What do you consider "Over-Pitching"?

[303Dan]

I've been in the habit for quite a while now of pitching at a rate of 1.25 Million Cells per ml per degree Plato for most styles. For certain styles where I want a significant esther profile, I would not necessarily use that pitch rate. So, for example: for a 6.25 gallon batch at an OG of 1.065, I would pitch around 475 Billion cells.

It seems to me that there is not a good definition out there on what exactly constitutes "over-pitching" and what the exact effects of that are. But I've seen many people make comments that would indicate that they believe the rate I described above would be over-pitching, or at least excessive.

I like the results I'm getting. I get short lag times (3-4 hours) and very fast and clean fermentations for temps in the mid 60's. So I'm not really looking to change my process, I'm just curious if there really is any solid data out there that defines what constitutes over-pitching.

Thoughts?

 

[jmitchell3]

I've heard Chris White indicate that yeast growth during fermentation is approximately 5x original pitch rate. Thus, for those who simply dump new wort on old yeast cake...that's probably overpitching!

Experience / Opinion -> I used to do 1-1.25 mm cells/ml and have recently reduced to .75m cells/ml and I think my beers are actually better. I'll do 1-1.25 when I'm doing high gravity stuff (i.e. > 1.080 OG). my $0.02.

 

[303Dan]

I've heard Chris White indicate that yeast growth during fermentation is approximately 5x original pitch rate. Thus, for those who simply dump new wort on old yeast cake...that's probably overpitching!

Experience / Opinion -> I used to do 1-1.25 mm cells/ml and have recently reduced to .75m cells/ml and I think my beers are actually better. I'll do 1-1.25 when I'm doing high gravity stuff (i.e. > 1.080 OG). my $0.02.

Interesting. I'm brewing a Pale Ale on Saturday, maybe I'll try .75M just for the hell of it.

 

[jmitchell3]

Interesting. I'm brewing a Pale Ale on Saturday, maybe I'll try .75M just for the hell of it.

The only caveat I'd mention is vitality...less is probably ok as long as they are super vital. I usually follow brewersfriend or mrmalty guidelines targeting .75m cells/ml for starter creation.

 

[troglodytes]

Preboil, I separate off 500-750ml of my runnings, cool, and pitch .75MM cells/ml into a starter of my actual beer onto a stir plate. It is just hitting the beginning of krausen 4-5 hours later at which time I've finished brewing and cleaning and am ready pitch into the finished cooled wort. That way I know my vitality is super high. This is for everything less than 1.080. Over that, I would do the same thing, but with 1-1.25MM cells/ml with double the sized vitality starter. Thanks to Brulosopher for this method, it has rocked my world and beers ever since I started.

I wouldn't worry about "overpitching" as a potential issue, unless I was just pitch a low to med gravity beer onto an entire cake, which I never do.

 

[303Dan]

Preboil, I separate off 500-750ml of my runnings, cool, and pitch .75MM cells/ml into a starter of my actual beer onto a stir plate. It is just hitting the beginning of krausen 4-5 hours later at which time I've finished brewing and cleaning and am ready pitch into the finished cooled wort. That way I know my vitality is super high. This is for everything less than 1.080. Over that, I would do the same thing, but with 1-1.25MM cells/ml with double the sized vitality starter. Thanks to Brulosopher for this method, it has rocked my world and beers ever since I started.

I wouldn't worry about "overpitching" as a potential issue, unless I was just pitch a low to med gravity beer onto an entire cake, which I never do.

That's a really cool idea, I'm going to have to try that. Do you think it would still be beneficial to do that if you only waited say 2 hours after you pitched into your pre-boil wort, as opposed to 4-5 hours?

 

[HausBrauerei_Harvey]

Preboil, I separate off 500-750ml of my runnings, cool, and pitch .75MM cells/ml into a starter of my actual beer onto a stir plate. It is just hitting the beginning of krausen 4-5 hours later at which time I've finished brewing and cleaning and am ready pitch into the finished cooled wort. That way I know my vitality is super high. This is for everything less than 1.080. Over that, I would do the same thing, but with 1-1.25MM cells/ml with double the sized vitality starter. Thanks to Brulosopher for this method, it has rocked my world and beers ever since I started.

I wouldn't worry about "overpitching" as a potential issue, unless I was just pitch a low to med gravity beer onto an entire cake, which I never do.

I've had this idea previously but didn't know if it was a bad idea to pitch unboiled wort into my decanted starter yeast cake. Any info for me here?

 

[rhys333]

Technically it should be pasteurized after an hour long mash at +148F and free from nasties (note: not sterile though). You're not boiling off DMS with the preboil wort, but its such a small amount as to be not worth the bother I suppose. One think I'd note - I've had both stored yeast and fresh pack yeast take a lot longer than 5 hours to wake up and reach high krausen.

 

[HausBrauerei_Harvey]

yeah I know all strains act differently and may not reach high krausen before pitching into the big batch, but it's a great idea. Either way it gives them a head-start and should shorten your lag time. I thought it was a great idea when I thought of it about a year ago but I convinced myself I was wrong and couldn't do it. Thanks for the results saying otherwise. I'll give it a go this weekend when I brew.

 

[Talgrath]

I've been in the habit for quite a while now of pitching at a rate of 1.25 Million Cells per ml per degree Plato for most styles. For certain styles where I want a significant esther profile, I would not necessarily use that pitch rate. So, for example: for a 6.25 gallon batch at an OG of 1.065, I would pitch around 475 Billion cells.

It seems to me that there is not a good definition out there on what exactly constitutes "over-pitching" and what the exact effects of that are. But I've seen many people make comments that would indicate that they believe the rate I described above would be over-pitching, or at least excessive.

I like the results I'm getting. I get short lag times (3-4 hours) and very fast and clean fermentations for temps in the mid 60's. So I'm not really looking to change my process, I'm just curious if there really is any solid data out there that defines what constitutes over-pitching.

Thoughts?

Well, there's a few different realms of thought on this, but for me after a while here's what it came down to: we aren't really as accurate as we think we are, so if you're satisfied with the beer, don't worry about it. The fact of the matter is that even at a professional laboratory there's no good way to count how many cells are in a sample. What they do is heavily dilute the liquid and then do their best to count the number of cells in the sample and then use the volume of the liquid to estimate the total number of cells. Given that a professional lab can't give you a to the number cell count, the chances that our roughly estimated cell counts are off signicantly is pretty high. My general rule of thumb is that unless you're over or under pitching by about 25% it's probably fine; if you're looking for yeast flavor err on the side of underpitching and if you're looking for a "clean" flavor err on the side of overpitching. There aren't a lot of experiments to back up this opinion, but this one at least Brulosophy vial vs starter seems to indicate that pitch rate, when you are at least pretty close, doesn't have much an influence on the flavor of the beer. Temperature, oxygenation and other factors are probably more important.

 

[Queequeg]

Its style dependant, i wouldn't do an abbey style at a pitch rate greater than 0.75. At said i wouldn't do an ipa above 1. To me a pitch rate of 1+ is reserved for imperials and lagers.

 

[troglodytes]

Technically it should be pasteurized after an hour long mash at +148F and free from nasties (note: not sterile though). You're not boiling off DMS with the preboil wort, but its such a small amount as to be not worth the bother I suppose. One think I'd note - I've had both stored yeast and fresh pack yeast take a lot longer than 5 hours to wake up and reach high krausen.

I should have clarified, I'm generally pulling those runnings out of the kettle as its about to hit initial boil, so the wort is definitely pasteurized. The yeast I am pitching has just completed its last step up starter to reach that pitching rate, so I am not expecting freshly packaged yeast to hit krausen in 4 hours. However,it seems that when going from a decanted starter to my "vitality starter" the yeast is always going within 4 hours.

 

[rhys333]

I should have clarified, I'm generally pulling those runnings out of the kettle as its about to hit initial boil, so the wort is definitely pasteurized. The yeast I am pitching has just completed its last step up starter to reach that pitching rate, so I am not expecting freshly packaged yeast to hit krausen in 4 hours. However,it seems that when going from a decanted starter to my "vitality starter" the yeast is always going within 4 hours.

Makes sense to me, and I experience the same with stepped-up yeast... tends to kick off very quickly.

 

[Jim311]

This is an issue that always seems to explode on brewing forums. But considering you have but a rough idea of how many cells you're pitching, and only a rough idea of how many will actually survive being reconstituted, or refrigerated, or whatever while being handled, it's really kind of a spitballing sort of thing that I don't understand why everyone argues about. I bet you could do exactly as everyone says you shouldn't and pitch a low gravity beer on top of a cake used to ferment a big beer and it would still make great beer. I don't stress too much about it one way or the other personally.

 

[brewerdoc]

I've been in the habit for quite a while now of pitching at a rate of 1.25 Million Cells per ml per degree Plato for most styles. For certain styles where I want a significant esther profile, I would not necessarily use that pitch rate. So, for example: for a 6.25 gallon batch at an OG of 1.065, I would pitch around 475 Billion cells.

It seems to me that there is not a good definition out there on what exactly constitutes "over-pitching" and what the exact effects of that are. But I've seen many people make comments that would indicate that they believe the rate I described above would be over-pitching, or at least excessive.

I like the results I'm getting. I get short lag times (3-4 hours) and very fast and clean fermentations for temps in the mid 60's. So I'm not really looking to change my process, I'm just curious if there really is any solid data out there that defines what constitutes over-pitching.

Thoughts?

To look for solid data for what you are describing as over-pitching yeast there are several studies out there that tried to take a look at what happens when one pitches above and below the regular pitch rate (20 X 10^6) which is what you are pitching per my calculations.

Turns out that there was not much difference other than time to end of fermentation. However, one key point is that many of the studies that I have read seem to have contradictory information as to how much ester and diacetyl is produced depending on pitch rate. My suspicion is that this is yeast strain dependent. I'll keep reading more studies and post an update if I find anything. For what its worth, I posted about this topic this week on my blog if you wanna have a read. http://www.brewerdoc.com/pitch-rate-and-its-effect-on-fermentation-and-beer-flavor/. Disclaimer: Currently working a 24 hour shift and didn't have time to update several things. The graph that I made for yeast replication is not completely accurate and needs to be corrected.

Let me know if this helps