When to do Diacetyl rest?

[abandler]

Hey paddlers, I’m doing my first real lager (finally got a fermentation fridge!). It’s a Helles Exportbier with w34/70 yeast. When should I turn up the heat on it? It’s currently sitting at about 75% completion. I read that I could do it at 80%, and I also read I should do it at 2-5 points above FG, which would be about 90-95% completion. I’m attaching the read-out from my Tilt. Any experience with optimal times/temps for a D rest with this yeast?

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[Spauld]

Hey Aaron – most German lager producers don’t do warm diacetyl rests. The belief is that it makes the yeast ‘lazy’ since it ramps up to consume all of the residual sugars, then simply goes to sleep after the feeding frenzy (kind of like me after a trip to the buffet). The thinking is that the yeast then doesn’t function well during the long cold lagering phase. I realize that you might not be doing a long lagering phase though, and so if that is the case then a warmer (60F or so) diacetyl rest is what many home brewers will do. If you ARE planning a longer lagering period, this is what I have read is recommended for that approach:

After primary fermentation (usually about 3 weeks for the 34/70 yeast), slowly lower the temperature (no more than 2 degrees per 24 hours) to 40F. Leave the bier at this temp for 7 days, then do a quick diacetyl test by filling a plastic PET bottle about half full (something like a 12oz. plastic bottled water container). Allow it to come up to room temp, then give it a good shake for a half minute or so, open it and smell for the tell tale buttery aroma of diacetyl. If none, you’re good to go and can then continue lower the bier to something like 33F (slowly). The thinking is that if diacetyl precursors are present, then this will activate them. The long rest at 40F is believed to give the bier enough time to chew through any remaining diacetyl, so if you do detect it in your test, you can simply give it another week or so before continuing your slow dive to 33F. By doing this, your yeast will remain super-healthy and will continue to function well at super low temperatures. Again, warming the bier to achieve a fast diacetyl rest is believed by traditional lager producers to ruin the yeast for this long haul.

Either way, Good luck…can’t wait to taste your Helles Exportbier!

[RyanP]

If you’re doing a quicker lager, this method works well – http://brulosophy.com/methods/lager-method/

There are other methods that work well too, but I’ve done the above method multiple times and it works well.

I now do the way Jim mentions, the more traditional German way, for the reasons he cites. I think it produces a cleaner beer in general. And it’s the method my favorite lager brewery here uses (Bierstadt) and their crisp clean characterization is what really sets them apart in my mind.

One main reason I don’t quick lager anymore is because I found that in order to get the same type of clean, crisp flavor as the low and slow method, I’d end up deep lagering in the 30s for almost just as long, so the “quick” lager method wasn’t really all that quick for me, it was just fermenting the beer faster, I still had to condition it lengthily to get the same type of quality for my tastes.

An example of the quick lager method was that coffee vienna lager that Dean and I made on his system and canned on SPE’s canner a couple years back. We brought a few to the club, it was a nice beer, but by the time we canned it it was probably 2-2.5 months old. It was done in 10-14 days bc we fast lagered it, and while it was pretty damn nice at 14 days, it was clearly better after 2 months of cold lagering. In that case, if we wanted a “pretty darn good but not great” vienna in 14 days, we could’ve started carbing then. But we were patient and rewarded with what was in my opinion a fantastic beer.

Your mileage may vary, and different tastes/perceptions/biases can all come into play. I’d encourage people to try both low and slow and quick/hot lager methods and see what they think.

Same with mashes, decoctions, step or infusion. There are good lager breweries in both the US and Germany that use any of those 3 methods. I personally would advise on doing what your equipment can easily handle.

[Author]

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