Diactyl Rest

[brente1982]

Its pretty hard to follow the different advice of 13 different people, so i went with what was commonly expressed.

 

[Adr_0]

It's not dormant on the way down though and you avoid shocking the yeast.

Try it one way. Try it another. It's the best way to compare these things. I've done quite a few lagers with the raise quick/drop quick method and got loads of diacetyl in the finished beer.

Whatever the theory, the practice works.

Just to clear a few things up, the yeast will remain active to around 4C. A refined method I now use is to drop 1-2C per day until I get to 4C and hold there for a few days. Then you can crash it to -1C where proteins and polyphenols drop out, the yeast drops out and even chill haze drops out - especially if you've used Whirlfloc in your kettle.

Back to the diacetyl rest. Not all yeast strains produce lots of diacetyl, some produce very little but raising the temperature is still a good idea. Why? Because if diacetyl is present the yeast which has become more active at this elevated temperature will absorb it. Other fermentation byproducts also benefit, acetaldehyde for example, a precurser to alcohol gets cleaned up. What else? You are in fact warm conditioning the beer. The conditioning phase is working at double speed at elevated temperatures and is also done commercially to speed things up. A few days at around 3 - 5 at 18C - 20C will reduce the time needed for the whole conditioning process. You get to drink it sooner!

Hippy has put a link in his post on page one to some older threads which explains most everything. The two distinct stages of lagering is (1) where the active yeast is cleaning up fermentation byproducts and (2) when the very low temperature causes the yeast to become inactive and malt and hop byproducts flocculate out along with the yeast.

-Steve

Just some interesting feedback on diacetyl and a good example of what NOT to do.

I recently got a 'dead last' in the QABC for a bohemian pils. I haven't received the feedback forms yet and while it could have used another 5 IBU, it was a pretty obvious butter-bomb and was no doubt marked down for this.

I used Wyeast 2000. Looking back at my records, I had cold pitched at 8°C, fermentation started well and sat at 10°C for a while. It was very very clean at this stage and tasting beautiful. Looking at my records, at about 60% AA I then lifted it gently to 14°C (fridge temp) for ~2.5d, before cooling it fairly steadily down to lagering temps. IIRC I had to be out of town for a few days and was trying to treat it gently on the warm-up, but I obviously didn't quite get high enough.

At carbonation (lagered for 2-3 weeks) it had marks of diacetyl but a level I would argue is acceptable in a Bohemian pils. It then seemed to build up further over time and had peaked nicely in diacetyl after about 4-5 weeks in the bottle (probably perfectly timed for QABC ). It has faded back again to what I would call acceptable for the style but still definitely there.

 

[Droopy]

From reading this thread, my only question is how fast is too fast when heating your brew for a D-rest and cooling your brew for a cold-crash??

What I mean is I have dropped previous brews from d-rest temps of 16-18C to cold crash temp of 2C instantly (read: takes fridge 12?hours to get the brew temp down), and anywho there hasn't been any problems with anomaly tastes and the yeast has woken well enough to carbonate bottles. So, how fast is too fast in heating and cooling?

 

[Adr_0]

From reading this thread, my only question is how fast is too fast when heating your brew for a D-rest and cooling your brew for a cold-crash??

What I mean is I have dropped previous brews from d-rest temps of 16-18C to cold crash temp of 2C instantly (read: takes fridge 12?hours to get the brew temp down), and anywho there hasn't been any problems with anomaly tastes and the yeast has woken well enough to carbonate bottles. So, how fast is too fast in heating and cooling?

You will struggling to get a solid answer unfortunately.

When you carbonate, you are adding extra sugar and stirring the yeast - so it will go into suspension again whether it's dropped out or has stayed active during lagering.

The theory behind everybody's approach is that you only have a tiny bit of sugar for the yeasties to eat by the stage you are lagering, so they have little reason to stay in suspension and are probably more susceptible to dropping out if you are too aggressive with your cooling. I guess that your lagering will be more "effective" if there is more yeast in suspension. Anecdotal much?

On a side note..
If you have your temp probe in the air of the fridge, you will generally cool the wort a little less aggressively as it cools the air in 1-2 degree chunks (which then warms again from the wort/fermenter) so you get quite a gradual drop. If you have the probe in the wort, your fridge will stay on the whole time until you get to your temperature. Pro's and cons of each.

As manticle suggested though, why not try different examples side by side, or chase someone down nearby who can offer examples?