When to do a diacteyl rest

I made my first lager an Oktoberfest 2 weeks ago as of tomorrow.. I was wondering when I should do my diacetyl rest? I am using Wyeast 2352 Munich Lager 2 at 54 to 56 degrees internal temperature. Also, the temperature range is 52-62 so what temperature should I bring it up to if I'm going to do one?

it's an "ask 10 people get 12 answers" question. i like to point to the data from an austrian university, shown on braukaiser's wiki:
http://braukaiser.com/wiki/index.php?title=Fermenting_Lagers
they measured diacetyl level in fermenting beers, and plot it against time while also showing extract (showing drop in gravity) and temperature, for a few different temperature regimes. basically this experiment says that if you just leave it cold for a long time (fermented at 9c and dropped to 1c) diacetyl continues to drop slowly even in the cold. so if you lager it properly on the yeast the diacetyl will f off. of course holding your ferm temp until diacetyl is gone will achieve the same result but faster. the two batches in the experiment where there was a diacety rest, one from 9 to 13 degrees and one from 9 to 20 degrees, both had the effect of very rapid decrease in diacetly. from the point of the home brewer, i doubt it matters which of these you do, as long as you do it towards the end of fermentation, as in the above experiment, so your lager yeast doesn't have the chance to get weird. i am not a hugely experienced lager brewer but when i brew them i ferment 9-11c and after 2 weeks i shut off the cooling to let it rise to ambient temp, which (since i only do them in the winter and in an unheated area) is nowhere near 20c, forget it for a week, then rack to a keg for cold storage. but that's just me

You shouldn't have let the temperature get above 55 F while it's fermenting vigorously . It could probably lead to producing esters in your Oktoberfest which is not desirable .

Ideally you want to start the diacetyl rest slightly before reaching finishing gravity so that there is still active yeast suspended in the beer. In practice this is difficult to determine, and you need to look for a slowing in vigorous fermentation to start the rest. Look for when the yeast head has collapsed back into the beer and relatively few gas bubbles are coming to the surface, but before the beer shows visible signs of clearing.

Carry out the primary at the recommended temperature, then bring the beer temperature up to 65 °F . Hold it there for two or three days then cool gradually to the desired lagering temperature.

To see if the diacetyl rest is complete , There's an easy “forcing” test that will only cost you a few ounces of beer. Pull a sample from your fermenter and split it into two covered containers. Refrigerate one and heat the other to 140°F for an hour, then taste them both. If they taste the same, you're ready to rack your beer out of the fermenter. If you can taste butter in the heated sample, your yeast is still at work, and you should give it another day or two.

Hector

I was planning on fermenting for 3 weeks so.. Basically you think I should ferment for 3 weeks then bring it up to 65 degrees and hold there for 2-3 days check to see if the rest worked by pulling out a sample and doing the test and then lager it. My yeast according to wyeast labs said it produces low diacetyl and low sulfur aroma.. Don't know if that changes anything or not. Also should I do a secondary fermentation? For 1-3 weeks, i would do to 2 to be safe, at 39-41 degrees and then lager it?

dmiller224 said:

I was planning on fermenting for 3 weeks so.. Basically you think I should ferment for 3 weeks then bring it up to 65 degrees and hold there for 2-3 days check to see if the rest worked by pulling out a sample and doing the test and then lager it. My yeast according to wyeast labs said it produces low diacetyl and low sulfur aroma.. Don't know if that changes anything or not. Also should I do a secondary fermentation? For 1-3 weeks, i would do to 2 to be safe, at 39-41 degrees and then lager it?

Click to expand...

I'd suggest bringing the beer up to diacetyl rest temperatures when the beer is 75% of the way to FG. Often, that's at about 1.020 or so, depending on the beer.

You want to do the rest while the yeast are still active, but winding down the bulk of fermentation. If you've already had the beer in the fermenter for 2 weeks, it's more than time to do the diacetyl rest. You may very well be able to skip the diacetyl rest with that yeast strain, assuming you pitched a big enough starter at a cool temperature.

I always rack before lagering, after the diacetyl rest. Once the beer is finished, and the diacetyl rest period is over, I rack the beer and begin lager.

For my Kolsch I did it at two weeks.

• I left it out for a couple days, it started bubbling when it warms up and the CO2 excapes.
• Then I lager it for a few weeks...

I pitched 250 ml of yeast that I grew it to that number using a stir plate. So.. I should have more then enough yeast. So skip it or do it? Just checked the gravity it's a little under 1030 right now.

dmiller224 said:

I pitched 250 ml of yeast that I grew it to that number using a stir plate. So.. I should have more then enough yeast. So skip it or do it? Just checked the gravity it's a little under 1030 right now.

Click to expand...

Where did you start for an OG? To be at 1.030 after two weeks is a pretty slow fermentation, unless it's a really big beer that is supposed to finish high. My lagers are usually in the fermenter 7-10 days before the diacetyl rest.

I'd do the diacetyl rest when the beer is 75% of the way to FG, unless you absolutely don't want to. There is no disadvantage to doing one, even if it isn't strictly necessary. If you're an expert at detecting diacetyl and don't taste any, or don't find any in a test, then it could be skipped- but it never hurts to do one.

My og was 1067 so i think it's doing pretty good... Should I let it ferment longer you think?

Marking this thread for reference. I've made my first noticably diacetyl beer.

dmiller224 said:

My og was 1067 so i think it's doing pretty good... Should I let it ferment longer you think?

Click to expand...

At 1.030, it isn't done.

Yooper said:

At 1.030, it isn't done.

Click to expand...

I was planing on going at least 2 weeks maybe ill do 6 weeks total instead of 4 and do the diactyl rest week 4 or 5

dmiller224 said:

I was planing on going at least 2 weeks maybe ill do 6 weeks total instead of 4 and do the diactyl rest week 4 or 5

Click to expand...

Did you do a proper sized starter?

isleofman said:

Did you do a proper sized starter?

Click to expand...

I believe so yes I stepped up my yeast twice and was using a stir plate. I achieved 250 ml of yeasts I checked it with mr.malty should of been more then enough

+1 on the diacetyl test. I brewed my first vienna lager 8 days ago. krausen collapsed a few days ago so I checked gravity and it's down to 1.017 (went fast, big starter and temps were slightly high for a lager 49-52). I tasted a sample and it was good, no butter taste at all. But I did the test (heat to 150 for 20 min, let cool and then compare to unheated sample) and there was a definite butter flavor, obviously different from the unheated sample. So heating really works to convert the precursor compound (alpha acetolactate) to diacetyl. So it's a little late for a diacetyl rest, but I'll try anyway. I've placed the fermenter at 69F and will let it sit a few days. Going on vacation so hopefully 4 days isn't too long.

BridgewaterBrewer said:

+1 on the diacetyl test. I brewed my first vienna lager 8 days ago. krausen collapsed a few days ago so I checked gravity and it's down to 1.017 (went fast, big starter and temps were slightly high for a lager 49-52). I tasted a sample and it was good, no butter taste at all. But I did the test (heat to 150 for 20 min, let cool and then compare to unheated sample) and there was a definite butter flavor, obviously different from the unheated sample. So heating really works to convert the precursor compound to diacetyl. So it's a little late for a diacetyl rest, but I'll try anyway. I've placed the fermenter at 69F and will let it sit a few days. Going on vacation so hopefully 4 days isn't too long.

Click to expand...

No, that should be fine.

One way I taste diacetyl before it gets "buttery" is by mouthfeel. Diacetyl in large amounts tastes buttery or like butterscotch, but in smaller amounts (when a diacetyl rest could be very effective), it presents more of a slickness in the mouthfeel. It also feels oily on the tongue and teeth. If you perceive that in the mouthfeel during an SG reading, you know you have to do a diacetyl rest.

The heating sample works great, as you've found, if wondering if a diacetyl rest is necessary- but some people are genetically unable to taste diacetyl anyway believe it or not! So doing a diacetyl rest at 75% of the way to FG is never a bad idea, and it can be done as a matter of course in lagers without any negative consequences.

I think I just made my first beer with diacetyl in it (well, first with un-broken-down and still-noticeable diacetyl, anyway!). It definitely has a bit of buttery flavor and the oily mouthfeel. The weird thing is, it is a Saison that I fermented for three weeks, starting around 68 and ramping up to 79 after two weeks, then leaving there (room temp) for a third week. I figured this third week at the high temp would be the D rest needed to avoid it. I used Safbrew T-58, properly rehydrated... But pitched at room temp (78*) into 60* wort. I'm thinking that may be the problem/cause? Thermal shocking of the yeast that killed some off (the one dry packet should have been enough based on the yeast calc i used) or stressed them enough to produce more diacetyl than they could effectively clean up? OG was 1.060 and SG was 1.012 (for 80% attenuation, which wasn't apparently affected by the possible yeast shock/death/underpitch, as that yeast lists 75% attenuation).

I went ahead and bottled at the three week point, adding enough sugar to get 3.5 Vol CO2 (I figured if the yeast hadn't cleaned up the diacetyl after that time and temp, keeping it for a week or so more wouldn't help much... Anyone have the opposite experience? Also, I'd never tasted diacetyl before, and wasn't sure - or more probably was just in denial! - and had everything ready and set up to bottle anyway, so just went ahead and did it - maybe a mistake?). I just tried one (after only 11 days carbing at room temp and one day in fridge - I know that's less than the three weeks and 2-3 days each I'm aiming for, but just wanted to check)... The carbonation and colder temps do lend a reduction in the taste of the diacetyl, but after it sat and warmed/flattened for a bit, it was still very apparent.

Do you think more time bottle conditioning (there are still active yeast in there, carbing it up, obviously) / aging will help reduce the oily buttery yuck-flavor, or should I just chalk this one up to my first "off" batch (its only my fourth, so I'm just happy I made good beer up til now!)? Is there anything else I can do to make it better at this point? Or for future batches (beside trying to match my yeast temp to my wort temp better at pitching, as noted)? It is still drinkable, just obviously flawed... I wouldn't pour it out - but would force myself to drink them as punishment to learn the lesson so as to not (hopefully) do it again!