2

I heard on one of the old Jamil shows that pitching actively-fermenting starter is a good way to get noticeable but subtle yeast character in a beer. You need to start with an adequate amount of yeast, but basically to 'get the yeast going' before pitching it. He was referring specifically to saisons, where you want a good amount, but (IMO) still subtle ester and phenol production, and a complete fermentation. He was saying it was better to do this as opposed to purposely underpitching or fermenting hot, both of which are risky to say the least.

We ended up trying this on two IPA's with Conan yeast (from which we wanted ester production) and the results were awesome. 78 and 82% attenuation with the esters we wanted.

My question is does anyone know the science behind this method, assuming, as stated, equivalent pitch rates? Why it creates SOME yeast 'character', but not too much? The yeast are already in the growth phase, and I guess it would maybe minimize lag phase?

  • I'm a bit confused, are you talking about pitching this starter into finished beer (like true kräusening), or just wondering about the difference between pitching actively fermenting starter into fresh wort as opposed to 'unawakened' yeast (straight from storage)? Also would you mind expanding a bit on this myth you mention? I'm not sure what exactly you mean when you say pitching 'oxidized wort into your beer'. – Franklin P Combs Aug 5 '15 at 17:49
  • My question pertains to actively fermenting wort vs. propagated wort that is otherwise inactive. The myth I am describing relates to the 'decanting' of spent starter above the yeast cake in starters, and how, at least on a homebrew scale, it does not seem to have any negative impact on beer, though many are continually appalled at not doing this. – Pietro Aug 5 '15 at 19:45
1

First off, it sounds like you're talking about step-propagation, not kräusening (which is adding actively-fermenting beer to end-fermented beer to induce a true secondary fermentation).

I find the issue here a bit vague, because you don't mention whether you're comparing pitching the same number of cells in both cases (one actively fermenting, and the other straight from storage), or whether you are comparing pitching the same number of cells (say, a vial) directly into your batch vs. pitching the same vial into a starter first then pitching that starter into your batch. In the latter case, you would not have the same pitching rate since the yeast will have budded several times over before introduction to the main batch of wort.

The second case being true, the subtle (read: lower) ester character is easily explained by a higher pitching rate. I would guess this is probably the answer.

If the first case is true, however, then it's most likely explained by access to a larger pool of key nutrients, especially oxygen (increasing the level of which will decrease your ester production).

Also, regarding the myth you mention, of course if it doesn't bother you, by all means go for it. But in starters that are highly aerated or oxygenated, it's almost definitely true that more oxygen is being added than the yeast can consume directly, and any excess will almost definitely go on to oxidize components of the wort. The key distinction here is between dissolved oxygen (which yeast can easily scavenge) and oxygen that has already oxidized other molecules (which reactions yeast has little, if any, ability to reverse). It's these oxidized wort components that go on to create off flavors. So I would argue that it's not a myth, especially when starters can easily exceed 10% of your total batch size.

  • wow good answer, I edited the question. i mentioned early on in the question that I was assuming you had an adequate pitch rate for either method (that is pitch inactive yeast cake or already-active yeast). To clarify, assuming you start with enough slurry for an adequate pitch rate, you are saying that if you pitch 'active' starter, you would essentially be overpitching, which would reduce ester production due to less growth? Also, deleted the mention of the oxidized wort 'myth'. – Pietro Aug 10 '15 at 19:15
0

I gotta disagree with JZ. I've used krausening for "fixing" lagers that had diacetyl issues. It works great for that, but I got no additional "yeast character" in the beer.

  • Denny I think the difference may be when you are 'fixing' a beer, the overall fermentation is much further along and you are seeking nothing more than dropping dissolved sugar levels, so in that case, production of phenols/esters would be minimal. I actually came upon Drew's Maltose article on saisons and warnings against purposefully stressing the yeast, which touches on my question. In your experience, does coaxing character out of the yeast depend on the strain, generation, other conditions, etc. more than anything else? – Pietro Aug 5 '15 at 17:23
  • 1
    In my experience, the 2 most important factors are yeast strain and fermentation temp. – Denny Conn Aug 5 '15 at 18:16

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.