Homebrewers Association | AHA Forum

General Category => Yeast and Fermentation => Topic started by: gmac on March 28, 2013, 07:57:26 PM

Title: Can you over pitch a lager?
Post by: gmac on March 28, 2013, 07:57:26 PM
I've got a 5 gal amber lager with WLP833 sitting out for a D-rest right now. 
I'm going to do another lager right away, probably a 1.060ish bock of some sort.  Should I just re-pitch the entire yeast cake?  Mr. Malty says I should pitch about 230 ml of yeast from a re-pitch but I have no idea how to factor in how "clean" my re-pitch is.  I wasn't planning on trying to wash it or anything.  I would expect that there are maybe 2 cups of slurry in the bottom of the bucket, depending on how much liquid I have to use to get it re-suspended to pour.

So, long way to get to my question.  Is there any downside to just re-pitching the entire yeast cake?  I was going to chill to about 45 or so and then pitch.
Thanks
Title: Re: Can you over pitch a lager?
Post by: klickitat jim on March 28, 2013, 10:44:17 PM
Autolysis? Maybe... I'll tune in for the pro responses

"Freedom is temporary unless you are also Brave!" - Patriot

Title: Re: Can you over pitch a lager?
Post by: davidgzach on March 29, 2013, 04:59:56 AM
If you are increasing the OG that is preferable, however I've pitched on top with an identical OG with no ill effects at all.  And it was a Pils so it would have been detected.  I'd say go for it and RDWHAHB.

Dave
Title: Re: Can you over pitch a lager?
Post by: kylekohlmorgen on March 29, 2013, 05:52:43 AM
After racking off the cake, just swirl it to mix and measure out your needed volume. You can adjust the Yeast Concentration to the low end (try 2) on the calculator.

You'll find you have much more yeast than you need. I've heard JZ mention several times that over-pitching is detrimental to beer flavor.

Also - if you plan on continue using the yeast in future pitches, over-pitching greatly increases the average cell age of the slurry. More yeast = less growth = fewer new cells in subsequent pitches.
Title: Re: Can you over pitch a lager?
Post by: blatz on March 29, 2013, 06:51:09 AM
yes, you can.  i've done it 2 times in the past, both resulting in acetylaldehyde, even after a 4 week primary with 1 week at diacetyl rest temps. 

both because I observed the viability factor on Mr. Malty and pitched almost 1500mL of loose slurry in 10gal.

I was able to rescue the beers by letting them sit at room temp (acetylaldehyde has a low boiling point - like 60s or 70s) and bubbling Co2 periodically from the bottom to degas the kegs, thanks to some advice from posters here.

As for your situation - 230mL is a little more than a cup - I would pitch a cup and a half and you will be in the ballpark and be fine.
Title: Re: Can you over pitch a lager?
Post by: gmac on March 29, 2013, 09:02:55 AM
yes, you can.  i've done it 2 times in the past, both resulting in acetylaldehyde, even after a 4 week primary with 1 week at diacetyl rest temps. 

both because I observed the viability factor on Mr. Malty and pitched almost 1500mL of loose slurry in 10gal.

I was able to rescue the beers by letting them sit at room temp (acetylaldehyde has a low boiling point - like 60s or 70s) and bubbling Co2 periodically from the bottom to degas the kegs, thanks to some advice from posters here.

As for your situation - 230mL is a little more than a cup - I would pitch a cup and a half and you will be in the ballpark and be fine.
Thanks. I will do a cup and a half and see how it goes. Maybe 375 to 400 ml.
Title: Re: Can you over pitch a lager?
Post by: euge on March 30, 2013, 04:13:23 AM
I don't like repitching in general due to autolysis and acetaldehyde concerns. Not that this technique can't be done successfully- but see it as a source of problems for the average homebrewer.
Title: Re: Can you over pitch a lager?
Post by: ynotbrusum on March 31, 2013, 05:15:35 AM
I just hit 20 batches of repitched WLP 800.  No problems with reuse - the first use was in 2011!  But I am ending there - pushing my luck further is not worth it.  I use Yeast nutrient each time, I am meticulous on sanitation and I repitch about 700-800 ml for a ten gallon batch. I've never overpitched a lager, but I did so with an ale - a lot of esters (cloves mostly) from US-05.  Use the Mr. malty calculator to get the amount of slurry and you will be fine.
Title: Re: Can you over pitch a lager?
Post by: klickitat jim on March 31, 2013, 01:24:31 PM
I'm learning,  guessed autolysis

"Freedom is temporary unless you are also Brave!" - Patriot

Title: Re: Can you over pitch a lager?
Post by: kylekohlmorgen on April 01, 2013, 06:42:22 AM
Not that this technique can't be done successfully- but see it as a source of problems for the average homebrewer.

I see fermentation issues stemming from low cell counts or low viability as the main source of problems for homebrewers at every level.

Making a starter for EVERY batch is difficult to accomplish, even if you're really dedicated. With good sanitation and storing practices, harvesting and repitching yeast can significantly increase the quality of your beer.

The keys are sanitation, storage, and repitching the correct amounts. Dumping fresh wort on an entire yeast cake creates almost (just?) as many problems as under-pitching.
Title: Re: Can you over pitch a lager?
Post by: davidgzach on April 01, 2013, 10:13:07 AM
I only did it once as I like to save slurry and stick with Mr Malty calculations.  I guess after this thread I will not do it again unless it's to a much bigger beer!

Dave
Title: Re: Can you over pitch a lager?
Post by: blatz on April 01, 2013, 10:24:38 AM
I only did it once as I like to save slurry and stick with Mr Malty calculations.  I guess after this thread I will not do it again unless it's to a much bigger beer!

Dave

I think that's taking it too extreme.  I repitch A LOT and most pros do 20+ generations as well, so I have no issue with repitching as a practice.  I think the issue I found is that the viability calculations for harvested yeast are inaccurate, which I previously treated as gospel.  I try to reuse my yeast within a month (hopefully less than 2 weeks) and just do 20-30% more than what a freshly harvested pitch is recommended according to MrMalty.com. 
Title: Re: Can you over pitch a lager?
Post by: davidgzach on April 01, 2013, 11:16:50 AM
I only did it once as I like to save slurry and stick with Mr Malty calculations.  I guess after this thread I will not do it again unless it's to a much bigger beer!

Dave

I think that's taking it too extreme.  I repitch A LOT and most pros do 20+ generations as well, so I have no issue with repitching as a practice.  I think the issue I found is that the viability calculations for harvested yeast are inaccurate, which I previously treated as gospel.  I try to reuse my yeast within a month (hopefully less than 2 weeks) and just do 20-30% more than what a freshly harvested pitch is recommended according to MrMalty.com.

Paul, I meant pitching on top of a previous cake, not saving and re-pitching at all......
Title: Re: Can you over pitch a lager?
Post by: kylekohlmorgen on April 01, 2013, 11:24:01 AM
I think the issue I found is that the viability calculations for harvested yeast are inaccurate, which I previously treated as gospel.  I try to reuse my yeast within a month (hopefully less than 2 weeks) and just do 20-30% more than what a freshly harvested pitch is recommended according to MrMalty.com.

I've heard JZ recommend using harvested slurry within 2 weeks, if stored properly. I'd assume the viability calcs are for slurry that's less than 2 weeks old.
Title: Re: Can you over pitch a lager?
Post by: blatz on April 01, 2013, 11:29:16 AM
Paul, I meant pitching on top of a previous cake, not saving and re-pitching at all......

oops - my bad - misread!

kyle - if you use a date 4 weeks prior to the current, the recommendation is over double the amount as if harvested today - that's what got me in trouble with acetylaldehyde - I pitched that double sized amount, and the primary was finished in 5-7 days (wasn't monitoring it close since most of my lagers take at least 10 days) and then if flocced and i guess didn't clean up after themselves.  I just find that to be too steep of a decline. 

if its over a month, though, I rebuild the colony. 
Title: Re: Can you over pitch a lager?
Post by: davidgzach on April 01, 2013, 12:02:33 PM
Sean has pointed out that he uses 25% viability drop per month in harvested slurry.  Just another way to get to the proper pitching amount.  I've reused several month old slurry with good results, but I'm going to try and move to selected "house" yeasts to use more often and get more out of them...

Dave
Title: Re: Can you over pitch a lager?
Post by: blatz on April 01, 2013, 12:05:12 PM
Sean has pointed out that he uses 25% viability drop per month in harvested slurry.  Just another way to get to the proper pitching amount.  I've reused several month old slurry with good results, but I'm going to try and move to selected "house" yeasts to use more often and get more out of them...

Dave

that is more reasonable to me.
Title: Re: Can you over pitch a lager?
Post by: davidgzach on April 01, 2013, 12:14:58 PM
Sean has pointed out that he uses 25% viability drop per month in harvested slurry.  Just another way to get to the proper pitching amount.  I've reused several month old slurry with good results, but I'm going to try and move to selected "house" yeasts to use more often and get more out of them...

Dave

that is more reasonable to me.

Same here.  I'm tired of looking at a container of slurry and wondering when I'll be able to use it again only to toss it because it's been several months.  I've got my lager yeasts down to 2-3 and I'm going to rotate in ale yeasts to use for several batches.  I also hope to start slanting so I can use what I want, when I want.  Got the tools and equipment, just have to do the research.....

Dave
 
Title: Re: Can you over pitch a lager?
Post by: gmac on April 01, 2013, 01:53:49 PM
Thanks again all.
I too am trying to get to a couple key strains that I use most of the time but I'm still so intrigued by new strains.  Plus I'm really trying to get better at making lagers but I just don't make enough of them to really master them.  I think I do a pretty good ale but I only make 4 or 5 lagers a year at most.  That's one of the reasons I wanted to start re-pitching lager yeast, to get more of a rotation going for summer (plus I made some back in the winter that were supposed to lager until summer and they "evaporated").
Title: Re: Can you over pitch a lager?
Post by: davidgzach on April 01, 2013, 02:13:12 PM
Another process I've incorporated for reusing slurry has been skimming at high Krausen.  You can see the difference in the amount of "gunk" on the top and sides from a fresh pitch to a slurry.  Just took a bunch of sludge from a 3x reused 1056.  It's definitely noticeable and I'm hoping it will prolong the number of times I can reuse it.

Dave
Title: Re: Can you over pitch a lager?
Post by: gmac on April 01, 2013, 02:24:43 PM
Another process I've incorporated for reusing slurry has been skimming at high Krausen.  You can see the difference in the amount of "gunk" on the top and sides from a fresh pitch to a slurry.  Just took a bunch of sludge from a 3x reused 1056.  It's definitely noticeable and I'm hoping it will prolong the number of times I can reuse it.

Dave

Sorry, not sure i follow.  You're skimming and discarding what you skim (braun hefe etc) or are you pitching what you skim?  I thought that skimming the top at high krausen was the same as top cropping and thus would be some of the better yeast (or at least the most "top" fermenting).  I've been top cropping WLP002 with good results when I want to brew a few days apart and don't have any yeast in a starter. 
Title: Re: Can you over pitch a lager?
Post by: davidgzach on April 01, 2013, 02:32:17 PM
I've been skimming the brown gunk on top of the Krausen.  The hop material and dead yeast.  Not top cropping and grabbing live yeast.....

Dave