[WattsOnTap]

I understand there are ideal cell counts and that you can, technically, overpitch yeast for a given batch.  Does it really matter if you overpitch?  And, if so, what would be the effects?  Is there a tolerance range?

I recognize I have underpitched batches in the past, and now build a starter for nearly every brew.  I'm just wondering if it's possible that I'm over-correcting.

[bayareabrewer]

IMO overpitching is tough to do at a homebrew level.

[Stevie]

IMO overpitching is tough to do at a homebrew level.

I disagree. Why is it hard to overpitch a relatively small amount of wort, yet easier in a large amount of wort?

From my experience beers can come out too clean. I've heard some say they also over attenuate, but I haven't experienced that.

If you are making a starter within reason, it will be fine. If you are repitching bottom cropped yeast, it's easy enough to do.

[jrdatta]

Absolutely possible to overpitch a homebrew batch (especially with dry yeast).  But it is strain and style dependent. Some strains need higher pitch rates some need lower to get the right ester profile.  So you really need to fit your pitch rates to your beer.  IE a British mild or bitter usually turns out better with a much lower pitch rate than we would use for an American Pale ale where we want a really clean highly attenuated profile.

[denny]

IMO overpitching is tough to do at a homebrew level.

I disagree. Why is it hard to overpitch a relatively small amount of wort, yet easier in a large amount of wort?

From my experience beers can come out too clean. I've heard some say they also over attenuate, but I haven't experienced that.

If you are making a starter within reason, it will be fine. If you are repitching bottom cropped yeast, it's easy enough to do.

I've had the opposite result from overpitching.  Because both cell growth and ester production use acetyl co-A, if you pitch too much yeast there is no need for cell growth and the co=A goes to ester production.  I get more estery beers by overpitching and less estery ones by pitching the proper amount.

[jrdatta]

I've had the opposite result from overpitching.  Because both cell growth and ester production use acetyl co-A, if you pitch too much yeast there is no need for cell growth and the co=A goes to ester production.  I get more estery beers by overpitching and less estery ones by pitching the proper amount.

Interesting.  Have you experienced across a wide variety of yeasts or certain strains in particular?  When I have over pitched WLP001 and especially S-04 I have a few times now gotten a really mealy gaminess (no idea how else to describe it) in the finished beer.

[dmtaylor]

IMO overpitching is tough to do at a homebrew level.

I disagree. Why is it hard to overpitch a relatively small amount of wort, yet easier in a large amount of wort?

From my experience beers can come out too clean. I've heard some say they also over attenuate, but I haven't experienced that.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.

[Todd H.]

Are you sure that "mealy gaminess" isn't just the taste and texture of too much yeast, if indeed you end up pitching so much that no cell division occurs?  I mean the taste and feeling of the cells, not by-products thereof.

Biochemically speaking, what Denny says makes sense.

I've noticed on forums that a lot of people use the term ester to refer to any flavour compound the yeast produce, not just literally esters.  Maybe that's where some of the confusion lies.

BTW, specific to this discussion, I've seen papers indicating that overpitching can lead to more diacetyl production.  Of course, there are also more cells to clean up that diacetyl, so maybe that doesn't actually matter?

WattsOnTapp, if you assume that the saturation point of your starter wort and your beer wort are the same, then a 1 liter starter should divide roughly 4-5 times in your beer.  On a cell number level, that translates into 16-32x more cells than in your starter.  So using a normal sized starter it probably is impossible to overpitch into 5 gallons of beer.  Pitching onto a fresh yeast cake will net you close to zero cell division and would be considered an overpitch, I imagine.

[jrdatta]

That's what I thought at first too, but it really doesn't taste like yeast, I am thinking it is a combination of fermentation byproducts?  I have tasted it in other beers I have tried made when pitching high rates of S-04 usually.  Almost a play-doh type flavor.  Thought it was a dry yeast thing but like I said I have noticed it in beers pitched with high rates of WLP001.  Maybe a overabundance of diacetyl?  I have really been at a loss for identifying it.

[blatz]

theres been a few times, maybe 4, that I used the mrmalty yeast calculator for repitching a lager slurry that was older (3-5 weeks) and questioned that it seemed like wayyyy too much slurry, but I followed it anyway. 

each of those beers ended up with some level of acetylaldehyde.

is it a correlation or a coincidence?  I'm not sure - I can't recall any other beers I've had the green apple monster rear its ugly head at otherwise, despite almost 240 batches. 

[denny]

IMO overpitching is tough to do at a homebrew level.

I disagree. Why is it hard to overpitch a relatively small amount of wort, yet easier in a large amount of wort?

From my experience beers can come out too clean. I've heard some say they also over attenuate, but I haven't experienced that.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.

For me too much turns out too estery...and to say pitching G rate has no affect on attenuation is an overstatement IMOLA

[HoosierBrew]

As for lagers, overpitching is theoretically possible. Also highly unlikely IMO. I do believe that overpitching ales can give you overly clean beers and that underpitching can (can, not will) increase esters. I like a clean profile on American ales and couldn't care less if it's a technical overpitch, where I pay more attention on Belgian styles to the amount of yeast (together with temp profile) I pitch. I also disagree that pitching rate has zero role in attenuation.

[dmtaylor]

IMO overpitching is tough to do at a homebrew level.

I disagree. Why is it hard to overpitch a relatively small amount of wort, yet easier in a large amount of wort?

From my experience beers can come out too clean. I've heard some say they also over attenuate, but I haven't experienced that.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.

For me too much turns out too estery...and to say pitching G rate has no affect on attenuation is an overstatement IMOLA

"The word Imola is of Roman origin and means 'over there, down there'. It refers to the view enjoyed by the people looking down on the inhabited zone from the valley at midday."

--
Dave Taylor... arguing with Denny since 2003.
https://groups.google.com/forum/#!searchin/alt.beer.home-brewing/sam$20adams$20GOOooOOooOOooD%7Csort:relevance/alt.beer.home-brewing/6vXpzVQHyMA/j03aLhlUx-oJ

[erockrph]

IMO overpitching is tough to do at a homebrew level.

I disagree. Why is it hard to overpitch a relatively small amount of wort, yet easier in a large amount of wort?

From my experience beers can come out too clean. I've heard some say they also over attenuate, but I haven't experienced that.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.

For me too much turns out too estery...and to say pitching G rate has no affect on attenuation is an overstatement IMOLA

To put a finer point on this, I think that for certain strains (hefe's and English ale strains in particular) you can get a muted flavor profile when pitched at typical ale rates based on Mr Malty. Personally, I don't consider this over- or under-pitching, but rather targeting a different pitching rate to get the results you are looking for. I haven't found a noticible difference in attenuation within this range of pitching rates.

[denny]

IMO overpitching is tough to do at a homebrew level.

I disagree. Why is it hard to overpitch a relatively small amount of wort, yet easier in a large amount of wort?

From my experience beers can come out too clean. I've heard some say they also over attenuate, but I haven't experienced that.

+100.  Too much yeast turns out too clean.  Pitching rate has zero effect on attenuation.

For me too much turns out too estery...and to say pitching G rate has no affect on attenuation is an overstatement IMOLA

"The word Imola is of Roman origin and means 'over there, down there'. It refers to the view enjoyed by the people looking down on the inhabited zone from the valley at midday."

--
Dave Taylor... arguing with Denny since 2003.
https://groups.google.com/forum/#!searchin/alt.beer.home-brewing/sam$20adams$20GOOooOOooOOooD%7Csort:relevance/alt.beer.home-brewing/6vXpzVQHyMA/j03aLhlUx-oJ