Gym socks?

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The Science Behind a Chocolate Funk

Faye Flam is a Bloomberg View columnist. She was a staff writer for Science magazine and a columnist for the Philadelphia Inquirer, and she is the author of “The Score: How the Quest for Sex Has Shaped the Modern Man.”
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It's been a horrible week for Mast Brothers Chocolate, and therein lies a scientific mystery.

Just days ago, serious foodies were buying the stuff for $10 a bar. Then, a series of posts on a blog called suggested the chocolate was not as authentic as the Brooklyn-based company claimed, and suddenly the food press was calling the product “crappy," “bitter” and “chalky.” One scathing review in the Guardian suggested that one of the bars carried “that sweaty gym sock sourness” associated with funky cheese.

If the chocolate really tastes that terrible, why is it only obvious now?

Start with the science of taste. Thanks to genetic differences, you and your friends don’t taste the same thing when you eat the same food. That’s especially true of foods such as broccoli and kale, which contain compounds some people can’t taste at all and others find unbearably bitter.

Beyond that, the experience of food is powerfully shaped by the sense of smell. And the human sense of smell is notoriously unreliable and quirky because it’s in the process of evolutionary degeneration.

In the 1990s, scientists discovered that humans have 1,000 olfactory genes – each one coding for a different smell receptor. Molecules wafting through the air trigger millions of possible combinations of these receptors, just as millions of songs could be played on a 1,000-note keyboard.

However, about half the receptors don’t work because the genes have mutated to the point of dysfunction. We don’t rely on scent the same way our mammalian ancestors did – or as much as mice, dogs and many other mammals still do. What makes our situation so interesting is that in each of us, a different half of the receptors are broken. So we each live alone in a unique odor universe.

Not that there's no common experience, especially when survival is at stake. Humans still rely on scent to signal that it's not a good idea to eat, say, rotting fish. Since there’s redundancy built into the system, bad fish stinks to most people, but it stinks differently.

Which takes us back to Mast Chocolate. The vagaries of human taste and smell can explain why it’s not for everyone, but not how the consensus went suddenly from gourmet treat to sweaty gym socks.

To investigate, I contacted the world’s most famous institution devoted to the science of smell and taste: the Monell Chemical Senses Center in Philadelphia. 

It sent me to a psychology professor who had recently been a visiting scientist there -- Debra Zellner, of Montclair State University. She said she was not surprised by the way people could turn against the taste of something as complex as chocolate.

Scientists have done numerous experiments, she said, to show that expectations can change the experience of eating and drinking. She cited a sneaky one conducted by a group of researchers at Cornell University, who offered restaurant diners a free glass of wine. The wine was all the same, but some people were told it was made in California, others that it was made in a winery in North Dakota.

The people who thought it was a California wine reported that it was delicious. Those who thought it came from North Dakota not only disliked the wine, they reported not liking the meal as much as the people who got the “California” vintage.

In another telling example, chefs from a fancy restaurant concocted a frozen dish involving salmon. One group of experimental subjects was told it was smoked salmon ice cream and another group that it was frozen salmon mousse. People enjoyed the salmon mousse. Not the ice cream. In scientific lingo, they had a different “hedonic response.”

In one of Zellner’s experiments, she asked people to sniff different samples of cheese. Those who were told it was cheese thought it smelled okay. Others, told they were sniffing various body odors, perceived them as stinky.

According to recent news reports, the Mast Brothers are defending the authenticity of their product and denying accusations that they cut corners on what chocolate makers refer to as a “bean-to-bar” process.

What might be a lot more damaging are the subjective accusations about the taste. Journalists describing the chocolate mostly reported their personal opinions as fact. If they conducted taste tests, they didn’t appear to do them blind.

That wouldn't be fair, but that hardly matters to readers. Once someone plants the association between a brand of chocolate and sweaty gym socks, it’s hard to enjoy it the same way again.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

To contact the author of this story:
Faye Flam at

To contact the editor responsible for this story:
Jonathan Landman at