[Steve L]

I'm somewhat perplexed with an IPA I bottled about a week ago. I brewed a Two Hearted IPA clone from the beersmith cloud which has a MAris Otter base malt and almost all centennial hops with a centennial and cascade dry hop for 14 days. I fermented with WLP001 at around 65F for 2 weeks then dry hoped @ around 68-70F for 2 weeks. THe fermenter sample at bottling tasted very good. At 2 weeks after bottling, it was even better. Over the next 3 weeks the malt profile started to intensify and at 5 weeks it was very strong. THe flavor was very much like a hoppy ESB. I've personally never tasted a strong diacetyl flavor that I was aware of but from the descriptions, my IPA had a definitive butterscotch like flavor. It wasn't sour at all, in fact the beer isn't too bad. I'm just trying to pin down why this intense flavor came up and is it in my process or ingredient choice, or both...

Here are the particulars:
90 minute boil
6 gal batch (although I scaled this down to 2.5 gal)
Mashed @ 152F  5.4PH
Batch sparge
Aerated 2.5 gallons with O2 @1 liter per minute for 45 seconds

12 lbs   Pale Malt, Maris Otter (3.0 SRM)
2 lbs   Vienna Malt (Weyermann) (3.0 SRM)   
8.0 oz   Cara-Pils/Dextrine (2.0 SRM)   
8.0 oz   Caramel/Crystal Malt - 20L (20.0 SRM)   
0.8 oz   Centennial [10.3%] - Boil 60 min   
0.5 oz   Centennial [10.3%] - Boil 45 min   
0.5 oz   Centennial [10.3%] - Boil 30 min   
0.8 oz   Centennial [10.3%] - Boil 15 min   
0.5 oz   Centennial [10.3%] - Boil 0 min
1.0 oz   Cascade [5.5%] - Dry Hop 14 days   
1.0 oz   Centennial [10.0%] - Dry Hop 14 days

[hopfenundmalz]

I can't say where the flavor is coming from exactly, but do you get a slick feel on your tongue and mouth? It could be Diacetyl coming from oxidation of the precursor in the beer.

Recipes on the web can be suspect. The MO will lead to some of the ESB flavor. Bells uses Breiss brewers malt and Briess pale ale for much of the grain, and a little C40 if I remember correctly. Two Hearted is also all Centennial. WLP001 is not a bad choice, if you can get some Bells, harvest some house yeast and make a starter. The house yeast adds a little bit of orangey ester to the beer.

[majorvices]

Oxidation can cause diacetyl to reform. The other possibility is infection.

I've stopped using MO in my American hoppy beers because I pick up some diacetyl-like flavors from MO, especially when used 100%, that clashes with hops.

[Steve L]

I wondered if using MO almost exclusively as the base malt may have added to this flavor. Another thing (something I am actively remedying in future batches) was indeed oxidation concerns. WHen I batch sparged, I tended to be a bit of a heavy stirrer. I also just dumped my sparge water in rather aggressively, Something I've recently read may contribute to oxidation. Maybe I'm dealing with a combination of the two?

[majorvices]

I'm only really concerned with post fermentation oxidation. Did you purge your kegs/secondaries with co2? Is this bottle conditioned?

[beersk]

WHen I batch sparged, I tended to be a bit of a heavy stirrer. I also just dumped my sparge water in rather aggressively, Something I've recently read may contribute to oxidation. Maybe I'm dealing with a combination of the two?

I doubt this, highly...

I think it could be oxidation post fermentation and possibly at bottling time.

I'm dealing with a beer, a rye pale ale, that had a slight butterscotch happening in the keg. It may have been oxidation from not adequately purging the headspace. It was 3.5 gallons in the keg, perhaps I didn't purge well enough. But I bottled a bunch of it off and noticed the butterscotch last night. No slick mouth feel though. I don't know where else it would come from (I am damn sure at this point that it's not coming from my gas lines).
Then again, I could be imaging it. It was with Kohatu hops, rye, 4oz special B, and 4oz Victory. It could be a combination of those malts that makes me think butterscotch when it could just be caramel/toffee that I'm tasting.
It's not too unpleasant either, in this case. But I've definitely had some IPAs ruined by contamination of my gas lines (mold in disconnect from back flow) that caused intense butterscotch after a week or so in the keg. I almost quit brewing because I couldn't figure out why that was happening.
So I'm usually put off when ever I perceive what might be butterscotch, anymore...

[Steve L]

I do bottle using a 5 gallon bucket and almost never secondary. I wish I had the room to keg! This IPA in question doesn't have any unusual mouthfeel to speak of, just teh flavor issue. I thought about getting a small CO2 tanks to purge my bottling bucket. I've read a fair number of posts that claim it isn't necessary, I really do not know myself. I'm all for doing it if it will help and not hurt. I have just purchased a ported better bottle for bottling so I can do Low Oxygen transfers to my bottling vessel. Another interesting thing I heard on an episode of BrewStrong was a suggestion that when bottling, you should fil and then just lay the bottlecap in top of the bottle and not crimp it right away to help drive off a bit more O2. I'm by no means an expert, so I'm willing to try anything I can to avoid oxidation of any kind. I wish I had a more sophisticated brewery, but it is what it is.

[majorvices]

It possible that you picked up oxidation during the bottling process. I have bottle conditioned numerous beers and on most never had a problem. But I would sometimes pick up some oxidation problems on some. Theoretically the yeast should reabsorb the o2 during the carbonation process but perhaps some beers are more perceptible than others.

At YHB we have a 4 head Italian bottler that is manual except it has auto shut off. Been using it for 2 or 3 years now to bottle 22 oz bombers. Only recently did I find that what I thought was a purge process was really only a pressurize process and I was bottling beer in un-purged bottles (I figured out how to purge and it works better now). Every IPA I brewed tasted great at first but quickly fell and developed either diacetyl or strange off hop flavor problems where the kegged beer remained stable and great tasting. Other higher gravity Belgians all tasted great even a year or two later.

[reverseapachemaster]

An ESB shouldn't have a strong note of diacetyl so if what you are tasting reminds you of an ESB it is likely just the use of MO and not diacetyl.

A good test for diacetyl, mentioned above, is to look for an oily sensation on the tongue like you just rolled raw butter on your tongue.

[denny]

WHen I batch sparged, I tended to be a bit of a heavy stirrer. I also just dumped my sparge water in rather aggressively, Something I've recently read may contribute to oxidation.

If those things caused problems, every batch I brew would be oxidized.

[ajk]

If it is indeed diacetyl, and it's intensifying over time, I would suspect infection.  You can probably find someone in your area who's good at identifying it if you're not sure.  (Heck, send me a bottle if you like.)

I had a diacetyl-producing bug infection in my brewery.  After several consecutive batches with diacetyl, I decided something was up.  I replaced hoses, boiled small parts, and sanitized everything else with a sanitizer I don't normally use.  Haven't had the problem since.

[Steve L]

WHen I batch sparged, I tended to be a bit of a heavy stirrer. I also just dumped my sparge water in rather aggressively, Something I've recently read may contribute to oxidation.

If those things caused problems, every batch I brew would be oxidized.

Thanks Denny, I was hoping to hear that.

I did read a few posts that suggested the butterscotch flavor will most likely fade over time unless it's an infection. I guess time will tell. I did enter this beer in a comp that judged this past weekend. When I sent it in the flavors we're somewhat better. Hopefully my scoresheets will be enlightening.

[kramerog]

I wonder if the diacetyl was created during dry hopping, but was not noticeable until the hop character subsided.  To reduce oxidation during dry hopping, you could dry hop while fermentation is waning, but still active.

[Steve L]

I wonder if the diacetyl was created during dry hopping, but was not noticeable until the hop character subsided.  To reduce oxidation during dry hopping, you could dry hop while fermentation is waning, but still active.

I've thought about this in the past. My only concern would be reduced hop utilization, but I could ad a bit more to compensate. I wonder if it would change the flavor characteristics of the dry hop?

[HoosierBrew]

FWIW, I've done a helluva lot of dry hopping and haven't had a diacetyl problem tied to that. The only instances of it for me were in earlier years when I rushed to package too soon, or before doing a D-rest for lagers.