Home Brew Forums - What does the yeast "clean up"

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What does the yeast "clean up"

When I was looking up the advantages of a longer primary over a short one the main thing that came up was that leaving the beer on the yeast for a while would "clean up any off flavours", but no real discussion of exactly what it improved.

As an Englishman I quite like a good amount of esters in my beer, and I don't mind diacetyl. I'm not looking for something that necessarily suits BJCP style guidelines, just something tasty. Is it these that the yeast cleans up or something else?

Basically I'm looking for an excuse to drink my beer faster! I'm fermenting a pale ale with an O.G. of 1.059 at 16C/60F external temperature (it might be a little warmer in the fermenter), so hopefully I'm not getting too many odd flavours to start with.

Hey, you want to drink your beer early, drink it early. See this thread for a discussion on the conventional "1 month in primary" and "1/2/3" mantras. Bottom line, if you like how it tastes, then drink up.

Basically the conventional wisdom is when you ferment, you will get off flavors, and the yeast need time to clean up after themselves. This is not necessarily true if you pitch plenty of yeast, control wort aeration, and keep fermentation temps low.

3 weeks in bottles is still pretty intractable for proper carbonation, but when kegging, "grain to glass" in 14 days is not uncommon for some people on this board.

I still think you should give it 2 weeks in primary
You can get away with a little less if the temps are right
But its better just to brew more

Take it out of primary when it's done fermenting. There will be plenty of yeast left in there to 'clean up' unless you did a bad job boiling or cooling or fermenting or whatever.

Or, be patient and let it sit a little.

Long times in primaries are overrated. Don't produce off flavors in the first place (re: what bernerbrau said about pitching enough healthy yeast and controlling fermentation temperature) and they shouldn't need to clean up much.

Some yeast strains are prone to produce more diacetyl, and this should be metabolized within 48 hours post fermentation around 20C. Aceytaldehyde (green apple) is a precursor to ethanol - so pitching enough healthy yeast shouldn't produce noticeable levels.

I made a Northern English Brown last weekend with a highly flocculent yeast (WY1728) and had it in the keg at day 5 and drinking carbed beer at day 7. I had a Nationally ranked judge try some at a brew day yesterday and while he said another week might do it well, we all agreed that it was more than drinkable at day 7.

Quote:

Originally Posted by How To Brew

Leaving an ale beer in the primary fermentor for a total of 2-3 weeks (instead of just the one week most kits recommend), will provide time for the conditioning reactions and improve the beer. This extra time will also let more sediment settle out before bottling, resulting in a clearer beer and easier pouring. And, three weeks in the primary fermentor is usually not enough time for off-flavors to occur.

One of the big ones that the yeast will clean up if given time is Diacetyl- Professor beer explains it well.

Quote:

http://www.professorbeer.com/articles/diacetyl.html

Three pathways lead to the creation of diacetyl. The first is through normal yeast metabolism. Brewer’s yeast form a precursor called alpha acetolactate (AAL), which is tasteless. This compound is converted to diacetyl as the beer ages. The reaction that changes AAL to diacetyl is accelerated by high temperature. At cool temperatures it will still occur, but more slowly.

Modern brewing practice dictates that beer be aged on live yeast until the vast majority of AAL is converted into diacetyl. Brewer’s yeast, while unable to metabolize AAL, will readily absorb and break down diacetyl into relatively flavorless compounds. By giving the beer enough contact time with the active yeast, the brewer can eliminate the diacetyl. It generally takes only about two weeks of aging an ale to assure that it will have no buttery flavors.

Also- "THE ROLE OF DIACETYL IN BEER
By Moritz Kallmeyer"

The Abstract begins...

Quote:

Diacetyl as a product of fermentation is more characteristic of ales than lagers. Diacetyl is produced early in the fermentation, and then most of it is reabsorbed by the yeast and reduced to flavourless compounds later on. Yeast strains differ markedly in their diacetyl reduction ability. Some ales and a few lagers (such as the famous Pilsner Urquell) contain perceptible amounts of diacetyl, but as a rule modern brewers consider it as a fault. This is because certain bacterial infections and other errors in brewing technique will increase diacetyl levels resulting in unacceptable beer aroma and flavour profile. This parameter thus serves as a quality check. However, it is important to remember that diacetyl flavour is a natural by-product of yeast fermentation, and in some beer styles it is an optional or even required flavour component in low amounts.

From here....

Drayman's Brewery and Distillery

There's two methods of rests listed in the Kallmeyer article...one for ales and warmer beers....interesting.

Quote:

Maturation of beer flavour requires the presence of yeast as a catalyst. There are many methods of finishing that have the sole objective of prolonging the contact of beer with yeast after primary fermentation is completed. I want to emphasize that a diacetyl rest with most of the yeast lying at the bottom of the tank and not enough in suspension is of no use. Most lager breweries, especially those that use Weinhenstephan 308 or similar “diacetyl producing yeast’s” employ a long diacetyl rest, in order to minimize diacetyl in the finished beer.

Method 1
If a very cold primary fermentation was used it involves allowing the beer temperature to rise from the controlled primary fermentation temperature of about 10°C to 15-18°C when the primary fermentation is coming to an end. Normally, the time is determined by the attenuation of the beer. If, for example the wort starting gravity was 1050 and the expected terminal gravity is 1010, then the diacetyl rest would be commenced when the beer has attenuated to about SG 1023 when two-thirds of the total fermentable material in the wort has been consumed. The diacetyl rest normally lasts for 48-72 hours, until primary fermentation is over and secondary fermentation is under way. At this time the temperature is lowered when the more traditional method is followed, probably 1°C per day until the lagering temperature of 0-1°C is reached.

Method 2
If a warmer primary fermentation temperature was used for ale or lager the diacetyl rest involves either lowering the beer temperature 2 or 3°C at the end of primary fermentation or keeping it constant for up to 6 days. In lager yeast strains with low diacetyl production it is common practise nowadays to employ a short diacetyl rest followed by centrifuging to remove excess yeast and then crash cooling to 0°C. When brewing ales, that should have very low diacetyl levels especially German Ales like Alt and Kölsch, the implications are to not use highly flocculent yeast and to allow an extended primary fermentation, albeit at cooler temperatures until sufficiently low diacetyl levels are reached. Yeast that settles in the cone is still removed on a daily basis.

Interesting for ALES one of the recomendations is to LOWER the temps a bit...or leave them at the same temp for 6 days...learns something new everyday...I'm going to have to try the cool rest.

I suggest you read THIS thread, it's become the "uber discussion" on this topic thread.

To Secondary or Not? John Palmer and Jamil Zainasheff Weigh In .

But like you said, you're just looking for rationaization for drinking fast beer, and you have folks giving you that, but if you really want information, then look at what's been posted and decide for yourself.

"Clean up the off flavours" is a catch all phrase used to rationalize leaving the beer on the yeast for 3 weeks or more, which is fine when you used non flocculent strains, such as 1056 or US-05, to let the cake compact and the beer clear. Since I'd wager that 80% of the beer that is brewed on HBT is brewed using the Chico strain, it's good advice. For that yeast.

The heart of the matter is, if you are careful about pitching good rates of healthy yeast in a temperature controled environement, there's not a lot to clean up in the first place. Ever since I've started pitching slurry in good amounts and making starters if the slurry has stayed in the fridge for a week or more, my beer has improved. But I use English yeast in English beers: I need esters and the yeast clears up on its own very well. I can drink my very young samples (think 3 days) and there's no green apple and no harshness. Yet, my samples using American (or Belgian) yeast strains don't taste nearly as good, sometimes even 14 days into fermentation.

Quote:

Originally Posted by Billybob7 (Post 3442065)

As an Englishman I quite like a good amount of esters in my beer, and I don't mind diacetyl...Basically I'm looking for an excuse to drink my beer faster!

I'm on the same mission as you. Been brewing for almost a year now, and have so far left my beer on the yeast cake for four weeks before bottling.

But...this last brew I decided to take a play from the UK brewers and try changing things up by double-dropping. Looking for the same thing - esthers and a touch of diacetyl in a pale ale. Get that British brew flavor. The brew is not ready to drink yet, but I plan on posting my results when it is. Here was my method:

1. Put the cooled wort in my bottling bucket and pitched a smack-pack of Wyeast 1469.

2. 16 hours later, "dropped" the beer from bottling bucket to a 6 gallon bucket fermenter. Just put the bottling bucket on the kitchen counter and the 6 gallon fermenter under the spout, opened it and let it pour. Left behind the krausen and trub. The drop was about two feet, so lots of air hitting the wort.

3. Within three days if pitching yeast, the beer had dropped to my estimated final gravity of 1.013 and formed a new, even bigger krausen. At this point, I top-cropped the krausen and saved it in the fridge for my next brew day.

4. three days after that, I checked the gravity again, and it was holding at 1.013. I transferred it to a glass carboy.

5. So, at this point it has been a little over a week. I plan on doing one more gravity reading and a tasting on day 14 of this brew's life. If all seems well, it's going in the bottle to condition for three weeks.

So, overall it will be a five week process. Two weeks of fermenting, three weeks of conditioning. I've shaved off two weeks from my process and am trying some techniques I've read on UK brewer's forums.

Verdict is still out on this one, though. Will let you know how it goes once the beer has conditioned.

Quote:

Originally Posted by bernerbrau (Post 3442085)

3 weeks in bottles is still pretty intractable for proper carbonation, but when kegging, "grain to glass" in 14 days is not uncommon for some people on this board.

Even the three weeks for proper carbonation rule is not set in stone: most of my beers are pretty low carb affairs to begin with (bitters, porters, etc.), so they are oftentimes fully carbed after 10-14 days (and sometimes in as little as 7 days).

But for the beers that need 2.3 + volumes, I agree that three weeks is probably the minimum in most cases.