Bernhard, professor of chemistry

By | October 31, 2008

With Halloween upon us, youngsters and adults alike will enjoy a night of regret-free linkurl:chocolate;http://www.the-scientist.com/article/display/20546/ bingeing. But how much do you really know about the sweet substance? If you're Stefan Bernhard, you can safely say you've made a lifetime study of the elixir of the gods. At a recent meeting of the linkurl:Experimental Cuisine Collective(ECC);http://experimentalcuisine.googlepages.com/ at New York University, Bernhard, professor of chemistry at linkurl:Princeton,;http://www.the-scientist.com/article/display/54332/ led a group of scholars, scientists, chefs, chocolatiers, food historians, journalists, performance artists, and foodies through the intricacies of chocolate production. He covered everything from chocolate's unique chemical properties to the ways in which those properties affect its manufacture. Bernhard spent three teenage years as an intern at Suchard-Tobler in Bern, Switzerland and has never lost his interest in chocolate. It came in handy when he was asked to teach a freshman seminar at Princeton which he titled __The Chemistry of Chocolate.__ It was, he says, a good way to introduce liberal arts students to science. He gave the ECC a distillation of that semester's course. The key to chocolate's taste is an linkurl:alkaloid;http://www.the-scientist.com/article/display/20546/ called linkurl:theobromine;http://www.phytochemicals.info/phytochemicals/theobromine.php (theobromine translates as food of the gods, which is what the Aztecs believed it to be). Chocolate contains some fifty molecules that interact to influence tongue-bound taste receptors. Bernhard put up a slide showing all fifty molecules. Pointing to one of them - described as having a buttery, popcorn-like taste - he said, "When you go to the movies and order buttered popcorn, you think you're getting butter but you're not, you're getting some kind of oil infused with this molecule." Grinning he added, "Which is why chemists should be kept away from our food." Chocolate has some similarities to coffee; the cacao tree, like coffee trees, thrive in the shade of larger, taller trees in the rain forest. Three varieties of cacao trees exist: criollo, nearly extinct but the most desirable, linkurl:forastero,;http://www.richart-chocolates.com/b2c/chocolate/history_of_chocolate/2 which is less rare, and trinitario, which resulted from a crossing of the two others and is now the most commonly grown. Forastero and trinitario grow in Africa which supplies large manufacturers such as Hershey and Mars. Cacao was first "domesticated" by the linkurl:Olmec,;http://www.crystalinks.com/olmec.html ancient inhabitants of current-day Mexico, who passed down the knowledge to the Maya and the linkurl:Maya;http://www.crystalinks.com/mayanagriculture.html to the Aztecs. The smallish tree now grows in an equatorial belt around the globe. These days good chocolate is produced in countries like Madagascar and New Guinea as well as in the Central American and Caribbean countries where it originated. Bernhard pointed out that serious chocolate lovers covet "premier cru," which is a term adopted for plantation-specific chocolate. He shared with his audience three small squares of dark chocolate, each distinctively wrapped and each from a specific plantation in a different locale. One chocolate was from linkurl:Madagascar,;http://www.infoplease.com/ipa/A0107743.html one from New Guinea, and one from the island of linkurl:Sao Tome;http://www.saotome.com/portugisisch/index.htm off the west coast of Africa. Each was distinctive in flavor, and all were definitely delicious. The one from Madagascar was much lighter in tone, less complex than the other two. He led us through the harvesting of the cacao pods, large football-shaped fruits that grow directly on the trunk of the tree. How the cacao seeds are dried and roasted determines the quality of the chocolate that will be made from them, Bernhard explained. The seeds, unlike coffee beans, vary in size, and this makes good chocolate all the more difficult to produce. The seeds must be dried slowly in shade. If not, the chocolate may be gritty and bitter. The dried beans are then bagged for shipment since the countries where cacao is grown tend not to have the sophisticated machinery necessary to churn out the smooth, seductive product we expect. After the beans are roasted, most often in the same kind of roaster used for coffee beans, they are ground and conched. The word linkurl:conche;http://www.britannica.com/EBchecked/topic/131142/conching comes from the Spanish for shell; the conching machine is shaped like an open shell in which the chocolate is stirred round and round to get rid of less desirable flavors. Bernhard explains that the word "goat" is often used by chocolate manufacturers in describing some of the off flavors that need to be eliminated. Once the chocolate is goat-free it's ready for the linkurl:melangeur.;http://www.scharffenberger.com/vtour4.asp This machine blends the cocoa powder, cocoa butter and sugar so that a smooth, even chocolate product results. It's difficult to get the cocoa butter to evenly coat the sugar particles and the chocolate particles so that they don't clump together and yield uneven flavors and textures. The amount of cocoa powder added at this point determines the strength of the dark chocolate (64-70% cocoa powder yields a smooth, rich, complex dark chocolate). This is also where the milk powder can be added to make milk chocolate. Milk chocolate is typically favored by Americans, and dark chocolate by Europeans, Bernhard explained, though dark is gaining ground here. Bernhard also said that to take advantage of the antioxidants present in chocolate, you need to consume dark, not milk, chocolate as the proteins in milk interfere with the human body's ability to absorb the antioxidants. White chocolate's a whole different story. Illustrating the composition of white chocolate on a slide, Bernhard said what you are eating is cocoa butter, which is the fat, without any of the chocolate flavors, loaded down with powdered milk and sugar. He said it has the same health benefits as eating lard, eliciting a lot of "Eeeews" from his audience. Correction (posted October 31): When originally posted, the article mistakenly noted that theobromine contains some 50 molecules that affect taste - it's chocolate that contains some 50 compounds that influence taste. The Scientist regrets the error. Correction (November 5) When originally posted the blog referred to the Mayan people; the correct term is Maya.
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Comments

Avatar of: m woodman

m woodman

Posts: 2

October 31, 2008

...gods, which is what the Aztecs believed it to be). Theobromine contains some fifty molecules that ....\n\nNo wonder the rating here is poor. I hope someone can fix that.
Avatar of: ROBERT HOLLOWAY

ROBERT HOLLOWAY

Posts: 1

October 31, 2008

After noting correctly that theobromine is an alkaloid, and implicitly one species, the article states that it is composed of 50 different molecules. Probably it was meant to say chocolate is composed of 50 ....\nDisappointingly did not mention any other of the 50. I'd like to know, for example, how important caffeine is and how important theophylline is, if they are present.\n
Avatar of: anonymous poster

anonymous poster

Posts: 29

October 31, 2008

While you are fixing the thobromine reference, also address conching, which simply grinds the chocolate down to very small particles. This produces a smooth texture, but I don't see how it can affect flavors.
Avatar of: anonymous poster

anonymous poster

Posts: 29

October 31, 2008

I stand partially corrected on conching. A perusal of Wikipedia says that conching can release volatiles that affect flavor, but primarily it is for improving the texture.
Avatar of: anonymous poster

anonymous poster

Posts: 1

October 31, 2008

This article is way too elementary for readers of The Scientist, even if they are not chocolate afficionados.
Avatar of: Adolfo Martinez

Adolfo Martinez

Posts: 1

October 31, 2008

After the cacao is harvested, it is taken out of the pods, selected for quality and then IT HAS TO BE FERMENTED, if you want good quality chocolat. If you do not ferment it, it will be of poor quality and poor flavor. Cacao should by dried in the sun or artificially. In the humid tropic, where cacao grows, it has to be dried in the sun, not shade. In the shade it will never dry and will develop fungi that will affect flavor.
Avatar of: anonymous poster

anonymous poster

Posts: 1

October 31, 2008

written for wrong audience too simple. see above errors as well.
Avatar of: anonymous poster

anonymous poster

Posts: 4

October 31, 2008

Yes, theobromine is not 50 molecules. One alkaloid molecule present in chocolate is phenethylamine a precursor to the neurotransmitter phenylethanolamine. Phenethylamine directly or indirectly acts as an anti-depressant (see references on Google or Wikipedia). This may explain it's association with Valentines day.
Avatar of: anonymous poster

anonymous poster

Posts: 11

October 31, 2008

...learned about chemistry (from his liberal arts previous background) in a CHOCOLATE FACTORY!!!\n\nMargaret Guthrie wrote a heckuvan article about CHOCOLATE on HALLOWEEN!\n\nThe rest of us contented ourselves with counting the theobromine molecules in chocolate, and/or giving informal dissertations on how it works in the human body; phenylalamine, etc.\n\nWe're in the wrong profession, folks. We should be encouraging our kids to A) vie for a summer internship at a writers' conference -- or, to B) go back to that liberal arts college and learn their chemistry the HARD way--by interning in a Chocolate Factory like Dr. Bernhard did!\n\nSeriously--a truly del.i.cious. article. Now please pardon me while I go brush my sweet tooth and try to log how many calories I can expect to land on my hips today, after I virtuously go (for protective purposes ONLY!) through my three kids' trick or treat haul...
Avatar of: Patrick Crothers

Patrick Crothers

Posts: 8

October 31, 2008

If this is a blog then it is fine and has stimulated a great response. Presented as a scientific article it lacks proper doumentation for one.\n\nThe methylated xanthines such as the theobromine molecule, as I understand it, can have an O2 attached in one of three places. One makes caffine, one makes theophline, and then theobromine. The precursors can have dramatic effects and I think most of us would like to read about findings rather than take a coco journey with a Jr. College paper. \n\nAs an anthropologist I can attest that the Mayan culture used the beans for currency and the Coca plant was at the core of their economic system. In my frosh "World Cultures" classes this is a -C paper although an xlnt blog.\nPerhaps some one can find the errors in my thinking and we can expand our knowledge.\n\n
Avatar of: anonymous poster

anonymous poster

Posts: 4

October 31, 2008

This article went to directly from conching the beans to what is done with the cocoa butter and cocoa powder. There seems to be a big gap in this description.
Avatar of: anonymous poster

anonymous poster

Posts: 1

November 1, 2008

Poorly written. Terrible chemistry. Felt dumber for reading it.
Avatar of: anonymous poster

anonymous poster

Posts: 2

November 13, 2008

Thank you for writing an enjoyable (some might say delectable) article about one of man's favorite foods! For those who delight in finding fault in others, go savor a piece of fine dark chocolate and see if it improves your mood (and disposition). This wasn't intended to be a PNAS submission; it was a timely article about the science of chocolate and it hit its mark on Halloween and the days since! Thank you again.
Avatar of: Jill Josephsen

Jill Josephsen

Posts: 3

July 4, 2009

I agree with you. I don't see how white chocolate is tasty. It is too sweet for me.

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