Recurring Diacetlyesque Off-Flavor Woes

My last 6 batches or so have all had a similar off-flavor. I have taken multiple steps to eliminate it but nothing seems to affect it.

The flavor to me is a slight diacetyl flavor. It always mutes hop flavor and aroma. These beers have all been IPAs or other hoppy ales. The full bitterness or hop aroma never seems to be reached that I expect and most of the flavor is dominated by this slightly buttery, sweet but dull flavor. The one beer it wasn't too bad on wad my Janet's Brown Ale and i expect the malt hid it mostly.

It seems to fade slightly with time.

I have used wlp001, harvested bells yeast and S-05 on these beers. I have either made a starter as per Mr. Malty's pitching rate calculator or re-hydrated a pack of s-05.

I always try to pitch within 5 degrees of my fermentation temperature.

I have kept my fermentation chamber temp between 63-66 on these batches. I usually ramp up my temp after 4-5 days to about room temp (70F) for a week or so.

I have replaced most of my tubing and plastic for fear of some infection. I still ferment in better bottles and have not tried new ones. The flavor usually isn't present in my hydro samples taken towards the end of fermentation. I have dry hopped all of these beers and the flavor is first present after I sample the beer a week into dry hopping.

I feel like I have tightened up my brewing technique and tried to maintain my fermentation as best I can. My sanitation is pretty strict. Pre dry hop everything tastes amazing. I always get my hopes up that this flavor won't come back. Then when I transfer, cold crash and put on gas it is there.

Most of my research on diacetly leads me to believe that me keeping my beer at room temperature for a week+ after a week or two kept in my ferm chamber should clear it up. If it is infection based it should get worse with time, not better...

Any input would be really helpful. I am looking into replacing my better bottle and fermenting in 1/4 barrel kegs. For what its worth, my sense of smell isn't that great. My fiance is a super smeller and says my beers have good aroma, but she definitely picks up on the same taste/smell that I do. I do not pick up this aroma from other heavily dry hopped commercial beers so its not a weird perception from me.

I feel like this is the one thing holding me back from brewing really good beer. I am pretty nit-picky and most people trying my beer say its good and don't pick up on the flavor until I talk about it. Though its hugely noticeable to me. I can only think it is an infection somewhere in my fermenters (and now in my new plastic equipment) or something to do with my dry hopping.

I dry hop with loose pellets in a keg at room temp for no more than 5-7 days. I cold crash and transfer to a new keg to serve.

Sorry for all of the info, but I want to put everything out there about my process that I can to eliminate too much back and forth.

As I understand it pediococcus in the draft lines can contribute diacetyl flavors. Perhaps that's your issue? How do you go about cleaning your keg lines? Do you use a caustic cleaner followed by a sanitizer regularly?

LoneWolfPR said:

As I understand it pediococcus in the draft lines can contribute diacetyl flavors. Perhaps that's your issue? How do you go about cleaning your keg lines? Do you use a caustic cleaner followed by a sanitizer regularly?

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I do after every batch or every other. I get this flavor straight out of the keg however, even before it touches a liquid line.

Bump

Besides sending a sample to a member here, maybe you can bring a sample to a local homebrew club meeting. They would probably have at least one bjcp judge in their ranks and could give you a first hand evaluation. I think this is one of those things that's hard to diagnose over ther internets.

Doing research the only thing I can find that produces diacetyl after kegging is pedio. Maybe you've got a part of your keg that is just not getting completely sanitized each time around?

"CHARACTERISTICS: A butterscotch aroma and taste, and a slickness on the palate. Not desired in excessive quantities.

CAUSES: A normal product of yeast during fermentation, it is re-absorbed during the course of a normal fermentation. Another cause is the gram-positive bacterium Pediococcus cerevisiae and similar strains in cooled beer, young beer, and aging beer. Lactobacillus strains in the mash can also cause this flavor if the mash held at low temperatures (below 131 degrees). Note that the aroma/taste produced by all of these causes is indistinguishable.

CHEMISTRY: One of a family of vicinal diketones. Presence recognized down to 0.05 ppm, but identified at 0.15 ppm.

HIGH RATES FROM PROCESS: Underpitching of yeast; long periods of wort cooling (overnight); contamination from equipment; poor yeast strain; too-soon clearing (fining) of yeast (before it can reabsorb the diacetyl); too long an acid rest in mash; high adjunct ratio in wort; low fermentation temperature; premature lagering; any process that stimulates yeast then immediately removes it from suspension; use of contaminated sediment for re-pitching (bacteria coexists with yeast in the sediment).

REDUCTION: Sanitation, quick wort chilling combined with adequate yeast starter amount (8 ounces of slurry to 5 gallons), adequate time for primary ferment before lagering or fining/filtering, all-malt recipe, higher temperature primary fermentation, pure yeast culture, washing yeast sediment prior to repitching.

EXAMPLES: HIGH: contaminated homebrew; MODERATE: Sam Smith’s Nut Brown Ale, Pete’s Wicked Ale.

It might be time to break down your entire keg set up from the towers on down if it hasn't been done recently. You might be surprised.