help me find out source of off flavor in keg

[zodiak3000]

here is the problem- i keg beer, beer tastes great even a few days after kegging. at about 3 weeks i start to get off flavors. the keg is usually about half empty and clear by this time. the flavor is slightly medicinal and astringent. im suspecting this is a phenolic characteristic, still not sure though. this problem has happened on the last several batches, mostly IPAs. here are few things i suspect that could be contributing to the problem-

1. pitching yeast at about 75. i cant get the temp down any lower around here in the summer. i pitch at 75, then get it in the temp controlled chest freezer and quickly get it to about 65. fermentation stays at 65.

2. water. last batch i used RO water with adjusted minerals via the primer. the problem is i noticed a leak in my wort chiller that got a few pints of sink water into the wort.

im just wondering why the beer tastes great at the start, then gets the weird off flavor at 3 weeks or when the keg is half gone.

 

[Yooper]

Since it shows up later, I'm almost thinking that it's the lines/shanks/faucets where you're picking up the flavor.

As an experiment, I'd consider using a picnic tap set up for a pour. the whole set up, sanitized, to see if it's a problem with infection in your lines.

Speaking of infection, could it be in the keg? How thoroughly do you take apart your kegs and posts and clean/sanitize?

 

[zodiak3000]

Since it shows up later, I'm almost thinking that it's the lines/shanks/faucets where you're picking up the flavor.

As an experiment, I'd consider using a picnic tap set up for a pour. the whole set up, sanitized, to see if it's a problem with infection in your lines.

Speaking of infection, could it be in the keg? How thoroughly do you take apart your kegs and posts and clean/sanitize?

i do use picnic cobra tap. even though cleaned and sanitized every batch, its been used a bit. ill replace it.

i break down my keg completely every batch, soak in pbw 24 hour. starsan is always used before kegging. i do notice kind of a soda smell that always lingers in the keg, no matter how much pbw i use to clean. i guess i could replace the o-rings as well.

 

[Bensiff]

Yeah replace the o-rings. Usually astringent characters are more an issue with the brewing process though.

However, some thoughts. If your sanitizing process is good and you aren't aging your beers for years than let the wort sit in the chiller until you hit temp then pitch your yeast. I do it for lagers all the time without issue. What types of hops are you using? You may be picking up astringency from using a lot of whole leaf hops or too long dry hopping. It maybe that the astringency is always present and that you only detect it when the beer clears so other characters are no longer masking it in which case you would have to look at your brewing process.

 

[zodiak3000]

Yeah replace the o-rings. Usually astringent characters are more an issue with the brewing process though.

However, some thoughts. If your sanitizing process is good and you aren't aging your beers for years than let the wort sit in the chiller until you hit temp then pitch your yeast. I do it for lagers all the time without issue. What types of hops are you using? You may be picking up astringency from using a lot of whole leaf hops or too long dry hopping. It maybe that the astringency is always present and that you only detect it when the beer clears so other characters are no longer masking it in which case you would have to look at your brewing process.

id say its more of a medicinal flavor than astringency. the flavor is somewhat phenolic. its def not hop astringency. could it be the few pints of tap water that leaked from the wort chiller?

 

[Dolomieu]

medical = phenolic?

from BJCP

Phenolic
This is an aroma and taste often compared to Band-aids (tm), medicine chest or disinfectant. Chlorophenols are particularly offensive members of this family with bleach-like flavors in addition to the ones listed above. High levels of phenols are generally produced by bacteria or wild yeast, both of which indicate a sanitation problem. Phenols may also be extracted from grain husks by overcrushing, oversparging or sparging with hot or alkaline water. Chlorinated water or sanitizer residue are possible sources of chlorophenols. Phenolic flavors are generally never desirable, the exception being the clove-like, vanilla-like or slightly smoky flavors and aromas in Bavarian wheat beers and some Belgian ales.

sound right?