Advice needed on really vile, smelly fermentation.

[Beerisyummy]

I recently made another batch of my dark strong Belgian style ale. This is the fourth time I've made similar batches using the White Labs Abbey Ale yeasties.
Everything was going along as normal until I made my first sugar addition, just as the ferment started to slow. It has now developed an odour that is enough to make me wretch. Something along the lines of rotten flesh (or a carnivores' rotten turd).
In comparison to the beautiful sweet malty smells of the first week, this has turned my garage and car into a stinking mess.

I have not yet encountered this type of smell during a fermentation so I'm concerned that the batch is F'd. Is this a normal sort of smell? I don't remember it from the last times, but I might've been away during the "open sewer" stage.

The main recipe difference with all the other batches is the type of sugar used. I've used the dark Belgian candi and had a go at making my own in the past. This time I used half raw sugar mixed with white sugar, and then darkened it up over a couple of hours in a pot. It had a totally different taste to the other stuff I've used.
Would this less refined sugar be causing the yeast to give off this very pungent odour? I can smell hints of it under the rotten smell.

The krausen looks the same as always for now, so I'll keep monitoring that for signs of bacterial infection. Man, I hope I haven't got an infected batch.
Either way, I'll let things carry on and see what happens.

 

[manticle]

Sounds bad. I have however had unpleasant flavours (not as bad as your description) from using a large amount of raw sugar in pale, strong Belgian brews and I onloy ever use either dextrose for pale or D2 syrup for darks now.

 

[Beerisyummy]

Thanks Manticle.
I've aired the garage out over the last couple of hours and have found the smell to be much more bearable at lower levels. It's still pretty rank, but I'm more confident that it will subside over the next few days.
Only time will tell I guess.

It's interesting that you say you had undesirable flavours with the raw sugar. I had decent results with the dark syrup I made, albeit with white sugar only.
As always, every new brew adds to the learning curve.

I'll post back on how the brew goes.

 

[Ducatiboy stu]

Taste it. If it tastes like shit..fair chance it is.

I would be bombing the beejezuz out that ferm with bleach, then caustic, then nappi-san to remove anything nasty.

 

[Beerisyummy]

Yeh, I couldn't help myself and poured a sample. It tasted ok and the aroma was totally different.

I'll take another sample on Sunday and see if the gravity has dropped drastically. It's already at the expected FG.

If it's infected, that fermenter can get the flick. Heck, I might even burn the ******* and save the world from a plague of beer that smells like rotten meat.

Enjoy your weekend guys.

 

[Ducatiboy stu]

Just bomb it. Caustic,bleach then nappi-san will cure it.


But different yeast give off very funky smells, especially if you just pop the lid and have a a big deep sniff.

If it tastes ok then all is good. If it leaves a soapy feel or taste then its gone..

 

[MartinOC]

Don't be afraid to ditch a suspect batch. Shit happens. It's no real biggie...just go back over your notes & see if you can nail the cause & learn from it.

...and clean/sanitise the absolute bejeezus out of everything that came in contact with it.

Then go back for another go. Ingredients are cheap compared to commercial examples.

 

[Ducatiboy stu]

Your not a real brewer until you have brewed a truly vomit inducing brew that had a thick wax like slime floating on top......more than twice...

 

[Dunkelbrau]

Why ditch it if it tastes good?!

I'd say you've just copped a build up of a crappy stink, I've opened a fridge and gotten big ass smell from a wheat, could just be something similar.

If it's just got krausen remnants, and gravity is stable, and it's tasting good, it's not infected. It could have been a combo of a smell in the area and the yeast stink too.. I know near my parents house the STP can stink around 5pm and linger past midnight! Absolutely horrid!

 

[MartinOC]

Your not a real brewer until you have brewed a truly vomit inducing brew that had a thick wax like slime floating on top......more than twice...

FIVE times......

'Though I've never had one that was THAT bad!

'Guess I'm just a bit more discerning than some...... :icon_vomit:

 

[Beerisyummy]

Update.

I didn't get to sample this on Sunday. Tuesday was the soonest I could draw off a sample.
SG had not changed and it tasted OK, if not a little yeasty.

The fermenter has dropped dark and clear. There is nothing on the surface and the smell is all but gone. Just a slight hint on the outside of the FV.

I added another addition of my version of D2 this afternoon and the bugger fired back up within 4 hours. The rotten meat smell has not come back this time.

I'll update again once the batch burns through this lot of sugar.

 

[Beerisyummy]

Update on the update!

After leaving this project alone for some time I decided to head downstairs and take a sample.

The brew has dropped clear as before and has the slightest hint of the previous smell. I tasted a sample and it is very drinkable, although it needs time to lose that fiery kick.
Once bottled and aged, I'll get some other opinions on the final results.

In short, if I were to do this again, I would not try to make a dark candi syrup from raw sugar. I found the whole process difficult and thus far have had some really funky results during fermentation.
I'll make sure to post more on this brew over time.

Edit: I marked this solved, but it comes up with this post as the best answer, so I unsolved it. The best answer is a combination of all the above posts. Thanks for all the help.