Why does oxygenating restart fermentation ... at least this time

[crabjoe]

When the hydrometer reading hit 1.040, I still stirring because I was thinking I wanted some yeast to settle by the time I was ready to move it to a carboy.

Two days later, I took another reading, and noticed barely any bubbles coming up and the hydrometer was still showing 1.040. The surface temp of the must was only 1/2 deg (f) more than the room temp. I was perplexed....

Since I had it uncovered, I decided I was going to degas then pitch some EC1118 to get it started again. In the mean time, I got busy and didn't make it back to the basement for about 4 hours. When I got back, I hear it sizzling... and sure as day follow's night, there were visible signs that fermentation had started again.

So instead of adding a new yeast, I added a tsp of nutrient. stirred again, and pretty much had it degassed. I just went back down and it's bubbling good still. I hit it with my infrared thermometer again and now the surface temp is 3 degs f more than the room temp. I'm guessing it's all back on track again.

So my question is, what could have caused the fermentation to stall, then to only have fermentation start back up, just because I stirred it?

 

[cmason1957]

Stirring provided oxygen, yeast like some oxygen and you have them some extra nutrition, you made them happy, they made you alcohol. I don't stop stirring until the yeast are done. You aren't degassing, at least I don't store that hard. You might be some, but that isn't the primary purpose, it is to keep the yeast in suspension, not dropping to the bottom of the must where they stop working.

 

[Rice_Guy]

you had the fermentation slow but it had not stopped

and noticed barely any bubbles coming up . . . . So my question is, what could have caused the fermentation to stall, then to only have fermentation start back up, just because I stirred it?

Oxygen is needed for cell reproduction, a larger population of yeast speeds the consumption of sugar and production of CO2 which you saw. Yes it might take a month to stop anaerobic fermentation which produces alcohol without more cell mass. , , , The unknown is would the fermentation have stalled when it got to 1.005 or so?

Patience is a virtue in wine making.

 

[Arne]

Did your basement warm up just a little bit. Sometimes all it takes is a little bit of warm air to get it going again. Arne.

 

[crabjoe]

Did your basement warm up just a little bit. Sometimes all it takes is a little bit of warm air to get it going again. Arne.

Not really, but I do keep the riesling fermenting next to the sliding glass door. The floor temp there is consistent at 55. I keep a foam mat on the concrete as a buffer and I take it's temp. That has been measuring at 59-60f. So I'm figuring the temp around my fermentation is 60f, although the fermentation bucket is sitting directly on the concrete. I keep a towel over the must and I either shoot that or if removed, I shoot the surface of the must itself. The temps between those have been a fraction of a deg.