Krausening / Pitching Actively-Fermenting Wort

Question

Krausening / Pitching Actively-Fermenting Wort

Pietro

2015年8月10日 19:13

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?

Topic krausen yeast-starters yeast homebrew

Category Mac

Franklin P Combs · Accepted Answer · 2015年8月10日 00:46

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.

Denny Conn · Accepted Answer · 2015年8月4日 16:58

1

Denny Conn answered at 2015年8月4日 16:58

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.

Krausening / Pitching Actively-Fermenting Wort

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