low level infection?

General Homebrew Discussion
1

First of all, Happy New Year to my fellow brewers.

I’ve been detecting a low-level vegetal-type taste in my last 6 or so beers.  Not enough to cause me to dump them, but enough to bug me (most of my beer drinking friends haven’t noticed it).  A couple judges at comps I entered this fall noticed it too, but just made notes like “you may have a slight infection in this beer; check your sanitation procedures.”  It has gone thru a fresh start with my favorite lager yeast, so while at one point I thought it was maybe one bad batch of beer that infected my yeast and screwed up subsequent batches, now I’m not so sure.

For sanitation, I mix up Starsan with distilled water every 2-3 brews, so it is a max of about 6 weeks old, and never cloudy when I use it. I have a stainless steel boil kettle with copper IC but a plastic run-off tube (but I chill with a big IC so only chilled wort is going thru the run-off tube into fermenters.) My fermenters are 7-gal plastic tanks about 5 years old.  Is it possible they harbor something? I soak in hot PBW solution overnight after every fermentation though…  or is it time to replace them?

I don’t think this is DMS because for all my pilsner-malt based beers I boil 90 minutes, and for all of them I chill quite rapidly (I can chill 10 gal of down to 60F in 10 min, on average).  So I’m wondering if there a bugs that survive Starsan?  Is there such a thing as a low-level beer infection vs. a “really bad” infection?  Or does anyone have suggestions?

One other thing I was thinking: I buy my hops by the pound, and vacuum pack them in plastic vac seal bags when I open the pound. I keep them in an industrial walk-in freezer at work at -15F. Some varieties are 18 months old when I finally finish the pound. Any chance these old hops are possibly causing my problem?

Any help would be appreciated…
Red

2

Sure there are low level infections. If you store your beer cool it will slow down most organisms alot. Plastic can harbor bugs and bugs can (maybe) become resistant to star san. try replacing your buckets and tubing. I doubt it’s the hops but out could be. How do they smell?

3

Vegetal doesn’t suggest infection to me. I think a low level infection is more likely to strip flavor and produce extra carbonation.

4

The hops smell fine, so I’m also skeptical, but like I said, some are old…

5

So what does vegetal suggest to you?

Also, I keg and force carbonate, so it would be hard to tell if an infection is producing something that would be a “gusher” in a bottle…

6

Hard to say without tasting it myself, but it could be DMS. Or it could be coming from the malt. Sometimes I get a grassy/grainy note from beers that have a lot of Pilsner or Pale 2-row, especially when they’re real green.

7

It could even be poor yeast health I suppose. Definitely a taste test. You might try bottling a gallon when racking each batch as a control/test group. See how they turn out vs the keg.