Beer went sour weeks after kegging...what happened?

[Knightshade]

Beer Type : Marzen Lager

This beer went into the keg and I had my first glass of it on August 19th. Fast forward, and I dumped what was left of it (about 4 pints) on the 27th of September because it had turned sour. I should have taken a picture of it, because the head would break up in the glass into separate islands, in some cases seemingly clumping together in small overlapping layers.

The beer itself was never a proper Marzen from a taste perspective. It was really fruity, which I assume is esters? I was also assuming that this was due to stressing the yeast at some point, or perhaps because I got impatient with the lagering process. Using Saflager W34/70, I fermented at 55 F for two weeks, then slowly decreased the temperature 5 degrees each day until I got to 36 F. After 3 weeks, I said the hell with it, kegged the beer and started carbonating it. 2 weeks later, I poured my first glass. Like I said, it wasn't what I was expecting at all, but found that I rather enjoyed it so continued to drink it.

Thinking back, about 3 weeks afterwards I noticed the beer seemed a little off. It wasn't as fruity. But thinking that maybe I had drink too many other beers that day and my palate was off I didn't think much of it. The next weekend, I gave some to a friend because I was curious what he thought. He is the one that said that the head separated weird so then I had to go pour a glass for myself. Same thoughts of "Huh..this does taste different..definitely not as fruity...is it bitter?" but I didn't notice the weird head. Until the next day when I couldn't stop thinking about it, I poured yet another glass. It was almost as if I couldn't confirm what I was tasting, until I saw that something was definitely not right.

But now, I'm wondering how the heck did this happen? Was this inevitable because I screwed up on the brew day or because my beer line cleaning process failed me?

This beer was on a previously used line and the line cleaning procedure was to use a bug sprayer:

Flush w/water, then flush that out with BLC
Let BLC sit in line for 10 minutes, then flush that out with more BLC x3
Repeat flush/sit process with StarSan
Fill now empty bug sprayer with air and attempt to dry the line out
Let line sit empty, then hook up new beer whenever.
(Also looking back...maybe I should have flushed with StarSan again prior to hooking up new beer?)

The biggest brew day screwup for this beer that I can remember stands out quite vividly for me because it is one of those, "I'll never do that again" type of mistakes. I had filled up my Speidel with over a gallon of StarSan from a 1.7G corny keg. It was still good because I had checked the pH, but it had been sitting for awhile so I was going to use it for this last time and then dump it. I had prepped the fermenter sometime during the boil and set it aside. Long story short, (too late) I didn't realize that I hadn't dumped the StarSan until I was a little less than halfway done with racking. Furious...I dumped what I had put into the fermenter, then went back to racking the beer and ended up with a little over half a batch. Is this last step when infection happened because I didn't re-sanitize the fermenter?

Or was it because I was unaware that due to such a long time in the fermentation chamber that excess humidity built up to the point that I actually had a bit of fuzzy growth in there? Some of which managed to pop itself right onto the handle of the spigot? I wiped and star san'd everything prior to keg transfer...but??

I'm curious about your thoughts on where this likely went south. Things I've changed.

1. I purchased an extra Eva-Dry so I can swap out in fermentation chamber vs. removing, drying, putting back in.
2. I figured out how to recirculate BLC/StarSan using pond pump vs. using bug sprayer (much less work)
3. I've decided to let line sit with RO water vs. air when not being used

Speidel? It is 2nd hand and I've got 2 other beers currently kegged that also used that same fermenter and previous beer line cleaning procedure. One has been kegged since 8/28 and the other since 9/19.

 

[Rob2010SS]

I'm not an off flavor expert by any means, so this is my take and I'm probably wrong...

With your yeast, you said the "fruitiness" is most likely from stressing them.
-Do YOU think you stressed the yeast?
-How so? Nothing in your description sounds like you stressed them, other than maybe not letting them finish.
-Acetaldehyde (green apple, jolly rancher, latex paint) and Isoamyl Acetate (banana, fruity, pear, nail polish) come to mind based on your description. Either of those descriptors kinda fit the bill for what you were tasting?

I see you didn't do an increase in temp for a diacetyl rest. This would usually lead to a caramel, buttery, butterscotch flavor.
-Do you KNOW that fermentation was complete?
-Did you take multiple gravity readings and get the same result to be sure?

I wouldn't' think it would have anything to do with your beer line. That wouldn't affect the whole keg so I think you can take that out of the equation.

Based on your description of what happened with your fermenter both on brew day and in the ferm chamber, I'm going to say this had more to do with your sanitation practices than anything else. The fact that it continued to change in the keg and went sour leads me to think some kind of bacteria got into it. I would look at your sanitation practices with regards to your fermenting vessel and improve on that. Make sure the vessel is clean - no debris or stuck on crap left over from past brew day. Freshen up your sanitizer more often to ensure it's working.

Unfortunately, if this is the case, you need to do a REALLY thorough job of cleaning your fermenter, or even replace it. It's plastic, right? Any kind of scratches or anything inside the plastic fermenters can harbor bacteria even when you think you've cleaned it thoroughly.

 

[IslandLizard]

Something got in there, no doubt.

Do you clean that spigot on the Speidel, including the washer and nut? How about inside of the spigot?

Do you use that spigot to transfer finished beer to a keg? Do you again, clean and sanitize it right before kegging?

I'd clean that Speidel very well, including spigot, lid, threads, any cavities inside (e.g, handles). Use (warm/hot) PBW or at least Oxiclean. Shake well. I prefer mopping with a small washcloth and/or a stiff nylon hand brush. Something that won't scratch. Rinse out and maybe use some bleach on it, same way. Instead of, or in addition to bleach, put outside in direct, bright sunlight for a few days. Make sure all inner surfaces get direct sunlight for a few hours. UV kills a lot of bugs.

Clean that keg well too, and anything else that touched your infected beer.

 

[Knightshade]

@Rob2010SS
Flavor: I tried multiple times to try and characterize what it was that I was actually tasting, and perhaps a fruit salad type of feel to it with some caramel overtones.

Diacetyl Rest: I did do that, forgot to mention it in the original post.

Gravity: I didn't check it throughout, which I tend to not do. This is due to the fact that my fermentation chamber is on the ground and the fermenters are on the floor of the FC extension. It is really difficult to sanitize the spigot, get a sample, etc., without taking the entire fermenter out, lifting up somewhere, putting back, etc. I did check it after ferment, rest, short lager period. It was supposed to be at 1.008 and it was on target.

@IslandLizard
I didn't clean the spigot, just wiped it all off and sprayed StarSan all over and up into it before kegging.

Regarding what I've done w/the equipment afterwards. I looked again at the Speidel Tuesday night(2 days ago)...and I did a REALLY crap job cleaning it out this last go around. I don't feel like I was lax in my process, but it was embarrassing how many areas needed a second go. I filled that thing up, dumped a bunch of oxyclean into and let it do its thing. Then scrubbed with a silicone scrubber thing, rinsed really well, etc. Did same w/spigot and lid. Speidel has been sitting dry for 2 days, but it still smells like beer. I'm honestly starting to look at this thing sideways because it is 2nd hand. It looks okay, but I don't know how well maintained it was by the previous owner. I guess if these other two beers go south....I'll know for sure???

Keg, I dumped in some hot water and PBW and let it sit for 30 minutes. Turned upside down and gave it another 30. Took apart both posts, threw the parts into the same liquid, scrubbed and let those sit for another 30. Rinsed a couple of times and let it air dry.

Thanks for your insights...and taking the time to read my long winded post and respond. Really helpful, seriously.

 

[Knightshade]

Speidel went in the recycling bin yesterday. A 2nd beer, on a different line in the kegerator started tasting...odd. Dumped it, ordered new lines and a new fermonster.