copper2hopper
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Is 40 billion cells over considered "over pitching"?
Over pitching?
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Depends on what volume and gravity you are pitching in to. Usually 40 billion is a vast underpitch on a 5 gallon batch. Keep in mind that your typical dry yeast satchel has 220 billion viable yeast cells. I prefer the Brewer's Friend yeast calculator (below) to other ones, but there are tons of yeast calculators out there.
http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/
That's not true at all. If you overpitch significantly your yeast won't replicate enough and produce the flavors you want. A slight overpitch or underpitch usually isn't a problem, but you want to pitch as close to the right amount as possible.
I think the OP meant that he/she is over the recommendation by 40 billion. Not that he/she is pitching only 40 billion.
QuercusMax
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If that's the case, then it probably won't matter a bit. 200 billion vs 240 billion isn't much, and that's assuming that the yeast counts are even accurate - unless you're using a microscope with a hemocytometer, it's pretty much just a guess anyway.
I agree with this. +1
hannibalmdq
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Yeasts growth is a log curve. Underpitching can lead to issues mostly due to possible infection. It could stress the yeast because they'd use up all their lipids reproducing, but you could use oxygenation to offset some of the stress from underpitching by providing the lipids necessary for a few extra splits to ensure the cell walls remain flexible.
I've been going back and forth with a buddy of mine and he's got an idea that given the growth curve that overpitching even to a factor of 4 (basically pitching directly onto the cake with a similar OG wort) might not really be all the noticeable. Maybe when you get to 16x overpitch or something where you'd really cut down the number of division that happen over the course of fermentation could see an issue in flavor profile.
Most of the stuff I've seen on overpitching is sort of a general warning. Like, if you do it repeatedly over multiple brews onto the same cake you'll start to loose ester profiles and see more petite mutants, maybe some incomplete fermentation. Stuff you'd want to avoid if you were a pro-brewer trying to get the most out of their yeast over the long term.
I've actually got an experiment drawn up with 3 way(1 gallon carboys) split batches and about 8 packets of US-05 to test this out.
Whoops, rereading the OP I think you're right. Sorry, my mistake.
Personally, I've never significantly overpitched, so I can't say from experience on large overpitches, but I've heard a double (or more) could definitely cause off flavors. To be safe, I just stick to being somewhere near the recommended pitch for the beer I'm making.
copper2hopper
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You guys rock. Thank you for all of you're info and detailed responses
I'm in complete agreement that if you significantly over pitch you won't get the ester profile you want. I think what we're disagreeing on is the definition of 'significant over pitch'.
If you're over by a factor of two, I doubt you'll see much difference. If you pitch straight onto another yeast cake, I'd say you'll definitely see reduced flavor.
brick_haus
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Well I'm really in trouble then. After watching my 11 gallon fermentation blow off for over four days, I checked out Mr. Malty calculator ( I always like to do things backwards). Says to pitch 250ml of thick slurry for my 1.073 batch. Well I pitched a starter that I made with my slurry using 300ml yeast into a 4liter starter!!! I have no idea how many cells that was, but it's definitely ACTIVELY fermenting.
Comparatively speaking, I suppose the OP's batch will be fine.
Comparatively speaking, I suppose the OP's batch will be fine.
I'm guessing over pitching is not as big a deal with yeast that ferments fairly cleanly (like US-05) but more of a problem when you are expecting more esters from your yeast, like with a Belgian strain. Right?
More or less, yes. But every yeast, even lagers, add a certain amount of flavor.
The figure of 220 billion yeast cells per satchel is very optimistic. According to the Fermentis website specification sheet for US-05 the actual number is closer to 69 billion. It says US-05 has a cell density of 6 X 10^9 / g (6 billion / gram) in an 11.5 g satchel = 69 billion. See link below:
http://www.fermentis.com/wp-content/uploads/2012/02/SFA_US05.pdf
I checked on Nottingham yeast and the website shows 5 billion cells per gram - similar to Fermentis. But Mr. Malty shows "Most dry yeast has an average cell density of 20 billion cells per gram". I understand that the manufacturer is considered the most reliable source, but Mr. Malty is a highly respected resource also, and I think most brewers pitch based on the Mr. Malty info. I'll probably keep going by Mr. Malty since it has been working, but I wonder if I'm under pitching.
Some websites I was just reading:
http://www.fermentis.com/wp-content/...2/SFA_US05.pdf Shows 6 B/g
http://www.danstaryeast.com/products...ale-beer-yeast Shows 5 B/g
http://www.brewersfriend.com/yeast-p...cells_per_gram Uses 10 B/g, but shows numbers from 5 to 20
http://www.mrmalty.com/pitching.php Shows 20 B/g
http://www.danstaryeast.com/articles...t-and-glycogen Discusses the 5 B/g from plate count and 20 – 30 B/g from microscope count. I think the microscope count is more accurate because colonies are often made up of multiple cells. I think this means the plate count under estimates the count, but would like to confirm this.
These will take you on a roller coaster ride as far as cells per packet. Based on these, and the last one in particular, I think 20 - 30 billion cells per gram is a reasonable number. But anybody can read these and decide on counts as low as 5 billion. Figuring on 20 billion per gram has worked for me, so I'll probably keep using that
http://www.fermentis.com/wp-content/...2/SFA_US05.pdf Shows 6 B/g
http://www.danstaryeast.com/products...ale-beer-yeast Shows 5 B/g
http://www.brewersfriend.com/yeast-p...cells_per_gram Uses 10 B/g, but shows numbers from 5 to 20
http://www.mrmalty.com/pitching.php Shows 20 B/g
http://www.danstaryeast.com/articles...t-and-glycogen Discusses the 5 B/g from plate count and 20 – 30 B/g from microscope count. I think the microscope count is more accurate because colonies are often made up of multiple cells. I think this means the plate count under estimates the count, but would like to confirm this.
These will take you on a roller coaster ride as far as cells per packet. Based on these, and the last one in particular, I think 20 - 30 billion cells per gram is a reasonable number. But anybody can read these and decide on counts as low as 5 billion. Figuring on 20 billion per gram has worked for me, so I'll probably keep using that
philosofool
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Yes. Pitch rate is one of the largest factors in developing dersirable fermentation character, as well as a factor in off-flavors. Underpitching tends to produce off-flavors (especially fusel alcohols) and also create excessive amounts of desirable flavors (too estery, for example). Overpitching is much less likely to produce off-flavors, but the loss of desired flavors is also a flaw,though less serious. (You've never poured out a beer because it wasn't estery enough.)
I believe in consistency in pitching rate, myself, and try to use strain, temperatue and gravity (the three other most important variables) to achieve my desired fermentation character.
Keep in mind that what Fermentis puts up on their site is a very, very conservative estimate. Liquid yeast will give the "actual" cell count of the yeast before shipment, but dry yeast gives the "guaranteed" cell count. What fermentis is saying is that, at a minimum, your yeast satchel will have 69 billion viable yeast cells in it. Fermentis claims that one satchel is enough to inoculate 5 gallons of 1.060 wort, but if you do the math 69 billion cells is not even close to what you need to inoculate 5 gallons of 1.060 wort, you have to make a BIG starter to get even close to that; so there's the obvious discrepancy in their documentation, on the one hand they give you a count, on the other hand that count is far short of what they claim you can inoculate with one satchel. For whatever reason, dry yeast goes by the minimum, liquid yeast goes by the maximum, probably because dry yeast has a longer shelf life than liquid yeast. Unfortunately, this means you can't "trust" the website of dry yeast for an accurate cell count.
I agree that there is a huge discrepancy on what is reported by various sources. There is some information on the Brewers Friend Pitch Rate Calculator.
http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/
If you scroll about 1/2 way down the page this topic is addressed.
Admittedly, it's a complicated issue; counting yeast is virtually impossible even for professionals. I've stuck to 20 billion cells per gram, approximately, for all but the oldest of yeast satchels and I haven't seen issues, but it is possible there are subtle off flavors I'm not realizing are present. Again, the manufacturers on most dry ale yeasts say that one satchel will inoculate 5 gallons of 1.060 beer, but in order for that to work with 11.5 grams of yeast you need 20 billion cells per gram. This article has a great picture to illustrate the issue with counting yeast:
http://www.microbehunter.com/the-hemocytometer-counting-chamber/ Though the main point of the article is to talk about a hemocytometer, their yeast picture illustrates a major issue with yeast counting, namely that yeast tends to clump and congregate; counting yeast in those clumps is pretty difficult and two counts of the same samples can have wildly varying results. We like to think that the pros have a good understanding and break down of things, but yeast (and cell counting in general) is still an area of expanding study, a great example can be found here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3829669/ where a research group is proposing a computer-based algorithm for yeast counting. For the moment, I'm sticking with 20 billion per gram on dry yeast satchels under 6 months old, the numbers work out when plugged in to a calculator and I get the flavorful ales one would expect with just such an estimate.
http://www.microbehunter.com/the-hemocytometer-counting-chamber/ Though the main point of the article is to talk about a hemocytometer, their yeast picture illustrates a major issue with yeast counting, namely that yeast tends to clump and congregate; counting yeast in those clumps is pretty difficult and two counts of the same samples can have wildly varying results. We like to think that the pros have a good understanding and break down of things, but yeast (and cell counting in general) is still an area of expanding study, a great example can be found here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3829669/ where a research group is proposing a computer-based algorithm for yeast counting. For the moment, I'm sticking with 20 billion per gram on dry yeast satchels under 6 months old, the numbers work out when plugged in to a calculator and I get the flavorful ales one would expect with just such an estimate.
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