by product clean up time, what's the truth?

[joshesmusica]

Ok, it's time that it's asked. I have been reading many people talking about that it's best to leave it in primary for 2-3 weeks to allow for cleanup (i read this at the beginning of my journey into brewing, and have been propagating this "truth" as well). While recently some people have come out and said that technically (or scientifically) speaking, once the beer has reached FG, the yeast will only take another day or so to clean up.
so what is it? what's the truth? and if you give an opinion, can you back it up with some kind of scientific data, or is your opinion just anecdotal (which i won't judge you or even automatically dismiss you if this is the case, just curious)?

 

[ghohn]

I've got no other scientific data that if it tastes good then drink it. If you work continually with a yeast strain, you get to know its rhythm, I feel like most of the beers I make 'peak' at about a month (I keg) but I'd be lying if I said I had never drunken a beer at day 4. For me, I brew because I drink beer daily and imports, awesome American IPAs, are cost prohibitive at ~ $5 a bottle. Is my beer better at 21 days versus 7? Generally, but it's no sweat off my sack. If you've got enough storage capacity, build yourself a decent pipeline and figure out what you consider 'peak'. Everyone gets excited at what they have in the fermenter. I totally understand that. As long as the yeast have settled and it was brewed correctly in the first place, my rule of thumb is 7 days. I could force carb it and drink it in 10 minutes or allow it to find its spot in the rotation. Personally, it's all about whatever I need at that moment.

 

[RM-MN]

If you do the ferment properly, including pitching at the right temperature and following good temperature control during the fermentation including warming toward the end of the period your beer will have little to clean up and it will be done in about 10 days. It will still have a bunch of suspended yeast so leaving it longer will allow more yeast to settle.

If your ferment is not done perfectly your yeast may have produced some compounds that you don't want. Some of those can be eliminated by allowing the yeast more time. How much more? Depends on what compounds and what quantity. While some will complain about the taste if the beer is left longer most of us prefer the extra time as it won't hurt the beer to stay longer but cutting the time can. That's where the 3 weeks comes from. 3 weeks allows time for any off flavors left from poor temperature management that the yeast can solve and drops out more yeast. 4 weeks will drop more yeast yet and starts the maturing process.

 

[madscientist451]

For a scientific explanation of the process of allowing the yeast to cleanup compound that can cause off flavors, check out this article:

https://byo.com/stories/issue/item/303-brewing-science-controlling-diacetyl

If you don't want to read the whole article, here's one of the important parts of it:

Give It a Rest
It is important to provide sufficient maturation time for diacetyl reduction. This step is commonly known as a “diacetyl rest.” Diacetyl reduction is slower at coldertemperatures, so it is essential to incorporate the diacetyl rest when making cold-fermented lagers.

The process is simply to raise the fermentation temperature from lager temperatures (50° to 55° F) to 65° to 68° F for a two-day period near the close of the fermentation. Usually the diacetyl rest is begun when the beer is two to five specific gravity points away from the target terminal gravity. The temperature is then lowered to conditioning temperature following diacetyl reduction.

For ale production, the fermentation temperature is usually 65° to 70° F, so temperature modification is not necessary. But the fermentation should still be “rested” at this temperature for two days to ensure proper diacetyl reduction. Many brewers make the mistake of quickly crashing the fermentation temperature following terminal gravity. Why not? The beer is done, people are thirsty, and there is no taste of diacetyl in the beer.

Even though the diacetyl can’t be tasted, however, the beer might contain high levels of the precursor, acetolactate, which can be converted to diacetyl. Once the yeast is removed, there is no way to get rid of the diacetyl.

 

[Merleti]

When I asked this question I was given a range of time as well. The consensus was it can depend on several things. Type of beer, how it's been brewed, what your taste says, and fermentation. For type of beer IPA will tend to be the shortest to tall beers taking the longest. I have found I can drink it at anytime after it's reached it's final gravity. If I want it to taste it's best I have to wait 2 months after carbing for the Belgium's I make. Having a pipeline like ghohn suggest will let you test that particular batch over the coarse of time so your pallet can tell you when you think it taste best. The good part is you get to keep brewing batch after batch to build up your inventory.

 

[Talgrath]

Ok, it's time that it's asked. I have been reading many people talking about that it's best to leave it in primary for 2-3 weeks to allow for cleanup (i read this at the beginning of my journey into brewing, and have been propagating this "truth" as well). While recently some people have come out and said that technically (or scientifically) speaking, once the beer has reached FG, the yeast will only take another day or so to clean up.
so what is it? what's the truth? and if you give an opinion, can you back it up with some kind of scientific data, or is your opinion just anecdotal (which i won't judge you or even automatically dismiss you if this is the case, just curious)?

Unfortunately, as with anything related to yeast, since yeast is a group of living creatures giving an exact, to the hour or day number is pretty much impossible unless you have advanced, professional grade testing equipment handy. Generally speaking, the period is 2 days if you want to be sure, but if you've got it really dialed in it, it might be a day. The link madscientist gave has a great breakdown of the details.