What happens if I am lazy when fermenting a lager?

[peteru]

I have a batch of wort for a dark lager split into a 16L cube and a 6L cube. I also have one packet of dry lager yeast. The normal process here would be to get the yeast onto the YeastForge and make a 3L starter, then combine contents of both cubes in the fermenter, pitch the starter and blast it with O2 for 90 seconds or so.

I'm interested in what is likely to go wrong (if anything) if I was going to get the 6L cube into the fermenter, pitch the packet of dry yeast, blast it with O2 for 45 seconds and let it ferment. Then, when it looks like fermentation activity is just past it's peak, add the remaining 16L and blast with O2 for another 45-60 seconds.

The first thing that springs to mind is that, I'm effectively oxidising the first 6L of partially fermented beer and thus contaminating the entire batch with oxidised beer. Is that how it works or am I worrying too much and this is a reasonable shortcut?

 

[malt junkie]

The germans do what you have outlined, the only other thing you should consider is a second dose of o2 a couple of hours after the first.

 

[manticle]

Drauflassen. Only thing I think might be different is oxygenate the second wort before adding in rather than the whole combined.

Check the science if you can - may make no difference but I remember reading about adding second oxygenating wort to first fermenting wort.

 

[homebrewnewb]

yeast forge, classy.

 

[Jack of all biers]

If you do what you have stated you will oxidize the wort, you are correct. I'd advise not to take that short cut. If you add O2 to the beer post pitch it needs to be before the 12-15hr mark, after which alcohols are being produced (for normal pitching rates). That includes adding O2 saturated wort to the beer as the O2 is just as likely to oxidize the alcohols than be used by the yeast.

You'd also be asking the yeast to change direction mid stream by doing this, and likely produce other fermentation problems.

 

[DJ_L3ThAL]

If you've grown up a decent 'starter' by fermenting the 6L at high Krausen should you even need O2 given you'd have cells in the beer making phase and hopefully plenty of them?

 

[Danscraftbeer]

I've done it twice now. Draufflassen. 2 cube pressure fermented brew.
Get the first half brewing with some o2 injected to ~5psi, roll shake it well with enough yeast for that much wort (50% required for the full amont etc). Ferment to around medium Krausen ~24 hours. Then add the second half wort and re-inject o2 as before, roll shake well and brew it out to completion. I'm yet to experience oxygenation off flavors described as cardboard flavor etc. I think all the o2 gets consumed.

 

[DJ_L3ThAL]

Hmm interesting. I thought it took a lot of energy/effort (read glycogen reserves, nutrients etc) for the yeast to switch from anaerobic fermentation to aerobic fermentation so isn't the second dose of O2 detrimental to performance if traded against the benefits it gives only to the growth phase?

 

[manticle]

If you do what you have stated you will oxidize the wort, you are correct. I'd advise not to take that short cut. If you add O2 to the beer post pitch it needs to be before the 12-15hr mark, after which alcohols are being produced (for normal pitching rates). That includes adding O2 saturated wort to the beer as the O2 is just as likely to oxidize the alcohols than be used by the yeast.

You'd also be asking the yeast to change direction mid stream by doing this, and likely produce other fermentation problems.

You surprise me, Jack.

http://braukaiser.com/wiki/index.php?title=Drauflassen

 

[Jack of all biers]

You surprise me, Jack.

http://braukaiser.com/wiki/index.php?title=Drauflassen

Shouldn't surprise, nor do I necessarily disagree with Kai or the Drauflassen method he describes. I personally wouldn't use it in home brewing, as it is easy enough to make/purchase an adequate pitch of yeast for a lager.

I was saying that if done the way it is written (stated) in the OP it will cause oxidation. That is because the method was described as;

6L cube into the fermenter, pitch the packet of dry yeast, blast it with O2 for 45 seconds and let it ferment. Then, when it looks like fermentation activity is just past it's peak, add the remaining 16L and blast with O2 for another 45-60 seconds.

The key thing I was addressing was the emboldened statement above. Fermentation activity past it's peak, suggests anywhere between 36-72hrs depending on yeast, lag time, etc. Taken at it's best, it would mean the kraeusen has started to lower from high kraeusen, suggesting most of the simple sugars had been converted to ethanol & CO2. Troester however, describes adding the extra wort as the kraeusen starts to form and expressly states 'just after 24hr', which should be after the lag phase and just into the growth phase.

Now I didn't describe what oxidation I meant, so that is my bad. I wasn't just talking about the typical cardboard flavour affect, but also about oxidation of the alcohols, which could cause some potential problems later on. For example, if oxygen is added to the fermentation at a time 'past peak fermentation' activity, then I would suggest that an amount of oxygen would react with the ethanol in the beer, creating higher levels of Acetaldehyde, which the yeast may not clean up later on.

Whilst Kai Troester works around 24hr, I stated 12-15hr, as I am conservative. My main reasoning for this, is due to the Yeast book, which talks about the lag phase being 0-15hr (at adequate pitching rates). Troester is probably correct, as the yeast book touches on a similar method, but for secondary O2 addition for higher gravity beers. They recommend adding O2 between 12-18hr, so 6 hr later probably wouldn't make a vast difference, though this method is for high gravity not a lager, which is more susceptible to off flavours like excess Acetaldehyde. Like I said, I'm conservative.

Peteru is not to take this as any criticism, as he was just asking the question, and might be able to clarify what he meant. I stand by my original post answering the OP though.

EDIT - spelling mistake (Troster to Troester)

 

[peteru]

The type of analysis that Jack of all biers is offering is exactly what I was after. I suspect that timing is critical to the success of the Drauflassen method and the most effective timing will depend on a number of factors, including original pitch rate, health of yeast and even the form (dry vs live). Factors that I am not familiar enough with, since I don't brew lagers very often.

At this stage I'm inclined to not be lazy and just grow a big enough starter for a 23L batch. While Drauflassen might be something that could work with enough experience, I'm probably better off taking the extra week to grow the starter and get a good pitch rate (or buy more yeast) so that I get a good beer for Christmas. However, I'm happy to listen to the scientific discussion on the merits and perils associated with staged fermentation.