I have a really funky fermentation going on. Brewed an extract Scottish Ale:
6/1/24 Brewed - No known problems. OG 1.052.
6/16/24 Early sample - 1.0080 - Smells and tastes very good. Very clear.
6/19/24 Bottling day - 1.0080 - Smells and tastes OK - but not good. Hazy.
7/5/24 Next sample - 1.0081 - Smells and tastes OK - but not good. Very hazy.
7/18/24 Next sample - 1.0082 - Smells and tastes OK - but not good. Murky.
(Note: I use a narrow range hydrometer with hash marks every 1/2 gravity point - I can easily read to the nearest 1/4 gravity point. Recorded gravities are adjusted for temperature.)
I bottle condition and don’t want to risk bottle bombs or contaminating my bottling equipment, so I plan to dump it since there might be a possibility of bacterial contamination. I would bottle and drink it if I knew it wasn’t contaminated. I can’t really make sense of it. A bacterial contamination or wild yeast could account for being murky, but either should cause a steady drop in gravity (I think). It seems that if it was any other likely problem, it would clear again, especially since it was initially clear. I can’t give a good description of the taste - the closest I can come is a little harshness. The only explanation that I can come up with is possible oxidation since that wouldn’t clear, but it doesn’t seem like the normal stale or cardboard flavor. I’d say it’s beyond hazy - what I would call murky. The process was a touch different for me. I had just brewed two BIAB batches. This was the first extract batch following the BIAB batches. Full volume boil. Any ideas? Any idea that steady gravity makes bacterial contamination is out of the question?
I’m pretty far from being an expert, but I don’t think there is a biological explanation for the gravity increases you’ve noted. Could it be that with that level of specificity, measurement issues account for it?
As for the murky appearance and taste, I wonder if a var. diastaticus had taken hold. When I’ve used commercial strains like Imperial Dry Hop with that variation, the beer takes on a cloudy appearance near the end of primary. It looks downright unappealing for another week or so (in my experience). As you noted, the fg should go done though. Maybe oxidation is the issue.
joelv: Sorry - I see I wasn’t clear about the gravity. The numbers running in the range of 1.0080 - 1.0082 is what I call steady as a rock. Within my accuracy limit.
As far as diastaticus, I’ve never used any diastaticus yeast, so hadn’t thought of it. I wonder if it’s possible that I’ve picked up some in my house accidentally. Probably unlikely, but something to consider. And even as slow as diastaticus acts, I think there would be a drop in gravity over the time period here.
Your gravity has been stable (within experimental error) for a solid month. I would think any ongoing fermentation by unexpected microbes would show up in a change in gravity.
I would assume there is microbial activity due to the change in appearance. Gravity stability doesn’t necessarily rule out the presence of an unwelcome guest. There may not be a lot of food available for your unplanned visitor this time. Some microbes will create cloudiness because they don’t drop out of solution easily even if they do not have food to eat. You may see other signs of fermentation with priming sugar in the bottles and/or in the equipment next time you brew. It’s up to you if you want to bottle and drink the beer as long as it tastes good, but any cold side equipment that touches this beer needs thorough cleaning and sanitation.
That is exactly my concern, but I didn’t know the answer. I had the impression that a bacterial infection would eat anything left. If I understand you correctly, that isn’t true - they could be unable to consume some of the sugars. Am I understanding correctly?
That’s correct. Wild microorganisms are not always able to or efficient at consuming sugars left behind by brewing yeast so you can end up with an infection in a beer that isn’t immediately apparent from the flavor despite a population large enough to make the beer visibly cloudy. For example, lactic acid bacteria are a common source of biological contamination in beer that can produce a lot of acid and other flavor compounds but barely move the gravity reading at all. It’s also possible that you’re seeing the early signs of an infection that will lead to more visual cues (e.g. pellicle) and start to affect the flavor and aroma.
Thanks for the help with this. I dumped the batch and will replace the fermenter. I’m keeping the items that weren’t in contact with the beer (fermenter lid and airlock) and gave them an overnight soak in OxiClean/TSP-PF followed by scrubbing with the same afterword. This has been interesting and educational. It seems that my routine of bottling only if the gravity is stable and the beer is clear is still valid. The concept of a bacterial contamination that doesn’t cause a drop in gravity pretty much mystifies me. I don’t know how I’ve brewed this long without knowing that.
The vessel would probably be fine with a good cleaning and sanitation. If it’s plastic or glass, a good iodophor soak or properly diluted bleach soak will sufficiently sanitize it. If you use hoses or other equipment between the boil and this vessel, they should be treated to the same process.
I would look at how the infection may have occurred to avoid repeating in the future. Are you milling or doing anything else that kicks up a lot of dust near where your store equipment or ferment beers? Was there something different about this batch versus prior batches? Sometimes you get an opportunitistic infection despite good cleaning and sanitation practices but it’s more likely to have a cause you can eliminate.
Hopefully, you aren’t dealing with a pernicious microbe. I once had a pediococcus infection (that was my guess, anyway) in a plastic bucket I was using as a fermenter and I had to retire it from fermentation use…it is a big part of why I use plastic only with clean fermenting lager yeasts these days. I use the Fermzilla All Rounder for lagers (for 5 gallon batches) and Kegmenter stainless (for 10 gallon lager batches).
I have two suspects for the cause of the infection.
First, I found that the 3-piece airlock was tilted over (not plumb) and wasn’t sealing. I just found it and don’t know how long it was like that, but the first sample looked and tasted really good, so I’m guessing it got tilted when I got that sample. I wouldn’t expect the lack of a seal to cause an infection, but maybe that combined with bad luck caused it. I can fix this problem.
Second, this was only the third batch using this bucket fermenter. The lid isn’t designed for removal of the O-ring - it’s a 5 gallon bucket from Lowes. I cut a notch in the rim of the lid to allow a popsicle stick to be inserted and remove the O-ring. It sealed well and made it easy to remove the O-ring. But now I wonder if any small nick from cutting it allowed microbes to hide there. I’m not sure about a fix for this since I don’t know if it’s the cause, and I need to be able to remove the O-ring. I might go back to a new lid and not cut the notch out, and see if I can work out a workable way to remove the O-ring.
Fermenter’s designed for fermentation are so cheap this would be a no-brainer to me. Grab a 7 gallon fermenter or something similar and move on. Even with massive leaks, I’ve never had a beer get contaminated because of the fermenter. I’ve had it happen because I didn’t clean well enough in my first 2 months of brewing, but it wasn’t the fault of my equipment. And probably my day is coming for when that’s going to happen because I too push my luck with plastic fermenters. We should probably retire them but we don’t. I’m a prime candidate because mostly I use a stainless conical and then two glass Big Mouth bubblers. It’s only when I’ve gotten more than 20 gallons going at a time that I moved to plastic. But the fact remains, sooner or later they will pick up an infection.
Just a follow-up on this issue. I dumped the batch and am replacing all plastic downstream equipment. For bottles, I cleaned and sanitized with bleach, followed by heat sterilizing in the oven. (I didn’t bottle this batch, but I’m taking precautions in case a previous batch might have had a minor issue that I didn’t notice.) Many thanks for the helpful comments.