OverPitching is as bad as underpitching

I recently read this in an article and I think I recall hearing it in the past as well. Pitch rates are just as damaging overpitching as under pitching. I hear using dry yeast and weighing grams is very direct method of controlling the exact pitch rate but as a science there is so many variables. Other than putting a sample under the microscope to cell count how does one truly evaluate what their pitch rate is. An educated guess/calculation is not exact enough for me. Slurry by mL is not exact enough for me. Finally, packets and viability assumptions is not exact enough for me. Thoughts?

It may be, but its very easy to underpitch at a homebrew level. Its very hard to overpitch at a homebrew level. Like if you had 50% of the recommended cell count, it would likely stress the yeast and create off flavors. If you pitched 200%, youd likely just loose a bit more final beer volume due to trub.

Bottom line - I would not worry at all about overpitching at a homebrew level

Given the prevailing cost of yeast these days I'd be surprised if homebrewers habitually over-pitch using fresh yeast.
Otoh, dumping a new batch on the yeast cake from a previous batch is pretty much guaranteed to be an over-pitch, with all that may entail...

Cheers!

I usually pitch a slurry from a mason jar.I use a full jar which I believe is 3 times as much as the yeast calculators recommend.Never have any off flavors.Some have pitched directly on a full yeast cake with no ill effect.I don't sweat overpitching any more

jjeffers09 said:

I recently read this in an article and I think I recall hearing it in the past as well. Pitch rates are just as damaging overpitching as under pitching. I hear using dry yeast and weighing grams is very direct method of controlling the exact pitch rate but as a science there is so many variables. Other than putting a sample under the microscope to cell count how does one truly evaluate what their pitch rate is. An educated guess/calculation is not exact enough for me. Slurry by mL is not exact enough for me. Finally, packets and viability assumptions is not exact enough for me. Thoughts?

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m00ps said:

It may be, but its very easy to underpitch at a homebrew level. Its very hard to overpitch at a homebrew level. Like if you had 50% of the recommended cell count, it would likely stress the yeast and create off flavors. If you pitched 200%, youd likely just loose a bit more final beer volume due to trub.

Bottom line - I would not worry at all about overpitching at a homebrew level

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I tend to agree with @m00ps. I don't worry about over pitching...yes I make a yeast starter and yes I try try to be exact but there is no exact way of knowing without using a microscope and counting which at the homebrew level is unrealistic...it's a hobby and meant to be enjoyable...if you're in the ballpark and building healthy starters with good fermentations and making good beer what does it really matter?

Like stated, it is hard for us to overpitch, unless throwing a low OG wort on a previous yeast cake. It is easy to underpitch though, and stress the yeast some.

I keep fresh yeast on hand at all times by reproducing the same strain via starters. I keep two jars of about 120b cells per jar so I can make a 10 gal starter from one and remake 2 jars of starter yeast again... All from the 1st gen strain.

If yeast flavor wasn't the star of my favorite beers. Such as category 4B/6/15/16. Getting that yeast character is all about fermentation temps, pitch rate, health, nutrients, Oxygen, Pressure etc. All while getting through lag phases into growth then finally stationary phases, yeast has got to have the right amount of troops to get the job done. Temperature is easy enough as long as equipment holds up right. Then getting the FAN, inorganic nitrogen (ammonia), B-vitamins, sterols, unsaturated fatty acids, and zinc for the yeast to get into the growth stage rather quickly from using good malts and nutrients. Since the byproducts of amino acid synthesis are the cause of most off flavors, which primarily occurs during the lag and accelerating growth phases. While talking about really high % wheat beers there are enough amino acids to cause me a problem. I feel like yeast management is on my plate for the next digestible skill set to improve on.

It really depends on what yeast you're using, type of beer you're making, your temperature control, etc. My last few beers have been made with a generous pitch because I have been reusing slurry. I don't use the whole cake, but around 24 fluid oz. seems to be rather generous as they take off and finish quite quickly. I haven't been finding any impact in quality, and I actually feel better with using more than I need, but not too much to be unreasonable. These past few have also been Belgians that obviously rely on their yeast derived flavor, and that hasn't been lacking. One of them as a Belgian IPA with a massive starter that took off insanely fast, within the hour, and the ester/phenol profile is delicious.

Believe it or not, a lot of recent (admittedly small scale) homebrew experiments seem to indicate that overpitching and underpitching, to a certain extent at least, don't matter nearly as much as proper oxygenation, temperature and other environmental factors. As long as everything else is fine, underpitching seems to just take a bit longer and overpitching doesn't seem to affect much at all. My general rule of thumb is that if I'm within about 15% of the target cell count I just let it ride.

I feel like you're asking how many grains of rice should be used to make 3 cups of cooked rice rather than just using what's written on the package. Both methods would result in great rice, but one is massively overkill bean counting. Basically, I think you're asking for exact numbers on something that literally cannot be exact. Even if you had a microscope it would be impossible to count every yeast cell. Even if you could count each of the billion yeast cells, some would probably have died by the time you finished counting. You HAVE to make educated guesses. Furthermore it doesn't even matter if you knew exactly how many yeast cells were in each pack, because some are going to die during reconstitution, storage, or even by the condition of your wort. Since all of these things can be exponentially different it cannot be an exact science, at least not at the homebrew level.

I like to see the first signs of activity in 12 - 24 hours so that I know I'm pitching a reasonable amount of healthy cells. I reuse my slurry and the only issue I've noticed is from over-pitching unhealthy cells (i.e.: too many fat, lazy, inactive cells that have been snoozing in the fridge for a couple months). The beers seemed thin and lacked character. I have my process dialed in well enough now that I'm able to predict yeast health, if a starter is needed, and how much slurry will get me that 12-24 hour turn around. Basically +/- 1.5B cells/ml slurry with estimated cell death of 15%/month. I will direct-pitch slurry up to one month old and make a vitality starter for anything older to replace old cells with new (sourced from woodlandbrew's research). Works a charm.

Jim311 said:

I feel like you're asking how many grains of rice should be used to make 3 cups of cooked rice rather than just using what's written on the package. Both methods would result in great rice, but one is massively overkill bean counting. Basically, I think you're asking for exact numbers on something that literally cannot be exact. Even if you had a microscope it would be impossible to count every yeast cell. Even if you could count each of the billion yeast cells, some would probably have died by the time you finished counting. You HAVE to make educated guesses. Furthermore it doesn't even matter if you knew exactly how many yeast cells were in each pack, because some are going to die during reconstitution, storage, or even by the condition of your wort. Since all of these things can be exponentially different it cannot be an exact science, at least not at the homebrew level.

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Within 250,000 is the idea there. .25x10^6/ml/P can make a difference to me. That is the accuracy I am talking about. I don't want to know down to the 1000's & 100's. It is a science and a sum of parts is pretty wide there. What did they say about pitch rate 20 years ago? nothing right?

jjeffers09 said:

Within 250,000 is the idea there. .25x10^6/ml/P can make a difference to me. That is the accuracy I am talking about. I don't want to know down to the 1000's & 100's. It is a science and a sum of parts is pretty wide there. What did they say about pitch rate 20 years ago? nothing right?

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Look, even if you had it in a lab you couldn't get it that accurate, at best you could get it roughly within the realm of 1 million cells, but even that's pretty optimistic. Here is how they count cells in a lab, something you can do at home if you really want to buy the equipment for it:

Counting Yeast Cells

But even this counting method is just a very rough approximation. If for some weird reason the yeast is really thickly in one section and light in another section and your sample is from either section, your count be off by billions of cells (and almost certainly is). There's no real way to get a count down to the accuracy you want, it doesn't exist even in the most accurate of scientific labs (unless of course the US government has some sort of hidden alien tech that will do it).

jjeffers09 said:

Within 250,000 is the idea there. .25x10^6/ml/P can make a difference to me. That is the accuracy I am talking about. I don't want to know down to the 1000's & 100's. It is a science and a sum of parts is pretty wide there. What did they say about pitch rate 20 years ago? nothing right?

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Have you asked any breweries with QC/yeast labs what accuracy they aim for? That would be a great place to start.