Cheers to the Science of Wine

The Naked Scientists pop some bottles... All in the name of science!
17 April 2018

Interview with 

Clare Bryant, University of Cambridge

Glasses of Wine

Glasses of Wine


"A rich fruity body with hints of vanilla and a smooth chocolate texture layered over a long finish…” For many, wine tasting and wine appreciation sounds like a foreign language. But there are many different grape varieties, the climate where wine-making grapes grow makes a huge difference, and even the microbes that live in the soil around the roots of the vine also affect the flavour. To explore how and whether we really can pick up on these subtle and rather delicate vinicultural nuances, Chris Smith and Georgia Mills were joined by Clare Bryant, who as well as being an expert on how the immune system works, is also a wine specialist and surprise, surprise, she brought some beautiful samples with her.  So what’s actually going in the mouth when we taste wine?

Clare - We’re experiencing a very large, complex chemical reaction. There are about 400 aromas in wine, so that’s the nasal part of the procedure. In each wine there’s at least 27 different organic acids, 23 different types of alcohol, 80 acids in aldehydes, six in sugars, and a long list of vitamins and minerals to name but a few.

TASTE #1: The battle of the Chardonnays - Exploring “Mouthfeel”

Chris - You’re going to demonstrate some of the principles that are at play when we put wine in our mouth. You’ve got three little tests for us to do; what’s the first one?

Clare - The first one is to taste the difference between a taut and a fat wine.

Chris - Taut and fat?

Clare - Yes. Taute and fat.

Chris - Educated?

Clare - What I’m talking about is richness. Some wines taste rich than others and this is nicely illustrated with Chardonnay. Chardonnay’s a white wine grape, widely grown around the world. It is also very good at taking on the flavours of barrels and oak and various other things. So richness in Chardonnay can involve some or all of the following processes including the oak. Oak’s very important, it gives vanilla, toasty oak, that kind of flavour.  There’s also a malolactic fermentation, which is a secondary fermentation after the primary event which softens the acid. And it’s also yeast aging, which is where the residual yeast particles sort of self-implode, and they release some sugars and amino acids and that also causes richness as well.

Our first wine is a taut, modern Chardonnay. It’s from Margaret River.

Chris - Western Australia.

Clare - Western Australia indeed.

Chris - You’re decanting out little tastette for each of us - a little soupcon for Georgia and I to try.

Clare - If you smell the Chardonnay first of all you’ll…

Georgia - Oh, it’s very smokey.

Clare - It is smokey, yes. It is smokey; there is some oak in this wine. And you can smell a bit of citrus, you can smell some nutty oak, you can smell potentially the smokey struck match so that’s a good effort. And then if you taste it… You’ll find a lemon citrus and then moving over to a bit of dried stone fruit: pear, grapefruit, melon, fig.

Georgia - Mmm, it doesn’t quite taste how it smells. If it tasted like it smelt I think you’d be a bit... cough, cough, cough.

Clare - Yeah, correct.

Then you take the second version which comes from South Africa, so this is a Lanzerac Chardonnay from Stellenbosch.

Chris - It’s much less smelly; there’s much less to smell about this one.

Clare - That’s interesting.

Georgia - Stronger flavour as well.

Clare - It does, yeah.

Chris - It’s much stronger. It’s a bigger; it’s a fatter isn’t it?

Clare - It is.

Chris - It fills your mouth more.

Clare - That’s the point. It’s a fatter more oaked wine.

Chris - Is that the oak that’s done that, that’s given it that vanilla.

Clare - It is quite a big hit.

Chris - There’s a big vanilla hit there and it is fruity, but it’s interesting it smells less.

Clare - Yeah, it’s a more restrained smell.

Chris - So adding oak gives you those stronger flavours?

Clare - Yeah, and it’s a more heavily oaked wine than he first wine we tasted.

Georgia - Why doesn’t the strength of the smell match the strength of the flavour?

Clare - It doesn’t always do that. Sometimes it also depends upon how long you’ve had the wine in the glass, the age of the wine. There’s a variety of factors that influence the nose. That’s interesting because in my opinion South Africa are making some of the great Chardonnays in the world.

Chris - That won’t please the Aussies! The second wine?

TASTE #2: Comparing Rieslings - Aging of wine

Clare - The second one is we’re looking at bottle ageing. What happens is that the wine continues to react from birth to being in the bottle and this is really nicely illustrated by Riesling, which is another white wine grape. It’s generally light in alcohol and has a refreshing, high fruity natural acidity but, as it ages, it has the ability to take on petrol notes.

Chris - Really!

Clare - Like we put in the car.

Chris - I’ve hear this. What’s the octane rating of this.

Clare - Well not very high. It’s treated with trimethyl dihydronaphthalene and that…

Chris - But that’s in mothballs, isn’t it naphthalene?

Clare - Yes, absolutely. And it comes from some precursors that undergo acid hydrolysis. And the presence of these precursors really determines the wine’s ability to age and so a good Riesling will have these compounds to do this.

The first one is a young Riesling. It’s the Magpie Estate Rag and Bone Riesling made in 2017 so it is young. It’s got a lovely perfume nose if you smell it.

Georgia - It’s peachy.

Clare - It is. It’s limey…

Chris - You’ve got a very good nose Georgia, you should be into wine tasting.

Clare - You should.

Georgia - I am!

Chris - Not just amateur in your living room. Yes, you’re right.

Clare - Yeah, perfumed, limey, red apple nose, hence the pineapple.

Chris - That’s a nice wine. But you’re saying that’s a young wine?

Clare - That’s a young wine.

Chris - It’s not been in the bottle very long?

Clare - No. 2017. It’s a nice lively fruit, good acidity.

Chris - We’ll compare that with?

Clare - This is Peter Lierman Wigan Eden Valley Riesling; it was made in 2011. And if we give it a sniff…

Georgia - It really does smell of petrol. That’s so weird!

Clare - It really does. It’s even more kerosene than petrol actually.

Georgia - If I put a match in this, would it explode?

Clare - I’ve never tried that actually.

Chris - If I’m honest though, having tasted this I prefer the young one.

Clare - Yeah, that’s interesting.

Chris - Do people tend to break down into two camps.

Clare - Yeah it does divide people.

Chris - Why has sitting in the bottle done that?

Clare - It’s just literally an acid degradation of the keratin precursors, which then leads these precursors to take on the chemical that then gives you the sort of petrol-ly, diesel-ly type smell.

Chris - So there is this ongoing chemical process in the bottle?

Clare - Ongoing chemical process, yeah.

Chris - Is there a sort of rule of thumb as to when a good time to drink a wine is? Do we know how different wines age because sometimes it’s going to work, sometimes, it’s not going to work to keep them longer isn’t it?

Clare - It’s complicated. You can predict according to how wine is made and this is something that a lot of the winemakers specialise in. They’ll give you drinking dates and it very much depends upon the wine, the winemaker and the vineyard.

Chris - Shall we do our final test?

TASTE #3: Food Pairing: Red wine plus blue cheese

Clare - This time we’re looking at the combination of wine and food. We have a red wine: it’s a Ripasso Valpolicella. It’s an interesting wine because you partially dry the grapes first, then they ferment, and then they undergo a second fermentation.

Chris - Why should that make a difference the drying them?

Clare - The drying them increases the sugar.

Chris - Right.

Clare - So you get a sweeter wine and this has a sort of perfumed rich nose with some cherry and oak. And if you taste it… you get a kind of chocolate, spicy, bittery type taste.

Chris - Mmm. It’s certainly got the spice there.

Clare - You can taste the sugar as well.

Chris - Mmm. Peppery.

Clare - And now you take a piece of cheese.

Chris - We’re being proffered some Shropshire blue cheese.

Georgia - Oh no, blue cheese.

Chris - I actually really like blue cheese. It’s not a bad one.

Clare - And now try the wine again.

Georgia - Ooh!

Chris - Mmm. The wine is enhanced - the combination.

Clare - Umm the combination.

Georgia - It’s become sweeter, yeah.

Clare - It brings out the sweetness and it brings out the difference in the flavour and that’s because there’s two different effects going on. When you take the cheese: it’s fatty, it coats your mouth, it lubricates your mouth. Whereas the wine because of the tannings in the wine, they cause an astringency, and what that effectively is is the tanning molecules bind to the proteins in your mouth. This then makes your mouth feel dry and kind of puckers up your tongue and puckers up your cheeks, and reduces the lubricant proteins that are present in saliva. We’re having a combination of the oily lubricant with the astringency of the wine, you’re then arriving at a new balance, so you change the flavour of everything in your mouth at the time.


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