Sour Off flavor

Our last 4 or 5 batches have had a distinctive sour flavor to them even though each has been a completely different style (wit, brown, 2 stout, hefe).

What are the common reasons to get a sour off flavor?

Extra Info / What we have tried:

  • Extra sanitization, but either we are still missing it or thats not the problem
  • we do BIAB
  • have a consistent 64F fermenter
  • not all done with the same yeast (but it was all dry yeast)
  • the sour is not wanted..

We ordered new tubing, new siphon, new yeast (not dry) and just did a batch last night hoping one of those will fix it. Any advice?

Topic sour off-flavor homebrew

Category Mac


Chlorophenols are sometimes identified as having a sour taste. Is your water by any chance chlorinated? If so, do you do a anything to remove the chlorine?


Bacteria and yeast are actually pretty tough little critters. My brewing buddy always says once you brew a sour beer you are very likely to do it again and again without meaning too. The reason is that the nasties get into tiny imperfections (e.g. scratches, etc.) and survive even the most thorough sterilization techniques. So what we can assume is that most likely somewhere along you process you have an infection stowing away that is souring your beer. Knowing where the infection comes from would help, but how many batches do you want to ruin before figuring it out?

Seems most likely that the infection you are seeing is happening during bottling but it could happen at multiple steps in the process and there is really only one way to get rid of the problem. Throw out what you can afford to replace (e.g. tubes, stirring implements, spigots, buckets, etc.). Then for those you can't replace easily sterilize the hell out of them and sterilize for a lot longer than you normally would shaking vigorously. Times like these are good opportunities to take a look at your sterile technique and get paranoid like crazy. Clean and sterilize everything very carefully. I mean everything!

P.S. BIAB is awesome!!! Good choice of mashing techniques.


"Graham's" post about "when do you notice the sour taste appear" is very important. If you don't already, next time you brew, draw a small sample at every step, if you can handle it, including your freshly cold full strength beer wort. When I was new to all grain brewing I had a batch go sour. When I went back through my notes, I had made a comment that there was a slightly sour taste after primary when I racked the beer into secondary. I was able to pint point the infection to my fridge where I had let the wort cool for 4 or 5 hours (didn't have a chiller yet)! If I had not made that comment in my log, I would have had no idea at what point the infection occur. It is strange that both your bottles and kegs are tasting sour. Although the spigot seems a likely culprit, it must be something else if the contamination has entered the keg as well.


Do you ever notice a little layer of film in the neck of your bottles from the bad batches? That's a "pelicle" and is a sign of Brettanomyces/Pediococus/Lactobasilus activity.

For what it's worth, I am leaning towards the theory that you had a contamination in your bottling line, probably in the spigot of the bottling bucket. I've looked in some of those and see nasty things growing when not rinsed out thoroughly after each use. There's a lot of areas for stuff to hide in those spigots and its cheaper to replace them every couple of batches than to risk a whole ruined batch.


My understanding is that the most common cause of sour flavors is a wild yeast or bacteria infestation. In a beer that is deliberately sour, a Brettanomyces yeast strain is introduced along with bacteria to create the sour flavor.

Ideas:

  • Do you bake a lot in your home? It is possible that you have airborne yeasts in your home if you bake bread at all.
  • Try making a yeast starter with the dry yeast or switching to liquid yeast as you mentioned. The faster you can start your fermentation, the less time any wild or undesirable yeasts will have to take root in your beer.
  • Is it possible that you are confusing the taste for that of tart, green apples? If you are making high gravity beers, the off-flavor could be Acetaldehyde, which is produced by yeasts during fermentation but dissipates as time goes on.

To answer your question, here is a very comprehensive list of potential off-flavors in beer.

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