Beer sweetening in the keg as it ages

[5B-brewing]

I've had this happen on a couple of batches recently. One a SMaSH blonde, one a dry-hopped pale ale. Hydro readings on both were 1.008 before kegging, so they were fully attenuated. (Hydrometer was checked with distilled water. Used California Ale with both.) Force carbed up to 2.5 volumes. For the first three weeks they drank great and I have gotten rave reviews on them. They've been in the keg for about a month and a half now, and I pulled a pint of the pale ale last night and it finished sweeter then it did in the beginning. My wife didn't notice until I pointed it out, but it is definitely different.

What could be causing this? Is there an infection that causes sweetness? My cleaning and sanitation regiment is pretty strict. I only have two CO2 lines running four kegs (next purchase is a gas manifold) so they were a little under-carbed. Could that have caused it?

These are two of my "house" beers that I've never had problems with before and two that I can't afford to have problems with. Ideas? Suggestions?

 

[Yooper]

As beer ages, it loses some hops flavor and aroma. That could create a perception of it being sweeter.

Also, is it losing carbonation a little? Losing some carbonation (which has an acid bite to it) could create a sweeter finish as well.

 

[5B-brewing]

Thanks Yoop!

The SMaSH blonde is only 18 IBU to start using a very small amount of Saaz, but the pale ale is 45 IBU and dry-hopped with Zythos. Could be the case with that one.

As for the carbonation, I only have two gas lines, so I run two kegs at a time. The two that aren't hooked up aren't getting constant pressure and are definitely loosing carbonation. SWMBO says to go get a manifold so who am I to argue?

 

[Yooper]

Thank Yoop!

The SMaSH blonde is only 18 IBU to start using a very small amount of Saaz, but the pale ale is 45 IBU and dry-hopped with Zythos. Could be the case with that one.

As for the carbonation, I only have two gas lines, so I run two kegs at a time. The two that aren't hooked up aren't getting constant pressure and are definitely loosing carbonation. SWMBO says to go get a manifold so who am I to argue?

Oh, I bet it's the carbonation issue! If you've ever drank an opened beer the next day, it has a definite sweet flavor to it that wasn't there when it was nicely carbed. If you turn the carbonation up, like in a gueze, it's spritzy in texture and almost tart as a result. I am thinking that the lack of carbonation in the beer is the cause of the flavor changes here.

 

[5B-brewing]

Off to the brew store then! Thank you! Hope that's all it is.

 

[Yooper]

Off to the brew store then! Thank you! Hope that's all it is.

Not that I would take anyone out of buying more gear(!) but you may want to just move the gas over to the kegs you have online, and turn it up to make sure it's at 12 psi at least (assuming 40 degree temperature inside the kegerator) for a few days and see if that helps.

 

[Spartan1979]

I had a Helles that got sweeter. Turned out it was freezing inside the keg. I was getting Eishelles.

 

[5B-brewing]

Carbonation was the ticket! All is good! Cheers!