Infection?

[EvilBrewer]

Brewed a trusted and true seasonal recipe recently. Everything seemed fine...OG (1.055 ish) was on target. Fermented down to expected FG (1.015 ish). The yeast I used was Safale S-04, which is a dry yeast. I mostly use liquid yeast for my beers but for this particular recipe, I've always used the same dry yeast and didn't feel the need to change anything this time.

Anyway, after about a month, I kegged the beer. Like I said, the FG was pretty normal...something around 1.015. And I think I remember it tasting normal going into the keg--can't be too sure though; I don't too pay much attention until it's carbed up because the flavor can really change.

Fully carbed now and the beer tastes really SOUR. Like, pucker-your-cheeks-sour. At first, I just thought it was estery from the English strain of yeast and I ignored it--just figured give it some time. It's also considerably cloudy even after using gelatin for fining; my usual procedure.

I've come to the point now where I'm not even gonna drink it; I need the keg for my next beer in the pipeline and I've gotta cut my losses.

So, I'm trying to figure out what might be causing this taste, and where it might have been introduced to the beer. Does this sound like bacteria? A wild yeast?

I've been brewing for a number of years and have never had an infection in my beers. It could be a fluke and maybe I overlooked something this time around...doubtful, but possible. I'm pretty OCD about sanitization when it comes to brewing (and in general, ha). But anyway...putting my pride aside, my objective is to ensure it doesn't happen again.

I double soaked and sanitized my better-bottle carboy before using it again...hopefully that eliminates the chance of cross contamination to my next batch (which is currently bubbling away).

I feel like I read somewhere that dry yeast can sometimes contain wild strains. Any validity to that?

Thanks.

 

[ArcaneXor]

What's the SG now? Is there a pellicle on the keg? What character does the sourness have - is it lactic or acetic?

 

[MalFet]

Puckering sour doesn't tend to be a characteristic of wild yeast, and it's a bit premature to blame dry yeast for the problems. I've not heard about dry yeasts being more prone to infection than liquid, but even if that is they case we're still talking about something that's very rare.

Sourness that strong is usually a bacteria, generally lactobacillus or acetobacter. More yogurt or more vinegar, would you say?

 

[EvilBrewer]

What's the SG now?

I don't know what the current gravity is...I wasn't sure how to accurately measure that once it's been carbonated? If I'm wrong, please let me know how this would be done.

Is there a pellicle on the keg?

Ha...I had to google that one. I haven't checked, but I guess I should if it will definitively tell me that there is an infection?

What character does the sourness have - is it lactic or acetic?

Hmmm...I admit I don't know how to distinguish between these two. Any advice?

 

[shutupjojo]

I would think dry yeast starts pretty fast so it would probably take over any wild bugs and stuff. Maybe there was something hiding in your keg like the diptube or whatever ?
Never had an infection myself, like you , I am OCD about cleaning and sanitation also.
I have had off flavors and most of the time was from bottles that got missed or the diptube in the keg.

 

[EvilBrewer]

Puckering sour doesn't tend to be a characteristic of wild yeast, and it's a bit premature to blame dry yeast for the problems. I've not heard about dry yeasts being more prone to infection than liquid, but even if that is they case we're still talking about something that's very rare.

Yeah, I agree infected dry yeast would be a long shot, and that is actually comforting. The thought of not being able to trust the QC process of the yeast producer is, well, kind of despairing.

Sourness that strong is usually a bacteria, generally lactobacillus or acetobacter. More yogurt or more vinegar, would you say?

The sourness is more like yogurt than vinegar. Kind of like a "sour patch kid" (that's a brand of very sour candy, btw) but not quite that intense.

 

[bmick]

That tastes leads me to believe you might have a lacto bacillus issue, which can provide sourness, rob flavor, and also lead to over-carbonation, as they're eat sugars that yeast doesn't. Draw a sample, stir or shake to flatten, then measure the gravity. If it's an LB infection, you'll have a lower gravity than 1.015 as the bacteria will have eaten through more sugars.

All that being said, take that beer off the gas, and let it ride. Could be a tasty sour-style brew in 6 months.

 

[EvilBrewer]

All that being said, take that beer off the gas, and let it ride. Could be a tasty sour-style brew in 6 months.

Haha...I don't think I'm interested in that. I do appreciate the insight though.

 

[badmajon]

why not just rack it to a brew bucket and let it turn into some nice malt vinegar?