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Everyone knows chocolate is supposed to melt in your mouth, not in your hands. But there is much more to properly tasting chocolate. You inspect it. Smell it. Break it in half to see if it snaps cleanly. Then go ahead and take a bite.

Chew it a little to release the initial flavor. Then let it melt in your mouth. Take a little air into your mouth, and after a moment or two, swallow the chocolate and wait for any aftertaste.

That, according to Patrick F. Fields, is the correct way to taste chocolate. "It's the most chemically rich and diverse naturally occurring food on the planet," says Fields. "And it tastes good!"

He should know. An adjunct instructor of biology at Olivet College who specializes in botany, Fields studies and teaches about the history and culture of one of the world's most popular confections. And he holds dozens of chocolate tastings every year. At the University of Michigan at Ann Arbor, Fields teaches a four-week adult-education course each spring in which students taste more than 60 types of chocolate. They range from your basic Hershey's bar to artisanal varieties from South America and luxury chocolates from France, Belgium, and Switzerland.

Fields, who favors a chocolate-colored lab coat and is affectionately known as "Doc Choc," doesn't need a classroom to pontificate about chocolate; the man lives and breathes the stuff.

He can rattle off who created the first commercial label for chocolate (Milton Hershey), how many naturally occurring varieties of cocoa beans there are (two), and the obscure health benefits of chocolate. (It can help asthmatics by dilating bronchial tubes, and can lower bad cholesterol, he says.)

Fields earned a Ph.D. from Michigan State University in botany and plant pathology, and he works with fossilized plants. His professional studies led him to the subject of chocolate, albeit indirectly. While earning a master's degree at the University of California at Berkeley, he noticed that the botany department offered a course on chocolate. It had a two-year waiting list, and he never got in, but he later agreed to teach a similar class at Michigan State. Now it has become one of his favorite courses and a personal pastime.

A tour of the instructor's home, outside Lansing, Mich., would give away his obsession. His shelves are packed with all sorts of books about chocolate — children's books, cookbooks, trivia books, academic studies, and even a chocolate murder mystery. His collection of chocolate paraphernalia includes chocolate soap from a spa at the Hotel Hershey, chocolate-themed playing cards, chocolate tins, empty chocolate Frappuccino bottles, and past issues of Chocolatier

Indeed, Fields is chocolate's cheerleader. He likes to dispel common myths about his candy of choice and insists, for example, that chocolate does not cause headaches or pimples. Nor does it make one fat — excess calories and sugar do, he says. "Chocolate has fat in it," he says, "but it's full of all the good fats or neutral fats." And contrary to popular belief, chocolate does not contain lots of caffeine. (It does, however, contain a compound — theobromine — that causes a buzz similar to a caffeine high.)

Fields prowls supermarket aisles and gourmet shops to check out the newest products on the market. He also has a network of suppliers, including a chocolatier based in Wisconsin who sells free-trade chocolate, produced in socially responsible ways, that is made in Ghana.

He insists he has no favorites, since he is constantly discovering new varieties, but he often prefers chocolate that contains between 55 percent and 75 percent cocoa. And he never ceases to be amazed that such a concoction ever came into being, especially considering chocolate's origins in a bitter, unappetizing bean tucked inside a pod growing from a tree.

Fields recently hosted a tasting over the phone, to give The Academic Life a sense of his style (not to mention taste a lot of chocolate and call it "work"). He chose 11 varieties and instructed that they be tasted in order of increasing cocoa content, the way he does most of his tastings. That meant starting with milk chocolates and working up to the darks.

Fields judges chocolate for six qualities: appearance, aroma, snap (meaning how the chocolate breaks), texture, flavor, and aftertaste. A good chocolate should have a lustrous, even color on the surface. "You don't want any kind of streaks or dots to bloom," he says. Those indicate the chocolate has either been chilled or heated. Ideally chocolate should never leave room temperature.

Quality chocolate should smell pleasant, he says — not smoky, musty, or chemically. Terms used to describe a chocolate's aroma are very similar to those used in a wine tasting, he points out: "Berry, citrusy, floral, flowery, fresh, fruity, gassy — I like that one — mellow, mildew, pungent, sour, spicy, straw, subtle, winy, or woody."

As for snap, tasters are instructed to break apart the chocolate to see what happens. "At room temperature, chocolate should break cleanly and firmly and not crumble or splinter," he says. Once popped in the mouth, chocolate should be smooth and creamy, even velvety — never greasy, waxy, gritty, or lumpy. And as those M&M's commercials have long taught us, it should also melt in your mouth, since cocoa butter, a major component of chocolate, melts at just below body temperature.

The flavor of a good chocolate should be pleasing, harmonious, and well balanced. "You ideally don't want wild extremes in your flavor," says Fields. It should not be too bitter or too sweet. Added flavorings like vanilla, nuts, or spices should blend well. Here Fields goes off on a tangent to explain how hazelnuts are chocolate's ideal partner. "It's one of the few things on the planet that humans have found that just blend seamlessly with chocolate," he declares. Nutella fans would concur.

Chocolate has a wide range of flavors — it can be bitter, burned, citrusy, earthy, flat, floral, fruity, rich, round, salty, smoky, spicy, tart, or taste like toasted nut. But flavor is a complicated subject. Tasting chocolates scientifically involves discerning three levels of flavor, not just one. There is the first impression, the immediate taste that comes through after the first bite.

"That's where all the little sensors in the various places on your tongue are responding to the sweet, the sour, the bitter," he says. "And then if you allow it to melt thoroughly in your mouth and then just open your mouth just a little and take in some air over it, the flavor will change. I suspect what's going on is the digestive enzymes in our saliva are starting to break down some of the sugars, and then the oxygen just seems to speed up that process."

Lastly, there's the aftertaste. A chocolate's flavor should linger in the mouth, says Fields. It should be pleasant, not overpowering, and should not have an "off" taste.

During tastings, Fields freely shares his impression of each confection but does not dictate what others should favor in a chocolate. To each his own, he says. This time around, he was partial to a Colombian dark chocolate with passion fruit, mainly because it was so unusual.

People who have attended his tastings or taken his courses all have their own favorites. And they know their chocolates. Elvera Shappirio, an artist who took his course at Michigan, tasted a Venezuelan chocolate called El Rey during one class and has stocked it at home ever since. She goes for varieties that contain 58.5 percent to 61 percent cocoa.

"The 70 percent is not as smooth as I'd like," says Ms. Shappirio, who now refuses to buy some inferior types of chocolate. Thanks to Fields's course, her palette is now sophisticated enough to tell the difference.

"He really covered everything I could imagine," says Ms. Shappirio. "I never will look at chocolate the same way again."

AN EXPERT'S TAKE ON A CHOCOLATE BUFFET

Patrick F. Fields, an adjunct botany instructor at Olivet College who teaches about the history and culture of chocolate, weighs in on a selection of chocolates from a recent tasting he hosted for The Academic Life.

Droste Milk Chocolate Pastilles (the Netherlands): "Over all I think this one's kind of nice, it is kind of glossy. It has a nice sheen to it. The aroma smells to me pleasant and chocolaty. I don't get any prominent fruity flavors out of it, and partly t's because it's fairly sugary. It's a milk chocolate that has a fair amount of sugar in it. The snap is nice and clean. The texture I like because it's smooth and creamy. It typifies the perfect Belgian school of chocolate making where they add a little extra cocoa butter, and you can sure tell."

Lindt Excellence Toffee Crunch Milk Chocolate (Switzerland): "This one has little nibs, little bits of toffee mixed in, so there's some extra sugar. It has a crunch if you chew it. Obviously those things are going to alter your impression of the mouth feel so you're then judging the addition rather than the chocolate. You can tell it's pretty creamy."

Milka Café-Crème Milk Chocolate With Mocha Creme Filling (Germany): "This one has coffee flavoring. It has a little bit more crumbly of a snap. It's not quite as lustery. The extra cocoa butter they add is probably less than what others use. ... There is a distinct steamy mocha aftertaste. It reminds me of the flavor of coffee ice cream. ... The mouth feel is a little powdery. It's not nearly as creamy as the ones we have tasted already. I'm reading the label; it says with a mocha cream filling. Technically this is a truffle. ... I'm pretty sure what they've done is to make it more chocolaty, they've added cocoa powder, rather than what we call chocolate liquor."

Cote d'Or Dégustation Milk Chocolate With a Dark Chocolate Filling (Belgium): You can tell there's a little bit of vanilla or something in this. I get an aftertaste. ... They've added, secondarily, cocoa and whey and milk fat to it to try and make it more milky, but it's kind of powdery to me. It's not nearly as creamy, so it's a different kind of a chocolate."

Lindt Swiss Bittersweet Fine Dark Chocolate (Switzerland): "It has a lot harder snap, and so when you bite it, even, it's crunchy. What I like about it is they have added vanilla to pretty good beans, and it leaves a distinct vanilla flavor in your mouth. We're getting darker and darker. ... It's about 50-percent cocoa content. ... This one is tried and true pretty good. It's not a great chocolate, but it's a pretty good chocolate. I like it."

Tom and Sally's Handmade Chocolate, handcrafted from French dark chocolate (United States): "I wanted to highlight a little American company. And they're pretty much candy makers, I think. ... I crunched that one and it's pretty hard. And it comes out to about 50-percent cocoa content. ... This is a mom-and-pop's organization doing small handmade batches versus the previous one we just tasted, the Lindt Swiss Bittersweet, which is a very large mega corp doing things, so the flavor is very different. It's very seasonal."

Ghirardelli 60% Cacao Dark Chocolate (United States): "There is a fruitiness to it. ... It does have kind of a funny aftertaste that can linger in your mouth. ... I do like it, clear up until the aftertaste."

Valrhona 61% Dark Chocolate With Hazelnut Pieces (France): "I find the hazelnuts a little distracting in texture. ... I find it hard to judge this chocolate because it has so much crunch, with so many things in the way. But they happen to be really good. And the only caution about any kind of chocolate with hazelnuts in it is that if the hazelnuts have spoiled, the chocolate is ruined."

Bernard Castelain Macaïbo 70% Dark Chocolate (France): "These people are using good beans and treating them well. ... The only thing I notice is that the aftertaste is a little bit astringent. You just feel kind of a weird kind of drying feel to your mouth after you've completely melted it, tasted it, and swallowed. If it were the perfect chocolate, it wouldn't quite have that. But I'd rate this pretty darn high. ... I like the fruitiness that comes through. You get it initially, then you get it again when you breathe in air, so I think it's a pretty darn good one. ... They're making it with love instead of a business-dollar profit margin in mind."

Santander 70% Cacao Dark Chocolate With Passion Fruit (Colombia): "It has passion fruit, and I didn't expect much. I thought it would be pretty yucky. But I like it. I like the tartness that hits you very quickly. Some people don't care for this, and if you don't, be honest. But I love the sour things."

Hachez 77% Cacao Cocoa d'Arriba Classic (Germany): "The first flavor I get is a little bit fruity, but once you let air in, it's becoming a bit more astringent. So it feels like almost peppery in your mouth, and the fruitiness seems to disappear and slowly the bitter is coming on. ... I personally don't care for it."