Off Flavor - Oxidation?

wow, I have the SAME exact problem with my hoppy beers. They just taste a bit dull, slightly vegetal, a little fusel-alcoholy, and caramel-ish (even though I use barely any caramel malt). I mean, the beers are good, but they are held back from being great.

Have you figured out what the problem was yet? I'm considering replacing all of the posts on my kegs just as a precautionary measure. I feel the actual keg is the last thing left...maybe there is some sort of infection going on. I've tried the water adjustments, tried purging EVERY step with CO2, dry hopping for less than a week, pitch enough yeast, aerate, ferment at the correct temp, etc. etc.

Unfortunately no. I haven't cracked this one yet. I'm running out of variables it seems. At this point I know my process is solid because my other beers come out on target. I actually did really well in a competition with my brown and wit. I suspect that it must be something to do with the water, even though I now use a filter, potassium meta, and make water adjustments. Ive also talked to other local brewers who have no problem with the water. even given that, I'm considering grabbing some store bought water for a test batch to see if it makes a difference. Im also tempted to bottle up a batch to see if that plays in. Here are the angles I have looked into...

Hop Freshness & Type
Oxidation
Mash pH
Sulfate levels
Dry Hop Duration & Elimination
Leaf vs Pellet

Hey Tagz, any new developments?

After brewing a couple delicious not-too-hoppy beers I recently brewed Janet's Brown Ale thinking a hoppy (also dry hopped) brown ale might stand up better to oxidation than a hoppy pale ale due to the darker malts. I only opened my primary fermenter once prior to kegging to take a hydrometer sample and toss in the dry hops. After 5 days I cold crashed it to drop the hops and help settle the yeast, then I racked to a keg. The keg had been filled to the top with star san then drained under pressurized with CO2. This should have filled the keg 100% with CO2 before I racked the beer into it. I then purged it 5 times and force carbed it. 2 weeks later it tasted young, but full of hop flavor/aroma. At a month it tasted totally muddled and the hop flavor/aroma were gone. The bitterness has a twangy lingering quality that is anything but crisp. What gives???

Could the issue come from transferring kettle hops and trub into the fermenter? I use whirlflock and pour through a strainer, but still get some sludge in the bottom of the fermenter.

If you've had any success or insight I'd love to hear how your endeavor is going.

So, I brewed a pale ale with fresh pellet hops (2012 Citra & Ahtanum) to see if hop age made the difference. It did not. Amazing aroma from the Cirta dry hops as I pulled them from the keg. However, after 2-3 days things got veggie/earthy. It was tolerable for a while, but I dumped the last gallon or so.

Last month, I decided to start brewing a series of light profile session ales with 1968 and a feature ingredient or two. The first one featured biscuit, which was decent, but I couldn't bring myself to add any flavor hops. It ended up tasting like Sam Adams. Made me want to give the hops another go...

I brewed a similar beer, dropped the biscuit and added a touch of aromatic. I was only feeling mildly brave so I used just an ounce of Mosaic. 20 IBUs from Warrior at 60, half an ounce whirlpool at 140 degrees, and half an ounce dryhop (3 gallon batch). Nice melon, apricot, tropical fruit for the first week. Things got slightly earthy for a few days. Then it settled into a more general fruity hop flavor. I thought it was going south that second week but turned out great in the end.

So I'm not positive about what is going on here but I would recommend trying a new hop, brew a single hop beer, and use a light hand. I think that using certain hops in large quantities at the end of the boil may be a factor. I'm brewing a very similar recipe to the Mosaic tomorrow, this time with an ounce of citra. I'll report back.

Well I'm glad you're having a small bit of success, but it sucks that you're avoiding brewing hoppy beers because of this issue. I stayed away from brewing hoppy beers for a bit as it's all I could do to stay sane. After getting my process down with tons of other great beers it's incredibly discouraging to have to force down or even dump every hoppy beer I make. Keep me posted and I'll do the same.

By the way I love that yeast (I use WLP002). It ferments fast without an absurd amount of blow off and it drops clear. It's pretty neutral, but gives a bit of character. I love it in porters.

I know these issues are getting worse over time for you all but I noticed a huge leap in my IPA's when I started adding gypsum to my filtered water. I can't say I experienced what you all are but the hops certainly didn't pop like they should have, and I would say it wasn't 'right'. Maybe the off flavor is unnoticeable with that fresh hop aroma, and when it fades, you taste the funk. Just a thought....

tagz,
Any samples from this latest batch? I've been following your thread as I have the exact same issue, and have also attacked each of the possible issues similarly, although in a different order. I'm onto potential oxidation now, but wouldn't think it'd take hold so quickly.

My latest batch is a Mosaic/Cascade APA/IPA that tasted fantastic at transfer time and at 1 week in the keg (albeit slightly young) and has now fallen into the "dull" state... For this batch I used all vacuum sealed hops from HopUnion.

Anyway, I'd be very interested in your latest experience.

Well, I brewed the Mosaic recipe again, but swapped Citra for the Mosaic. Ive been drinking it for about a week now and it seems i have another clean tasting pale ale. It had a nice tropical nose when I pulled the first few pints and now its turning into a more general hoppiness. But, its definitely a clean flavor; no earthy, vegetal, herbal flavors. So that makes two batches without the issue. The two variables I've been working with in these batches is hop strain and quantity.

After working through a series of commercial examples, I've come to the conclusion that Amarillo has the earthy notes that I find objectionable. So that accounts for two of the batches. That said, I did have a ahtanum/citra batch that developed the same flavors. I tend to blame that on the ahtanum, because I know it has that musty aroma based on my experience with stone pale ale. I did use the ahtanum in a saison in very small amounts and I believe got a nice grapefruit edge from it, with no earthy favors. so i think the fact that i was very reserved in the quantity helped. I doubled the ahtanum addition on my latest version so we'll see how that plays out.

All this makes me think that some varieties give off these flavors when used in large quantities. I also think some of us are more sensitive to the flavors. In the book For the Love of Hops, it says that we all have over 1000 aroma receptors and we only use 300 or so of them. It also explained that not everyone uses the same 300, so we may be able to detect aromas that the next guy will not.

My bottom line at this point is to keep trying different varieties and slowly increase the quantity I am using. Im not at the point where Im getting the juicy hop flavors I'm looking for but at least i haven't had to pour any batches out lately. I'll probably use some centennial next round, as I know I've never had any unpleasant flavors with Two Hearted or home-brews that have highlighted the hop.

Hey - thanks for the update. I'm leeting that keg sit another week before touching it to see if its character changes again by 3 weeks in. Since you should mentioned the Centennial - I've got NB's Dead Ringer dry-hopping now and plan to brew BierMuncher's Centennial Blonde next, as I've got quite a bit of these in the freezer.

I don't have For the Love of Hops, but sounds like a good read. I can attest that my girfriend always describes the flavors and aromas differently than I do.

Tagz, still having luck having swapped out hop varieties?

I seem to be having troubles with oxidation type flavors from dry hop.

NHMikeT, Wesjmc, Jwood, Cwheel- you guys have any luck figuring out your off flavors? Anyone wanna compare brewing techniques?

I was thinking about carb pressure and its affect on oxidation. I've made some hoppy beers without the flavor so i am thinking it's process related.

grathan,

In response, I've since brewed two beers with zero off-flavors, but they were not hoppy brews. The one that's drinking now is an excellent amber, about 35-40 ibus from one bittering charge of Chinook (finishing hops were with wild/backyard hops).

The only thing I changed on these brews was the water. I used well water from my girlfriend's parents' house instead of treating my tap water (I had both tested by Ward Labs). I'm thinking (hoping...) that for some reason my sink Pur filter and campden treatment did not remove all the chloramines in the tap water.

I brewed an IIPA today using RO water from the machine at the grocery store, so I'll know in 6-7 weeks if there's an issue. Interesting you mention carb pressure... I've only been kegging for a few months now, and I only feel like the carbonation influences the flavor in the first few days (I usually wait 10 days before starting to really drink a keg).

Feel free to PM if you want to discuss process in more detail.

-MT

If you don't mind, I'd discuss process in the thread? I came here from a Google search about dry hop oxidation and there isn't really much info out there. So perhaps this could help someone else.

My ipas taste great at first keg pull. The very next day things start going bad. And they continually get worse. Beautiful tropical fruit flavors/aromas gone. Replaced by dull, sherry, cardboard. I would rather not drink after day 3 and 3 months things still are get progressively worse to the point it no longer resembles beer.

This has me believing that carbonating plays a hand in things. I know that I may be over-carbing and I am new to kegging also (I don't have a set process yet, sometimes I crank up to 30+ psi and sometimes I let sit at serving pressure for 2 weeks). My latest ipa was cranked to 37psi and the flavors disappeared almost overnight. Could be carbonic bite masking the flavor, it's not ruled out yet, but hard to believea beer goes from best ipa ever tasted to bleh in the coarse of a single day at 15 psi 35*F. My wild theory is that high pressure (30+psi) or the presence of cabonic acid rapidly progress oxidation.

Another theory not discussed much at all in the brewing community. Oxidation of hop oils by aerating wort with pure oxygen. I use an 02 tank. 0.2 micron stone with pressure so that not maximum bubbles, but some reach the top of the wort for 0-2 minutes.


Another thought is oxidized hops causing oxidized beer. I was trying to use up an old 1LB bag of centennial in all my oxidized ipas this year. Again, there is nothing turning up on Google for this happening so just some wild theory.


My most solid lead at this time is my fermenter. It is a massive 8 gallon plastic speidel tank that I dry hop and cold crash in. I've made hoppy beers in glass carboys this year that didn't oxidize. I've brewed hoppy beers in bottles that taste fine after 5 years. I suspect the massive head space ( at least 3 gallons ) after opening to drop in oxidized dry hops and then cold crashing after a week. There is vacuum leaks because there is no negative pressure at racking time.

I am pretty careful about purging kegs with co2. I never open fermenters other than for racking. I don't secondary. I take that back. I did secondary the latest iipa. I placed the dry hops in a co2 purged keg and racked on top of them. This turned out oxidized, but I suspect because of the cold crash in the speidel before the rack onto dry hops.


I have a iipa in the works where I didn't cold crash. I am also force carbing at serving pressure. I also added dry hops during primary fermentaation. Gonna go sneak a taste right now after 24 hours at 5 psi. Bleh, it doesn't taste like carboard yet, no cabonation. Very cloudy from no cold crashing. will post back on how this turns out.

I eliminated oxidation from my list. And, after several successful beers with citra, mosaic, and centennial, I'm pretty sure my primary issue was hop type and quantity. I've used Ahtanum in smaller quantities with some success. Amarillo I will just avoid from now on. By the way, the problem got worse over time with me as well. I was typically pretty happy after sampling at the end of fermentation. After kegging and carbing, it was gross.

Hey that is good news tagz, you couldn't share a recipe and hop vendor so that I could try it out?

I've been getting most of my hops from Farmhouse Brewing Supplies. Although I have ordered from Grain to Glass recently as well. I like the 4 ounce packs, because it allows me to try out several strains.

Here's the grain-bill I've been using for the single hop beers I brewed to get to the root of the problem:

82% Pale Ale Malt
6% Aromatic
6% Caramel 40
6% Flaked Barley

OG ~1.050

Technically, they are not single hop beers, as I bitter with a small charge of Warrior (25 IBUs). But, Warrior is a clean bittering hop, and I was really trying to evaluate flavor. I started off really light handed on the flavor additions (because the bad batches made me gun-shy). They were 3 gallon batches and I used .5oz for a hopstand and .5 oz for dryhop. After the first few successful runs, I increased to the amounts. However, I have stuck to the 60 min, hopstand, and dryhop schedule because I liked the results. When using these small amounts, the dryhop flavor fades quickly, so I started adding a small dose of hops in the keg as well (tea ball). It keeps the flavor bright for a longer period of time.

All that is to say, I would recommend doing some small batch, single hop beers to see if hop variety might be the variable causing you the trouble. Based on the descriptions, I should like Amarillo and Ahtanum, but turns out... not so much. Or, I just got a bad batch.

So glad I found this thread, so I can vent. I'm having this EXACT issue with my IPAs and it's super Fn frustrating! Last week I bottled a black rye IPA (Wookey jack clone). It tasted amazing when I racked to secondary and on bottling day. The rye came through, hop flavor and aroma was awesome (double dry hopped with citra/Amarillo). I was really excited about this beer. I cracked one last night, 10 days in bottle, just to see how it's coming along and right away I noticed that smell. And of course the taste is right there with it. I no longer get the nice citrusy hop aroma or the rye maltiness. It just has a harsh aroma/taste - hard to explain the taste but it sounds like the same thing you're experiencing. Don't have this issue with my non-hoppy beers either. This is my 4th IPA I've brewed, all different recipes with different hops but ALL of them have ended up having this issue.

My first thought is its time to retire the bottling and start kegging. Seems like it would be a lot easier to limit the amount of contact with oxygen but you're kegging and having the same issue.

Last month I helped my friend brew his 1st all grain beer - NB dead ringer IPA. We used my equipment and process but his tap water (no water adjustments) and he kegged instead of bottled. It was one of the best home brews I've ever had. Didn't even have a hint of "that" off flavor. So maybe it's my water? I have a ward labs water report and use Brunwater to make adjustments and check my mash/sparge PH.

I might try store bought drinking water and brew a small batch. No more $60+ recipes until I get this sh*t figured out!

I'm glad I found this thread too. I started two threads a few weeks ago titled "fix my twang" and "where'd the hops go?" as I thought I had two separate issues. From reading here, it sounds like others are experiencing the same thing and maybe it's a single problem. I'm down to yeast troubles, water troubles, or bottling practices. I have an imperial IPA fermenting now that I added campden tablets to. I also switched to US-05 (two packs) to eliminate any human error in my starters. I fermented a little cooler than normal and gradually increased the temps. I'm planning to cold crash and rack to secondary for dry hopping. Then I'm going to cold crash again before bottling.

I hadn't thought about the carbonation levels though. I've had a tendency of over-estimating how much beer I'm going to end up with in my bottling bucket and as a result have over-carbed almost all of my IPAs. In fact, all except the ONE that I think turned out good. Maybe I'll start aiming a little lower on my CO2 volume as well.

I should know more sometime after the first of the year.

Just curious if anyone has changed their milling protocol during experimentation. Can over-milled grains or leaving them too long after milling and before using cause the off flavor reported here?

Francis said:

So glad I found this thread, so I can vent. I'm having this EXACT issue with my IPAs and it's super Fn frustrating! Last week I bottled a black rye IPA (Wookey jack clone). It tasted amazing when I racked to secondary and on bottling day. The rye came through, hop flavor and aroma was awesome (double dry hopped with citra/Amarillo). I was really excited about this beer. I cracked one last night, 10 days in bottle, just to see how it's coming along and right away I noticed that smell. And of course the taste is right there with it. I no longer get the nice citrusy hop aroma or the rye maltiness. It just has a harsh aroma/taste - hard to explain the taste but it sounds like the same thing you're experiencing. Don't have this issue with my non-hoppy beers either. This is my 4th IPA I've brewed, all different recipes with different hops but ALL of them have ended up having this issue.

My first thought is its time to retire the bottling and start kegging. Seems like it would be a lot easier to limit the amount of contact with oxygen but you're kegging and having the same issue.

Last month I helped my friend brew his 1st all grain beer - NB dead ringer IPA. We used my equipment and process but his tap water (no water adjustments) and he kegged instead of bottled. It was one of the best home brews I've ever had. Didn't even have a hint of "that" off flavor. So maybe it's my water? I have a ward labs water report and use Brunwater to make adjustments and check my mash/sparge PH.

I might try store bought drinking water and brew a small batch. No more $60+ recipes until I get this sh*t figured out!

Click to expand...

Dead Ringer uses centennial exclusively. I would brew you next few batches with centennial. Since you know you like the hop, you can play with the other factors. Once you get that dialed in, try some other varieties as single hops beers. You might find that certain varieties are more prone to the off-flavor.

After further experimentation, I finally tossed the rest of my amarillo and a good amount of ahtanum. They both give off the harsh vegetal/herbal flavor that masks the other hop flavors. I haven't had any problems with citra and centennial, very clean fruity profile for both. Mosaic is tropical fruity at first, turns slightly herbal after a week and then finishes out citrusy. The herbal notes don't detract enough to make me avoid it.

Your problem may not be variety, but it's an easy variable to test with some small batch single hop beers. It was one of the last factors I tested, but what a relief it is to finally be able to brew hoppy beers!

While I haven't tried your recipe yet. I did try the IIPA i made without cold-crashing and the oxidized flavors were considerably subdued. I think to further reduce my oxidation I will need to use natural carbonation (yeast consume oxygen). I think something about big dry-hopped beers makes them incredibly sensitive to oxygen.

interesting to see how common this problem is...

grathan –
sorry for the delay but in response to your post on 11/5/13 I wanted to wait until I’d sampled a bottle of my latest batch before responding. Unfortunately, since this batch wasn’t kegged, it won’t address your issues with kegging, but I’ll briefly tell you how I’ve been kegging just for another data point:

I’ll usually move the carboy to the countertop before starting anything else in the process, so that anything kicked up will have time to settle some. After Starsanning the keg and parts, and reassembling, I run starsan through the keg and picnic tap to sanitize everything, (some people think this is a waste of CO2, but to me it’s worth it to purge the keg and lines). Then I purge the lines of the autosiphon, and rack to the keg with the lid open and covered by sanitized foil (you should see the CO2 “cloud” in the keg). I’m hoping to eventually start racking through the liquid out post to completely get rid of air contact…

Once full, I seal it up, and purge the headspace four times. Then I set the pressure between 8-12 psi depending on the beer and put it in the kegerator. FWIW, I usually don’t start drinking it 10days or more on gas. I do not do the “boost carb” method, but many people do so I’d be surprised if that process alone was enhancing oxidation more quickly for you. I’d guess the oxidation you’re having is from using oxidized hops, or something in your transfer methods. I can’t say I’ve solved this problem either as my hoppy beers haven’t turned out well lately.

My latest IPA was bottled because I’m about to move and have to break down my kegerator this weekend. First off, here’s the recipe (I was basically cleaning out the freezer and fermentables):
12# Rahr 2-row
2.5# Breiss Golden Light DME
11oz dextrose
8oz Crystal 40L
2oz Pale Chocolate (200L)

4oz Simcoe
3oz Centennial
2oz Citra
2oz CTZ
0.75oz Chinook
(all pellets)

2 packs rehydrated US-05
1 whirlfloc
1/2tsp Wyeast nutrient

RO water
4 g each gypsum and CaCl2 in mash
4 g gypsum in kettle

HOP schedule:
Centennial, Chinook, Simcoe @ FWH
Centennial @ 30
Chinook, Citra, Simcoe @ 15
Citra, Simcoe, Centennial @ KO
Centennial, Simcoe, Citra, CTZ @ Dry Hop for 3 days only (5+ oz)

Process:

Mashed at 151F, 1.3 qt/lb ratio for 70 minutes. Mashout 10 mi settled to about 165F. FWH added to first runnings. 15 minute batch sparge at 164F, collected approximately 6.5 gallons, topped up to 7 gallons with RO water (in hindsight this was not enough pre-boil volume given the amount of hops).

Boil as usual, chilled to 63F, oxygenated for 90 seconds with pure O2 and 0.2 micron stone on as low a setting as allows bubbles to appear. Pitched rehydrated yeast. Fermented at 63-65F in swamp cooler. The yeast went to town on this batch, blowing off for 3 days after starting fermentation within 8 hours. After 5 days, carboy removed from swamp cooler and raised to 68-70F, fermentation complete in 8 days (1.074 to 1.011). on 12th day racked to secondary on top of dry hops (autosiphon hoses and carboy both purged with CO2 as best I could). Dry-hopped at 68F and then put in cold closet for 24 hours (this only dropped temp to about 50F, which was enough to drop the hops out). Bottled on day 17.

I’m drinking the first bottle of this stuff now, after putting in the fridge two days ago and I must say, it’s undoubtedly the best hoppy beer I’ve ever made. At first pour the hop aroma is explosive and resinous, though not nearly as fruity as the gravity samples were, which is definitely disappointing. When I tasted the gravity samples from this beer I thought it was going to be one of the best beers I’ve ever had, but it’s just a really good hoppy beer (not on par with my commercial favorites). I get a slight hint of alcohol in the aroma and flavor after a few minutes in the glass (I think, at least) and also some slight vegetal-ness in the aroma too (*disclaimer: This is only my 23rd batch, so I’m not an expert at describing the subtleties by any means).

One thing I noted while dry-hopping was that the first two days, the smells from the airlock were unbelievable, and then on the third day they turned somewhat dull and muted (maybe more veggie and grassy?), so that’s when I decided to move the carboy. Next time I brew an IPA I think I’m only going to dry-hop for 24-48 hours with pellets, then keg-hop with leaf/cone hops. I should note that almost all these hops were freshly opened 2oz packs, except a little of the Centennial and the Chinook.

That’s all I’ve got to add at this point…. I’m hoping that this DIPA I have doesn’t go south. Let us know how your next one turns out and what you changed.

This has been an informative thread. Same issue here with a Heady clone. Absolutely awesome for the first week but now very dull. I've had similar issues with previous IPAs but good success with other brews. No secondary, dry hop in keg, purge when transfer.

The high kegging pressure is an interesting thought, along with the old hops. I don't know what the age of my hops were but I did dry hop in the keg in a sack with pellet. Very murky, but again, the first week was one of the best beers I've brewed. Could it be residual hop matter interacting with suspended yeast? Not sure what the relationship is over time, but I've read there is a concern. It seems all the great hoppy/aromatic brews are pretty clear. Could filtering help?

More co-miserating than anything else. I wish I had the time to do all the test brews that tagz does!

knucklenitz said:

This has been an informative thread. Same issue here with a Heady clone. Absolutely awesome for the first week but now very dull. I've had similar issues with previous IPAs but good success with other brews. No secondary, dry hop in keg, purge when transfer.

The high kegging pressure is an interesting thought, along with the old hops. I don't know what the age of my hops were but I did dry hop in the keg in a sack with pellet. Very murky, but again, the first week was one of the best beers I've brewed. Could it be residual hop matter interacting with suspended yeast? Not sure what the relationship is over time, but I've read there is a concern. It seems all the great hoppy/aromatic brews are pretty clear. Could filtering help?

More co-miserating than anything else. I wish I had the time to do all the test brews that tagz does!

Click to expand...

A dull profile makes me think of pH. Do you adjust your water at all?

tagz said:

A dull profile makes me think of pH. Do you adjust your water at all?

Click to expand...

I bought the additives and have only adjusted once some time back. For the past few brews, no, including the Heady clone that was awesome for a week, then pooped out.

Although one example isn't enough data, I did an extract Black IPA prior to the Heady and had similar results. I should note also that I've have great beers l previously but a real test would be to do a control batch (with water adjustment) to make sure a non - IPA or another IPA has no issues still. The Heady clone is to expensive to test with.

If you can find your water report, you can punch it into the Bru'n water spreadsheet and get a reasonable idea of your pH. I used a pH meter in combination with the spreadsheet for a while and found it to be pretty accurate. High pH can cause dull hop flavors. A measured dose of lactic acid might brighten things up and make the flavors a little more crisp.

tagz said:

If you can find your water report, you can punch it into the Bru'n water spreadsheet and get a reasonable idea of your pH. I used a pH meter in combination with the spreadsheet for a while and found it to be pretty accurate. High pH can cause dull hop flavors. A measured dose of lactic acid might brighten things up and make the flavors a little more crisp.

Click to expand...

Thanks tagz. Will give it a shot.

Since my last post, all my hoppy beers have had varying degrees of this off flavor. I have also ruled out oxidation. Most recently I even transferred from my fermentor to the beer-in post on my purged keg, essentially getting as close to a "closed" transfer as possible from a glass carboy. I was talking with the head brewer at a local brewery about it, and he said it sounds surprisingly like diacetyl. He used the word "surprisingly" because the off flavor wasn't the trademark "buttery" taste, but my process, ingredients, and timeline of this off flavor all point to diacetyl.

First, I have been using WLP002 (same as Wyeast 1068 that tagz has been using) at a low temp to keep the esters low (pitch at 63F and rise to 68F). On White Labs site they have data from forced fermentations of some of their most popular yeasts, and this strain produces more diacetyl than any other British or American strain that I could see.

Second, in my experience this yeast ferments crazy fast (2-4 days) and then drops like a brick. I always liked this as I got very clear beer, however, it may have been flocculating before cleaning up the diacetyl. At day 5 my carboy is brilliantly clear.

Finally, the precursor to diacetyl, acetolactate, is completely flavorless. It can exist in my beers at the time I rack from fermentor to keg without any off flavor. When it undergoes an oxidation chemical reaction, the acetolactate is converted to diacetyl, and the off-flavor emerges. This sounds like it is happening at the same 2-3 week timeframe as my beer is carbonating. This explains the flavor transformation in the keg. Check out this article: http://www.whitelabs.com/files/Diacetyl_Time_Line.pdf

Low levels of diacetyl don't always present themselves as the classic butter-bomb. This could be the exact off-flavor some of us are having that seems to dull the hop profile of our beers. I feel this off flavor has probably existed in my porters and other dark beers, but my palate simply doesn't pick up on it in any of my beers aside from my light, hoppy beers.

I currently have a batch fermenting away with WLP001. I will post back in a month or so when it's finished.

Cheers!

I don't think Diacetyl because it is always IPA. Something more to do with chemical reactions with Co2 and polyphenols dropping and oxidized high beta acid hops.

I had back to back successful ipas at the end of last brewing season. I took Tagz advice and used a single hop for all the additions. Limited dry hops to 2oz and added them while the yeast were still active. ALso used only freshly opened packages of hops. Also stopped oxygenating with pure o2 and removed cold-crash/gelatin from process.

grathan said:

I don't think Diacetyl because it is always IPA. Something more to do with chemical reactions with Co2 and polyphenols dropping and oxidized high beta acid hops.

I had back to back successful ipas at the end of last brewing season. I took Tagz advice and used a single hop for all the additions. Limited dry hops to 2oz and added them while the yeast were still active. ALso used only freshly opened packages of hops. Also stopped oxygenating with pure o2 and removed cold-crash/gelatin from process.

Click to expand...

Good to hear you've made some progress! I've actually cranked my dryhop and flameout additions back up now that I've isolated some hops and proportions that work for me. I have a citra/simcoe/galaxy on tap that I'm really enjoying.

Wes - It's a good thought. I haven't heard about diacetyl showing itself as anything other than buttery flavors, but it's worth a test batch. Let us know how it works out. I recently switched back to 002 from Conan, because, like you, I love how quickly it ferments and drops clear. Plus, I got burnt out pretty quickly on the Conan profile.

I suspect oxygen is the culprit. I had been dealing with this issue as well in all of my dry hopped beers. Beers would be fantastic at first, but anywhere from a few days up to a couple of weeks after kegging, it would turn into what I can best describe as a caramel bomb that tasted very much like an old or oxidized beer. It would only show in dry hopped beers, all non dry hopped beers would remain nice, bright an clean. Here is what I did to eliminate oxygen exposure.

• Began adding first dry hop addition 3/4 way through fermentation
• No longer rack to secondary. Instead all dry hop additions are done in the primary.
• Flush carboy with C02 before and after each dry hop addition
• No longer cold crash in the carboy. If you listen to the most recent Session, Jamil states that cold crashing can introduce as much as 4% 02 into the beer.

In addition, I'm now going to experiment with a closed transfer from carboy to a purged keg, where I will do my dry hopping and, ultimately, cold crashing. From there, I will then transfer to a second keg for serving.

There was also a Sunday Session a few years back where Nate Smith and Tasty talked about Double IPAs. They stressed how absolutely important it is to reduce all oxygen exposure during the process as the addition of dry hops can add a considerable amount of O2 to the beer.

Regardless of how careful you are minimizing O2 exposure during your process, think about how much you are potentially introducing from the following:

• Transferring to secondary
• Multiple dry hop additions
• Cold crashing (O2 is drawn into your beer during this process)
• Transferring to keg

The main difference between a pro brewer's process and a home brewer's process is their ability to transfer everything in a closed system and reducing the amount of Oxygen. By really focusing on this aspect, I think you'll begin to eliminate this off-flavor completely.

Additionally, I would also stress to make sure all of your other processes are solid as well. Pitch a nice healthy pitch of yeast, properly oxygenate your wort prior to pitching, pay attention to your mash and kettle pH, be sure you're leaving your beer on the yeast long enough to clean itself up, and ensure you are making proper water adjustments to suit the style you are brewing.

Wow, great post. I'd like to learn more about closed system transfers. Lately I have doubts about simple flushing effectiveness. I'm gonna try another huge dry hop beer this summer.

grathan said:

Wow, great post. I'd like to learn more about closed system transfers. Lately I have doubts about simple flushing effectiveness. I'm gonna try another huge dry hop beer this summer.

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Really not too complicated, here's the method I use to transfer from carboy to keg.

https://www.homebrewtalk.com/f35/carboy-keg-closed-system-37725/

Going from keg to keg is even easier. Just create a jumper line and attach to the liquid side on both kegs. Pressurize the keg you are transferring from and it will push the beer to the new keg.

Neat, is that what the pro brewers are doing then?

Maybe fashion some type of airlock bubbler to the gas out port. There was another thread that mentioned using a bathroom scale to measure level. I am thinking maybe let it overflow, then force a six pack out into bottles before force carbing.

tagz said:

Argh!! Well I kegged it up and it has that same stale flavor! I went back through my notes and the only other thing I can think of is old hops. I realized that one variety of hops I'm using is about 2 years old now. I bought a bunch of centennial and Columbus a while back and each batch has one of the two varieties in it. The last batch was Columbus and a fresher batch of Amarillo. Would it make sense that the Amarillo made the initial samples taste good but the oxidized hops took over? Can anyone tell me what oxidized hops taste like post fermentation? I know some hops smell cheesy when they get old but what do they do to a beer once it has been fermented?

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Old hops sounds like what you're describing to me. I've had it too and switched my next batch to fresh, new hops and it was gone. I've also tasted it in several beers I've judged. People commonly think "DMS" when someone says "vegetal" but in hoppy beers, I've found it to be old hops more often then not.

HossTheGreat said:

I suspect oxygen is the culprit. I had been dealing with this issue as well in all of my dry hopped beers. Beers would be fantastic at first, but anywhere from a few days up to a couple of weeks after kegging, it would turn into what I can best describe as a caramel bomb that tasted very much like an old or oxidized beer. It would only show in dry hopped beers, all non dry hopped beers would remain nice, bright an clean. Here is what I did to eliminate oxygen exposure.

• Began adding first dry hop addition 3/4 way through fermentation
• No longer rack to secondary. Instead all dry hop additions are done in the primary.
• Flush carboy with C02 before and after each dry hop addition
• No longer cold crash in the carboy. If you listen to the most recent Session, Jamil states that cold crashing can introduce as much as 4% 02 into the beer.

In addition, I'm now going to experiment with a closed transfer from carboy to a purged keg, where I will do my dry hopping and, ultimately, cold crashing. From there, I will then transfer to a second keg for serving.

There was also a Sunday Session a few years back where Nate Smith and Tasty talked about Double IPAs. They stressed how absolutely important it is to reduce all oxygen exposure during the process as the addition of dry hops can add a considerable amount of O2 to the beer.

Regardless of how careful you are minimizing O2 exposure during your process, think about how much you are potentially introducing from the following:

• Transferring to secondary
• Multiple dry hop additions
• Cold crashing (O2 is drawn into your beer during this process)
• Transferring to keg

The main difference between a pro brewer's process and a home brewer's process is their ability to transfer everything in a closed system and reducing the amount of Oxygen. By really focusing on this aspect, I think you'll begin to eliminate this off-flavor completely.

Additionally, I would also stress to make sure all of your other processes are solid as well. Pitch a nice healthy pitch of yeast, properly oxygenate your wort prior to pitching, pay attention to your mash and kettle pH, be sure you're leaving your beer on the yeast long enough to clean itself up, and ensure you are making proper water adjustments to suit the style you are brewing.

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^ This! I've had the same problem as many of you and I too heard Jamil on the latest session. I've been cold crashing in my buckets and it's the only thing I think could be messing up my IPAs and APAs.

What if we only cold crash to ~50*F? I've heard that's sufficient to drop the yeast and should limit the amount of 'vacuum' from the pressure change. Would that limit some oxidation?

I'm currently fermenting in a 6.5gal bucket and racking to a 5gal bucket for dry hopping. Sounds like I should get at 5gal carboy to limit surface area. Or better yet, start kegging and flushing my system with CO2. That'll be my long term plan.

There was a post on HBA forms from Kai I think that showed the formula for figuring how much 02 gets sucked in, but I could never find it again after first seeing it.

Kegging is a good plan. crashing under co2 pressure would be ideal. Of course you could just serve out of the same keg so in essence, everyone cold crashes in the end anyways. Unless perhaps employing gelatin, which may clog dip tube with a gummy.

Wesjmc said:

Finally, the precursor to diacetyl, acetolactate, is completely flavorless. It can exist in my beers at the time I rack from fermentor to keg without any off flavor. When it undergoes an oxidation chemical reaction, the acetolactate is converted to diacetyl, and the off-flavor emerges. This sounds like it is happening at the same 2-3 week timeframe as my beer is carbonating. This explains the flavor transformation in the keg. Check out this article: http://www.whitelabs.com/files/Diacetyl_Time_Line.pdf

Low levels of diacetyl don't always present themselves as the classic butter-bomb. This could be the exact off-flavor some of us are having that seems to dull the hop profile of our beers. I feel this off flavor has probably existed in my porters and other dark beers, but my palate simply doesn't pick up on it in any of my beers aside from my light, hoppy beers.

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I've read something similar to this in a technical journal article and in my opinion this is what the problem that most people are reporting. I've been dealing with this off flavor problem for nearly a year and a half. I've been using the same grain bill and water profile with the same hop schedule varying the varieties of hops. I've used english, american and belgium yeasts. Fermented in buckets, glass carboys, and stainless conicals. dry hopped in primary and secondary. None of these things consistently eliminated the problem. I've probably made 15 IPAs in the last 1.5 years, and most of them have had this off flavor. 2 of them have been really great, with no noticeable off flavor, 2 have had just a hint of the off flavor, and the rest were just awful. I don't know what the genesis of these problems are, but with the steps I have gone to to avoid oxidation, and the steps i haven't gone to avoid oxidation and had good batches I am convinced the issue is an infection that causes the diacetyl issue.
I can't seem to pin the sanitation issue down. I use stainless fermentors, which can be aggressively cleaned with few places for infections to hide. Although they do use silicon gaskets, so perhaps things can live in there, but I clean them with PBW and then star san. I keep my fermentors completely closed until adding the dry hops. Even then I just add the hops through the airlock port, so there is very minimal oxygen exposure. And the batches have the off flavor when I go to keg them, so it's not in my kegging system. Nothing really touched the wort after the boil other than a silicon tube and camlock fitting on my kettle to drain into the fermentor. I run boil wort through that hose before chilling though. I do use an oxygen wand, so maybe I should bake that, but I usually just soak it in star san. I pitch the yeast(dry hydrated or from a starter) and then close the fermentor until adding the dry hops. I keep all IPAs fermenting between 64-68F with a fridge, thermowell, and temperature controller. Basically, there are not many places for an infection to take hold.
Near my wits end, I think I'm going to buy a microscope, staining solution, slides, etc. That should show something.
In the meantime, I've decided to dose my last 2 IPAs that had the off flavor with Brett B. That may remove the diacetyl, only time will tell. Will report back.

If it's only in IPA that you have an off-flavor, then you have to blame the hops, unless that is the only style that you brew. Hops can get oxidized in the pellet making process. Where do you buy your hops from?

I've gotten this flavor in a saison I dry hopped as well. None of my other beers get this off flavor. I get some of my hops from Label Peelers and some from Fresh Hops. I get them right after the harvest. Even gotten hops from my local supplier. The source hasn't mattered, and I don't have any hops older than 1.5 years old. Most of them are from this past harvest. I buy by the pound and use a vacuum sealer and bags to store unused hops in a freezer.
My guess is that whatever is causing the problem it only effects hop oils that haven't been isomerized, i.e. dry hops, or whirlpool hops.