Brix vs. ph level vs. fermentation time in rum distillation

[Alexdistills]

 Hello, I’m in the process of distilling a %100 blackstrap molasses rum. I’ve done a lot of small 30 gallon fermentations and seemed very successfull. Using backseat(dunder) and infected fermentation or muck pits? Infected backset. My biggest questions are what’s the most important? Brix level? Or starting gravity, amount of sugar? Is it the ph level? 4.5-5 to start? My goal is to ferment for 3 weeks. Then strip and spirit run. I am using a 100 gallon pot still. 
 

 My last ferment yielded 60 gallons at 25.5 proof. Does this sound right? Can I be doing something more efficiently? Thank you cheers. 

[stillwagon]

If you have had previous success, you should repeat the process but measure your brix and pH at the beginning and at completion of fermentation. 12% is a good place to be at. Then scale up. Larger fermentations will require cooling.

[JustAndy]

On 10/18/2022 at 5:56 PM, Alexdistills said:

 

 My last ferment yielded 60 gallons at 25.5 proof. Does this sound right? Can I be doing something more efficiently? Thank you cheers. 

It is impossible to say, as you don't say the volume or gravity of the wash it was distilled from. 

[Alexdistills]

Hello stillwagon, thanks for the reply. What do you mean by cooking? Cooking the wort? 
 

Justandy, you are correct! Totally forgot that. The last ferment was 225 gallons, honesty I tried to just hit a target of 10 Brix at 225 gallons then ferment down to 0-1 Brix. Which I did. And that was my yield of 60 gallons @ 25.5 proof. 

I did start a new fermentation this one is at 15 Brix 175 gallons. Gravity of wash was 1.0553. Potential alcohol around 7.53% ? Cheers, 

[Stonecrest Distillery]

Do you mean 25.5% = 51 proof or am I reading this correctly at 25.5 proof = 12.75%.  Asking to understand true yield.

[stillwagon]

It was supposed to say cooling. Larger fermentations generate their own heat.

I start at 20-22 brix, and do a second feeding at 30% sugar depletion.

[Alexdistills]

Hi stonecrest, yes it’s 25.5 proof so 12.25 percent at the end of my stripping runs. Does that sound appropriate or can I get a bigger yield? 

[stillwagon]

It should be around 10-15% after fermentation. I get about 45-48% after stripping, and about 80% after my finish run.

[Alexdistills]

So I’m not getting those higher numbers, so I feel when I go to do my spirit run I’m not going to be able to reach that 80%. Is that a fair assessment? And I should prob try a second feeding of the fermentation with bigger ferments? 

[stillwagon]

It sounds like there are a number of issues. Molasses fermentations tend to crash pH causing it to stall. I buffer pH with calcium carbonate, and adjust with calcium hydroxide. I use a number of fermentation supplements to aid yeast growth and fermentation. I also control fermentation temperature. Warmer temps speed fermentation and if too warm, stress the yeast. Cooler temps stretch out the fermentation. What type of molasses do you use? I use a baking grade black strap. Some feed grades and agricultural grades don't ferment well, and produce off flavors. Some refined molasses are not much more than a can syrup, which needs yeast nutritional supplements.

What type of yeast do you use?

Do you add any fermentation supplements?

Starting pH?

Finish pH?

Fermentation temperature?

Second feeding is accompanied with additional yeast nutrients and pH adjustment. It will depend on what type of yeast you use, and if it can tolerate a slightly higher abv.

[Alexdistills]

Thank you stillwagon. I have been using organic sulfur free black strap molasses. My last ferment I used a Belgian strong ale and distiller yeast blend plus yeast nutrient fermaid. Starting ph 4.5 

fermentation temp 80-77 degrees down to 60 degrees. 

[stillwagon]

I keep my pH above 5 to keep a robust fermentation. When the pH drops below 4, it usually stalls. Temperature is maintained at 81f + or - 1 degree and it ferments out in 7 days. 85f in 5 days, 90f in 3 days. I don't ferment above 85 anymore, I don't care for the flavor.