Glycerol - a taste smoother

Salut les gars!
How was your last week? Mine was pretty busy and I am so happy to have now a weekend of rest and some peace, even though I was planning to spend some time with friends together, but health is sometimes more important so I slept pretty well and late. Now I am refreshed for another post again! The sun is shining outside finally again in Finland and before jumping off and enjoying a nice walk in it (with all the snow around glimmering and shining) I remembered I promised to post something about glycerol! :D

When presenting you last time the wine I found - La Jasse Castel - I mentioned about the glycerol content of the wine. Mais (French word for "but"), what does this actually means, what is it good for and why is it even in the wine??? All of them are good questions.

 

Glycerol is a product that occurs during the wine fermentation. It is basically produced as - let's just say - "side-product" of the yeast. While the yeast is performing the alcoholic fermentation a lot of different metabolic products are consumed by it and also produced. The average content of the glycerol within wine can vary and depends also on the yeast strain or starter cultures they used for the wine fermentation. Concerning the different yeast strains and how much they produce is one of the huge discussion topics if you happen to encounter a wine maker. Some of them say that the different yeast strains don't not significally increase or lessen the glycerol content when added to the wine. The average concentration that a yeast can produced ranges from - oh.....pfffff.... attend les gars je suis en train de me souvenir (what guys.. I am trying to remember it)... - 4.5 to 13 g/L less or more. But with the numbers I am not anymore so pretty sure, but it should have been in this range.

Glycerol chemical structure

Anyway, my personally impression is that the glycerol production of the yeast simply depends on the nutrition within the grapes juice. Therefore, it could vary from each year, as each year different weather and soil conditions impact the composition of nutrition within each grape. And yes it is highly possible that some yeast strains (Saccharomyces cerevisiae) might produce more, if I speak from my experience as biologist.

 

However, why is it important to have glycerol in wine? Basically, because glycerol is supposed to support the mouth feeling. I use the word suppose, because there is kinda of fierce battle between the people in the wine community about the importance of glycerol and effect towards the wine tasting and quality. Glycerol is for itself an odorless viscous liquid with a "sweet" taste. Therefore, some people tend to say it is not so important and has no overall contribution towards the wine in its taste and smell, cause this depends a lot on the different aromas and tannins within the wine. Other people again praise the glycerol in wine (some who are talking about Botrytis cinerea - a grapes pathogen, but also used for wines that have high sugar concentration such as dessert wines - more of that in my next post!) and so on.

If you ask me, it's kind of mixed thing. It's like I mentioned it very often: a wine is the sum of its compounds not of each single one! So therefore I see glycerol as a "transmitter/transporter" to be able to have a nice mouth feeling and start to taste the different aromas. (In terms of biology or chemistry I would consider glycerol - cause of its structure and some chemical properties - as a "carrier" for the aromas..... and yes some of the chemistry and biology people might shot me for this blurry and not 100% correct explanation. Just go with it, please. If I start here with an explicit explanation I will sit here and keep writing a book!) 

So could someone not just easily add some more glycerol to a less good vintage? Ouais, that is possible and I could assume some people did before analytic devices were used in the wine making and wine evaluation (to make competition and wine production that what it is: A summary of nature's gift and the talent of the wine maker).

 

Maybe you guys have now some kind of idea what glycerol is and why it is - that is for you to decide - important in wine. At least, next time you meet some into-wine-people you can talk with them about this and proof some info ;)

 

The curtain (left: after swirling, right: 8 secons later)
This wine was having less glycerol content

Just a tip on the way, you can also check the glycerol content of a wine by yourself. How? Pretty easy, but not like saying it has the following concentration of x g/L in it.
You simply swirl your wine glass and see how long the - let's call it - the "curtain" (sorry I don't happen to remember the correct term for it anymore!) stays on the glass (see pictures). The longer it stays on the glass, the higher the glycerol content is.

 

Bon les gars! I am off to enjoy the sun and later some good food and sauna! Have a relaxing and whatever you do nice weekend! :)

À bientôt