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Do Yeast "Swim"?

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bkisel

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Like I've noticed with almost all the wines I've done... ~48 hours after pitching my yeast there is a lot fermentation activity. Looking at the surface of the wine in the bucket it looks as if the must is about to reach a rolling boil - you can even hear the bubbles breaking surface from a short distance away from the bucket.

What is going on at this point of the fermentation with respect to the yeast moving around.. or are they? I've not stirred this batch since pitching the yeast and the fermentation is as active as batches where I have stirred. How is it the the entire surface of the must/wine is bubbling? Are the yeast swimming around? Are the just sitting on the bottom of the bucket kinda evenly dispersed and doing their thing?

Thanx...

Ps. I've seen microscope videos of yeast budding but not of actually pooping alcohol and CO2.
 

AZMDTed

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I don't know how much swimming they do, but they certainly do a lot of body surfing on their CO2 fart bubbles which is what I think we see when it looks like the must is roiling.
 

bkisel

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I don't know how much swimming they do, but they certainly do a lot of body surfing on their CO2 fart bubbles which is what I think we see when it looks like the must is roiling.
Yeah, I got that part about the CO2 bubbles coming to the surface. But why is it that if we've not got grape skins or such in the primary there is no need for stirring? I'll often stir just to be involved in the process but from my experience the stirring is not needed - the yeast will do their thing well enough without my stirring. How do they do that?
 

AZMDTed

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Just my educated guess, 2 things in action:

1. Slight temperature differences in the must will create currents that carry the multiplying yeast all over.

2. The CO2 bubbles will rise, being lighter than must, hit the surface and pop. Without the CO2 to hold them up, the yeast will then start to sink and the process repeats itself.


At least that's my thinking.
 

bkisel

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Just my educated guess, 2 things in action:

1. Slight temperature differences in the must will create currents that carry the multiplying yeast all over.

2. The CO2 bubbles will rise, being lighter than must, hit the surface and pop. Without the CO2 to hold them up, the yeast will then start to sink and the process repeats itself.


At least that's my thinking.
Both your points make sense to me, especially number 2.

BTW, room temp is 70F and must is 78F in a standard 7.5 gallon primary bucket with just a loose lid on the bucket. That temp delta kinda amazes me. The yeast packet was at room temp when sprinkled two days ago, how does all that heat get generated? I know it has to do with chemistry and physics but it still amazes me.
 

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