Is there a science to wine tasting?
At almost every occasion or dinner event wine is on the menu. It’s a topic for discussion, a chance to share knowledge and some may enjoy the snobbery of a fine drop, while others simply enjoy a sharing a drink. Science events are no exception and at every meeting, conference or social with colleagues and others working in similar fields where wine is available I’ve noted how bottles of wine disappear at such a rapid pace I’m not sure if people are drinking it or inhaling it. It seems most people enjoy wine, but do we understand what it is we’re drinking? Or why some wines taste better than others?
What is wine?
Wine is fermented grape juice, which is essentially a chemical cocktail containing acids, ethanol and other forms of alcohol, sugars, vitamins, minerals, esters, aldehydes and sulphites. Together, these boil down to three basic qualities; bitterness, sweetness and sourness; and a good wine balances these perfectly. A list showing where wine flavours come from can be found here. Another layer of complexity in wine are volatiles (aromatic compounds with a low boiling point) some of which are present in the grape. Others (secondary volatiles) come from yeast activity during fermentation, while the tertiary volatiles are formed as the wine matures, either in a bottle or barrel. Knowing that wine is simply a mixture of chemicals and making it requires excellent knowledge of them, so is there a science to tasting wine?
Essentially, there is science to everything that we eat and drink and wine is particularly interesting because it is such a complex amalgamation of chemicals that exude different aromas and flavours. Drinking wine involves three senses; sight (vision), taste (gustation) and smell (olfaction). Sight can tell us the approximate age of a wine. White wines are pale yellow and turn darker amber as they age whereas red wines appear as a deep purple when young and a more red-brown when they are older.
Taste occurs on the tongue where our taste buds are capable of sensing five key flavours; sweet, sour, salty, bitter and umami. Our tastes buds are also able to sense texture of food and drink such as oiliness, how spicy something is and menthol.
Perhaps the most critical sense to tasting wine is our sense of smell. A human nose has ~400 different scent receptors and can distinguish ~1 trillion different odours which should come in handy considering how intricate wine is. There are actually two ways in which we smell wine:
- Orthonasal olfaction; what we smell through our external nares (nostrils),
- Retronasal olfaction; what we smell through internal nares, located in the mouth.
Fun fact; retronasal olfaction is why pinching your nose when drinking something horrible actually doesn’t work.
Scientific research has repeatedly shown that none of our senses can help us to choose a good wine because we can be influenced by our mood, the cost of the wine, the colour of the wine and even listening to music!
In fact, even wine tasting experts are easily fooled and research by Robert Hogdson has shown that wine awards are given out almost by random. Hodgson performed an experiment at the California State Fair Wine Competition, testing professional wine tasters. He presented the same wine three times (poured from the same bottle) and each time the wines were judged differently. On top of this, judges who were consistent one year were found to be not as good the next year, showing that even good wine judging is due to chance.
In 2001 French academic Frédéric Brochet tested the effects of both colour and bottle label. He gave volunteers a glass of white wine and a second glass of the same wine but added a tasteless red food dye to the second. The second glass was described as a red wine, despite being the same! For his experiment with labels, he gave the same wine in two different bottles to volunteers. The wine in the fancy-looking bottle was described as far better than the wine in the standard bottle. This was replicated in 2011 by Richard Wiseman who asked 578 people to do a blind taste test of a variety of white and red wines that ranged in price from $7 to $50 and discovered that people could only tell the difference ~50% of the time.
The taste of wine is also affected by music, which has been shown to increase the scores that wine judges give, and temperature which influences the volatiles. These are more active when wine is warmer, so serving wine too cold can block the amount of smells that we can detect.
Basically, the taste of wine is purely subjective and if you are happy with what you’re drinking, then that’s all there is to it. And on that note, I think I might go have a glass.
Related Past Events:
- Chemistry in a Cup
- Alchemy in a glass
- Adelaide Fringe 2012: Faraday's candle (theatre)
- Fizzle & Pop: Chemistry @ Rochester
- Chocolate Coated Science @ Whittington Flamefest
- What Your Tongue Won’t Tell You About Taste
- Tasting Notes: the Sensory Perception of Wine
- What is Scurvy?
- Book Review: The Periodic Table by Primo Levi
- Stinky science: why compounds smell (12 October 2010)