Possible Contamination Question

[Brian Parfitt]

Hey folks. I'm concerned I have a contamination issue in my setup...

Last Feb I brewed an Imperial Bourbon Stout... When I kegged it, I noticed that it was tangy, almost sour tasting. Initially attributed this to the Bourbon being on the oak chips too long and over extracting tannins. figured I'd let it mellow over time and see how it did.. News flash. Still the same about a year later. Tangy/sour.

Back in early December I brewed another stout. This was the first batch brewed after the stout last Feb. Initial samples taken after a few days of fermentation showed promising flavor.. No off aromas etc. A touch sweet as it had not finished fermentation. I just took another sample as I setup my carb stone and it has a similar tangy/sour flavor to the stout brewed last winter.

I have never brewed a sour in my brewery and am using a spike conical. All loose pieces of the conical are cleaned with PBW and soaked in starsan prior to assembly. Assuming this is some type of contamination, am I able to clean the equipment I have? I'm pretty fastidious when it comes to cleaning and am concerned that I have an unfixable problem with my equipment.

One interesting observation I had was the gravity data logged that clearly shows a primary, rapid fermentation taking place over the first 10 days(12/8 - 12/18).. The gravity stabilizes for a period of time at about 1.020. After some time, a secondary fermentation seems to start (around 12/18 or 12/19) that drops the gravity another few points from 1.020 to 1.015 over the course of 2.5 weeks. Could that have been signs of an bacteria/wild yeast going to work?

Appreciate any insight and hoping this isn't a lost cause.

Brian

 

[day_trippr]

What yeast strain do you use for your stout?

After some time, a secondary fermentation seems to start (around 12/18 or 12/19) that drops the gravity another few points from 1.020 to 1.015 over the course of 2.5 weeks. Could that have been signs of an bacteria/wild yeast going to work?

It could. Or not

Cheers!

 

[Brian Parfitt]

What yeast strain do you use for your stout?



It could. Or not

Cheers!

Fermentis US-05

 

[McMullan]

Looks like an under pitch to me. Crapping out at about “the dreaded” 1.020 then struggling to get home. Attenuation looks fine. My stouts always under attenuate slightly relative to expected. The off flavour is possibly associated with under pitched/crap yeast. Or it could be due to some kind of infection. Probably best to deep clean and use something like iodophor or bleach. Did you treat your brewing water and check mash pH? Any chance of checking the pH of the beer?

 

[mac_1103]

These are Imperial Stouts. They're probably supposed to finish at 1.020 or higher with US-05.

edit - depending on just how Imperial they are of course

 

[McMullan]

These are Imperial Stouts.

With an OG = 1.056?

 

[DuncB]

Call it a weak keeping stout and blend it with a fresh running stout for that authentic old style stout.

 

[mac_1103]

With an OG = 1.056?

OK, let me rephrase - he said they were supposed to be Imperial Stouts so I assumed that graph didn't start at the beginning. It would be nice to know the grain bill, mash temp, etc.

I know that you think everybody underpitches all the time, and you kind of have a point with that. But if the OG is really only 1.056 then the standard lazy homebrewer's dry yeast underpitch shouldn't do this. I direct pitch one sachet of US-05 on bigger beers than that all the time and then ignore them for three weeks and I've never seen less than 77% AA.

 

[Brian Parfitt]

Some more details:
US-05 in Propper Starter setup 24 hours in advance on stir plate
Wort was oxygenated in fermenter

Mash pH was 5.4

The graph is the entire fermentation.

This was just a regular stout. The previous batch was the imperial stout. I was shooting for a 1.062 OG and missed by a few points...

Grain Bill:
10 lb (69%) — Muntons Maris Otter Malt — Grain — 2.8 °L
2 lb (13.8%) — Weyermann Munich II — Grain — 9.2 °L
1 lb (6.9%) — Crisp Crystal Malt 60L — Grain — 60 °L
8 oz (3.5%) — Weyermann Carafa Special II — Grain — 412.8 °L
8 oz (3.5%) — Bairds Chocolate Malt — Grain — 369.7 °L
8 oz (3.5%) — Muntons Roasted Barley — Grain — 388.1 °L

RO Water treated with:
5 g — Baking Soda (NaHCO3) — Mash
8.3 g — Calcium Chloride (CaCl2) — Mash
2.6 g — Epsom Salt (MgSO4) — Mash
2.6 g — Gypsum (CaSO4) — Mash

I can grab a pH from the beer later tonight.

 

[Brian Parfitt]

Forgot to add, I was looking for a 1.016 FG, so that ended where I was hoping it would.

Just checked pH on the beer in the fermenter.. 3.6.
Checked the previous stout out of the keg.. 4.1

So pretty much a confirmation of bacterial infection that led to souring?

Iodophor everything? Disassemble valves? Replace tubing?

 

[day_trippr]

Sorry for your loss.

Iodophor everything? Disassemble valves? Replace tubing?

Sounds like a start. Definitely clean out any valves and disinfect anything with which that beer came in contact.
Disinfection with bleach would call for a 600~800 ppm solution. If there is an equivalent for iodophor, you can go with that...

 

[McMullan]

The pH is borderline on the low side. With the taste too it’s bet to assume it is an infection. Clean thoroughly with PBW or similar before using bleach or iodophor, to remove any biofilm from surfaces, nooks and crannies. It’s not a bad idea to use bleach or iodophor occasionally regardless, as a preventative measure.

 

[Brian Parfitt]

Thanks for the feedback all..

I'll start working this today. One question I have is related to the gas manifold I have on the fermenter lid. There is a pressure gauge that threads into this manifold. This last fermentation was very active with trub/yeast blowing out of the blowoff hose, also attached to the manifold, and into my sanitizer airlock. This would mean there is a good chance that material touched the gauge as well. That gauge has a small hole in the threaded fitting (by design of the gauge) like this:

I'm pretty sure I can't immerse the gauge in liquid. Any suggestions on how to properly sanitize this for reuse? Aside from burning with fire?

Once again, thanks for the input here.

B

 

[J.Miller]

Brian, just today saw this thread, and read about your contamination issue. Also skimmed through the replies. I had a similar experience years ago with a stout that I brewed, and put bourbon-soaked wood chips into my serving keg before transferring the beer onto the wood chips.

I believe you got the contamination from the wood chips.

Because I ended up with the beer in the serving keg having an acidic taste, like green apples, weeks later after I tasted the beer during the transfer to the keg to have a malty sweet taste that I expected from my grist, I sought out how other brewers wood-aged their beers.

I got two replies on the process that was different than what I did with the wood chip preparation. One homebrewer said to steam the chips in a colander over a boiling water pot of distilled water for 15 minutes before adding to beer. The other reply from a local brewery brewmaster that if using wood chips that are not flame-scorched, like the inside of a whiskey barrel is prepared, to take a torch and scorch the chips and then whiskey soak the chips - because the alcohol content of 80 proof liquor is not high enough to kill some organisms.

Briefly, this is what I remember. I soaked the wood chips I bought from a homebrew supplier in bottom-shelf bourbon for a week or so and put them in a woven hop sack also soaked in the bourbon alongside the chips.

I brewed this batch before I started to track the fermentation and pH testing of my beers - probably because I never had a contamination issue before that batch. Doing the testing throughout the brew process is wise, like you did.