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Brews & Views Bulletin Board Service * Brews and Views Archive 2005 * Archive through August 27, 2005 * Pitching onto an existing yeast cake - comments from the experts < Previous Next >

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Miker
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Username: Miker

Post Number: 241
Registered: 02-2003
Posted on Monday, August 08, 2005 - 03:35 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Sorry, if this is kinda long, but thought it might be of interest to some who missed the Fortnight of Yeast 2005 on the HBD where homebrewers can post questions to the yeast experts at Lallemand. Here's my question and a couple of responses. I would appreciate any further discussion on this issue since I know many of you follow this practice whenever practical.
Thanks go to Rob Moline (Jethro Gump) for setting up this forum every year. Sure hope I'm not breaking any rules by reposting some things here.
Miker

Can you please discuss the advantages/disadvantages of pitching onto an existing yeast cake (assuming the cake, and previous beer, smelled and tasted clean). Specifically, I have seen it argued that while there may be obvious advantages such as no starter prep, less cleaning, and perhaps a
shorter lag time, there may be negative effects created due to too many old or dead yeast cells, or perhaps maybe even problems with over-pitching?
How might using an existing yeast cake affect the taste and quality of the resulting beer.

Response:
Tobias may have a better answer, since he works with pitching almost on a daily basis. My feeling is that pitching into an existing yeast defeats the assurance of uniform quality and fermentation kinetics that the brewmaster has when starting each time with a batch of new yeast. You never know how many dead cells, stressed cells, mutated cells and damaged cells that you have in the existing yeast. You would never know at which repitching cycle would be best to pitch into unless you have extensive laboratory data.

Clayton


Mike,
I believe that in some instances there may be a benefit in placing fresh wort on top of an existing yeast slurry. You are correct in stating
that there may be an advantage in terms of lag phase, particularly if the beer has not been sitting on top of the yeast for a long period of
time. However, the effects that you see are likely to be dependent on the yeast strain and the characteristics of the previous fermentation.
For example, high gravity or high alcoholic fermentations can leave the yeast severely stressed. Such yeast will invariably perform poorly as there is likely to be a number of dead cells which could influence the clarity, foam and pH of the subsequent fermentation (due to products of autolysis).

The wort utilized in the subsequent fermentation may also need to be adjusted to accommodate the differing population. This may be hard to
achieve without having a detailed knowledge of the yeast strain. For a dried yeast inoculum the yeast is in perfect condition, highly vital and
well aerated and contains enough lipids within the cell wall to achieve the required number of cell divisions. Yeast which has been through a
fermentation will generally be depleted in sterols (as well as other compounds such as glycogen) and may not be able to produce daughter
cells, or if they do, these cells may be fermentatively 'weaker' than normal. The wort may therefore require a higher degree of aeration to provide enough oxygen for sterol synthesis.

The subject of cell division also raises a serious issue as yeast generally divide approximately 3 times during a fermentation (again this is strain specific and dependent on extrinsic factors). Consequently, you are correct in stating that by simply adding beer onto the yeast you are effectively overpitching. For example instead of starting with 15million (1.5E+07) cells/ml wort you would be adding around 120million (1.2E+08) cells/ml. Couple this with an additional 3 fold increase in the new fermentation and theoretically you could end up with almost 1000 million (1E+09) cells/ml! In practice the population is not likely to get quite this high, but it would still lead to major flavor variations.

One other issue with reusing yeast is the possibility of transferring contaminants. Bacteria present in low numbers at the end of one
fermentation will rapidly overtake the yeast if pitched into fresh wort, due simply to shorter division times.

To summarize, it is possible to achieve good, clean fermentations by reusing yeast. However, given the number of variables involved (not
least the strain and type of fermentation performed), it's difficult to predict the characteristics of a beer produced by repitching a yeast culture. Suffice to say that without adjustments to a number of fermentation conditions the subsequent fermentation may not be as predictable or reliable as when using fresh yeast.

Chris
 

Bill Pierce
Moderator
Username: Billpierce

Post Number: 3202
Registered: 01-2002
Posted on Monday, August 08, 2005 - 04:06 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Commercial brewers usually have a nearly unlimited source of fresh, active yeast. Therefore the comments from the yeast suppliers are somewhat more applicable to ideal situations than those faced by the majority of homebrewers.

If you purchase fresh yeast for each batch and make a sufficiently large starter to achieve an optimum pitching rate, you should produce excellent beer. However, if you practice good sanitation, I predict that you will be pleased with the results and the savings in both time and money from pitching onto the primary yeast cake from a previous batch. If you are unhappy with the results, then go back to using new yeast each time.
 

Skotrat
Advanced Member
Username: Skotrat

Post Number: 939
Registered: 04-2003
Posted on Monday, August 08, 2005 - 05:51 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Ahem...

I will paraphrase for Bill Pierce:

"Both will work just fine"

C'ya!

-Scott
 

Ken Anderson
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Username: Ken75

Post Number: 877
Registered: 11-2002
Posted on Monday, August 08, 2005 - 07:03 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I think the number of home brewers that praise repitching far outnumber those who don't. As a matter of fact, brewers who reuse yeast stop after several batches not so much because they've noticed a change in the resulting beer, but because it's the conventional wisdom. (Gee, where did THAT come from?)
I don't think repitching is nearly as risky as the quoted guys would have you believe.
Ken
 

Skotrat
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Username: Skotrat

Post Number: 942
Registered: 04-2003
Posted on Monday, August 08, 2005 - 07:20 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Ken,

I have had no major issues pitching on a yeast cake. I also never pitch on a yeast cake that is older than 10 days old (Primary ferm on it the entire 10 days that is...).

I have also re-used slurry from batches up to about 14 batches. That being said I also was yeast washing from the 3rd batch on to make sure that I was getting "good" yeast.

Time being as short as it has been in the last couple of years I have not done so much of that though and just chosen to go the new yeast route with most beers that I am brewing.

Yeast is cheap.

-Scott

(Message edited by skotrat on August 08, 2005)
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 1346
Registered: 03-2004
Posted on Monday, August 08, 2005 - 07:43 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I made 15 gallons of mild ( air cooled Scott - taste it at "Beer and Sweat!)using three packs of Coopers, I repitched a Pre Pro on the yeast cake and now am going back to another mild. The Pre Pro seemed fine at racking. I may want to push this cake another time with another mild wort barrel I have.

Dan Listermann
Listermann Mfg.,Co. www.listermann.com

 

Ken Anderson
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Username: Ken75

Post Number: 878
Registered: 11-2002
Posted on Monday, August 08, 2005 - 07:50 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Pre Pro? Took me a second. Dan, did you coin that one?
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 1347
Registered: 03-2004
Posted on Monday, August 08, 2005 - 07:59 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

When I say Pre Pro, I mean Pre-Prohibition Ale. I think Jeff Reanner (sp?) came up with it.

Dan
Listermann Mfg.,Co. www.listermann.com

 

ScottDeW
Intermediate Member
Username: Scott

Post Number: 351
Registered: 03-2003
Posted on Monday, August 08, 2005 - 08:06 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Wow. Didn't know he was that old.
Scott
http://texanbrew.com
 

Sand
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Username: Sand

Post Number: 152
Registered: 03-2003
Posted on Monday, August 08, 2005 - 08:06 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Phre Phro, maybe a basketball hoop on the loaking dock?
 

Fredrik
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Username: Fredrik

Post Number: 2452
Registered: 03-2003
Posted on Monday, August 08, 2005 - 08:13 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I don't read the FOY response as "don't reuse yeast, and you can't be consistent when reusing yeast"...

They just seem to say that without analysis, and accounting for various factors, it is generally harder to maintain consistency in yeast pitching. And unless you care to pay this extra attention and can't test the yest when needed, by making a starter in a consistent procedure, you can get a pretty consistent yeast without lab analysis.

I think there has been threads on here with likely inconsistent fermentation performances. How often have I seen explanations to various performance anomalities that we should follow yeast scheduele, and not the brewers scheduele. While this is true, I think the cause of it is most of the time inconsistent yeast pitching. So unless the yeast pitched is consistent, there is no basis to expect consistent results.

If you just reuse yeast that are a few days, and avoid high gravity grown yeast, then you're probably better off, but from what I've seen many have yeast cakes and slurries sit around during various varying conditions and then use them at will. In such a scenario, I think one could expect inconsistent results.

/Fredrik
 

Ken Anderson
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Username: Ken75

Post Number: 879
Registered: 11-2002
Posted on Monday, August 08, 2005 - 09:11 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Yeah but science guys get hung up on differences that may well be meaningless and unnoticeable to the home brewer guy.
 

Skotrat
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Username: Skotrat

Post Number: 944
Registered: 04-2003
Posted on Monday, August 08, 2005 - 09:17 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Ken,

That is why it boils down to a taste thing. That is why I started washing the yeast and making sure that if I was going to be constantly re-using a strain I wanted to make sure that I was pitching clean and viable yeast into the new batches of wort...

-Scott
 

robert rulmyr
Advanced Member
Username: Wacobob

Post Number: 637
Registered: 02-2003
Posted on Tuesday, August 09, 2005 - 02:08 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Hey, read my thread a few days ago ( poor attentuation ). My saved yeast cake was a month old, it was also 2 or 3 weeks in the primary.
 

Denny Conn
Senior Member
Username: Denny

Post Number: 4920
Registered: 01-2001
Posted on Tuesday, August 09, 2005 - 05:08 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I totally agree with ya, Ken! And one of the problems with that is that instead of giving you the knowledge you need to solve problems, it can lead you astray and make you think you have a solution when you really don't. Like WacoBob's problem...while I can't definitively say that his yeast cake was or wasn't the problem, I CAN definitively say that I've done the same thing he did many times without experiencing the problem he had. So, does the science answer his problem, or does it lead him away from the real answer with it's purported "knowledge"?
LIfe begins at 60...1.060, that is.
 

Fredrik
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Username: Fredrik

Post Number: 2462
Registered: 03-2003
Posted on Tuesday, August 09, 2005 - 05:22 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Denny, while I don't quite agree, I can also find that sometimes the expert answers tend to end up in technical details of such abstraction that it leaves us no wizer but merely puzzled and intrigued. This may well be a good point, but I still think they gave a good answer although it wasn't very hands on.

/Fredrik
 

Skotrat
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Username: Skotrat

Post Number: 958
Registered: 04-2003
Posted on Tuesday, August 09, 2005 - 05:36 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

But "puzzled and intrigued" is what homebrewing is all about isn't it?

I mean beside the final product that is what keeps us coming back to books, process and message boards right?

Just a thought.

For a long time I got lost in the science of brewing... Then I went completely towards the art of brewing. Currently I am somewhere in between the two but I still have my seriously Geeky brew science moments as well as the "whatever works" artsy moments

-Scott

(Message edited by skotrat on August 09, 2005)
 

Denny Conn
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Username: Denny

Post Number: 4923
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Posted on Tuesday, August 09, 2005 - 06:21 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Damn, Scott, I can SO relate to that! Puzzled and intrigued....
LIfe begins at 60...1.060, that is.
 

Bernardo
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Username: Bernardo

Post Number: 47
Registered: 05-2003
Posted on Tuesday, August 09, 2005 - 06:37 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Damn, Scott, I can SO relate to that! Puzzled and intrigued....

Buy him a drink! He's yours!
 

Paul Muth
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Username: Pjmuth

Post Number: 150
Registered: 10-2002
Posted From: 68.210.104.40
Posted on Sunday, August 14, 2005 - 10:41 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)


quote:

Bernardo:
"Damn, Scott, I can SO relate to that! Puzzled and intrigued...."

Buy him a drink! He's yours!



WTF?
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 1411
Registered: 03-2004
Posted From: 65.27.159.15
Posted on Monday, August 15, 2005 - 01:17 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Getting back to the subject, yesterday I pitched a mild ale wort on to a yeast cake of Coopers that also fermented two other milds plus a Pre Prohibition ale. The second mild ( third pitching) seemed fine at kegging. I may have to brew something more just to see how long I can keep the cake going.

Dan Listermann
Bernardo wants nothing here and he says he did not troll.
 

ERD
Junior Member
Username: Rico

Post Number: 34
Registered: 11-2004
Posted From: 67.182.39.91
Posted on Monday, August 15, 2005 - 03:31 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I think that the response from Lallemand is targeted for a pro brewer who wants perfect repeatability every time. Without quality control and lab analysis they will undoubtably be some variation from mutation and contamination over successive generations. The resulting beer, though good, may not be exactly the same as it was with the clean, lab cultured strain.

I reuse yeast all the time. I like the larger pitching rate and cost savings.
 

Bill Pierce
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Username: Billpierce

Post Number: 3254
Registered: 01-2002
Posted From: 24.57.229.8
Posted on Monday, August 15, 2005 - 01:14 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

When I worked at a brewpub I would sometimes use a homebrew batch as a yeast starter for a seasonal strain at the pub. The sediment from a 10 gallon batch would be just about right for 1 barrel (31 gallons) of wort in a spare fermenter onto which we would pump a full 10 barrel batch of the beer we were brewing. Of course I would be careful about sanitation, but the results were good and predictable.
 

Miker
Intermediate Member
Username: Miker

Post Number: 252
Registered: 02-2003
Posted From: 67.1.138.21
Posted on Monday, August 15, 2005 - 02:51 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Is Cooper's a dry yeast?

What are the advantages of repitching onto a yeascake made from dry yeast? Perhaps a shorter lag time, but surely this would be outweighed by the other possible disadvantages mentioned above. Pitching a couple packets or more of fresh dry yeast would seem just as easy and better to me.
 

Hophead
Senior Member
Username: Hophead

Post Number: 1678
Registered: 03-2002
Posted From: 167.4.1.38
Posted on Monday, August 15, 2005 - 02:54 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Yes, it's a dry yeast.

Nothing (to me) is fresher than a fresh yeast cake?! Tho I get yer point that it's cheap and easy to just pitch a coupla packets too...

I use 1/3 to 1/2 of the yeast cake for the next batch, depending on OG, great results, fyi.
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 1424
Registered: 03-2004
Posted From: 216.23.31.197
Posted on Monday, August 15, 2005 - 03:05 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I have discovered a new found respect for Cooper's yeast. I fermented three batches of cream ales next to each other at about 75F. The yeasts were Nottingham, US56 and Cooper's. The Nottingham seemed to have a fusal aroma. The US56 smelled of solvent. The Coopers was just fine. I believe that I will use Coopers frequently during warm weather.

I am on my fourth batch of repitching Cooper's yeast. I am doing this just to see. Actually I did not repitch the yeast as much as just use the freshly drained primary over again without cleaning. Interestingly the yeast cake does not seem to be growing much.

Dan

____________THIS SPACE HAS BEEN INTENTIONALLY LEFT BLANK.____________

 

Chris Vejnovich
Member
Username: Cjv85vmax

Post Number: 189
Registered: 06-2003
Posted From: 198.203.245.8
Posted on Monday, August 15, 2005 - 03:16 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Dan, I will say that US56 is very clean at appropriate temps for that yeast. I fermented at 63F and it produced a very nice brown ale. And sometime in the future I will be doing a Psuedo Pils side by side with Wy 1007 and US56.
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 1425
Registered: 03-2004
Posted From: 216.23.31.197
Posted on Monday, August 15, 2005 - 03:27 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I did a prior batch using US56, 1056 and 001 at cooler temps and could not distinguish between them although the beer was very hoppy. they all were just fine!

Dan

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Hophead
Senior Member
Username: Hophead

Post Number: 1679
Registered: 03-2002
Posted From: 167.4.1.38
Posted on Monday, August 15, 2005 - 04:25 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Good info DL..

Ya know, if ya just get rid of the sig in the profile, it won't waste bandwidth...

Of course, I could be wrong about this... :-)
 

Dan Listermann
Senior Member
Username: Listermann

Post Number: 1426
Registered: 03-2004
Posted From: 216.23.31.197
Posted on Monday, August 15, 2005 - 04:30 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I will consider that but I am trying to make a point for a bit here.

I could be totally misguided.

Dan

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HEU Brewer
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Username: Heu_brewer

Post Number: 149
Registered: 01-2002
Posted From: 146.137.248.1
Posted on Monday, August 15, 2005 - 04:46 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

Nature abhors a moron. - H.L. Mencken
 

Hophead
Senior Member
Username: Hophead

Post Number: 1680
Registered: 03-2002
Posted From: 167.4.1.38
Posted on Monday, August 15, 2005 - 06:03 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

But apparently the US voting public loves them.

Oh, sorry, that should go in world expressions?!

I thought nature abhors a vacuum??
 

Nathan Eddy
Junior Member
Username: Nathan_eddy

Post Number: 59
Registered: 03-2005
Posted From: 65.243.16.166
Posted on Monday, August 15, 2005 - 06:40 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I just bottled a Belgian IPA (can't get enough of that recipe) off a 3 week old yeast cake. I didn't use a secondary, so a fairly strong beer sat on that for 3+ weeks. I don't do hydrometer readings anymore (since breaking two and swearing not to buy another), but I used 10-11 pounds of LME, and the finished product doesn't taste too sweet. Basically, it's a strong beer, is my point.

So my question is, is this yeast cake still good to reuse? I've never left such a strong beer that long on a cake. I don't know if the yeast is too stressed.
 

Fredrik
Senior Member
Username: Fredrik

Post Number: 2471
Registered: 03-2003
Posted From: 213.114.44.244
Posted on Tuesday, August 16, 2005 - 05:42 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I think it's generally really hard to *know* without testing it, which is part of the essence of the expert responses. How well it can withstand the ethanol probably also depends on how well it was aerated previously, and lots of oter things.

If you make a low gravity beer, and take care of the yeast cake immediately after primary, and don't store it. I think you should be able to rest assured it's in decent shape most of the time unless it was a sugarbrew or something(except needing areation of course).

But that much dme in 5 gallons, while not outrageous it seems a more than what I would suppose is ideal. You could always try it, but I would consider it a game. If you don't want to take chances, I would just take some of it and make a starter, just to be sure.

If you want to be absolutely sure, you might either need to tests the yeast - which is a hassle itself, and in that case it might be as easy to make a fresh starter.

But if you don't think a flawed batch is the end of the world, you could try it, and report back the data point.

/Fredrik