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I brewed an imperial red recently. The first few pints seemed okay-not great…This passed weekend I kegged another beer so I took the Imperial red off carbonation so I could force carb the other beer. Other beer is good now so I put the Imperial red back on carbonation and poored a pint…I am now getting heavy butterscotch flavor from this beer. I was kind of afraid of this happening on brew day but it seemed okay a couple weeks ago. Could taking off carbonation for two days have made this beer get this bad?


Hmmm, did the keg still have pressure when you added it back to CO2 tank? Maybe the keg has a significant leak and the beer was being oxidized?

I have never experienced anything like that with my kegs and I will often times cut the flow of CO2 to them.

There was less carbonation than when I pulled it off co2 but not a significant difference and there was still a good amount of carbonation…it was a little over carved prior anyway…,y poppets have seemed a bit sticky…but again nothing major and since I know they stick I check them.

What yeast did you use? Many English yeasts will produce diacetyl so it should be expected. If not English, then I’m not exactly sure what’s happening.

US05… Had trouble with thermometer and ended up pitching probably around 75 and fermenting around 71-73… But what gets me is the butterscotch flavor has become more pronounced over the last week. Is that typical? This the first I have had this happen.

Infection can cause this. Also, I think theres a diacetyl precursor that can convert over time and come on strong. I don’t think it had anything to do with being on/off gas unless there was something nasty in the post that broke loose when you pulled the coupling off.

Also, if your gas lines or gas disconnect is moldy, it will give you butterscotchy flavors in the finished beer. I’ve had this exact thing happen to me for the last 2 or so years. I ruined a lot of beer figuring it out and the last place I looked was my gas lines/disconnects. I found a moldy gas disconnect. So I broke everything down and gave them a good soak and a rinse, let air dry for a couple days and hooked it back up. Been good since then. If it wasn’t there to start, but showed up after the beer was carbonated, check your gas lines/disconnects. Sometimes beer can back up into the lines if you seal the keg with 30 PSI without bleeding the pressure off then hook it back up at 10 PSI or whatever. I believe this happened to me once without realizing it.

Diacetyl can come from a few different sources. It can come from a contamination or from yeast when they are exposed to oxygen. As others have said, check your lines. The precursor to diacetyl can also survive in beer for a long time and then get converted to diacetyl later, especially if the beer is exposed to oxygen. If the keg didn’t hold pressure when you took the gas off, that could be it.

Chris Colby

Could throwing more hops in the keg mask that?? At this point I don’t have much to lose contamination wise, right?

You only get bitterness from hops when the alpha oils are heated above about 175 F, so if you add hops at this point you would only be masking the odors that you are picking up and not really effecting the taste much.

There is a chance your beer is still conditioning and the flavor may subside as time goes on. I would not write it off just yet. Maybe give it another two weeks before you make any final decisions on it.

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