Discussion point - degassing

[MKG]

Degassing is the mechanical removal from a recently-made wine of dissolved gases. Here's my stance ...

There's no reason to degas at all if the wine is going to be matured as all of those dissolved gases will come out under their own steam given time: therefore it appears that degassing is beneficial only if the wine is to be drunk young. However, knocking the hell out of a wine to degas it makes it taste flat and lifeless, and it has to be left for a while to regain its character - so if it has to be given time to recover, what was the point in the first place?

What I've written there may or may not be true. It may or may not be something I've just made up for the sake of a discussion. But I've never actually seen a good discussion of degassing anywhere, so why not have one here?

Go on - have a go

Mike

[ojay54]

Well ,intrigued by the tagline to the thread,I looked this up.Correct me if I'm wrong,Mike,but it seems the only reason to do this(quite involved) process,is to cut the time the wine takes to mature naturally.
My old man liked to make wine,as do a couple of my friends,they bang on and on about the various stages,and they like the making almost as much as the drinking.Why hurry something you enjoy?

[MKG]

I quote from Winemakers'Academy ...

"The easiest way to degas a wine is through patience. Given enough time all the carbon dioxide will come out of suspension and leave your wine. This is the method employed by most wineries. Since they usually age their wine for months or years degassing is a lot less of a problem for them."

I'm as convinced as it's possible to be that any commercial winery would use mechanical degassing if it speeded up maturation with no unwanted side effects. If a home-made wine is stored in a cool place (as it should be) then the low temperature is going to encourage the CO2 to come out of suspension anyway.

A very light home-made wine (most flower wines, for instance), if treated properly, can be ready to drink a month after finishing. They'll go on improving for a while but if we're looking at speed, then a month seems OK to me. From the experience of my own taste buds, I reckon that a wine which has been severely assaulted with a fast-spinning bit of metal will take about a month to recover anyway.

I just don't see any point.

[Odsox]

If a home-made wine is stored in a cool place (as it should be) then the low temperature is going to encourage the CO2 to come out of suspension anyway.

Is that true Mike ?
I have to say I know nothing of dissolved carbon dioxide, and even less about wine making, but I do know a thing or two about dissolved oxygen in liquids, and that is just the opposite. Dissolved O2 will come out of suspension at high temperatures and be at it's maximum stable concentration at just above freezing point.

[Zech]

Dissolved O2 will come out of suspension at high temperatures and be at it's maximum stable concentration at just above freezing point.

That's interesting. If you want to dissolve solids in water (e.g. sugar), then more can be dissolved at high temperatures. It's possible to get a supersaturated solution by dissolving as much sugar as possible at high temperature, then gently cooling.

As for wine, in my limited experience, storage for six months in my fairly cool store room does not always result in degassed wine. I know nothing about about spinning bits of metal; my solution is to use a vacuum pump. You know - the very simple kind that are sold with rubber stoppers for keeping half-drunk bottles of wine. That's pretty effective, though it can be a lot of work with a young blackberry wine.

[MKG]

But it's not in solution - it's in suspension. Tiny, tiny bubbles of CO2 being wafted around by any little thermal disturbance. As the wine gets cooler, those thermal currents lessen and the bubbles have a greater chance of actually reaching the surface and dispersing to atmosphere. Any CO2 in solution will contribute to the overall acidity of the wine and can be adjusted chemically.

[Odsox]

Ah sorry, I thought you were referring to dissolved CO2, like you get in Champers.

Zech, dissolved gasses are a bit different to dissolved solids and different rules apply. Dissolved oxygen in water is necessary for fish to breathe (or absorb oxygen). That is why salmon, which need large amounts of oxygen, are restricted to cooler waters. The warmer the water the less O2 it can absorb, or sustain.

[MKG]

My fault - I did use the term dissolved in the initial post.

I will scourge myself later.

Mike

[MKG]

Zech, using a vaccuum pump to degas is one of the accepted methods, but it's always concerned me a bit. If you lower the pressure, you're going to increase evaporation and alcohol evaporates a lot more easily than water. If the wine stays under decreased pressure for long enough, the ABV will be lowered, which is a bit upsetting after you've spent all that time and effort getting it to where you want it to be in the first place.

How much effect a partial vacuum may have, though, is beyond my knowledge. Odsox has just exposed himself ( ) as a knowledgeable chap in that area - over to you, Lavoisier

Mike

[Odsox]

Sorry Mike, my knowledge of dissolved gasses is from Biological Oxygen Demand (BOD5) in seriously polluted water, as in water mixed with slurry. I can talk all day on that subject, but maybe not a lunch time topic and quite irrelevant anyway.
I'll have to watch exposing myself in future (not literally though).

That statement has now probably popped up on someone's screen in an Internet Big Brother Government department somewhere.

[Zech]

But it's not in solution - it's in suspension. Tiny, tiny bubbles of CO2 being wafted around by any little thermal disturbance. As the wine gets cooler, those thermal currents lessen and the bubbles have a greater chance of actually reaching the surface and dispersing to atmosphere. Any CO2 in solution will contribute to the overall acidity of the wine and can be adjusted chemically.

I have now spent far too much of this morning learning about solutions, colloids, and suspensions. This website http://chemwiki.ucdavis.edu/Physical_Ch ... es/Colloid gives a nice clear explanation - the difference is defined by particle size. I've found no mention of gases in suspension (the largest particles) and if it was a colloid, gas in liquid would be a foam. I think, whatever the Winemaker's Academy says, the carbon dioxide is dissolved, but I'm prepared to be educated if you have better information, Mike.

My skepticism about WA's chemistry is reinforced by this this point: "Carbon dioxide increases the sensation of acidity in wine. While the acid isn’t really there it tastes like it is." No, carbon dioxide dissolves to form carbonic acid. It actually increases the acidity, it doesn't perform some magic trick on the taste buds.

Zech, dissolved gasses are a bit different to dissolved solids and different rules apply. Dissolved oxygen in water is necessary for fish to breathe (or absorb oxygen). The warmer the water the less O2 it can absorb, or sustain.

Well I've learnt something. Thank you.

Zech, using a vaccuum pump to degas is one of the accepted methods, but it's always concerned me a bit. If you lower the pressure, you're going to increase evaporation and alcohol evaporates a lot more easily than water. If the wine stays under decreased pressure for long enough, the ABV will be lowered, which is a bit upsetting after you've spent all that time and effort getting it to where you want it to be in the first place. Mike

I hadn't thought of that. Do you think wine stored with those pumps will gradually decrease in strength? I'm not actually that bothered about precisely what the ABV is, provided the wine tastes OK. I only use the pump for about 15 min on average, so I doubt there's much evaporation in that time, anyway.

[MKG]

Well, let me try to go back to my long-distant schoolboy chemistry.

If you dissolve sugar in water to obtain a sugar solution, then you still have sugar and water (there's no chemical reaction and the sugar is recoverable). If you dissolve carbon dioxide in water, then something slightly different happens. Rather than simply dissolving, the CO2 and the water actually take part in a chemical reaction and what you end up with is carbonic acid (H2CO3 - can't do the necessary subscripting). Stick a vacuum on top of H2CO3 and you end up with just that - a vacuum on top of carbonic acid. The original CO2 will not surrender and dissipate into the vacuum because it no longer exists as such.

Chuck a base into there (let's say precipitated chalk for the sake of the argument) and you then get the desired release of the CO2 as the result of yet another chemical reaction. That's why you can buy precipitated chalk from winemakers' suppliers.

You can also mechanically whip a carbonic acid solution to death with an electric drill-borne gadget from the same supplier and the carbonic acid, despite having a rather exciting fairground ride, will just stay where it is. The only form of CO2 which can be extracted mechanically is free CO2 in the form of bubbles (very small bubbles, I give you, but bubbles nonetheless).

Given that my schoolboy chemistry precedes the Vietnam War, this may all be poppycock - but I'm pretty sure it still stands. I hope so, or else I'm going to look like a complete idiot (quiet at the back there!!!).

Mike

EDIT: You are, though, absolutely correct about ...

"Carbon dioxide increases the sensation of acidity in wine. While the acid isn’t really there it tastes like it is."

... which is, as Shakespeare put it, bullshit.

[Zech]

Well, let me try to go back to my long-distant schoolboy chemistry.

If you dissolve sugar in water to obtain a sugar solution, then you still have sugar and water (there's no chemical reaction and the sugar is recoverable). If you dissolve carbon dioxide in water, then something slightly different happens. Rather than simply dissolving, the CO2 and the water actually take part in a chemical reaction and what you end up with is carbonic acid (H2CO3 - can't do the necessary subscripting).

Oh! So "dissolve" means different things with relation to sugar and carbon dioxide? Hmm, I think I need to do more studying...

[Odsox]

... which is, as Shakespeare put it, bullshit.

For goodness sake get your quotations right Mike, Shakespeare said "oxenshit"

[MKG]

I am mortified. Of course. Sos, Bill.

OS will, I'm sure, replace BS as the standard defintion of, well, OS