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mixed signals on oxygen exposure

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gordonm

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I've read two different stories about oxygen. Oxygen exposure to the must is bad, but the yeast during inoculation needs some oxygen. ok, I put my must in a five gal. plastic bucket, added camden tables and let it sit 24 hr. Then I added my yeast starter, closed the top tight so NO oxygen can get in and added a airlock. Is this correct? Should I open the top every day to check the SG or just leave it until it stops bubbling and therefore not exposing it to oxygen. I did check the sugar, acid, ta before inoculation and this is white wine. thanks, gordon
 

cmason1957

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Oxygen is a good thing during initial fermentation. Many folks (myself included) ferment open to the air or with a cloth of some sort over the bucket to keep flies and dust out. Now after alcohol fermentation oxygen is a bad thing.

So to answer your question, yes you should stir that must every day.
 

Scooter68

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In reality your wine is only 'exposed' to oxygen until that fermentation is fired up. At that point the gases coming off the fermenting batch pushes out the oxygen. That's one of the reasons for stiring during the first days of fermentation 1) to incorporate a little oxygen to keep the yeast happy until it produces it's own and 2) To keep the pulp/fruit cap wet and breaking down the fruit.

So you aren't hearing two different things, it's just that at certain point the wine generates it own protection against oxygen. Fruit flies, dust and dirt are another matter. That's why folks put a cloth cover over their buckets. Lets gases OUT and keeps bugs/flies, dust OUT. Think of it this way - Remember seeing on Halloween a witches cauldron boiling away (With dry ice fog spilling over the edge of the cauldron.) Same thing with your wine fermentation. The invisible gases are creating a protective blanket. Now as that fermentation completes, the gases are diminished and you then need protection from oxygen.
 

stickman

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If this is white wine, stir for the first few days, then close it up and airlock, it would be best to transfer to a carboy sooner rather than later. white wine is a little more sensitive to oxygen than reds.
 

balatonwine

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Remember seeing on Halloween a witches cauldron boiling away (With dry ice fog spilling over the edge of the cauldron.)
While CO2 is denser than air, the sinking fog you see is water vapor, not CO2. CO2 is a colorless gas.

That is the sinking fog you see is just water vapor cooled by the dry ice, and it is this water vapor which condenses into a visible fog. Then this visible water laden air fog sinks, not because of CO2 density, but because the water vapor is cold and thus denser than the warmer surrounding air.
 
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balatonwine

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but the yeast during inoculation needs some oxygen.
If you properly hydrate your yeast for 24 hours prior to adding to the must, then that yeast has had enough oxygen during that time period to progress on its own from then on anaerobically with the primary fermentation container air locked (as is often the process done with white wines).

But as already said by others, the CO2 produced by fermentation keeps air off the must. Many who do red wines leave the top open and just covered as they need to punch down the cap many times a day, which is easier to do if one simply needs to more a cloth off the primary fermentation container. But that also requires constant vigilance to know when to then rack and airlock to prevent oxidation when fermentation slows.

Also, some red wines are actively fermented "oxidative". You see this in some types of open "over pumping" systems. It simply creates a different wine.
 
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Scooter68

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I would say that vigilance is required for ALL wines during fermentation. Since wines can ferment at a different speeds for a variety of reasons, checking the wine at least once a day is called for with any variety of wine. Home/Hobby vintners don't always have precise temperature controls as well as varied chemistry in the various wine batches. Not everyone can check on their wine several times a day so those folks should not be discouraged simply because they are unable to pop in and check on their wines every few hours.

As to the fog comparison I mentioned - Who cares what the scientific reason is, the effect is the same, there is a blanket of CO2 on the top of a fermenting wine. The 'blanket,' be it water fog in a Halloween cauldron or CO2 in a wine fermentation bucket, covers the container and spills out as the volume rises above the lip of the bucket. THAT is the point I was trying to make. A visible gas (the water vapor) acting in the same manner as the CO2 blanket. ( Read my post please - I never called the dry ice fog a CO2 fog.)
 
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bkisel

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What you did is fine as long as you gave your must a stirring to begin with. Many of us don't lock down for primary just so we can look, stir, take temp and SG measurements before going to secondary. I generally do the later but have many times locked down after pitching the yeast and waited 2 weeks or so to pop the lid and move onto the next phase.
 

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