Brett Strain production of ATHP

[ne0t0ky0]

I've been picking up a flavor in some of my sour beers I've been working on for the past year or so. After a bit of research, I believe what I'm picking up is ATHP[1] or the known "mousy" character from Brett, here's a description from Chad Yacobson's Brett Project:

Two forms of substituted tetrahydropyridines, 2-ethyltetrahydropyridine (ETHP) and 2-acetyl-3,4,5,6-tetrahydropyridine (ATHP), can be produced by Brettanomyces spp. Their metabolism involves the amino acid L-Lysine and ethanol with oxygen having a stimulatory effect in their production (Heresztyn, 1986a; Snowdon et al., 2006; Oelofse et al., 2008). The aromas associated with ATHP are similar to cracker biscuit, although under low pH conditions can be described as metallic or bitter (Oelofse et al., 2008). Little is known about these compounds and their production by Brettanomyces spp.

There doesn't seem to be a lot of information the production in beer of this compound. I'm reaching out to various breweries and the yeast labs, but I've not yet heard anything back about how this compound forms, whether it can be eliminated or aged out, or if it can be minimized by selecting different strains, or environmental factors.

Has anyone else experienced this flavor/aftertaste? If so, what strain was used? Any details about the fermentation/aging environment could be useful in collecting further data on this compound. Did the flavor age away? Was the beer already bottled or still in a carboy?

Discussion Links I've found:

http://ucce.ucdavis.edu/files/repos...romatic_Diverswity_of_Brettanomyces-82350.ppt
http://518124.cache1.evolutionhosti.../presentations/2008/GregDoss_BrettBrewing.pdf
http://www.themadfermentationist.co...howComment=1379714666490#c7801756970553901391

 

[jhay_x7]

Have fun!

http://www.aseanfood.info/Articles/11018301.pdf

 

[ne0t0ky0]

Have fun!

http://www.aseanfood.info/Articles/11018301.pdf

Thanks. It took quite a while for that link to load, but I got it. My take aways were:

1) all bretts produce ATHP, some more than others, but the study focused on Brett B.
2) pre-cursors to production of ATHP (which happens in the growth phase) are lysine, oxygen and glucose/fructose
3) ATHP can be metabolised into ETHP (which is less detectable) but no details on this process (how long, for example)

I'm still interested in feedback from others about whether they detect this aftertaste, if so at what point during the lifetime of the beer, and what sort of environment the beer is being kept in.

My short term process change will include flushing the carboys with co2 before and after pulling a sample, as well as minimizing any movement of the carboys.

I'll also be bottling at least one of these beers that has this flavor to see if it changes over time in the bottle under pressure.

Further data on the metabolism of ATHP into ETHP is cited, but I've not found a copy of the paper available yet:

Grbin, P. R. Physiology and metabolism of Dekkera/Brettano-
myces yeast in relation to mousy taint production. Ph.D. Thesis,

The University of Adelaide, Adelaide, 1998.

 

[dantheman13]

Interesting discussion. I have never had these flavors in sour/Brett beers (although I haven't done more than a dozen of them), and I don't often recall tasting it in commercial beers, although I believe I have. I tend to not oxygenate my wort that is meant for souring, regardless of what kind of yeasts are involved. I wonder if someone who has this problem in their Brett beers were to stop aerating, if that would help or hinder?

 

[ne0t0ky0]

Unless I'm doing 100% Brett primary beer, I don't aerate either. The several beers that I've had this aftertaste were pitches from bottle dregs, no aeration, sitting anywhere from 3months to 9 months in a glass carboy, silicone stopper lid.

I've not tasted this in any commercial beer either; but every one I've had has been from a bottle; presumably conditioned for multiple weeks, if not months.

 

[dantheman13]

Unless I'm doing 100% Brett primary beer, I don't aerate either. The several beers that I've had this aftertaste were pitches from bottle dregs, no aeration, sitting anywhere from 3months to 9 months in a glass carboy, silicone stopper lid.

I've not tasted this in any commercial beer either; but every one I've had has been from a bottle; presumably conditioned for multiple weeks, if not months.

Were the bottle dregs Brett only?

 

[ne0t0ky0]

Were the bottle dregs Brett only?

Some were, others had more than Brett (including pedio and lacto).

 

[dantheman13]

I wrote up an article over on the MTF Wiki to try and get some of this information in one spot: http://www.milkthefunk.com/wiki/Tetrahydropyridine

 

[amoheban]

I have some experiences I would like to add to the discussion. The first time I experienced this flavor (honey nut cheerios type of flavor which only comes through at the very end of the finish) was when I attended a sour beer tasting. Several of the offerings from Mikkeler had this aftertaste and to be completely honest, I actually enjoyed the flavor. My SO thinks I'm crazy because she describes the flavor as "garbage" , "rancid" and "rotten trash."

Later on, I made a starter with the dregs of 3F Gueze. I wanted to see what flavor profile I would get before committing to a large batch, so I aged the starter wort for a couple of months (honestly I totally forgot about it). When I tasted it, it tasted like the gueze but it had that cerealy/cheerios flavor except way more intense than in the commercial beers. I liked it and used it along with fresh Supplication dregs in a 5g sour blonde recipe. I added the bugs along with the Sach yeast for primary fermentation. Tasted the ATHP at every step since (3 months, 6 months, 8 months + rasberry puree).

Now I am 9 months into it and there is still a strong amount of this flavor on the finish. I personally think it adds complexity, but my SO cant stand it so I am hoping it ages out. What is strange is most people experience this flavor post bottling. At least for me I know exactly where the flavor came from and so next time I wont use 3F Dregs.

 

[ne0t0ky0]

What is strange is most people experience this flavor post bottling. At least for me I know exactly where the flavor came from and so next time I wont use 3F Dregs.

It can occur any time you have sugar + O2 and ATHP producing specimen. For most folks, bottling time is where one would get the most exposure to oxygen (racking from carboy into bottling bucket) and adding priming sugar; the exact ingredients when ATHP occurs.

But nothing prevents it from happening sooner during bulk aging, just a matter of what sort of vessel , access to sugars (say a fruit addition) and O2 (maybe using a bucket or constant opening of the airlock for sampling).

I've experienced it both during fermentation and only after bottling.


Thanks for sharing!

 

[amoheban]

I read in another thread where you mentioned it not dissipating in some of your batches. Those posts were old. Any new updates?

 

[ne0t0ky0]

Yes, it look approximately a year in the bottle for it to disappear. I honestly never thought it would, but as with many things beer; time heals wounds.

That said, I apply a number of techniques to minimize the amount of time it takes for ATHP related flavors to subside:

1) minimize exposure to O2 as much as possible; this includes
a) avoid frequent sampling
b) flushing carboy after sample
c) push via co2 when transferring from carboy to kegs
d) bottling via Beergun under co2 flushed bottles.

2) utilizing champagne yeast for bottle carbonation; oldsock suggested this since it can consume the sugars faster than the brett and lacto can.

my anecdota data here is that a batch I bottled with champagne yeast in December 2014 had minor AHTP flavors at the time of bottling and at 4 months (or sooner, I only sampled this a week ago) none of that remains.

3) avoiding bulk aging temperatures above 65F. This is a work in progress. So I wont have any results until I complete insulating and cooling my shed for beer fermentation/cellaring. Jester King Brewery does all of their barrel/bulk aging at about 60F; their beers come out fantastic though freshly bottled batches sometimes (IMHO) have a very very tiny hint of the flavor; usually gone after another month of aging in the bottle.