[KilroyWasHere]

I have a rather complicated question about fermentation and yeast character. I have been doing BIAB for about 7 years, before that extract for about 5 years. Currently I can make some great beers following the advice I find on this forum and from Podcasts like experimental brewing. As such I am diligent about sanitation and rarely if ever have I had to dump a batch because of infection. I love to do Belgians, but do a variety of other brews annually ranging from Stout/Porter/Dubbel/Belgian Dark Strong to summer time Wit/Hefe/Kolsch. A testament to sanitation is the consistency with which I can produce a nice clean Kolsch. All that said, the thing I struggle with is maintaining yeast character throughout fermentation. That probably sounds strange, but typically when I am looking for good yeast character, like from a Hefe or a Saison, I have it early in fermentation and by the time the beer is kegged it is gone. Trying to figure this issue out has led me to do some goofy things, like taste the starter wort that I decant before pitching. I also regularly taste the gravity samples. Those confirm the gradual but consistent fading of the yeast character. My temperature control is impeccable. My fermenter is a 7 gal Speidel fermenter, I modified the lid for a thermo well and a stainless cooling coil. The coil is fed by an ice and water bath with an aquarium pump controlled by some software that runs a bang-bang controller. The temp is held within a range of +/- .25F during fermentation. For a 5 gallon batch I typically am left with .5 to .7 gallons of trub which always smells fantastic when I dump it. Attenuation is good. I am either hitting my target FG, or over attenuating by a few points. I try to get near the pitch rate recommended by Beersmith using starters made from Wyeast smack packs.
Does this sound like an infection? Oxidation? Trub in the fermenter? Has anyone struggled with the same thing, or does anyone have thoughts? Any input would be appreciated. 

[denny]

Before I can make a guess, I need a better description. What yeast character are you specifically missing? Every batch? Every yeast?

[neuse]

It's common for a hefe to loose that special yeast character with time - many brewers try to drink it while very fresh. But fading out before it's even packaged seems really extreme. Any chance it could be oxidation?

[KilroyWasHere]

Before I can make a guess, I need a better description. What yeast character are you specifically missing? Every batch? Every yeast?

Apologies Denny I meant to add that and forgot. Anything where the malt dominates is fine. Every batch of the Hefes, Saisons, and Wits, basically anything where I am trying for the spicy phenolics, I lose it. I think I am losing some of the esters from the Belgian yeasts but enough does remain so that is recognizable as a Belgian. The Hefes will start out with both the clove and Banana and both will fade away and be lost by the time it is carbonated in the keg (3 weeks). For the Hefes I've tried a number of ferm temps from 62 to 70 using the Wyeast Weienstephaner. My LHBS carries mostly Wyeast so I use those by default for any brew. For the Belgians I've also tried a range of ferm profiles including the 'start it low and let it go'. I've also varied the pitch rates from those predicted in Beersmith down to just the single smack pack for 5 gal (awful). 

[KilroyWasHere]

It's common for a hefe to loose that special yeast character with time - many brewers try to drink it while very fresh. But fading out before it's even packaged seems really extreme. Any chance it could be oxidation?

I suppose there is that chance but my fermenter is well sealed and that seems to be where most, if not all, of the degradation occurs. I really don't know much about oxidation. When transferring from the boil kettle I open my stainless ball valve at the bottom of the kettle and let the wort drain into the fermenter through a 1/2 inch silicone hose. Not a lot of splashing to it, but I will usually aerate the batch after that anyway. My transfers to the kegs are closed to a C02 purged keg.

[KilroyWasHere]

Here is the last 5 gal Hefe batch step by step, got the process from BYO.com

5.5 lb Pils
5.5 lb wheat malt
.25 lb Melanoidin
.8 oz Hallertau at 60 min
1 pkg 3068 (intentional under pitch)

Step mash at full volume BIAB 8 gal distilled
pre mash 3g gypsum, 2.4g CaCl, 2g Epsom, 30 ml 10% phosphoric, stir to dissolve
110F for 10 minutes, up to 150 for 60 minutes
Mash ph 5.27, pre boil vol 7.4 gal
Boil 60 min, nice fluffy hot break
Cool to mid 60s, whirlpool and let sit 20 minutes, drain to fermenter 5.5 gal
Aerate with aquarium pump and hepa filter 10 minutes only
Pitch fresh, smacked and slightly bloated smack pack
OG 1.054
Set fermenter temp control to 62F
Slow air lock activity the next morning, steady the following morning.
Took a sample through the valve 2 days in. 1.031, sweet but very noticeable clove and banana
Took sample 4 days in, 1.020, very light clove and banana
8 days in, 1.012 no clove no banana. Kegged.
Force carbed after chilling. No clove or banana.
Boiled up 1 cup water and made a solution of ground clove and banana extract (I've gotten pretty good at this part). Added to keg. Pretty good.

[NNVbrewer]

Aging will reduce the banana (acetate of some sort) and buttery (diacetyl) flavors in beer. I think the yeast actually cleans some of these up after fermentation is complete. The comment that fresh beer has more of these flavors fits into this process. So I would guess that if you want to have these flavors you would keg the beer as soon as primary fermentation is done and force carbonate right away and drink as soon as possible.

[reverseapachemaster]

Oxidation could be an issue of muting yeast character (and everything else) but I'd have to see a photo of the beer. If you're using stainless equipment and closed transfers, oxidation is probably not your problem. If you can successfully brew a kolsch with no problems, a hefeweizen shouldn't have oxidation problems.

Serving temperature may be a contributing issue. How cold are you keeping the kegs? The colder the beer, the less expressive flavor. I don't think this is your only issue if the flavor is disappearing before you keg, but it might be a contributing issue if you're keeping those kegs at 30F for Miller Time.

I think you're fermenting the beer too cool and this is the primary problem. Yeast are less expressive at cooler temperatures. I would consider 62F too cool for any hefe/saison/abbey/Trappist strains. At cooler temperatures the beer can taste and smell full of yeast character but they'll uptake some of the compounds as fermentation winds down, some break down and with transfer some of the captive CO2 holding those aromas come out of solution. I suspect this is your issue if the trub smells more intensely of banana/clove than the beer. I would try another batch at 66-68F and see if you get better results.

[KilroyWasHere]

Aging will reduce the banana (acetate of some sort) and buttery (diacetyl) flavors in beer. I think the yeast actually cleans some of these up after fermentation is complete. The comment that fresh beer has more of these flavors fits into this process. So I would guess that if you want to have these flavors you would keg the beer as soon as primary fermentation is done and force carbonate right away and drink as soon as possible.

Thanks NNVBrewer, to be clear I am saying that the beer only has this character in the fermenter. Kegged after 8 days and by that time the character is gone.

[KilroyWasHere]

Oxidation could be an issue of muting yeast character (and everything else) but I'd have to see a photo of the beer. If you're using stainless equipment and closed transfers, oxidation is probably not your problem. If you can successfully brew a kolsch with no problems, a hefeweizen shouldn't have oxidation problems.

Serving temperature may be a contributing issue. How cold are you keeping the kegs? The colder the beer, the less expressive flavor. I don't think this is your only issue if the flavor is disappearing before you keg, but it might be a contributing issue if you're keeping those kegs at 30F for Miller Time.

I think you're fermenting the beer too cool and this is the primary problem. Yeast are less expressive at cooler temperatures. I would consider 62F too cool for any hefe/saison/abbey/Trappist strains. At cooler temperatures the beer can taste and smell full of yeast character but they'll uptake some of the compounds as fermentation winds down, some break down and with transfer some of the captive CO2 holding those aromas come out of solution. I suspect this is your issue if the trub smells more intensely of banana/clove than the beer. I would try another batch at 66-68F and see if you get better results.

Thanks that describes to a tee what I am experiencing, and sounds like great feedback. I had the same thoughts about the Kolsch. I have explored serving temp by adjusting my fridge temp. It's usually in the low 40's. However, the yeast character is gone by kegging time. I often keep some Allagash White on hand in the same fridge (I'm 1 hour from Portland so it's pretty fresh) and that is loaded with character. So is anything else I store in there with the kegs. I will definitely try your suggestion, I've fermented warm before. Got esters but no phenolics.
I never ferment the Belgians that low, only the Hefe as recommended in Brewing Classic Styles. The last Belgian I did was right before the Hefe, an homage to LaChouffe using the Ardennes yeast fermented in the mid to high 70s. Totally bland by kegging time after suffering the same degradation.

[KilroyWasHere]

I think you're fermenting the beer too cool and this is the primary problem. Yeast are less expressive at cooler temperatures. I would consider 62F too cool for any hefe/saison/abbey/Trappist strains. At cooler temperatures the beer can taste and smell full of yeast character but they'll uptake some of the compounds as fermentation winds down, some break down and with transfer some of the captive CO2 holding those aromas come out of solution. I suspect this is your issue if the trub smells more intensely of banana/clove than the beer. I would try another batch at 66-68F and see if you get better results.

This paragraph supports a theory I have been entertaining. I have not been struggling with this for a long time. I have had this nagging feeling that it might be the my internal cooling coil in the fermenter. It is supplied by cold water that is between high 40s and high 50s, depending on how long the gel pack has been in the water  during active fermentation. Active fermentation is when most of the character degradation occurs. The stainless coil is inside the fermenting beer and has cold water running through it when the controller turns the pump on. I've often wondered if this is hard on the yeast, but have written it off due to the Kolsch and the darker beers and always getting very good attenuation. But your reply is suggesting to me that it may be encouraging the low temperature character uptake that you describe. That also supports my results of clean Kolsch, and good dark beers where my poor old taste buds wouldn't detect much yeast character anyway.
To that end, I almost never see anyone mention, in books or on forums, cooling a fermenter using anything but cooling from the exterior of the fermenter. Fridge, swamp cooler, glycol chiller ... all exterior. 
I think I will try my next fermentation using a different temp control design. Thanks!

[ynotbrusum]

With Hefe’s I had always heard that fermentation temp favored phenols (clove) emphasized on the cooler end and esters (banana) on the higher end of the fermentation range.  But if you are slipping into real cold fermentation, perhaps it suppresses yeast expression even more so…..

[KilroyWasHere]

With Hefe’s I had always heard that fermentation temp favored phenols (clove) emphasized on the cooler end and esters (banana) on the higher end of the fermentation range.  But if you are slipping into real cold fermentation, perhaps it suppresses yeast expression even more so…..

Thanks for the reply. I get the same behavior with Saisons, Wits, anything lighter in color where the yeast character is supposed to be a big part of the flavor profile.


BTW how many people has Drew Ban Hammered?