Help Me Identify an Off-Aroma

[jmhbutler]

Hey everyone, hope somebody might be able to help me out with an issue thats been bugging me.

I have a house blonde recipe that I've been brewing for some time: 1.048, 30IBU, 2-Row base, 20% Marris Otter, 20% Wheat, 5% Carapils. Centennial and Cascade, US-05 (usually on the colder side).

The last two times I've brewed it I've ended up with an aroma that I find unpleasant. I can try my best to describe it as a heavily sweet malty aroma, but not in a pleasant fresh sense but more reminiscent of overripe fruit. I can pick it up without drinking the beer and if I take a sip with my nose plugged I cannot detect it.

Can anybody offer any suggestions what this might be? I've noticed the same aroma before in the odd commercial craft beers. I just want to put my finger on what it is and whats causing it.

 

[RPh_Guy]

Did you change the recipe at all?

Are you repitching yeast?

At what point in the brewing process does the off-aroma first occur?

Is the malty aroma reminiscent of Cheerios or Capn Crunch?

Is this being kegged or bottled?

How long does it sit until you package it?

Do you leave it in primary?

Any other anomalies? (E.g. cloudiness, higher attenuation, etc)

 

[jmhbutler]

Did you change the recipe at all?

No.

Are you repitching yeast?

No. Using fresh packages rehydrated in water before pitching.

At what point in the brewing process does the off-aroma first occur?

Coming out of the primary into the keg I did not notice the aroma. It wasn't until the beer was cold and carbonated it became distinguishable.

Is the malty aroma reminiscent of Cheerios or Capn Crunch?

No. It is more reminiscent of over-ripe fruit.

Is this being kegged or bottled?

The beer is kegged.

How long does it sit until you package it?

I went straight from primary to the keg on this one. I immediately put the keg in the fridge after transferring.

Do you leave it in primary?

The beer was left in primary for 5 weeks. A little longer than usual as I had to free up some kegs.

Any other anomalies? (E.g. cloudiness, higher attenuation, etc)

None that I'm aware of.

 

[kh54s10]

You listed 45% of the malts, what else is in the recipe?

 

[RPh_Guy]

You listed 45% of the malts, what else is in the recipe?

2-Row base

^ 55% 2-row

....
Contamination could be causing over-ripe fruit aroma, but that doesn't seem particularly likely based on what you've said.

5 weeks in primary is too long in my opinion. Oxidation maybe? The "sweet fruity malt" character in certain beers comes from late-stage oxidation, but 5 weeks doesn't quite seem long enough for that.

I'm not really sure; it's hard to determine without tasting it. I'd try to get some opinions from local brew store folks, professional brewers, or a homebrew club, especially with judges.

 

[kh54s10]

^ 55% 2-row

Oh, I see that now. I read that as 2 row base of Maris Otter at 20%, since Maris Otter is one of the many 2 row base malts...

 

[jmhbutler]

Thanks RPhguy,

I considered Brett. contamination because I do brew a lot of funky weird stuff and I've stopped using isolated plastic gear between my clean and wild batches (drink it too fast for contamination to occur). That being said I feel confident in my ability to distinguish bacterial and brettanomyces related funk. I also noticed this aroma on other lighter US-05 beers when I was meticulously diligent within my brewing operation to isolate all possible contaminating factors, which helps me further rule out contamination.

I'm curious about your statement that 5 weeks is too long in primary. While this was more circumstantial and not my regular practice (after 10-21 days my beers typically go straight to keg or to secondary to age for 10+ weeks), I've heard the argument that yeast autolysis is more of a myth in homebrewing and secondary has limited benefit while only further exposing you to potential oxidation problems... I'd be curious to hear your take on this. The aroma did make me think of oxidation but how would an extended primary under airlock create potential for oxygen exposure?

I've been doing a little more digging and read that other people have stopped using US-05 because its fruity esters. I did ferment in the low 60s which is said to kick off ripe peach notes. While this beer is not "bad" by any means, this subtle aroma (which my spouse can't even distinguish) I find unpleasant. I'm starting to think maybe I'm just a bit sensitive to the esters being kicked off by US-05 that are only noticeable in lighter beers and masked in bigger Stouts, Porters, IPAs and Pale Ales. I might try the recipe again with something like San Diego Super or 1056 and see if it resolved itself.

Think I'm on to something?

 

[Vale71]

Hey everyone, hope somebody might be able to help me out with an issue thats been bugging me.

I have a house blonde recipe that I've been brewing for some time: 1.048, 30IBU, 2-Row base, 20% Marris Otter, 20% Wheat, 5% Carapils. Centennial and Cascade, US-05 (usually on the colder side).

The last two times I've brewed it I've ended up with an aroma that I find unpleasant. I can try my best to describe it as a heavily sweet malty aroma, but not in a pleasant fresh sense but more reminiscent of overripe fruit. I can pick it up without drinking the beer and if I take a sip with my nose plugged I cannot detect it.

Can anybody offer any suggestions what this might be? I've noticed the same aroma before in the odd commercial craft beers. I just want to put my finger on what it is and whats causing it.

That sounds like you might be very sensitive to diacetyl and are picking it up at very low levels, that other people such as your spouse cannot even detect. At low levels diacetyl and pentanedione can give off a sweet, honey or malty sensation.
How is your fermentation profile? Are you pitching warm and then cooling? At what temperature do you let the beer sit in primary?

 

[jmhbutler]

Haha, so... my fermentation practice is probably the weakest aspect of my brewing. I do have a controlled fermentation chamber but it only fits one 20L carboy and I usually brew 40-60 litres.

I usually just cool the beer to the temperature at which I intend to ferment, put it in the house in a place at which I think I can best maintain that temperature, and tape an STC-1000 probe to one of the carboys so I can loosely monitor it.

Last time I fermented at 19C and had this issue so this time I went around 17C to try to suppress esters (with no success). After a week I usually move the beer somewhere closer to 20-22C to finish up.

How can I reduce diaceytl in ales?

 

[jmhbutler]

"Sweet, honey/malty" is bang on!

 

[RPh_Guy]

I'm curious about your statement that 5 weeks is too long in primary. While this was more circumstantial and not my regular practice (after 10-21 days my beers typically go straight to keg or to secondary to age for 10+ weeks), I've heard the argument that yeast autolysis is more of a myth in homebrewing and secondary has limited benefit while only further exposing you to potential oxidation problems... I'd be curious to hear your take on this. The aroma did make me think of oxidation but how would an extended primary under airlock create potential for oxygen exposure?

I try to package soon after fermention completes in just a few days, barring any off-flavors.
A liquid-filled airlock is not great for keeping out oxygen over a longer period. It's a simple matter of diffusion. Atmospheric oxygen diffuses into the airlock liquid, and then into the headspace, and then into the beer.
Oxygen also seeps through other parts of the fermention vessel, at varying rates based on material. Plastic and rubber/silicone gaskets are all oxygen-permeable.
Again, I doubt this is causing your issue. Aging can add sherry, wine-like stale fruit esters, but probably not in this timeframe.

"Sweet, honey/malty" is bang on!

I've had commercial beers with the honey aroma and flavor, presumably from pentanedione. To me I detect a very distinct "honey" rather than a more vague sweetness. Though, I haven't formally tasted a range of control amounts, so maybe more beers have it than I know.

Think I'm on to something?

"Fruity" definitely means esters of some kind.
It certainly could just be esters from US-05 produced using your method of ambient temperature control.
I don't use US-05 much because I don't really care for its character.
You could try a new yeast and see if it changes/improves.

I wouldn't take the possibility of contamination entirely off the table. Airborne contamination is always possible, and wild yeast (not necessarily Brett) is more likely to cause unexpected off-flavors than US-05.

How can I reduce diaceytl in ales?

VDK compounds (diacetyl and pentanedione) are removed by doing exactly what you're doing: allowing the beer to warm up after fermention completes while it's still on the yeast cake. The yeast absorbs and metabolizes them.

 

[Soulshine2]

Did you change the recipe at all?

No.

Are you repitching yeast?

No. Using fresh packages rehydrated in water before pitching.

At what point in the brewing process does the off-aroma first occur?

Coming out of the primary into the keg I did not notice the aroma. It wasn't until the beer was cold and carbonated it became distinguishable.

Is the malty aroma reminiscent of Cheerios or Capn Crunch?

No. It is more reminiscent of over-ripe fruit.

Is this being kegged or bottled?

The beer is kegged.

How long does it sit until you package it?

I went straight from primary to the keg on this one. I immediately put the keg in the fridge after transferring.

Do you leave it in primary?

The beer was left in primary for 5 weeks. A little longer than usual as I had to free up some kegs.

Any other anomalies? (E.g. cloudiness, higher attenuation, etc)

None that I'm aware of.

FWIW dry packaged US-05 does not require rehydration before pitching. It is direct pitch.
5 week primary is a long time. I'm drinking my beers by then.

 

[jmhbutler]

...depends who you ask. Some believe that the direct exposure to the acidity of the wort kill a large percentage of yeast cells when you do not rehydrate. But either way I don't think yeast hydration is a contributing factor.

 

[Vale71]

I too am blessed with heightened sensitivity to VDKs. I've been tested as part of my training and I've been able to detect them at 0,06 ppm which is half of the currently accepted average threshold. Luckily I find this honey note yummy and find that it complements a classic continental Pils nicely, so it's a win-win for me.

Excessive VDK levels can be caused by:

underpitching
over-oxygenation
pitching warm and then cooling significantly as soon as fermentation starts
cooling prematurely and too fast before the yeast has had time to clean up
insufficient FAN (aminoacids) in wort

Then there are external causes such as infections (but they usually will manifest in other ways too) and some strains have a genetic deficiency that will guarantee detectable levels of diacetyl like the famous Urquell strain currently settling out of the Pilsner Urquell clone I recently brewed. It's still young but already has high levels of diacetyl (yummy!).

 

[Vale71]

VDK compounds (diacetyl and pentanedione) are removed by doing exactly what you're doing: allowing the beer to warm up after fermention completes while it's still on the yeast cake.

You take issue when I scoff this ridiculous notion and still you stubbornly perpetuate it.

 

[RPh_Guy]

You take issue when I scoff this ridiculous notion and still you stubbornly perpetuate it.

Things aren't black and white or one-size-fits-all.

It's a fact VDK is removed by yeast contact. Different processes and different yeast characteristics can affect the amount of yeast contact and therefore the amount of VDK removal.

In this case, US-05 doesn't as rapidly flocculate as other stains, so cleanup of VDK shouldn't be an issue especially given the prolonged time and increased temperature.

I really don't want to be at odds with you. Clearly you have professional training and have a lot of information to offer us here. Please just keep in mind not everything from the commercial brewing world directly translates to the homebrew scale. It helps everyone to keep a positive attitude so we can learn from each other.

Cheers

 

[TheMadKing]

Is it the same with every pint? I get a similar flavor of I forget to pour out the first slug of beer that's been sitting in my keg lines. It happens quickly too, within 10-15 mins. I'm fairly certain it's oxidation but it could also be a pediococcus infection in my keg lines which can produce diacetyl.

 

[couchsending]

You mention Over ripe fruit... was this beer dry hopped by chance? If so for how long were the hops in there?

 

[Soulshine2]

...depends who you ask. Some believe that the direct exposure to the acidity of the wort kill a large percentage of yeast cells when you do not rehydrate. But either way I don't think yeast hydration is a contributing factor.

without getting into what too many posts have been (argued) about...lots of questions pertaining to yeast pitching answered here. Right from the proverbial horses mouth.

https://fermentis.com/en/tips-n-tricks/questions-and-answers/

 

[jmhbutler]

without getting into what too many posts have been (argued) about...lots of questions pertaining to yeast pitching answered here. Right from the proverbial horses mouth.

https://fermentis.com/en/tips-n-tricks/questions-and-answers/

FWIW dry packaged US-05 does not require rehydration before pitching. It is direct pitch.
5 week primary is a long time. I'm drinking my beers by then.

Wow, thanks Soulshine2. I guess there is a definitive answer. Good to know!

 

[ncbrewer]

FWIW dry packaged US-05 does not require rehydration before pitching. It is direct pitch.

It's worth noting that in the US-05 info, Fermentis states "Ideally, the yeast will be added during the first part of the filling of the vessel; in which case hydration can be done at wort temperature higher than fermentation temperature, the fermenter being then filled with wort at lower temperature to bring the entire wort temperature at fermentation temperature." This procedure doesn't work for me. I prefer to pitch a couple of degrees cooler than fermentation temperature, so I still rehydrate.

 

[Soulshine2]

It's worth noting that in the US-05 info, Fermentis states "Ideally, the yeast will be added during the first part of the filling of the vessel; in which case hydration can be done at wort temperature higher than fermentation temperature, the fermenter being then filled with wort at lower temperature to bring the entire wort temperature at fermentation temperature." This procedure doesn't work for me. I prefer to pitch a couple of degrees cooler than fermentation temperature, so I still rehydrate.

I transfer and wait for fermentation temp, then pitch.