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Jun 08, 2022 View:

Sulphur and oily

We're making a variety of products including vodka, gin, and starting to age some bourbon. On our bourbon stripping runs (no plates, just pot, helmet, condenser) we are getting a sulfur smell in the low wines and they are fairly oily. In fact, I get some residue in my holding tanks after the low wines are removed. The distillate cleans up nicely on the whiskey run but I keep wondering if we are doing something wrong.

I know corn has a tendency to be oily. I've cleaned my still to make sure I'm getting good copper contact to remove the sulfur. Another distiller mentioned to me that my yeast might be stressed but I've spoken with a few folks I know in the yeast business and they don't think it's a bad fermentation. The fermentations smell fine and we're pretty religious about cleanliness. We're using 60% that the culprit and it's just the way it is?


WIthout seeing things first hand, a few things can be the culprit. How active is your fermentation? Are you able to consume all your sugars? How many days is your fermentation? How many days after you reach terminal gravity do you ferment? What temp do you pitch at?

It could simply be your yeast strain, although that's a bit unusual for a top fermenting strain.

If you're happy with the aroma and flavor of your distillate after it's been fully aged, it's likely just that you don't have enough copper in your wash/mash still, and the second distillation and re-exposure to copper is cleaning it up.

If you have a place in the first still to place some cut up copper pipe in the vapor path....that's your cheapest and simplest 1st step to solving this problem.....if you consider it to be a problem.

And no, it's not the corn, assuming you're using clean corn.

Edit to add.....I forgot to address your residues. They're SOP, and the main reason Bourbon or Corn Whiskey tastes sweet, and has such a nice mouthfeel. So long as they disappear after the second run, you're all set. You shouldn't see the same thing in your spirit still.

Also, if you use malted barley, you can get DMS-P if the malt is kilned at too low of a temperature....but this is an unlikely source for sulphur that's noticeable after one distillation, but not noticeable in your fermented mash.


Our mashes have been anywhere from 22 Brix to 24 Brix. We were pitching at 30C (around 3 in the afternoon) but found that by the time we got back the following morning, that the fermentations were too hot, around 36-38C. We've since began pitching around 26C which allows us to come back the next morning before the temps start to get too high and monitor the cooling.

We are fermenting in closed tanks, only venting off the CO2 via a hose in a bucket. It usually stops fermenting after 4-5 days and we distill it on the 6th or 7th day. It's about 10 Brix when it's finished. We don't roll or mix our fermenters. Our equipment supplier has recommended that we do it everyday, but some other folks say it's not the best idea as it could lead to bacterial infection. I'm unsure how to proceed. The fermentations are in the 28C to 32C range cooling with fresh water in our jackets.

We are using malted barley, it's a distillers malt from Cargill.

I'm going to get a little more aggressive on the Acid part of the CIP this week and really clean my still. We'll see what happens.


Ok, you asked, so here's my suggestions:

Finishing at 10 Plato is a big, big problem. Your Final Apparent Gravity should dip below zero Plato. We can worry about Real Gravity some other time. You're losing a TON of extract from your mash, and spending nearly twice as much on your grain as you should.

If you're starting at 22 and finishing at 10, you're getting a distiller's beer of around 6.9% abv.

You'd be much better off shooting for 13 Plato (essentially a standard German Fullbier), and getting that finishing gravity down to zero.

If you're crapping out at about 10 Plato, you've got some fermentation or mashing issues. You could be underpitching, or underaerating your mash, leaving your yeast unable to reproduce before fermentation. 10 Plato is what is known as a hung fermentation, and this could lead to all kinds of congener issues, the least of which is sulphur.

Funny how a little more info. can totally change your diagnosis. How much yeast are you adding? Is it dry, or liquid? How many cells per ml are in the yeast slurry are you pitching? I see you're pitching at 26 C. I'd drop that down quite a bit to eliminate the chance that high temps are cooking your yeast. I can get one recipe for a 15 plato Bourbon mash down to 0 Plato in less than 4 days starting at 20 C.

How are you mashing the corn and distiller's malt.....time, temp, pH, etc.? How much D. Malt are you using, expressed as a percentage?


Denver....Can we talk on the phone?

Anyway, I'm using 60% corn, 20% wheat, and 20% malt. I go up to 90C, hold and then go back down to 60C to add malt and then hold. I take it down to 26C and pitch my yeast. I'm about 5.5-5.8 when I add the corn and wheat and its about the same when I add yeast. While I'm holding my malt to get my last conversion, I'm use a dry yeast and hydrate it in RO water. I use about 2.75 pounds of yeast per 2200 liters of mash. It usually hydrates for an hour or so before I get the mash down to 26C and it's pitched.

To measure Brix, I'm using an electronic meter. I guess it could be off, but that's probably unlikely.

Edit to add....

I wonder if something isn't reading correctly on my meter because I get lots of yield. I'm getting 200-220 PG out of 3000 pounds of grain.

Also, I wonder if I should be rolling the fermenters during the process. As I mentioned, there is no aeration or mixing at all....just letting the yeast do it's thing.


Dropped my phone in a pail of water over the weekend, so no can do until tomorrow ! : ) Whoops.

I'll send you my # via pm.

22 Brix (Plato, percent sugar, whatever) is a tall, tall order for any yeast strain but the very toughest (champagne yeasts, a couple ale strains I'm aware of). You need a bunch of FAN, zinc, etc, but above all, a whole bunch of oxygen. Some brewers I know would oxygenate twice in with a brix this high, or add kraeusen to mop up the remaining sugars. If I were you, I'd find a way to oxygenate that mash with the yeast already pitched.

But your yield in proof gallons doesn't make any sense to me, given the data you've sent. It makes sense that your yeast would poop out in a 22 Brix solution with no added oxygen. But it doesn't make sense to me that you're able to get ~80% of the total theoretically available alcohol in your fermented mash, when you're leaving a full 10% Brix in an unfermented state. I'd absolutely check your math as well as your instrumentation.

Hope this is helping. We'll speak this week.



Y'know, we all are interested in not only the solutions, but the problems. I would appreciate hearing the full story , so the more that is done on PM or telephone, other than select sensitive informantion, would defeat our purpose of information exchange. Also there are some who "hide in the weeds" until they have an opportunity for a unique contribution can be made. You would not like to exclude their contribution. I look forward to hearing the continued story on this.


Bob Ryan


Fine by me, Bob. I can never tell if this stuff is helpful because so few respond.



I'll put as much as possible down on here without giving away too much. I'm much better talking things out on the phone, so that was why I suggested it. Either way, if I figure out my problem, I'll put it down here.

Denver, I wonder if I'm getting poor readings because I'm reading Brix with the grain in the mash. For instance, I don't get good test results with iodine test, but after talking to some very experienced folks (including the old Master Distiller for a large corp) he said that iodine tests on a grain mash usually don't work so well since there's always some grain that doesn't convert.


Do you have hydrometers for Brix? Double check the meter. I don't trust iodine for bourbon mashes either.


You think my PH is too high?

5.5-5.8 at corn mash in takes a bit of citric.

I need some more citric to get down to 5.5 at malt mash in

And more citric to get down to 5.0-5.5 at yeast addition.


No. A pH of 5.5 will work just fine assuming that we're simply trying to get starch conversion, i.e., we're trying for optimal pH for enzymatic degradations. A pH of 5.8 is too high, imho.


Some more notes for those interested....

I put the mash into the tank on Monday around 5PM at 24 Brix and a PH of 5.4.

This morning, I took a Brix reading and it's at 12. PH is 4.5.

Smells great.


PM sent with my phone number.......


Hey all,

I agree with Bob...great info and I'd be waiting in the weeds. Thanks for posting! very interesting read.


Spoke with John in WV yesterday. I'm sure he'll post more about what we hope are the solutions when he has time.

Cheers, and happy and safe distilling.........


Thanks Todd for your time on the's greatly appreciated.

I'll be mashing on Monday with some of the changes we discussed and then we'll see what happens at the end of the week. I'll post my results.

I mashed this Monday and rolled my fermenters once on Tuesday. I have a feeling this is going to help drop the Brix as well but I don't have any hard evidence yet. I will say that the bubbling in my C02 bucket seems to have kept a more steady pace early on and slowed down faster. My fermentation temps are also more steady. I'll check Brix tomorrow.