12 replies to this topic

[SchwanzBrewer]

I think I have actually managed to overpitch on my duss alt and kolsch beers. The last 3 versions of these beers have had an off flavor and we figured it out tonight. Acetaldehyde. I have been getting a fresh cut pumpkin flavor in those beers. They have all been using german ale yeast. I think it may be more susceptible to it. I thought maybe it was the saaz hops, but I think we nailed it down. The first versions were made with a starter without a stir plate, so I think I was closer to the optimal pitching rate.

 

I have been making HUGE starters for these beers for 10 gallon batches. I've been using yeastcalc.com which is great, BUT up until recently with Kai doing some independent research and testing, I had been using the lower curve. Well, in more delicate beers and using the german yeast that is non flocculent, I think I have been getting about 1.5 times - 2 times as much yeast as I thought I needed.

 

So, for my next batch of alt I am going to use kais curve to estimate my yeast growth on the stirplate which should mean a smaller starter.

 

Jamil's calc - 10.5 gal, 1.054 wort, 3.5L starter with 1 smack pack - 397M cells- OPTIMAL

Kai's calc - 10.5 gal, 1.054 wort, 3.5L starter with 1 smack pack - 590M cells- Overpitching

 

I've heard Jamil comment that he LOVES what Kai is doing and admits that his info may not be totally correct.

 

Kai's calc - 10.5 gal, 1.054 wort, 2.15L starter with 1 smack pack- 397M cells- OPTIMAL

 

I wish I would be able to verify this with cell counts. I'm guessing that my next alt will prove it though.

 

This is just the most recent and best theory we have at the moment, because everything else in my process seems to be accounted for as good operating procedure. I could be wrong, but I hope that's all it is.

 

Cheers.

[Brauer]

I've had acetaldehyde problems in the past, particularly in Koelsch, that seem to come from cold-crashing and lagering too soon after fermentation.  Now I give those and Alts a warm conditioning phase to promote yeast metabolism, which seems to have eliminated the problem.  When I ferment them cold, I try to warm them before fermentation is completely finished, if I can hit that window.

[SchwanzBrewer]

I've made the kolsch 3 times and the duss alt 5 times. The first kolsch didn't have the problem, the first 3 duss alts didn't have the problem, they were both made with starters that weren't on a stir plate. All of them were never rushed and weren't cold crashed until about a month after pitching. All the while in the mid 60's. Shouldn't be a problem. 

 

Next time I brew I will make a proper starter and use my lagering fridge for these beers so I can control the temps better.

[Clintama]

I've made the kolsch 3 times and the duss alt 5 times. The first kolsch didn't have the problem, the first 3 duss alts didn't have the problem, they were both made with starters that weren't on a stir plate. All of them were never rushed and weren't cold crashed until about a month after pitching. All the while in the mid 60's. Shouldn't be a problem. 

 

Next time I brew I will make a proper starter and use my lagering fridge for these beers so I can control the temps better.

If you make 2 changes, how will you know which one corrected the problem, assuming it is corrected?

 

My personal opinion is that your problem is not from overpitching.

[SchwanzBrewer]

If you make 2 changes, how will you know which one corrected the problem, assuming it is corrected?

 

My personal opinion is that your problem is not from overpitching.

The rest of my process is proven to make good beer. It's only these two non flocculent beers that have the acetaldehyde. 

 

From How to Brew...

 

To reduce likelihood of acetaldehyde in your beer

[*]Use a lower pitching rate[*]Don't underaerate[*]Use a cooler fermentation temp[/list]

To clean up acetaldehyde in the fermentor

[*]Use a warmer lagering or conditioning temp[*]Keep the beer on the yeast[*]Rouse the yeast to keep it suspended[*]Use a less flocculant yeast strain[/list]

I ferment at 64, could go a little lower, but it's well within the acceptable range of temps for those yeast. I definitely overpitched. I shake for 5 minutes which should give me 6-8ppm O2, I have O2 and a stone on the way so I won't be shaking anymore. They are both non flocculant strains. They stay on the yeast for a month. I could lager at a higher temp. Currently its lagered around 36 in my fridge.

 

I agree that it's not just one thing, almost never is, but I'm not willing to test a bunch of variables with 10 gallon batches. I'll make sure to hit all of the marks and see what happens. 




Edited by SchwanzBrewer, 10 May 2013 - 05:48 AM.

[Clintama]

I agree that it's not just one thing, almost never is, but I'm not willing to test a bunch of variables with 10 gallon batches. I'll make sure to hit all of the marks and see what happens. 

I wasn't suggesting that you had more than one problem, only that if you really want to know what the problem is, you only make one change at a time, IE reduce the cell count, but leave all the other processes alone. I appreciate your concern about making 10 gallon batches. I do the same and it's a lot of beer to playing with.

[MtnBrewer]

I think I have actually managed to overpitch on my duss alt and kolsch beers. The last 3 versions of these beers have had an off flavor and we figured it out tonight. Acetaldehyde.

Yepper! I learned this one the hard way too. I made a series of Belgians, the last two of which were Belgian IPAs. I used the entire yeast cake from the previous beer for the next one in the series and by the time I got to the end, I had a nice appley IPA. The penultimate one was ok but the last one was an acetaldehyde bomb. I remember taking both of them to the GABF homebrew tasting to illustrate what overpitching can do.

[SchwanzBrewer]

What I am going to do though, since I have 10 gallons of acetadehyde duss alt is let one keg warm up, decarb, and pitch some fresh yeast into it to see what happens. If it clears up, good. If not I'll probably drink the second keg and dump the doctored one.

[Big Nake]

I think a lot of homebrewers suggest that overpitching is not a concern for homebrewers.  I have mentioned this before but on one of the Brew Strong (I think...) shows they talk about pitching the right amount of yeast, what can happen if you overpitch, etc.  If someone experiences an "apple-like" flavor in a beer (I'm thinking green apple), is that always a sign of overpitching?  In that show Jamil mentions that when yeast is pitched into a wort there are various stages that the yeast go through (which we all have heard about) and that there are flavors and character that occur during those phases that beer drinkers find "pleasing".  When you overpitch, some of those stages are skipped or reduced and those pleasing flavors are not present.  I know that doesn't sound very technical but that idea alone got me to refer to the calculator to make sure I was not overpitching.  When I transfer a beer from primary to secondary, I'm convinced that there is enough yeast slurry at the bottom of a primary to pitch into another 8 to 10 beers if one was inclined.  Cheers.

[davelew]

I once found some 3 year old bottles of Bohemian Pilsener.  Three of the bottles were kick-ass beers, the other three had a strong green-apple flavor, which I assumed was from an infection.

 

Moral of teh story: not all acetaldehyde is from overpitching.

[SchwanzBrewer]

I'm extremely anal about sanitation, so I doubt it was an infection. I also think that the last few times this beer was judged they confused acetaldehyde with "sour" notes and claimed it was infected. 

[zymot]

Wow! A homebrew forum about pitching yeast and somebody is even saying that it is possible for a homebrewer to over pitch. Wow!

[Mya]

Wow! A homebrew forum about pitching yeast and somebody is even saying that it is possible for a homebrewer to over pitch. Wow!

personally if using a fresh cake i think overpowering is a distinct possibilty