Black coffee. Hot peppers. Truffles. Oysters. The world is full of polarizing flavors and foods, beloved by many, despised by just as many. Why is that? Scientists have untangled some — but not nearly all — of the mysteries behind our love and hatred of certain foods.

Taste vs. flavor

While we might say, “That tastes like strawberry,” scientists who study these things would disagree. Our tongues actually perceive only five basic tastes: sweet, sour, bitter, salty and “umami,” the Japanese word for savory. To go from merely sweet to “Mmm, strawberry!” the nose has to get involved. The taste and olfactory senses, along with any chemical irritation a food creates in the throat (think mint, hot pepper or olive oil), all send the brain the information it needs to distinguish flavors.

“We as primates are born liking sweet and disliking bitter,” said Marcia Pelchat, who studies food preferences at the Monell Chemical Senses Center in Philadelphia. The theory is that we’re hard-wired to like and dislike certain basic tastes so that the mouth can act as the body’s gatekeeper.

Sweet means energy; sour means not ripe yet. Savory means food may contain protein. Bitter means caution, as many poisons are bitter. Salty means sodium, a necessary ingredient for several functions in our bodies. (By the way, those tongue maps that show taste buds clumped into zones that detect sweet, bitter, etc.? Very misleading. Taste receptors of all types blanket our tongues — except for the center line — and some reside elsewhere in our mouths and throats.)

‘Coffee is too bitter’: The genetic component

Researchers have found only one major human gene that detects sweet tastes, but we all have it. By contrast, 25 or more bitter receptor genes may exist, but combinations vary by person. Some genetic connections are so strong that scientists can predict fairly accurately how people will react to certain bitter tastes by looking at their DNA. In addition, nearly everyone has at least one “specific anosmia,” meaning you can’t detect a particular odor despite having an otherwise normal sense of smell. A great example is androstenone, the chemical that gives truffles their scent. To many people, it’s offensive, like body odor. Others find it earthy and pleasant, like sandalwood. A quarter of people can’t smell it at all.

Taste and the brain (Patterson Clark/The Washington Post)
‘Mom’s pot roast is the best’: The experience component

Research has shown that we are predisposed to like flavors of foods our mothers ate while pregnant. These flavors are passed through amniotic fluids and later through breast milk, possibly signaling to the baby that if Mom ate it, it must be readily available and safe.

‘Jalapenos rock!’: The cultural component

You simply can’t teach a rat or dog to like spicy food; scientists have tried. But in humans, it’s easy. Culture often overrides our genes and takes over the mouth’s role as the body’s gatekeeper. Few people immediately like bitter beverages or extreme spices, but many learn to love them through repeated exposure. We often learn to like what people around us like.

‘I need chocolate!’: The sex component

Cliched but true, researchers have found a clear sex difference in food cravings. Women are more likely to crave sweets, by a 60 percent to 40 percent margin. By the same margin, men are more likely to crave salty foods.

‘Oysters are gross’: The texture wild card

Some people can’t stand slimy, gritty or creamy foods, regardless of the flavor. Science cannot fully explain where texture issues come from, but a study released last fall by the Monell Chemical Senses Center offers a clue: People with more of a certain enzyme in their bodies tolerated the feel of thick, starchy foods better. In addition, texture can affect flavor by altering the release of aroma molecules in the mouth. Manufacturers pay special attention to this when trying to make a low-fat substitute taste and feel like a high-fat food.

Leftover jelly beans?

Take this test to tell the difference between taste and flavor:

• Get one jelly bean in each of these very different flavors: banana, black licorice and cappuccino.

• Now hold your nose. Without looking, pop one of the beans into your mouth and chew it, keeping your nostrils closed.

• Try to identify the flavor. Very few people will be correct more than a third of the time, the percentage you’d get right just by guessing. Why? Because all three taste sweet and a tad bitter, our tongues can’t tell the difference.

• Let go of your nose. Suddenly you can easily distinguish the flavor. (This explains why food doesn’t taste right when you have a stuffy nose.)

In the name of research and because we like jelly beans, several dozen people in the newsroom tried this test. Exactly 33 percent got it right, the number you’d expect if everyone just guessed. Two people were correct twice, but one of them cheated. Even the newsroom’s top palate, that of food critic extraordinaire Tom Sietsema, couldn’t distinguish just by taste. He was kind of bummed about that.

Sources: Marcia Pelchat of the Monell Chemical Senses Center; AAAS symposium with Gary Beauchamp of Monell and Jane Leland of Kraft Foods; Society for Neuroscience