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okiedog 01-21-2013 06:10 PM

Diacetyl rest lager or just rack it?
 
Yesterday I noticed that the krausen on my Pre-Prohibition lager had fallen and I had missed it happening. It probably happened over night or I didn't realize it was happening when I last checked it. Is it still okay to do a diacetyl rest, or is it even needed?

Fermentation took 10 days with White Labs American Lager Yeast WLP840, pitched at 69F (I know I should have cooled it more). Brought down to 54F within the first 24 hours. I have no temp controller yet, but was able to keep temp mostly between 48 - 50F, with occasional short time low of 47.8F and high of 52.5. I am slowly bringing the temp up to 55.

Should I rack it or rest it first?

bwarbiany 01-21-2013 07:54 PM

Best I can figure with d-rest when I did research on it prior to my first lager:

Pros) Cleans up diacetyl.
Cons) Takes an extra 2-3 days?

I didn't see any other downside than time, so I see no reason not to do it now. The krausen may have fallen, but I think you have enough active yeast to still clean up diacetyl, as yeast typically are capable of cleaning up diacetyl during the lagering process anyway, so they haven't become too dormant to do their job.

JimRausch 01-21-2013 08:53 PM

oops, apparently double posted

JimRausch 01-21-2013 09:12 PM

Yep, a D-rest at 60-65 for a couple days is easy insurance(assurance?).
Slighty sideways topic- I was never sure I knew what Diacetyl tasted like until this weekend when I sampled my Oktoberfest brewed back in November vs. a Special Bitter that I brewed 12/31. The bitter definitely had a buttery taste. It's only been in the bottles for a week so will probably cleanup some.

okiedog 01-22-2013 04:09 AM

Is it okay to do a D-rest after the Krausen has dropped?

dinnerstick 01-22-2013 11:48 AM

the good old brau kaiser has posted some diacetyl readings in different lager fermentation regimes (pinched from TU vienna whatever that is) here
http://braukaiser.com/wiki/index.php...menting_Lagers
look that the graphs just over halfway down the page. in these instances you can see that just leaving the fermentation alone the diacetyl level slowly continues dropping even after terminal gravity is reached in cold storage (A) or when it is held for long periods at fermentation temp (D), but indeed it drops more quickly with a temp increase for D-rest (F), even in this case the D-rest is done after terminal gravity is pretty much reached. these are specific examples but are useful when thinking about your strategy; according to these data your increase after terminal gravity (did you check the gravity?) is still highly effective for reducing diacetyl.

okiedog 01-23-2013 12:57 AM

Thank you guys so much for all the information and input to my question. Since I had pitched the yeast about 10F above fermentation temp range, I decided to do a D-rest. I read somewhere that higher pitching temps can contribute to diacetyl, though lagers aren't prone to high D. No SG taken yet, didn't want to open the primary until I have to. Anyway, I'll D-rest at 60 -62 for a couple of days, then cool and rack to secondary and check SG. It'll be interesting to see (and taste) the results. I have another lager lined up for the primary. I'll pitch at fermentation temps, skip the diacetyl and compare the results. Sound reasonable?

Yooper 01-23-2013 01:01 AM

Quote:

Originally Posted by okiedog (Post 4815108)
Thank you guys so much for all the information and input to my question. Since I had pitched the yeast about 10F above fermentation temp range, I decided to do a D-rest. I read somewhere that higher pitching temps can contribute to diacetyl, though lagers aren't prone to high D. No SG taken yet, didn't want to open the primary until I have to. Anyway, I'll D-rest at 60 -62 for a couple of days, then cool and rack to secondary and check SG. It'll be interesting to see (and taste) the results. I have another lager lined up for the primary. I'll pitch at fermentation temps, skip the diacetyl and compare the results. Sound reasonable?

Check the SG before cooling and racking! If it's at FG with absolutely no hint of diacetyl, then it can be racked and the lagering period begun. If it's not quite done, or you have any oiliness in the mouthfeel at all, then extend the diacteyl rest until any slickness is absent in the sample!

okiedog 01-23-2013 04:49 PM

Thank you. Will check SG and taste sample tomorrow.

okiedog 01-25-2013 01:19 AM

Well. this afternoon I pulled a sample of my (1st ever) pre-pro Lager after 1 days in primary and 2 days D-rest.

expected OG: 1,042 - 1.048; actual:1.054
expected FG: 1,008 - 1.014 SG currently: 1.011
Taste test: Darn Good! (concenus of 4 people)
My son-in-law said he could drink it now! I'm happy - going to rack to secondary

I welcome any additional advice or recommendations. Thanks!


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