Aerating/degassing Wine

[CanadianJesus]

Does regular fruit/grape wine need to be aerated and de gassed as much as mead does? I understand that mead is much harder to infect than wine or beer, so I'm just wondering if regular wine needs to be opened to be degassed and aerated as much (daily) as mead does?

 

[jgmillr1]

In my opinion, wine never needs to be degassed. It will naturally degas over a short few weeks. After all, when you open a soda goes flat pretty quickly even without you shaking it. The whole degas process risks oxidation with the only benefit that it slightly speeds up time to bottling.

 

[Yooper]

At the beginning of fermentation, the wine is often stirred to break up any cap that forms and to release C02. After the wine reaches 1.020 or so, it can be moved to secondary and airlocked.

 

[CatawbaCat]

Wine will naturally degas with time. I don’t do more than splash rack and age, and I’ve never had a problem with it.

 

[CanadianJesus]

Ok thanks. I just added my last round of nutrients (not much as this is wine, but it is mostly sugar with water and 5 bottles of Welch's grape juice). This is not going to finish as a wine as I intend to use heat to extract the alcohol if you know what I mean (new rule, I'm allowed to talk about this on this forum now )

 

[JimRausch]

My question along these lines is : I understand that the degassing is done to get rid of CO2 which if allowed to build up is toxic to yeast, and we want the yeast to get every gravity point they can. But why aren't we worried that all that agitation will lead to oxidation? Is it just that wine is not beer and don't worry?

 

[CanadianJesus]

I'll probably degas it once more tomorrow and check gravity. If it still has a ways to go I may degas one more time, but I have a feeling that when I check it tomorrow it will be nearly done fermenting as it has picked up speed rapidly as of the last few days.

 

[jgmillr1]

get rid of CO2 which if allowed to build up is toxic to yeast

If this were true then champagne could not be made via the champenoise method. Fortunuately for us, Dom Perignon and Moet have proven for hundreds of years that CO2 build up is not toxic to yeast.

 

[JimRausch]

Is there still live yeast in champagne bottles after it's finished? I can't remember where I've read it and I'm not anywhere near my copy of 'Yeast", but my understanding is that one reason yeast reach their attenuation limit is that the buildup of CO2 drops the pH below their comfort level.
And it brings back my original question- why do makers of wine and mead degas their fermenting product?

 

[jgmillr1]

Is there still live yeast in champagne bottles after it's finished?

No, the yeast is riddled to the the neck of the upside down bottles and disgorged.

buildup of CO2 drops the pH below their comfort level.

The pKa of carbonic acid is 3.6. Significant carbonation of a beverage is under 10g/L CO2 which is about 0.15 mole/L. So in short, acidification due to dissolved CO2 alone never gets close to driving the pH even to 3.6. And the yeast are happy as can be at that pH anyway.

And it brings back my original question- why do makers of wine and mead degas their fermenting product?

and that brings my original response

In my opinion, wine never needs to be degassed

 

[CanadianJesus]

Strange. I will need to run a side by side experiment with mead to test this. My most recent batch of Bray's One Month Mead turned out far better than my first ever batch or the one I screwed up by adding DAP too late and it seems like degassing is a very important step in the process. I guess I will have to donate $40 in honey to do this experiment for the sake of science. And yes, honey is that expensive nowadays if I want the best locally sourced stuff available to me. This is going to be two 1 gallon batches I'm talking about too.

But yeah, I haven't opened up my fermentation pail since my second and final nutrient addition for fear of oxidation and it seems to be fermenting along happily. I won't take any gravity readings until I stop seeing airlock action to determine whether or not it's actually finished fermentation.

 

[hambiguous]

I just opened two bottles from a winery in Wyoming that were slightly carbonated. Tasted great. Not sure why it would be necessary and I concur that it would naturally degas IMO.

 

[bernardsmith]

I guess I don't really understand the anxiety people have about oxidation during active fermentation. Half the weight of the fermentables is produced as CO2 and that CO2 is being belched out and will have saturated the mead and be blanketing the liquid. How will oxygen (read, air) burst through that pressure to glom onto the ethanol being co-produced? If you bang home an airlock and fill it with water the pressure, coming from the liquid, is clearly and unquestionably greater than the pressure coming from the air.

OK - on the other hand, the CO2 that is saturating the mead creates two problems - the first is that like a diver that is swimming a couple of hundred feet under water the yeast is subject to enormous amounts of pressure, relatively speaking, and the greater the gravity you began with the more pressure this yeast needs to endure. That's a recipe for stress and stress is a recipe for poor quality mead. Strike ONE.

Strike TWO is that CO2 drops the pH of the mead and pH in connection with honey can be a messy problem, honey having no chemical buffers to control the pH which can (not always, but sometimes) swing enough to cause the fermentation to stall.

So, we have a model where oxidization is unlikely to occur given the amount of CO2 being produced and a model where the amount of CO2 being produced is likely to stress the yeast mechanically and chemically. Degas? Don't degas? My money is on removing the CO2 DURING ACTIVE FERMENTATION - and that has nothing, nada, zip to do with reducing the time to bottling and everything to do with removing potential problems from the fermentation... Defense rests.

 

[bernardsmith]

If this were true then champagne could not be made via the champenoise method. Fortunuately for us, Dom Perignon and Moet have proven for hundreds of years that CO2 build up is not toxic to yeast.

Not sure I follow your point. When Moet and Dom Perignon make a sparkling wine they allow the wine to ferment bruit dry and allow that bruit wine to age for as many years as is their wont. Just before they are ready to bottle they add a little sugar together with a priming yeast. That yeast needs to be quite specially cultivated in order for it to thrive when pitched into a high ABV solution. That yeast is used to PRODUCE CO2 - not to thrive in a high CO2 environment. In fact champagne bottles hold about 9 g of CO2. (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3275598/) So, neither Dom Perignon nor Moet have proven anything about the lack of toxicity of CO2 during the active period. Their method of producing a sparkling wine side steps the problem. It doesn't challenge it. Sorry, jgmiller1.

 

[jgmillr1]

Degas? Don't degas? My money is on removing the CO2 DURING ACTIVE FERMENTATION

Feel free to degas if that is something you desire to do. There is far too much anxiety about degassing. It is not done commercially, which should tell you all you need to know.

When Moet and Dom Perignon make a sparkling wine they allow the wine to ferment bruit dry and allow that bruit wine to age for as many years as is their wont. Just before they are ready to bottle they add a little sugar together with a priming yeast.

Yes, the wine is initially fermented dry in tanks then racked into bottles with a carefully measured amount of sugar and yeast (aka the dosage), the bottles are capped, fermentation proceeds and then the wine is aged under pressure with yeast for up to several years. The bottles are finally riddled and the yeast disgorged at final corking.

My point is that IF dissolved CO2 is so toxic or stressful to yeast during regular fermentation at normal atmospheric pressure, then they would never be able to continue to thrive and build up to the 6 atmospheres of pressure typically achieved during the methode champenoise used by countless sparkling wine producers around the world.

And I'm sure nearly every home winemaker who has ever made a sweet wine will attest to corks being blown out of their bottles at some point from bottle refermentation, so it is not as if Dom or Moet are using a special magically CO2-tolerant yeast strain.

The main factors to a successful primary fermentation are keeping the temperature in the correct range, ensuring the yeast has sufficient nutrients, and protecting the must/wine from spoilage organisms. Degassing is both unnecessary and increases risks of spoilage.

 

[bernardsmith]

Let's, for the sake of argument, assume that Moet, for example, does not actively degas but clearly some CO2 leaves the barrels just as some oxygen enters the barrels (micro-oxygenation) and some wine evaporates from the barrels (the angels' share). Yes? Then Moet has absolutely no way to control precisely how much CO2 is in any bottle since "this" batch may have much more CO2 still trapped than "that" batch. So are they then measuring the amount of CO2 in each batch before they add more sugar (this precise but presumably VARIABLE dosage) since the precise dosage must be determined by the amount of "residual" CO2 in the batch? Because if that is NOT what they are doing then any bottle you buy would have an unknown volume of CO2 in it - and possibly enough to create a bottle bomb... Their insurance would be astronomical... and of course, it might be...

 

[jgmillr1]

Not sure how barrel aging came into this thread as it has nothing to do with sparkling wine production. Yes, aging in barrels (typical for quality dry red wines but not whites) utilizes micro-oxygenation for tannin polymerization. Evaporation through the wood of both water and alcohol occurs. I typically lose ~1L per month in 53-gal barrels, depending on the barrel age and temperature/humidity. Any residual dissolved CO2 will degas on its own over the course of the year it ages.

Moet/Dom do indeed control precisely how much CO2 is in each bottle by precisely controlling the sugar addition during dosage. As you commented earlier, the sugar determines the amount of CO2 produced. These are most certainly little bombs and I noted upwards of 1% of the bottoms of the bottles were blown out when I toured Freixnet in Spain a few years ago. I honestly doubt that any sparkling wine operations in the US would allow tours like that given the potential for one blowing and getting sued.

 

[CanadianJesus]

Well I recently read an article on open fermentation of wine, where much more CO2 can escape much faster than the traditional method of using an airlock during primary. I notice a lot of people in the mead forum do exactly this, placing a towel over the bucket rather than clamping down the lid and fitting in an airlock. I can't do this due to cats. I recently made my first ever grape wine, and I stirred to degas and aerate up until the halfway point of fermentation to sort of simulate this. I tasted it recently and it already tastes like a half decent table wine. I assume that my methods produced a better wine than I would have ended up with had I just clamped down a lid, fit in an airlock and forgot about it until I stopped seeing airlock action. At my last gravity reading, there was only about 15 points of sugar left to be fermented, so it should be done any day now. I'll taste it then and see how it changed.

I also added half of my nutrients up front, and the other half of my nutrients halfway through fermentation. It seems that the process of making wines and beers is evolving quickly due to instant access to years of experience and experience sharing via the internet.

 

[Yooper]

Winemakers often stir to break up the cap- and to resuspend any fruit that is on top so it doesn't dry out. And by stirring, some of the c02 is driven out, for healthier yeast. Oxidation is bad for wine, of course, but during active fermentation that is not an issue. When the wine reaches a SG of 1.020 or under, the wine is generally racked to a carboy, topped up, and airlocked at that point to protect it from oxygen.

 

[Yooper]

A brief (free) snip-it from a paper on the subject:

Inhibition of yeast function by ethanol and by high substrate concentrations is well recognized and, to a limited extent, quantified. The role of carbon dioxide in affecting yeast metabolism (particularly growth processes) is not clear although inhibition is generally found at moderate to high concentrations of the dissolved gas. A similar situation exists with other microorganisms and with other fermentation systems. An understanding of the role of carbon dioxide, and particularly of its inhibitory effects on enzyme action and membrane function, is required if the observed global inhibition of yeasts and other fermentation systems is to be partitioned to its appropriate causes.

https://www.sciencedirect.com/science/article/pii/0141022982900345

As we know, yeast will also die of alcohol toxicity as well, so by starting with the healthiest yeast possible and stirring to help disperse the c02, we can encourage the yeast to ferment. For really high ABV wines, often times incremental feeding is done to gradually acclimate the yeast. Yeast is a living organism, and as it dies, it produces off flavors so you want to keep it healthy.

 

[jgmillr1]

A brief (free) snip-it from a paper on the subject:

Yes, thank you for helping bring more scientific information to the discussion. Too often anecdotal experience replaces hard science and pretty soon people are doing the hokey pokey to get their fermentations to finish.

I dug through my photos of my Freixenet tour and found one that wasn't blurry. A rough count of bottles in the photo suggests under 1/2 % of bottles have their bottoms blown out. It was striking to see though and made you concerned about your head being cut off!