Friday, January 15, 2010

Diacetyl Rest - Go for a Week!

In mid-late 2009 we brewed our first lager, an Oktoberfest. For our first lager (and having no temperature control device, just a fridge), it went really well. The final beer was malty with a nice hop bitterness, beautiful amber color, and crystal clear from the lagering (why filter a lager?).

I brought a sample to a Chicago Beer Society event, and one guy said he tasted a hint of diacetyl (a buttery by-product of lager yeast). I was unsure of this, having yet to train my palate for this flavor. But everyone really liked it and drained the bottle. Next day I brought a sample over to Half Acre brewing, and had a little lager schooling from head brewer Phil, who also tasted just a hint of the buttery diacetyl. After drinking this brew for a week or so, I was able to just pick it out too. He asked if I did a diacetyl rest, and I did do one for a few days. Phil said to just leave it out for a week! So next time, a week it is!

We've since brewed another lager, an American Premium. We had excellent temperature control, never letting the beer get above 50F (we pitched in the upper 40s), and a post-fermentation sample tasted great. So instead of doing a rest, I  just crashed it down to 36F and will be kegging it up soon for the super bowl. We'll see how that goes, but I think it should be fine. The yeast I used, Wyeast 2007, didn't say anything about needing a diacetyl rest, whereas the 2308 Munich Lager I used before clearly states that it benefits from one. So I guess the moral of the story is to read up on your yeast, and if a rest is needed, make it a week - cheers.


  1. Hmm... I generally use White Labs lager yeasts, so I can't speak to 2308, but I've never had any diacetyl issues with a 48-hour rest (and it sounds like we're pitching comparable starters). If you're really worried, there's a test you can do where you draw two samples, heat one in the oven for a few minutes, and then compare the two for any hints of diacetyl. I can't remember where I read it, but I'm sure you could find it with a little googling. That way you're not keeping your beer at room temp any longer than necessary.

  2. Thanks for the tip! I'm not too worried, just relaying info and maybe something to try. I don't think I had an issue, and have actually come to think a slight hint is OK in a malty Marzen (Mosher writes about this). I guess it just depends on what you like - we'll see what happens next time ;) Cheers!