Sulfur smell in (nearly) all corn mash

[grumbles]

I started my first batch of corn liquor, and I've been smelling sulfurous gas coming off the ferment. The first time it happened, I walked out to the garage on day 2 or 3 and just got punched in the face by sulfur smell. I did some reading and found that corn just isn't a complete meal for the yeast, so I stirred in some DAP and yeast nutrient, and everything was clear the next day. Sadly, I didn't measure the amounts. I distilled it through this rig with the column packed with copper scrubbies, and the low wines smelled and tasted good. Well, the low wines tasted bad, but in a good way. You know what I mean.

I started another round this weekend, and I'm still detecting a faint sulfur smell even though I added DAP and nutrients from the beginning. I followed the amounts on the packages (roughly), and I'm wondering if
A) I didn't add enough
B) A little sulfur is normal
C) I used the British spelling sulphur when searching last time and missed out on 80% of the information...

Here's the recipe:

11.5 lb cracked corn, ground to course meal
0.5 lb toasted oats, ground with the corn
5.25 gal water, added to corn at a rolling boil
high temp liquid enzyme at the beginning
insulated and stirred occasionally for 2 hours before allowing to cool to mashing temp
alpha and glucoamylase added at the usual temps
held at 145 F for about an hour
cooled naturally overnight
OG 1.066 with full conversion.

3.5 grams DAP
3 teaspoons Fermax yeast nutrient
Aerated with a drill for as long as it takes me to get bored. Say, 90-120 seconds.
Red Star baker's yeast sprinkled over the top.
Temps are holding around 74 F on PID controllers.

[NZChris]

Smell the corn. Could it have come from there?

[grumbles]

It's all gone now (or else I'd have 12lbs in there), but I don't recall any sulfur there. It was just pungent and sour.

[NZChris]

What was pungent and sour? The corn?

[grumbles]

Yeah, the dry, unground corn. It's feed corn.

Dang, I just remembered that I only stirred the nutrients into one of the two buckets. The other one got it at the same time as the yeast, post-aeration. Could that contribute?

[NZChris]

Not all corn is the same. I had the misfortune of buying some cheap feed corn from a neighbor that smelled like poo. Freshly harvested, so age wasn't the problem, the problem was the variety.

[Saltbush Bill]

Most ground / crushed grains supply ample nutrient for the yeast without adding any.

[PalCabral]

Feed corn is not uncommon to create sulphur smells so it’s most likely the source. Buy from somewhere else next time, or use flaked corn.

Sulphur develops easier in warm ferments, so you could try to ferment at a lower temp. And maybe swap the yeast, that’s probably the first thing I would have done. A proper distiller’s yeast or Kveik, which handles lower temps. Follow the instructions for hydrating, pitching temp and fermentation temp. I bet your baker's yeast doesn't have any of those instructions.

You’re now adding nutrients and you’re aerating the wort, that’s what you should do. Corn is, as you have found out yourself, low in nutrients. Whether you add the nutrients first or after the yeast wont make difference although DAP should not be hydrated with the yeast - I always add nutrient first, then aerate before adding yeast. If you're not using boiled yeast or backset, I would suggest you add dead yeast to your nutrients list. Boil your Red Star and pour it into the fermenter with the rest of the nutrients.

I am assuming you have fermented at your locale before. Otherwise, the water composition could have a finger in the smells too. And if the smell carries over to your product, put some copper scrubbies in the boiler too. Good luck!

[grumbles]

Morning update. Garage smells fine, so it was just a transient. I noticed the smell yesterday at about 24 hours after pitching. It's at 36 hours now.

So yeah, I'll take all of the advice in this thread going forward. Thanks, everyone. Changing corn is easy because I'm out, but the yeast will wait a while. I've been planning to switch yeast anyway, but I'm still working diligently working through this 1lb brick. I'll also increase the nutrient a bit, but what about the DAP? Are there risks associated with going over 3.5g per 5 gal?

DAP should not be hydrated with the yeast

Yyyyep. Lesson learned there. The stirred bucket started ripping after just a couple of hours, and the one that got the DAP and yeast at the same time took a whole day. It's still bubbling way slower at this point. I was thinking that it was just a bad lid seal before I remembered.

[PalCabral]

When I am fermenting 6g batches and I will be using 6gr of DAP when Corn constitutes more than 50% of the mash bill. If the bill is more towards malts, then I will be using less or none at all.

[Jsto6132]

Could you let us know if you detect any sulfur after you distill it?