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.

2 comments:

  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.

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  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!

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