overpitching in the time of isoamyl acetate

I went through a phase where I thought I didn’t like Bavarian Weissbier. I got over it.

Much like my wife thought she didn’t like Scotch (she just hadn’t found the right Scotch), I don’t think I had ever had a really fresh Weissbier up to that point, and was basing my opinion on some sadly stored examples. This is a style that loses charm with age and poor storage conditions. But my mind was changed by Schneider, Weihenstephaner, Paulaner, Ayinger, and others in situ, and more recently some very nice efforts from American breweries (New Glarus Dancing Man and Sierra Nevada Kellerweiss come to mind immediately) keep the impression vivid. So Weissbier re-entered my brewing rotation.

Enough historiography, let’s manipulate environmental factors in a fermentation to affect the flavor profile:

The past … oh, several batches of Weiss I’ve brewed have been open or at least un-sealed fermentations, which fosters isoamyl acetate and made my basement smell like banana cream pie. Not a bad thing by any means, but change is the only constant and this time around I felt like switching things up.

The Weihenstephaner wheat beer strain, by whatever lab number it’s called, is a beast of a gem of a fungus, and arguably more than almost any other strain can create a vastly different beer through slight alterations to the fermentation parameters: single-temp mash, underpitch, underaerate, ferment warm, and you get a banana bomb. Multi-step mash with a rest for ferulic acid, overpitch, give it lots of O2, ferment cool, and the 4-vinyl guaicol responsible for the spicy, clove, cinnamon, and plastic phenols dominates the banana out of existence. Do some of both and find a balance, but in any event it showcases the malt character without which it just wouldn’t be Bavarian.

Here’s what I did:

  • Multi-temp mash with rests at 111, 130, 156, and 170F
  • Oxygenated well and pitched with an embarrassment of Wyeast 3068
  • Sealed the conical from the get-go
  • Started fermentation at 66F and let it run warm – up to 72F at high krausen

This was a 10 gallon batch in a 14.2 gallon fermenter … so 29.5% headspace. Lesson learned: when it says 33% headspace, do not short it when pitching a lot of this strain.

airlock uncontained

Full recipe and tasting notes to follow.

6 thoughts on “overpitching in the time of isoamyl acetate

  1. Wy3068 is a particularly favorite strain of mine. Like any good POF+ strain, 3068 can decarboxylate ferulic acid (FA) to make 4-VG, but what about the FA sources? I’ve always wanted to know which malts contain the most ferulic acid. I’ve also read that hops contain FA. Which cultivars are rich in FA? Has to be something noble, right?

    In regards to isoamyl acetate production, I’ve wondered if brewers could steal a page from the vinters playbook and simply add ammonium hydrogen phosphate (i.e. “diammonium phosphate” or DAP) to the wort to keep that ester in check. Here is my train of thought on this: 1) yeast metabolize amino acids via the Ehrlich pathway, consequently producing fusel alcohols (e.g. valine —> isoamyl alcohol); 2) the first step in the Ehrlich pathway is the so-called Strickland reaction, which involves the removal of the amino group; 3) fusels can undergo esterification, producing all of the wonderful “beery” esters we know and love, or hate; 4) perhaps the brewer can modulate the Ehrlich pathway by enriching the wort with FAN via DAP, thus partially mitigating the production of a “banana bomb” via the normal Ehrlich process. IIRC, fermentor geometry also apparently plays a role in isoamyl acetate production (Hieronymous).

    A piece of advice I’ve also read about comes from JZ via Harold Gulbransen. Ferment 3068 strictly at 62*F for ultimate balance. I do this with all of my Bavarian wheat beers with good results. A friend of mine took this advice while brewing a dunkelweizen, and he ended up with a fart bomb that, when packaged, tasted like an American wheat beer. Fittingly, my buddy named his beer “fecalweizen.” So, there’s that…

    • Dan K!!!

      And IIRC, wheat malt itself has FA or FA precursors, right? The higher the % of wheat in the grist, the more 4VG action there will be. I’ll have to read up on the FA in hops … it’d make sense that for this style it would come from something noble and from southern German/Czech fields.

      In regards to isoamyl acetate production, I’ve wondered if brewers could steal a page from the vinters playbook and simply add ammonium hydrogen phosphate (i.e. “diammonium phosphate” or DAP) to the wort to keep that ester in check.

      This is interesting … doesn’t seem very German, though, in that it’s not a complicated solution (and I mean that in the best possible way) and it’s additive-based. ; )

      IIRC, fermentor geometry also apparently plays a role in isoamyl acetate production (Hieronymous).

      That’s my understanding too – wider & shallower = more isoamyl acetate. This was done in a 14 gallon conical, so the overall w/d ratio is pretty close to 1:1.

      I’ve fermented with this strain as low as 58F (just to see if it would go) and had results similar to your friend – really, really mild flavor, stronger presence of sulfur.

      • Much to my surprise, ferulic acid is a widespread and abundant constituent of plant cell walls. Wheat seems to have a lot of this stuff, but it’s also quite common in other cereal grains, too. One thing that I find particularly striking about ferulic acid is it’s molecular structure. I spent some time as a grad student looking into the redox chemistry and iron chelation properties of another phenolic phytochemical called curcumin. Curcumin is the major component of turmeric and is putatively responsible for a myriad of beneficial health effects seen in those cultures that have curry-rich cuisines. If you look at curcumin’s structure, it’s basically two ferulic acid moieties attached via a beta-diketone (think VDK, but with an interstitial carbon atom). Not to get too geeky here, but I wonder if FA/4-VG beers possess antioxidant properties.

        I’ve also learned that vintners are particularly put-off by vinyl phenolics; something about Brettanomyces and other offending POF+ microflora in the winery (?). I guess 4-vinyl phenol gives wine an unpleasant “medicinal” note.

  2. My first brew was a Hefeweizen. Used 3068. I found that during the first 3 weeks of its life it was reasonably unpleasant, then after that it really settled down. I fermented it out at 70F (21-22C) and got banana in spades, was great.

    This one definitely needs the head space. Mine was at least 33% and it still managed to almost dislodge the airlock.

    Interestingly I had a few bottles that remained and tried them months later. I actually quite enjoyed them at first. Really big ripe banana tending to cooked apricot. I know they’re all about being fresh, but there was an element to this that I quite liked.

  3. Pingback: Weiße 4.1 | the beer engine

  4. Have you ever come up with a banana bread beer? I know of only one commercial brand (Well’s Banana Bread Beer) and it is indeed delicious. I’ve heard of several people attempting to clone this brew but I’ve yet to come across any bullseye recipe that perfected the balance between banana and bread. I’m thinking that a bready grain bill is key: maybe something like maris otter with some biscuit or victory malts and maybe a dash of chocolate malt and carapils. What’s your take on making a bakery fresh beer like this?

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