Legs : Dr. Lipton, please report to the information desk

Hi, Mike - I can clear this part up. Glycerine and glycerol are the _identical_ compound: 1,2,3 propanetriol. Of the two names, glycerol is the more correct chemical name because the ending indicates that the compound is an alcohol. It is produced as a side product in alcoholic fermentations by the action of yeast. IIRC, the side reaction is favored by the presence of sulfur dioxide in the must/juice. Glycerol adds both viscosity and apparent sweetness to wines. Supposedly, an old trick in Burgundy was to add a glassful of glycerol to a barrel of wine to improve its organoleptic properties.

I'll leave the part about legs to Mark or someone else who understands the physics to answer. :^)

Tom S

OH!

(sorry, 'in' joke)

Oh, the pressure! :P

Glycerin is the older (deprecated) name for glycerol. And, yes, AFAIK there are trace quantities of glycerol in most wines.

True. Glycerol's boiling point is 290° C (actually, it decomposes at that temp) whereas ethanol's is 78.5° C. What actually boils, however, is a 95.6:4.4 mixture of ethanol/water (known as an azeotrope) that boils at 78.2° C. {Hey, Ian! Can you imagine that some of it evaporates at 25° C? Surely that violates all the laws of physics!!! :P} FWIW, that's why "pure grain alcohol" is 95% (190 proof) and why absolute (100%) ethanol was long considered undrinkable because of the residual benzene needed to remove the last traces of water.

It's a complex topic, Mike. Many liquids climb the glass surface, giving rise to the familiar concave surface of many liquids (the "meniscus") in glass containers. The factors at work are the hydrogen bonding between water (and ethanol) and the glass surface, the surface tension of the liquid and the viscosity of the liquid. Because ethanol is a surfactant (it lowers the surface tension of water), it increases the climbing up the glass surface. And, yes, the nature of the glass surface matters, too. In an extreme example, one can modify the glass by silylating the surface, thereby making it water-repellent. A commercial product (RainX) in the US treats windshield glass on cars in this way to make them more rain repellent, though it's a fairly transient effect owing to wear on the glass surface.

Well, you can get legs by swirling the wine to coat the inner surface of the glass and then watching the legs develop. In that case, the legs are similar in content to the wine and do contain the trace glycerol, making them more viscous and persistent. OTOH, you'll see legs in a glass of wine that's standing, in which case those legs are colorless and composed entirely of a 95:5 mix of ethanol:water.

It certainly changes its mouthfeel. Whatever other organoleptic qualities it has, I cannot say.

Thank you doctor, you saved my life.

Mike

Mike Tommasi, Six Fours, France email link

Salut/Hi Mark Lipton,

For the chemistry, I wouldn't presume to expand, comment or say anything.

le/on Thu, 22 Apr 2004 14:18:04 -0500, tu disais/you said:-

I confirm. (gulp, I wasn't going to)

Chuckle.... don't say you've been STILL following.

Confirm.

And as some dishwashing rinse aids contain such substances, it behoves us to be extremely careful over washing glasses in a dishwasher, if one is going to look at the legs afterwards - and I like looking at legs.

No, I'd not agree with that.

Exactly

In that case, the legs

Slightly sweeter on the finish, I think.

What I'd say about legs in a wine, is that they can be a useful hint as to what to expect of the wine.

I know some say that any solution of alcohol in water will show legs, and that may be true, but the _way_ in which legs form after swirling, (width and speed of formation and speed of decay) gives some hints (I feel) as to what to expect of a wine, and perhaps, clues as to whether a wine is showing badly.

Talking of whites, for example, if the wine has very marked legs, and a fair gold colour, (without the brassiness of oxidised wines), I think it's fair to say that the indications are there that the vines have had to work hard to get their water/nutrients, and that (by implication) this will lead to greater complexity, due to the trace elements they'll have probably picked up while going looking for them. So if you get a wine with a good gold colour and marked legs, with NO nose worth talking about, or not much flavour, then there's something adrift. It may be that the wine is going through a closed-in phase, or it could be (unless blessed with your excellent nose for TCA Doctor) just that the wine is very slightly corked and shows it by "not showing well".

That's my use of/feeling about legs, for what it's worth, and I don't know whether anyone else has had similar thoughts or experience. I'm far from being dogmatic on this either. I just get this feeling!

Nope, not really. Just ducked my head in there twice, confirmed the amount of sheer nonsense being posted, and decided that I'd let others weigh in on that one (no "troll" am I!)

ROFL!! I can confirm that last statement. As for the previous statement, the rinse aids I'm familiar with are nonionic surfactants with some additives for removing lime from the rinse water. Are things different in your part of the world? While on that note (and dragging that thread back kicking and screaming on topic), I shun the scented rinse aids because of the lingering smells in wine glasses.

Very useful advice, Ian. That helps define, for instance, what one can do in scoring a wine for "appearance" in this era of clear, well-made wines. The story related in Harry Waugh's obit regarding his ability to correctly identify a wine by mouthfeel alone is an object lesson in how much information one can get apart from smell and taste.

Mark Lipton

Obviously a taster can insulate himself from the aroma by holding his nose - but how could one separate mouthfeel from taste? Sounds like urbane legend to me...

Tom S

In the case of Mr. Waugh, it was the result of a car accident in which he lost his sense of smell (so, not entirely without a sense of taste, just mostly)

Mark Lipton

Legs are evidential of the alcoholic strength of wines. The fatter the legs, the higher the alcohol.

Legs generally appear after two or three swirls of the glass.

A german auslese, while fat in the mouth and full of glycerin, will not show legs due to the lower alcohol content. It will sheet, not drip into legs.

I particulary enjoy reds whose legs drip the deep color of the wine, exhibiting much extract, sure to indicate deeper flavors and skillful winemaking.

I am of the opinion that legs are created due to the different evaporative qualities of water and alcohol, not due to the content of glycerin.

Salut/Hi D T,

Isd this the first time you've posted here? I don't recognise your name I'm afraid. If it is, "welcome to the madhouse".

le/on Sun, 25 Apr 2004 01:30:44 -0700, tu disais/you said:-

Yes, I know this is often said.

I'd like to be able to agree with you but then how to explain the immense legs that I observed in a Tokaji Eszencia - still fermenting - with only around 3-4% alcohol. Also, I'm afraid that I DO find that Auslesen and higher (with low sugars therefore) can have very fat legs, if they are from areas where the vines have worked hard.

I feel (without any experimental data, but nevertheless some 30 years observation of the behaviour of good wine) that it's a lot more complex than that.

Sorry, no.

Having tasted some 160 Austrian Beeren- and Trockenbeerenauslesen in the last two weeks, of which roughly one half had an alcoholic content of 11.0 percent or less, I definitely can assist Ian here: They *all* showed significant legs on the glass.

M.