Hunting the dreaded off-flavour.... marzipan.

[TheMadKing]

So I wanted to bring this back, I have another Scottish export with this flavor and I'm 99% sure it's ethyl acetate except I can't understand what I did to my yeast to stress them. I fermented with white labs Scottish ale yeast at 63F, I used direct oxygen in the wort, I used yeast nutrient, and a 2L starter.

But my wife says it tastes chemically up front, and I taste strong almonds with a hint of hot solvent at the end. I've had this show up in almost all of my malty beers lately, and it's especially prominent in beers with simple sugars and crystal malt.

I'm pretty frustrated since this is the third iteration of this beer I've made and it's gotten much worse not better. Has anyone got any ideas?

 

[TheMadKing]

I just found a write up from Scott Janish where he found a study that showed adding Servomyces yeast nutrient increased esters

"the addition of ZnS04 and L-leucine [Servomyces] Specifically, 0.12 g/l of ZnS04 resulted in a 27% increase in acetate esters and 123% increase in total ethyl esters compared to unsupplemented sample. The addition of 0.750 g/l of L-leucine resulted in a 41% increase in total acetate ester concentration and 84% increase in total ethyl ester concentration compared to unsupplemented sample.11"

http://scottjanish.com/esters-and-fusel-alcohols/
I've been using Servomyces in all my beers for the last couple years and it definitely coincides with noticing this off flavor starting to appear.

 

[pvtpublic]

I have a few questions to throw out there that I don't believe have been asked yet (correct me if I'm wrong).

What yeast are you pitching? How old is it? What pitching rate?

What temp are you fermenting at? Is it consistent? How do those Temps compare to when you were in England?

What is your ferment schedudule? Do you use a primary and secondary? Or do do you do straight through primary?

This almond flavor, is it a bit like bubble gum? Fresh or stale almond? Cardboard? Fresh cut green apple?

 

[TheMadKing]

I have a few questions to throw out there that I don't believe have been asked yet (correct me if I'm wrong).

What yeast are you pitching? How old is it? What pitching rate?

What temp are you fermenting at? Is it consistent? How do those Temps compare to when you were in England?

What is your ferment schedudule? Do you use a primary and secondary? Or do do you do straight through primary?

This almond flavor, is it a bit like bubble gum? Fresh or stale almond? Cardboard? Fresh cut green apple?

I believe we've discussed most of those variables.

Different yeast, calculated cell counts and building up starters with stir plates, fresh yeast

Various fermentation temps (my latest batch was 63F). Controlling temps with a glycol chiller and coil in a spike conical.

I do a single stage ferment until terminal gravity is reached and cold crash under pressure and closed transfer to a liquid purged keg.

The almond flavor to me is like someone added almond extract right at the flavor threshold in the beer. There's no hint of oxidation cardboard and there are low levels of acetaldehyde green apple to it but that is standard for English ale yeasts and an acceptable flavor.

Sorry I've been through all the standard off flavors many times. I've been brewing for 15 years and am a beer judge as well. I've thoroughly examined all the basics and am convinced this is a more complex issue.

From the article I posted above I'm really leaning toward Servomyces being the problem, but I'd like @Miraculix to confirm whether he's using that (or a similar yeast nutrient).

 

[TheMadKing]

I know you don’t like information from books written by old dead Germans however Kunze gives us some interesting clues here:

3.4.1.6 Thermal exposure of the wort
During boiling, further Maillard products and Strecker aldehydes are formed, tannins oxidized and thus the the thermal exposure of the wort is further increased.

And here we find in this paper..
Impact of Wort Amino Acids on Beer Flavour:
Inês M. Ferreira and Luís F. Guido
these descriptions of the compounds in question.

Strecker Degradation Products
2-methylpropanal - Grainy, varnish, fruity
2-methylbutanal - Almond, apple-like, malty
3-methylbutanal - Malty, chocolate, cherry, almond
Methional - Cooked potatoes, worty
Phenylacetaldehyde - Hyacinth, flowery, roses
Benzaldehyde - Almond, cherry, stone

It certainly looks like the smoking gun.

What percent of the initial volume do you lose during the boil?

Hey Bilsch

Do you know whether there are other pathways for these aldehyde productions by yeast? Or maybe @Northern_Brewer or @VikeMan has any insight?

I'm pretty skeptical that it's oxidation or heat stress on my wort and here's why:

I presently have a Scottish export and a marzen, both brewed using the same system, both brewed using the same mash and lauter processes, same yeast handling techniques, same amount of wort oxygenation, same yeast nutrient. I use an electric spike system and boil at 3850 watts every time. (the heating element will run at 100% or 5500 watts until it registers boiling on the PID, so there may be some heat stressing during initial heating to boil.) my boil-off rate is 1.2 gallons per hour.

The marzen has no hint of this almond-like (almond extract, artificial cherry, very slight alcohol warmth) flavor, while the Scottish export is a bomb straight from the fermenter!

The biggest differences between the two recipes are that the marzen obviously used a lager yeast and the Scottish ale used white labs Scottish ale yeast, and the Scottish ale also contained a high percentage of simple sugars (invert and dark brown sugar). I fermented both right at the low end of the respective yeasts' temperature ranges as well, so they should not be throwing excessive esters.

I notice that this flavor seems to occur in beers using English ale yeasts which tend to favor ester production. I've had it most prominently in an irish red, 2 scottish exports, and an english brown ale, and a english strong bitter.

I feel that I'm very strong on cold side oxygen reduction and use a closed process from yeast pitch to a liquid purged keg.

So I suspect that what I'm tasting is one of these aldehydes but I think it has been synthesized from some chemical change to a yeast ester. OR I'm tasting a combination of yeast esters and my brain is simply mistaking the combination for almond-extract (I'm certainly not ruling out that this is simply a sensory/descriptor issue)

Does any of that sound plausible to you?

 

[Miraculix]

I for myself found the main source, but this obviously doesn't have to be the reason for your problem as well.

The hot side stuff with the vitamin c helped, but the almonds showed still up now and then. Not as strong as before, but still sometimes there.

I found out that my fermenter developed a small leak. After fermentation finished, my air lock would not keep floating but slooooowly start to sink in the water. Indicating that gas can leave the space below it and so it could also enter. If I recognized that quickly and screwed the lid back on tightly, almond results were very small. If I ignored it the almonds popped up again much stronger.

I fixed that, plus all the hot side stuff and the combination resulted in zero almonds.

So fast chill, no hot side transfers that introduce an abundance of 02, optional vitamin c plus an air tight fermenter did it for me.

Not that much magic... I'm pretty sure that I'm a bit overly sensitive to these almond flavours though, which doesn't help.

I forgot, I never use nutrients in my beers.

And another thing, I also had the feeling that the almond gets emphasized by English yeasts somehow.

 

[TheMadKing]

I forgot, I never use nutrients in my beers.

And another thing, I also had the feeling that the almond gets emphasized by English yeasts somehow.

Well that's disappointing, that yeast nutrients aren't a silver bullet here. I'm pretty convinced that I'm getting extra ester expression from my yeast somehow, since all else being fairly equal, I don't taste this flavor unless I use an expressive yeast. Maybe I need to play around with pitch rates and see if I can affect it that way - I'd rather change one thing in my process to fix it, rather than overhaul my entire yeast handling procedures.

Thanks!

 

[Miraculix]

Well that's disappointing, that yeast nutrients aren't a silver bullet here. I'm pretty convinced that I'm someone getting extra ester expression from my yeast somehow, since all else being fairly equal, I don't taste this flavor unless I use an expressive yeast. Maybe I need to play around with pitch rates and see if I can affect it that way - I'd rather change one thing in my process to fix it, rather than overhaul my entire yeast handling procedures.

Thanks!

Drop the nutrients just for one batch and see where this leads you. It's certainly possible to brew great beer without any.

 

[TheMadKing]

Drop the nutrients just for one batch and see where this leads you. It's certainly possible to brew great beer without any.

Oh I certainly plan to after reading Scott's article. Maybe I'm being too nice to my yeast and they are getting all excited and spraying esters everywhere!

 

[Miraculix]

Oh I certainly plan to after reading Scott's article. Maybe I'm being too nice to my yeast and they are getting all excited and spraying esters everywhere!

Please let me know! I'm actually also giving them an abundance of nutrients, as I'm throwing in most of the trub after the boil.... So this might put me in a similar spot.

For head retention reasons, I'm going to try to limit the trub within the next batch though.

 

[TheMadKing]

Please let me know! I'm actually also giving them an abundance of nutrients, as I'm throwing in most of the trub after the boil.... So this might put me in a similar spot.

For head retention reasons, I'm going to try to limit the trub within the next batch though.

Scott mentioned that in his write up as well and indeed he found a study showing a correlation between hi trub and higher ester levels

I wonder if we have an amino acid problem on our hands

 

[Miraculix]

Scott mentioned that in his write up as well and indeed he found a study showing a correlation between hi trub and higher ester levels

I wonder if we have an amino acid problem on our hands

I was thinking the same thing.... I think I even read what Scott wrote that you are referring to.

 

[pvtpublic]

I believe we've discussed most of those variables.

Different yeast, calculated cell counts and building up starters with stir plates, fresh yeast

Various fermentation temps (my latest batch was 63F). Controlling temps with a glycol chiller and coil in a spike conical.

I do a single stage ferment until terminal gravity is reached and cold crash under pressure and closed transfer to a liquid purged keg.

The almond flavor to me is like someone added almond extract right at the flavor threshold in the beer. There's no hint of oxidation cardboard and there are low levels of acetaldehyde green apple to it but that is standard for English ale yeasts and an acceptable flavor.

Sorry I've been through all the standard off flavors many times. I've been brewing for 15 years and am a beer judge as well. I've thoroughly examined all the basics and am convinced this is a more complex issue.

Sorry, I had just came from a BJCP study group and we did weizenbock, doppelbock, and eisbock, so I definitely wasn't tracking as well as I thought was haha.

 

[schmurf]

@Miraculix did you find out the cause of your problem?

Several years ago, when I started brewing, I had some problems with an off flavour I couldn't put a name on nor find the cause for. The problem disappeared though and I didn't think more about it. However, two of my latest brews has that same off flavour, and perhaps my taste buds has changed some but now I actually can say it reminds me of marzipan/almond.

I'm trying to recall what I did differently these last two brews from the previous but nothing stands out to me.

 

[Miraculix]

@Miraculix did you find out the cause of your problem?

Several years ago, when I started brewing, I had some problems with an off flavour I couldn't put a name on nor find the cause for. The problem disappeared though and I didn't think more about it. However, two of my latest brews has that same off flavour, and perhaps my taste buds has changed some but now I actually can say it reminds me of marzipan/almond.

I'm trying to recall what I did differently these last two brews from the previous but nothing stands out to me.

I think it's oxidation. It is mainly cold side oxidation but also hot side oxidation might play a role. I was able to enforce this taste by putting a partially filled bottle for quick bottle carbonation on a heater. The result was super almond.

My guess is that crystal malt might push this taste as well, but I'm not 100% sure. Sometimes it comes still through in my brews, unfortunately...

 

[HM-2]

Quick thought on this one...are these typically beers with a larger amount of roasted/speciality and crystal malts, and/or simple sugars/invert added during the boil? I think Benzaldehyde is associated with almond-ish flavours which seems to be linked with oxidation of melanoidins.

 

[Miraculix]

Quick thought on this one...are these typically beers with a larger amount of roasted/speciality and crystal malts, and/or simple sugars/invert added during the boil? I think Benzaldehyde is associated with almond-ish flavours which seems to be linked with oxidation of melanoidins.

I was thinking the same thing and my next beer is going to be 100% Pilsner malt for that reason.

A rarely brew a beer without crystal, but I think my last bitter was chevallier only. But about ten percent invert was in there as well. Do you think the invert might play a role as well?

Could be also a storage thing? My crystal is often a bit older and stored crushed.... Maybe it's stale?

 

[HM-2]

When are you adding your invert? If it's going in during the boil, then I would 100% think it could be a contributor to melanoidins and therefore run the risk of benzaldehyde if oxidised. I only ever put invert or simple sugars in at flameout.

 

[Miraculix]

When are you adding your invert? If it's going in during the boil, then I would 100% think it could be a contributor to melanoidins and therefore run the risk of benzaldehyde if oxidised. I only ever put invert or simple sugars in at flameout.

I actually don't remember when I throw it in. Always late during the boil but probably a few minutes before flame out so that it mixes correctly and I am able to take a correct gravity reading. Hmmmmm........... Maybe you're onto something.