The Basic Human Tastes

Our society has traditionally recognized four tastes: sweet, salty, bitter and sour. In modern times however we’re better able to get to the root of taste, seeing what molecules are detected by our taste buds, and it has become apparent that there are more basic tastes than we once thought. The most well known one is umami, a savory taste, but LiveScience brings us some other candidates for basic tastes, excerpted below:

1. Calcium

The element calcium is critical in our bodies for muscle contraction, cellular communication and bone growth. Being able to sense it in our chow, therefore, would seem like a handy tool for survival.

Mice seem to have it figured out, kind of. Recent research has revealed that the rodents’ tongues have two taste receptors for calcium. One of those receptors has been found on the human tongue, though its role in directly tasting calcium is not yet settled, said Tordoff.

Calcium clearly has a taste, however, and counterintuitively most mice (and humans) don’t like it. People have described it as sort of bitter and chalky – even at very low concentrations. Tordoff thinks our calcium taste might actually exist to avoid consuming too much of it…

2. Kokumi

That calcium receptor might also have something to do with an unrelated sixth-taste candidate called kokumi, which translates as “mouthfulness” and “heartiness.” Kokumi has been promulgated by researchers from the same Japanese food company, Ajinomoto, who helped convince the taste world of the fifth basic taste, umami, a decade ago.

Ajinomoto scientists published a paper in early 2010 suggesting that certain compounds, including the amino acid L-histidine, glutathione in yeast extract and protamine in fish sperm, or milt – which, yes, they do eat in Japan, and elsewhere – interact with our tongue’s calcium receptors.

The result: an enhancement of flavors already in the mouth, or perhaps a certain richness. Braised, aged or slow-cooked foods supposedly contain greater levels of kokumi…

3. Piquance

Spicy-food lovers delight in that burn they feel on their tongues from peppers. Some Asian cultures consider this sensation a basic taste, known in English as piquance (from a French word). Historically, however, food scientists have not classified this undeniable oral sensation as a taste.

That’s because certain piquant compounds, such as capsaicin from peppers, directly activate our tongue’s touch, rather than taste-bud, receptors. The key piquancy receptor is called TRPV1, and it acts as a “molecular thermometer,” said John E. Hayes, a professor of food science at Penn State….

4. Coolness

At the opposite end of taste sensation from piquance’s peppers is that minty and fresh sensation from peppermint or menthol. The same trick of sensory perception is at work here – activated touch receptors, called TPRM8 in this case, fool the brain into sensing coldness at normal oral temperatures, said Hayes.

As touch sensations, both piquance and coolness are transmitted to the brain via the trigeminal nerve, rather than the three classical nerves for taste. “The set of nerves that carry the burn and cooling sensation are different than from taste sensation,” said Hayes.

Still, there is an argument that temperature sensation, both in the genuine sense and in the confused-brain phenomenon of piquance and coolness, deserves to be in the pantheon of basic tastes. Interestingly, Germanic people dating back to 1500 had considered heat sensation as a taste, Hayes said, and the modern debate over temperature’s status is far from over.

5. Metallicity

… Some Asian cultures place gold and silver leaf, as it’s called, atop curry dishes and candies, while Europeans fancy a bit of these metallic foils on pastries…

Although usually tasteless, such garnishes are sometimes reported as having a distinctive flavor. Researchers have shown that this sensation might have something to do with electrical conductivity, in effect giving the tongue a little zap…

Lab tests have failed to turn up a metallic-taste receptor, Lawless said, and it remains unclear if electrical conductivity or something more is going on for those shiny culinary embellishments. “We’re leaving the door open,” Lawless said.

6. Fat

The jury is still out on whether our tongues can taste fat, or just feel its creamy texture…

Mice can taste fat, research has shown, and it looks like humans can too, according to a 2010 study in the British Journal of Nutrition. The study revealed varying taste thresholds for fatty acids – the long chains that along with glycerol comprise fats, or lipids – in participants.

Intriguingly, the subjects with the higher sensitivities to fat ate fewer fatty menu items and were less likely to be overweight than those with low sensitivity…

7. Carbon Dioxide

Yet another strong sixth taste candidate: carbon dioxide (CO2). When dissolved in liquids, this gas gives soda, beer, champagne and other carbonated beverages their zingy fizz.

That familiar tingling was thought to result from bubbles bursting on the tongue, and had therefore been consigned to the touch category. “It’s tricky because CO2 was always considered a trigeminal stimulus,” said Tordoff.

Researchers presented a strong case for dedicated, taste bud-based carbon dioxide sensors in a Science paper in 2009. They found that an enzyme called carbonic anhydrase 4, which appears on sour taste-sensing cells, specifically detects carbon dioxide in mice…

Pretty interesting stuff. This is another scientific topic where it pays not to get emotionally attached to convention – the fact that there aren’t 5 senses or 9 planets or 4 tastes should be exciting new developments, not scary challenges to our worldview.

It’ll be interesting to see when our culture catches up to these realities; we already acknowledge foods as spicy or minty, but how long will it be before advertisers say their food is more umami or kokumi than their rivals’? 

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