Molasses rum fermentation stuck

[RandallThorp]

Hey everyone,

I'm hoping to get some advice on my latest batch of SBB rum with some tweaks. This is my fifth time making it, but unfortunately, the fermentation seems to have stalled completely. My previous 4 batches were back-to-back, so it was easy to follow the recipe exactly, but there's been a gap since I last ran it and I added a couple of variables.

Here's what I did (and what went differently this time):

1. No fresh dunder: My last run was 9 months ago, so the dunder I had was aged and infected. I think it is called muck at this point. I boiled it for 30 minutes before adding it to the molasses.
2. New yeast: I tried Omega Hornindal Kveik yeast for the first time.
3. Under-pitched initially: I heard this helps with funky esters with Hornindal, but after 48 hours with no activity, I added more yeast.
4. Low pH: Checked the pH after another day - it was below 4.01! I calibrated my tester and confirmed the reading. Raised the pH to 5.26 with oyster shells and 2.5 tsp lye.
5. Confirmed yeast viability with a starter: Made a starter with the Hornindal yeast, and it fermented well, proving the yeast was alive.
6. Switched to Red Star: After further inactivity, I pitched a healthy amount of my usual Red Star yeast (used in previous SBB batches).

Additional details:

• Temperature: Started at 95°F for Kveik, then lowered to 89°F after day 2. Used a ferm wrap hooked to a Inkbird temp controller and Reflextix insulation in a Styrofoam cooler.
• Molasses, Fermentation vessel, and Top up: Used the bottom roughly 1.5 gallons of Golden Barrel Blackstrap molasses and the bucket it came in - no other fermentables. Blended the hot dunder with molasses. My pressure washer didn't want to cooperate that morning, so I used tap water and an immersion blender for aeration. Topped up with water to reach 1.055 OG.
• Extra aeration: Used an electric whisk when adding the starter for additional oxygen.

It's been 8 days now, with absolutely no bubbling or activity. The gravity remains at 1.055.
I'm at a loss here. Is there something I'm overlooking? Can I still salvage this batch? Any advice would be greatly appreciated!

Anyone else have experience using aged/infected dunder in SBB rum? Thoughts on under-pitching Kveik yeast for funky esters - is it worth the risk of a stuck fermentation?

Thanks in advance for the help!

[JustinNZ]

Just to help: how much dunder did you use? And what was your wash volume? Are you sure about the OG? It’s very low for an all molasses wash. More of a final gravity.

[RandallThorp]

Very good questions, I should have included that info from the start.

It was about 1 gallon of dunder and about 4.5-5 gallons total wash. You're right, I was surprised too because the gravity is pretty dang low - perhaps I had less molasses in the bottom of that bucket than I thought. I was eyeballing it, but In hindsight I should have weighed the bucket.

When I drop molasses in the Brewer's friend calculator, it tells me that I may have had as little as 3/4 of a gallon or 8lbs which which is half of what I assumed. That's a pretty silly mistake.

I don't believe that it has fermented, because the sweet taste is still there. My previous SBB runs that were precisely following the recipe finished much drier.

[JustinNZ]

Hmmmm. So it seems like your dunder and molasses are unbalanced and the yeast aren’t happy. Could you add some water - I don’t know if you’ve got much space, but a gal or two - and a couple of kilos of sugar - any sugar- and see if that makes for a better wash. Also it could turn into an experiment of a lighter style. But you can always blend your final product with existing ones.

Or if you have more molasses available (and another's big bucket) you could split the current wash in half and make two new washes that are close to your previously successful efforts.

I only had one stuck SBB and it was I think because I put way too much molasses in by mistake. I diluted it, aerated, warmed up and repitched and it came back to life.

Others might have better ideas.

[MooseMan]

I'm with Justin.

Split it over 2 vessels, add water and more molasses (Sugar if you have to) and aerate the living shit out of it.
Add bakers and keep at 30-35c

[RandallThorp]

Thank you both for your suggestions. I'll try that! I have some panela on-hand, so I may go for that as that was the bottom of my molasses bucket. Time to order some more of that too!

Thank you again and I'll report back with what happens!

[MooseMan]

Thank you both for your suggestions. I'll try that! I have some panela on-hand, so I may go for that as that was the bottom of my molasses bucket. Time to order some more of that too!

Thank you again and I'll report back with what happens!

Yeah please do let us know how it turns out Randall.

[NZChris]

What was the pH?

What is the pH?

[RandallThorp]

What was the pH?

What is the pH?

It was 4.01 and is now 5.26 after adjusting. Thank you, NZChris

[Yummyrum]

When you say you topped up with water to 1.055 , were you aiming for that , or is that what it ended up when you followed Saltys recipe proportions ?

Did you use only 10% Dunder ?

The OG for this recipe is typically closer to 1.130
The pH is typically at around 5-5.5 initially .

All very strange .
I often use Dunder that has been sitting around for 6-9months and have never had issues with it . I also boil it first and have done same as you with just using a hose ti top up and use an aerator ( paint mixer in a Drill)

[RandallThorp]

Yummyrum, thank you for your probing questions - you led me to uncover another error I made. Looking at my notes, I mistakenly targeted 20% dunder. Serves me right for waking up at 4am to squeeze this in before work and not double-checking like I should have. Haha

My plan was to follow the SBB ratios - I was not targeting 1.055. Looking back, I carelessly doubled the dunder and by my calculations probably had half the molasses I thought I did in the bottom of the molasses bucket. Looks like I screwed the pooch on this batch, but it's been a good learning. After 5 rounds of success with the SBB recipe, I thought I had it down better than I actually did - embarrassing.

I'm still going to try to salvage something with panela, but it won't be anything close to the SBB rum recipe after all. Looking forward to getting another 5 gallons of molasses in to try it properly again. Thank you for helping me to see where I took a wrong turn!

[shadylane]

Looks like I screwed the pooch on this batch, but it's been a good learning. After 5 rounds of success with the SBB recipe, I thought I had it down better than I actually did - embarrassing.

Let's see the possible reasons you pissed off the yeast.
Too much dunder and almost no nutrients.
Poor abused yeast never had a chance to take off.
On a side note, are you using a hydrometer or a refractometer for the SG measurement?

[RandallThorp]

And don't forget initial under pitch!

I am using a hydrometer for the SG measurements. Thanks!

[RandallThorp]

Over the weekend:

1. I made another 1.25 L starter with the Hornindal yeast, cold-crashed and decanted the beer off.
2. I poured about 3 gallons/11L of the wash into a big 10 gallon/38L SS pot and dissolved 6.5 lbs/3kg of panela sugar into the wash with a little heat and a beefy paint/concrete mixer attached to a drill. The heat never got above ~120F/49F.
3. I added the rest of my stuck wash and about 10L of water to bring the total volume up to about 7.5-8 gallons/28-30L.
4. Agitated with the paint/concrete mixer for about 5 min to incorporate air
5. Pitched starter into wash at 97F/36C

The new wash with the added sugar was 1.109 and the pH was 5.36. 36 hours later, I'm still not seeing any activity and the hydrometer is still at 1.109.

Should I be more patient or take some action? Thank you all for your kind advice so far.

Edit: I should add that the Fermwrap is having a little more trouble keeping up with the big pot and it is maintaining about 86.6F vs the target of 92F. I tightened the Reflectex wrap this morning to try to improve the contact.

[RandallThorp]

Update, the Reflectex rewrap fixed the temp, but still no activity since this morning.

[Saltbush Bill]

When you say no activity, what are you relying on to tell?
An air lock bubbling? Sight? Fizzing or froth on surface? Hydometer readings? Sound ? Can you hear it fizzing if you get close and listen hard?

[RandallThorp]

Good question. My Hydrometer is still showing 1.109 52 hours later. There is no krausen, no fizzing, and no sound when I put my head in there - those are all normally present when I ferment. I'm essentially fermenting open; I just have a sheet of Styrofoam to cover to keep the heat in, so there is no airlock. If I stop and watch carefully for a while, there is a tiny bubble that surfaces every 5-10 seconds or so.

Should I just be more patient? I could certainly pitch dry bread yeast if that would help too. Thank you again for considering the next best option

[NZChris]

If you add more yeast, make a yeast bomb. Plenty of yeast, properly rehydrated to get it working then feed it until it's going nuts before pitching.

[RandallThorp]

I gave that a try this morning - I hope I did it right.

I rehydrated about a cup of Red Star bakers yeast in about 800ml of water at 95F/35C. Once hydrated, I added about 700 ml of my wash with a crushed B vitamin and it took off. When the krausen reached the top of the Erlenmeyer flask about 5 minutes later, I pitched it into wash. I'm hoping this does it!

[RandallThorp]

Success! I got home from work and it is chugging away after the yeast bomb. Thank you Chris for your suggestion and thank you all for your advice. I'll check back with how it finishes and runs.

In addition, my molasses just arrived, so I'm looking forward to another proper batch

[shadylane]

Success! I got home from work and it is chugging away after the yeast bomb.

I'm thinking a "yeast bomb" is a concoction of boiled yeast, DAP and epson salt that's used for nutrients.
First time I saw it was in PUGIDOGS recipe viewtopic.php?t=5994
What you did was rehydrate yeast and give it some food to make a yeast starter.

On a side note.
Pitching bakers yeast was a great idea. I use it for everything other than beer or wine.
Bakers is bullfrog tough, it can survive almost anything, even Newbie mistakes.

[JustinNZ]

Yeah baby yeah!

[Yummyrum]

Just keep Bakers close to 30°C . At 20°,it’s slow as buggery . Could take a month to ferment out .

[RandallThorp]

Thanks guys, I really appreciate it. I have my temp control set to 31C and it is cruising along now - lots of fizzing again this morning.

I'll report back when I run it. Thanks again for you help saving it!

[RandallThorp]

Checking in! The wash fermented down to 1.020. I did my stripping runs yesterday and I'm looking forward to the spirit run tonight.

With more molasses on-hand now, I'm rolling right into the next batch with proper SBB ratios.

Thank you all again for your suggestions to help me out.

[JustinNZ]

Excellent news. Rum cuts are tricky but there’s only one way to learn! Remembering that you’re going to recycle (I’m assuming) the feints can help you take a nicer, narrower hearts cut. Easier said than done, of course…

SBB’s hearts are a wonderful thing once you get them right. The smell is amazing.

Good luck out there.

[MooseMan]

This is becoming a habit, but I'll echo what Justin has said again! Haha

Make your hearts cut tight and think of everything that doesn't "Make the cut" as free bonus yield, and more flavour, on your next batch.

Even then don't expect a miracle from the keeper cut until it's been on oak for a good while. Mine was vastly improved after 5-6 months and a year later it's so much more rounded, it's like magic!

[RandallThorp]

Thank you, JustinNZ and MooseMan. I'll heed your advice! This batch is definitely not true to SBB's recipe since most of the fermentables ended up coming from panela after all, but I'll still make it a tight cut, get it on oak, and use my feints for the next round fermenting now.

I've got 10 gallons of molasses that arrived a couple weeks back, so I should have a nice little cycle going now to fill the Badmo-style barrels I'm building.

Thanks again, guys!