Low ph stuck fermentation

[Ludi2shoes]

If there is any one that can help I would sure appreciate it.
I have 3 batches of muscadine 2 five gallon and 1 seven gallon batch. All 3 batches we started together and split into the three batches at secondary fermentation. The SG was 1.108. I used lalvin 71b 1122 yeast with yeast nutrient and energizer. My ph at start was 4.2. All three batches continued side by side at 70° to 74°. My 2 five gallon batches finished at .994. However the 7 gallon batch is stuck at 1.020. I made a nice starter of EC 1118 and repitched. Nothing! The only thing I can find is the ph has for some reason dropped to 2.83. I know I can mix the 3 together to get my desired results. But it is bugging the heck out of me why this one batch dropped the ph so low. The 2 five gallon batches are both at 3.63. I would love to get this batch to finish out on its own. Any help or ideas would be greatly appreciated.

 

[Johnd]

If there is any one that can help I would sure appreciate it.
I have 3 batches of muscadine 2 five gallon and 1 seven gallon batch. All 3 batches we started together and split into the three batches at secondary fermentation. The SG was 1.108. I used lalvin 71b 1122 yeast with yeast nutrient and energizer. My ph at start was 4.2. All three batches continued side by side at 70° to 74°. My 2 five gallon batches finished at .994. However the 7 gallon batch is stuck at 1.020. I made a nice starter of EC 1118 and repitched. Nothing! The only thing I can find is the ph has for some reason dropped to 2.83. I know I can mix the 3 together to get my desired results. But it is bugging the heck out of me why this one batch dropped the ph so low. The 2 five gallon batches are both at 3.63. I would love to get this batch to finish out on its own. Any help or ideas would be greatly appreciated.

While it is very suspect how one batch of must, presumably the same grapes and conditions, could have such a huge drop in pH while the others did not, the assumption is that your readings are correct. First, warm and degas a small sample of the wine, letting it return to room temperature, and take pH reading. If it's still 2.8ish, use some potassium bicarbonate to increase the pH to a more yeast friendly level, 3.2ish should do it, and see if you can get it kicked off again.

Did you take initial SG readings in all three vessels? The alcohol tolerance for your yeast is only 14%, but by the calculations of the ones that finished, you produced 15.5% alcohol on those. Did you add sugar to raise the SG of the must before you started? Any way more sugar could have ended up in the larger vessel or not been equally distributed or not mixed well before separating the batches? Just trying to help diagnose..........

 

[Scooter68]

One possiblity for the difference would be the siphoning process. IF your siphoning initially captured the wine at the bottom of the container (Logical if the tip is put on the bottom to begin with) then that must would logically contain more sediment which released more acid as the fermentation continued. My 'guess' is that the 'solids' / sediment transferred in greater percentage to your more acidic carboy. This could also happen in you started the tip of your racking cane in the upper portion of the original container and later moved it down to the bottom to get the last carboy filled - that movement down -again sucked up more of the sediment.

In any case my suspicion is that the difference has to do with what portion of the must ended up in the carboy that became more acidic. Difficult thing is that we don't like to mix the must up just before transferring.

ONE solution might be to briefly mix the contents of those 3 carboys back into your original container and then re-rack back into the separate carboys - balancing the acidity of the must in all three containers. 3.63 is of course at the upper end (Less acidic end) of the normally desired level and since the measurement is not straight line but logrithmic, the mix might achieve a more acceptable acidity in ALL three containers - something closer to 3.4x.

I imagine other ideas will be presented but that's just one thought/possibility for the cause and a solution. Personally I hate to add anything to the must if I can avoid it even just to balance the acidity.

 

[Ludi2shoes]

While it is very suspect how one batch of must, presumably the same grapes and conditions, could have such a huge drop in pH while the others did not, the assumption is that your readings are correct. First, warm and degas a small sample of the wine, letting it return to room temperature, and take pH reading. If it's still 2.8ish, use some potassium bicarbonate to increase the pH to a more yeast friendly level, 3.2ish should do it, and see if you can get it kicked off again.

Did you take initial SG readings in all three vessels? The alcohol tolerance for your yeast is only 14%, but by the calculations of the ones that finished, you produced 15.5% alcohol on those. Did you add sugar to raise the SG of the must before you started? Any way more sugar could have ended up in the larger vessel or not been equally distributed or not mixed well before separating the batches? Just trying to help diagnose..........

OG was a bit of a "oh crap" as I forgot to take the temp into consideration. Yeah I know that was a numbnuts move. But the original fermentation was done as one batch in a 25 gallon barrel. I did add sugar as a simple syrup. But nothing added after I pitched the yeast. Until I added the EC 1118 at the time I noticed it had stuck.