Off flavor in finished ales

I have been brewing all grain for almost a year. Recently I noticed a slight chlorine taste in a couple of bottles of three different recipes. (Milk Stout, and two different Blonde Ales) The Stout was almost three months old, and the Blondes were six weeks, and four.
I have always used filtered water, and as I said it was not present in every bottle of the batches. Any idea where this may come from?

How long has it been since you changed your filter membrane?  Does filtering eliminate chlorine or chloramine?

The filter is as old as the Stout, so about three months. Documentation with the filter claims to remove chlorine.

You don’t happen to be using bleach as a sanitizer do you?

I use StarSan for sanitizing. I recycle my bottles and any “new” bottles are cleaned with PBW to remove labels, rinsed, then sanitizes.

I’m going to guess it is not chlorine flavor you are getting and you are confusing this off flavor with another flaw. Chlorine will cause a phenolic/band aid/plasticy flavor.

You also say that it is not present in every bottle. Unless you are sanitizing your bottles with chlorine, and you say you are not, then the off flavor must be from something else.

Do you have any other descriptors to explain what you are experiencing? Are you controlling fermentation, limiting oxygen post fermentation onset, racking beer into a secondary that has not been purged of o2? Give us a brief description of your brewing process.

Agreed, Keith.

I can think of other way to describe it, some have a slight but noticeable bleach flavor. I have only noticed this in the three batches I mentioned. I have brewed a total of 14, this was my first attempt at a stout, and the second batch of one of the blondes. The other “blonde” is technically a SMaSH, using Maris/Saaz.
As far as my process, I do everything I can to minimize oxygen after the yeast has been pitched (no splashing, stirring, etc.). I did utilize a secondary on the Stout as I also added cocoa nibs (soaked in vodka). The other two were not racked into a secondary, but stayed in the primary for 14 days each. Used Wyeast 1084 (no starter) on both the “blonde” ales and a Wyeast english ale (I forget the number) on the stout (starter).
I did not purge the secondary, as I am not sure how this would be accomplished.

I personally can’t think of any off flavor that smells like bleach or chlorine. That said, everyone experiences beer from a subjective standpoint. I wonder if it isn’t oxidized flavors. Any chance it smells like sherry or cardboard?

perhaps a bit like cardboard.

That’s classic oxidized flavors (wet cardboard). Be very careful to rack extremely carefully and minimize splashing post fermentation. You might look into getting oxygen scavenging caps. If you have access top Co2 you can purge secondary vessels.

Bottle conditioning should be able to handle some dissolved O2 since the yeast will scavenge O2 during bottle conditioning but if there is a lot of splashing via transfer oxidized off flavors may still result.

Anyway, that’s my best guest without trying the beer personally.

Thanks for the assistance, I will start using O2 scavenging caps on my next batch, as well as purging secondary vessels with CO2 when I use them.

If it’s a few bottles and the rest are good it sounds like bottles that weren’t fully clean before being sanitized

Be aware there’s no evidence those caps actually do what they claim.