04 Jan 2012 Humans may taste at least six flavours
Western food research has long been dominated by the four “basic tastes” of sweet, bitter, sour and salty. In recent decades, however, molecular biology and other modern sciences have dashed this tidy paradigm. For example, Western science now recognises the East’s umami (savoury) as a basic taste. But even the age-old concept of basic tastes is starting to crumble.
For all our sophistication in the kitchen, the scientific understanding of how we taste food could still use some time in the oven. Dating back to ancient Greece and China, the sensation of taste has historically been described as a combination of a handful of distinct perceptions.
“There is no accepted definition of a basic taste,” said Michael Tordoff, a behavioural geneticist at the Monell Chemical Senses Center in Philadelphia. “The rules are changing as we speak.”
Our ability to sense the five accepted categories comes from receptors on our taste buds. These tiny sensory organs appear mostly on the tongue, the roof of the mouth and in the back of the throat.
The sense of touch also plays a key role in experiencing taste, as evidenced by the strong opinions on crunchy versus smooth peanut butter. Smell, too, impacts our tasting abilities. Just ask anyone with a stuffed-up nose picking away at what seems to be a plate of bland food.
In the mouth itself, though, food scientists continue to discover new receptors and new pathways for gustatory impressions to reach our brain. Here are some taste sensations vying for a place at the table as a sixth basic taste.
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.
An over-sensitivity to calcium-rich foods such as spinach could help explain why four out of five Americans don’t get enough calcium. “There is a strong relation between people not liking vegetables and calcium,” said Tordoff.
As for milk and other calcium-loaded dairy, the calcium in it binds to the fat, so we don’t taste the mineral all that much, Tordoff noted.
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 flavours already in the mouth, or perhaps a certain richness. Braised, aged or slow-cooked foods supposedly contain greater levels of kokumi.
If all that sounds a bit vague, it does to Western scientists also. Ajinomoto representatives have visited Tordoff’s group “and given us foods they say are high in kokumi – but we have no idea what they’re talking about,” he said. “Kokumi may be something that the Western palette is not attuned to.”
The other candidates are Piquance, Coolness, Metallicity, Fat and Carbon Dioxide…..