Urea smell during fermentation

[Ben Matthews]

Hey peeps. My first post here so Hi! I'm looking for some advice on my current batch which is my 7th all grain brew.

It's a Belgian Blonde Ale started a couple weeks or so back. It's basically
3kg pilsner malt
100g wheat
100g munich
350g sugar
25g hallertau at 60 mins.
5g saaz at 5 mins

(Bristish so sorry for all the metric measurements)

Used a new yeast for the batch; WYyeast 3522 Belgian Ardennes, and for the first time some wyeast nutrient blend. I made a couple consecutive starters with the smack pack to try and get a good pitch going. Both of these starters went crazy and did end up blowing off what i thought was a considerable amount of yeast to the point where on pitching I was unsure how much yeast I was actually pitching.

Mash and boil went really well hit target og of 1.067

Pitched at 17 degrees C (63 F) and temperature was held until after high krausen and then slowly increased up to 20C (68F) over a week and 22C (72F) by end of second week. Now at 23C. Fermentation took off quick. Yeast went bonkers and nearly blew the lid off. Managed to contain it with a few blow off tube changes. A little seeped from the plastic lid in one spot. Smelled amazing; yeasty and fruity as you'd expect from a Belgian yeast. Then as the Krausen dropped down a bit the smell changed. I couldn't put my finger on it but it was maybe a little peanut buttery. This increased and near the week and a half to two week mark it started smelling like peanut butter mixed with urea. Quite weird and rank.

I assumed it had got infected so took a sample. The sample smelled and tasted pretty normal. Quite darn nice taste infact and my gravity was at 1.017 so nearly there but going to leave another week and see if it goes lower. Lids been back on and a small amount of airlock activity since and more of the urea smell. The urea smell is pretty rank and I've never encountered this before. Every time my fermentation chamber is opened its not nice. I thought this will maybe condition out. I'm currently at about 2 and a half weeks into fermentation.

I did however find a couple things about urea that it is produced by yeasts and is a intermediate in the production of a known carcinogenic substance called Ethyl Carbomate. This is found in pretty much all fermented food and beverages in varying quantities. It sounds like it has no acute effect on human health but is a pretty bad carcinogen so I'm worried that even if this smell disappears during conditioning it maybe that because I'm getting a lot of urea smell there may well be a **** ton of this compound in the beer?

https://academic.oup.com/femsyr/article/17/7/fox072/4411803
https://en.wikipedia.org/wiki/Ethyl_carbamate
Has anyone ever encountered a urea smell from fermentation? The only things done different this batch are the new yeast variety and the use of the Wyeast nutrient blend (Which may actually contain urea)?

Could I have an infection?

Should I risk it or just ditch it? I was super excited about this brew as I've heard the yeast is awesome and was my first brew where everything in the process went spot on. Frustrating.

Thanks in advance peeps

Ben



Thanks peeps.

 

[Ben Matthews]

I have just read that Urea has no smell so perhaps its more of an ammonia smell? Basically like a toilet that hasn't been flushed for a few pees. Anyone had an ammonia smell before?

 

[camonick]

I’ve never experienced a smell like that but I almost always use dry yeast. Fermentation can produce all kinds of strange smells. A quick google search reveals a few situations similar to yours and it seems there probably isn’t anything to worry about.
https://www.homebrewtalk.com/threads/ammonia-odor-from-yeast-nutrient.471241/

 

[passedpawn]

I’ve got a 50# bag of urea in garage. Def no smell. Oh, and what he ^^ said.

 

[Ben Matthews]

Thanks guys. Ill just see if the smell disappears and then if that fails I'll try racking to a secondary maybe? Its slowly got worse over the last week so will be interesting to see if it clears off.

 

[RPh_Guy]

Basically like a toilet that hasn't been flushed for a few pees.

So, like Budweiser, Miller, Heineken, etc?

 

[Ben Matthews]

So, like Budweiser, Miller, Heineken, etc?

Ha ha. It's even worse.

 

[bkboiler]

Actually urea does have a smell, but the lab where they research it has covered up that discovery...
It's at Urea-51...

 

[passedpawn]

Actually urea does have a smell, but the lab where they research it has covered up that discovery...
It's at Urea-51...

 

[Ben Matthews]

That my friend is good!!!

 

[Ben Matthews]

Smell has now changed to rotting shellfish. Lovely. Pulled another sample which again looks, smells and tastes good. Beer now down to 1.013 and looks to be clearing. A lot of gas still coming out of solution (bubbles). Might rack over to the bottling bucket now see if getting it out of the Primary helps with the smell? A lot of CO2 coming out of solution still so might help reduce oxidation as well.

 

[day_trippr]

If it's still changing character I'd leave it on the yeast awhile longer...

Cheers!

 

[passedpawn]

Hmmm, something can't be right. Eau de Urinal and Shellfish Rot doesn't sound good. Rhino Farts is typically the goal for the smell of fermentation. You might not have enough grimature in your muffler bearings there.

(all fun, you're probably doing fine)

 

[Ben Matthews]

Mystery solved. I had a thought the other day perhaps when some of the krausen seeped out of the lid in a spot or two some of it had run underneath the fermenting bucket and missed being mopped up. Turns out that theory was right. When I moved the bucket out of the chamber this morning to bottle it tonight there was a pool of slimy crusty yeasty yuck. Maaaaaan did that stink. Not sure my chamber will ever be totally free of the smell again and my nose seems traumatised by the experience of cleaning it up. The outside of the bucket here and there smells a bit bad too. Im hoping nothing has managed to track it's way in under the lid to effect the beer. It smelled and tasted fine last check. Feel stupid now not thinking about this sooner. At least the beer will still hopefully be my best one yet!