Diacetyl rest

Here's another "My first lager" question:

I've got a 5 gal batch, OG was 1.055, and it's been in a chest freezer at 52 degrees for almost 3 weeks. I made a 1L starter with saflager 23. It has been fermenting slowly the whole time.

I hadn't heard of diacetyl rest until after I made this batch, and now i'm wondering exactly what to do. (I dont have a wine thief, so I havent taken a sample yet, but I will be stopping by the LHBS today...)

For the d-rest, is it as simple as removing the carboy from the fermentation chamber and letting it sit at room temp for a few days before transferring to secondary and bringing the temp back down for lagering? Also, does safelager23 have alot of diacetyl?

Thanks

You are supposed to rehydrate dry yeast, not make a starter. Follow the product sheet instructions.

Yes, it's as simple as letting taking your beer out of the ferm chamber and leaving it at room temperature. It may or may not have diacetyl, but doing a rest costs you nothing and can save you a lot of heartache later. You should do your d-rest when you are somewhere between 5 and 10 points above expected FG (1.020 is a decent rule of thumb for most normal-strength lagers); leave your beer on the yeast until you reach FG (or longer), then rack to a secondary and cool to lagering temperatures.

I would not expect much diacetyl with S-23, but certain brewing practices can cause it to occur anyway (i.e. it's not always or even "often" the yeast's fault).

Good luck!

This was a batch of firsts... I had just finished my stir plate and picked up a 2L flask, so it was also my first starter. I rehydrated the yeast prior to pitching in the starter. For future reference, is that OK?

Thanks for the help!

Just rehydrate, no need for the starter. Great that you have a stir plate; it will allow you to get to correct pitching rates when you use liquid yeast. With temperature control and pitching rates taken care of, you are doing great! Next step--oxygenation.

Yes it's ok. I made a starter with a pack of brewferm lager because it was expired and I didn't have any more lager yeast. I did NOT rehydrate it and it took 3 days for it to rehydrate in the starter wort and another 2 days to ferment.

I kind of have the oxygenation covered, I use an aeration pump with a stainless steel stone and a sanitary filter, aerated the wort for about 45 minutes.

I did the starter because I had read that lagers require alot more yeast than ales, and I figured that they would multiply in the starter and be ready to go when I pitched into the wort.

"I would not expect much diacetyl with S-23, but certain brewing practices can cause it to occur anyway (i.e. it's not always or even "often" the yeast's fault)."

What brewing practices can cause higher diacetyl levels?

True to form, for me, I brewed first and asked questions later... I found very little reference to diacetyl in the "Complete joy of homebrewing" book, and have gleaned most of my information from this forum.

Thanks again!

60sd said:

What brewing practices can cause higher diacetyl levels?

Thanks again!

Click to expand...

Some strains of yeast simply produce more diacetyl than others- so that's one way.
there are even a couple of ale yeast strains that are notorious diacetyl producers (like ringwood). So staying away from a strain that is known to make diacetyl bombs is a good first step.

Another source is infection- pediococcus is known to produce diacetyl as well.

Most commonly, it's just due to unhealthy/stressed yeast. As an example, yeast love being warmed but don't do well being chilled. So pitching lager yeast warm, and then chilling can encourage them to produce more diacetyl than normal. A good way to minimize that is to chill your wort to 45 degrees or so, and add the yeast (I take my yeast starter out of the fridge for that) when the yeast is 42 degrees or so, and then allow it to warm up to fermentation temperatures (normally around 50). That seems to get healthy yeast going, with less diacetyl.

Diacetyl is actually produced by the yeast and then the point of the "diacetyl rest" is to encourage them to finish fermentation and then to scour for other less preferred foods, including their own waste products. That's when the diacetyl is "cleaned up", if that makes sense.

Not sure I can follow that.

Lager yeast starter - this would be at a "warm" temperature, typically room temp for me. Are you suggesting keeping your starter in the refrigerator and pitching to cold wort?

I understand some like pitching to a cool wort, but I've always pitched to room temp wort, allowed primary fermentation to begin, then placed it in the cold garage until krausen falls. This way I know competitive inhibition gives me a fighting chance against bugs in an otherwise slow fermentation.

Oh, after krausen falls, inside for a few days diacetyl rest, rack, and then back outside again. Never bothered with a refrigerator as ambient winter temperature is usually between 3-11 degrees C here, just wrap with an insulating blanket to modulate fluxuations.

Chris

OK, so I tried it! Sort-of. It worked fine. Pitched at room temp, then refrigerated the culture for about 4 days. I did pitch to wort that was at about 11 degrees C. Whether it makes a difference in quality I'll have to see.

Chris