Diacetyl Rest

Kind of yeast dependent...some lager yeasts seem to require a week at the elevated temp. As far as dropping it back down...there are the gradual and the "it doesn't matter" schools of thought

Doesn't seem to matter as much with ale yeasts...Noonan discusses on pgs 184-185 for lagers

 

From Yeast (paraphrasing): For lagers raise the temp to 65 - 68 near the end of fermenation (2 to 5 points to go) for a two day period.

For ales (typically 65 -70 ferm temp) it is not absolutely necessary to raise temp but an additional two day rest after FG is reached is advised. If fermentation was sluggish, they suggest raising 5 degrees to accelerate diacetyl reduction. Use caution to not let the temp drop after reaching FG, as this will result in yeast becoming dormant and no diacetyl reduction.

As a matter of technique, I always raise my ale temps. After about day 4 of fermenting, I boost one degree a day until it's near 70, then give it 2-4 days of rest. Typically I'll drop it a few degrees to come back into normal ferm temp range for 'bout a week, then cold-crash if I have space in a spare fridge. I feel the yeast are happiest when everything is in slow motion.

 

Yes ...any specific timeframe is purely arbitrary...the healthiness of the original fermentation is probably the biggest factor.

If you insist on an answer, I would have to say after it has reached the desired temp as that will result in a longer timeframe at some higher temp.

 

Personally I start the clock when the higher temp is reached though it's not a strict clock. Works for me but that doesn't mean I'm doing it right.
My methodology is to pull the fermenter from the temp controlled chamber when the krausen peters out and place it in a 70-72 ambient. It will sit there 4-6 days then get cold crashed for kegging. I'm assuming it takes 24-36 hours for 5.5 gallons of liquid to acclimate to the new ambient temp but you know what happens when you assume.

 

I try and let the beer decide, not a clock. Pull a sample, smell and taste. Put sample in a microwave raise to 100F, smell and taste. No D, crash. D present, wait, repeat.

 

I just leave the temperature up, usually for about a week, before bringing it back down. Because lazy, and because, I think a longer D rest is more beneficial than an arbitrary 2-dayer.

 

Exactly what I do. For the same reasons!!

 

You might be one of those lucky ones who can't taste it...what a blessing

 

Yup, something like 20% of the population is 'blind' to diacetyl. No need to conduct a diacetyl rest if you are part of the 20% and you solely drink all your beers.

A funny related story. I am good friends with the assistant brewer of a local brewpub. They would use the Ringwood yeast as their house ale yeast strain for their core beers. They preferred this yeast since it drops bright (no need to filter those beers). I asked about the diacetyl issue with that strain. He confessed that he personally could not perceive diacetyl and that it was the head brewers job to periodically (once a day?) taste the ales in the brite tank and declare them to be ready to be served.

Cheers!

 

I am not blind to Diacetyl, but I have a high threshold. The beer has to be an example wth high levels. Often I can detect it as a slick mouthfell on my toungue against the roof of my mouth.

Last night night it gave my wife a 100F sample, and said "get any Diacetyl?" As she is sensitive to it.

 

I am going to be of little help to you here. I am very sensitive to diacetyl and I have been homebrewing lagers for over 15 years, utilizing a variety of lager yeast strains, and I have:

• Never conducted a diacetyl rest
• Never perceived any diacetyl in any of my numerous batches of lager beers

Based upon my homebrewing experience I could instruct you to not conduct a diacetyl rest but since your homebrewery is not my homebrewery that would not be something I would do.

Cheers!

 

I got into a big heated argument on a Best of Show judging, me the Certified guy vs. another National guy, and he insisted that a certain IPA was just phenomenal and deserved Best of Show, while myself and another Recognized judge did not agree based on presence of diacetyl, which is not appropriate in an American IPA. The National guy then stated that he cannot detect diacetyl, so that must explain the discrepancy, and yet he still insisted that the beer deserved BOS and said "for the record I do NOT agree with you guys". Finally he agreed that we at the BOS table must vote on it. The National guy lost the argument. The IPA with diacetyl took 2nd place. He was just FUMING. It was kind of funny, and sad, all at the same time.

 

Ever eat microwave popcorn? Can you taste the (artificial) butter flavor? That's mainly diacetyl. Beerwise, try Pilsner Urquell or pretty much anything from Samuel Smith's. The flavor (like a lot of flavors) is more prominent when the beer is warm.

 

I attended a presentation entitled “Sensory and Flavor Training for Brewers” at the 2015 NHC in San Diego. This presentation was ‘multi-media’ in that they served a base beer along with four versions spiked with off-flavors (including diacetyl). When the presenter (Pat Fahey) discussed diacetyl he made mention that they stopped using diacetyl for artificially producing buttered popcorn like at the movies because workers at the factory(s) were getting sick from a long disease commonly referred to as “Popcorn Lung” due to the inhalation of diacetyl.

There are artificial flavorings out there for food items like popcorn but I do not know what ingredients are in these products today.

Cheers!