A Sense of Taste?
Posted on Mon 13th Jul 2015 at 14:35
Considering that our senses of smell and taste must have been vital to the survival of early humans trying to distinguish food from poison, it is remarkable how poorly understood these senses are.
Most of us probably grew up with the old concept of four types of taste receptors on our tongues – salt, bitter sweet and sour, while the discovery in 1909 of the umami (or savoury) receptor was largely ignored till around 1980s (probably because the original paper was published in Japanese). Finally in 2000, the first taste receptors for bitter compounds were identified, then sweet, umami, sour and finally salt as recently as 2010. Researchers continue to look for more too. Taste is detected by the bumps or papillae that speckle the tongue. There are 4 types: the filiform papillae simply detect texture, whereas the other three — fungiform, foliate and circumvallate — contain onion-shaped taste buds. Each taste bud is packed with taste cells, with sensors for the five basic tastes. The once common belief that different taste buds were mapped to different places on our tongue is plain wrong: every part of the tongue is sensitive to all five tastes. This leads me onto to explore differing taste thresholds in tasters, which is important to help us understand why our tastes for wine vary so much. It’s fairly widely known that tasting sensitivity is divided roughly into super-tasters, normal tasters and non-tasters. Super-tasters are notably more sensitive to bitterness, tested using a compound called 6-n-propylthiouracil (PROP), which tastes intensely bitter to super-tasters, mildly bitter to normal tasters and flavourless to the rest. About 25% of us are believed to be super-tasters and the trait is more common in women, while a further 25% are non-tasters. It was also believed that this sensitivity to bitterness was linked to the number of taste papillae on your tongue, but recent research in Denver, Colorado tested 3,000 people and found no link at all between number of papillae and perception of bitterness with PROP. Another long-held belief busted!
With wine tasting – especially with levels of phenolic bitterness (tannins, polyphenols and many more complex compounds) common in wine, it is really critical to know where you fit on the scale. Similarly perceptions of sweetness, sourness and umami (savoury) characters also vary. Taste is also about physical tactile sensations. “Mouth-feel” is a term that sums this up nicely as it literally means how the wine feels when you taste it. Sensations you might have noticed include whether the wine gives a drying sensation – or astringency, and whether it seems “fat” and rounded. Even less well known is how many of us are anosmic or physically unable to smell certain aromas simply because we don’t have the right receptors in our noses. We have something like 400 different olfactory receptors but the exact combination varies widely. Another piece of recent research suggests that the old myth that humans could only detect around 10,000 different odours is also wrong. Scientists at Rockefeller University in USA now reckon their research proves we can distinguish around 1 trillion different odours. Total loss of smell is rare but researchers now think that all of us have aroma “blind spots”. Even for aromas as common in our diet as vanilla, up to 3% of people can’t smell it at all, while a massive 30% can’t smell androstenone, which is a key component in the attraction of truffles. Our sense of smell is so critical because much of what we perceive as taste is in fact odorants detected in our noses. There is clearly so much more to discover about how our senses of smell and taste really work, but in the meantime, we can all enjoy a bit of practical research by pouring a nice glass of wine! Cheers! Written by Caroline Gilby; Master of Wine, for Signature Wines Ltd.