Yeast Overpitch/Underpitch Experiment From a Microbiologist

...at brooklyn homebrew! they just started doing classes and the last one caught my eye. it's since sold out so i'm happy i got my ticket early. this experiment will test the effects of overpitch/underpitch, we will be the guinea pigs!

"The experiment will based on the following criteria:

Beer style: Blond ale. I chose a blond ale because any off flavors will have little to hide behind.
Yeast strain: Wyeast 1056. I had a tough time choosing the yeast. I could have gone with a very expressive yeast to detect changes in flavor. I eventually went with a popular strain that many brewers use for their batches.
Every sample will be treated the same and the test batches will be fermented in 1 gallon batches. The original gravity of the beer will be 1.046 and only one hop will be used (see recipe below).

Samples:

Control pitch: 0.75 million cells/ml/º Plato – 32.9 billion cells.
Overpitch: 2.5 million cells/ml/º Plato – 112.8 billion cells.
Underpitch: 0.1 million cells/ml/º Plato – 4.7 billion cells.
The recipe (4.5 gallon batch to be split into 1 gallon fermentors):

7 pounds 2-row Pale malt
1 pound of Carapils
Mashed in at 153ºF for one hour. Raised temps to 168ºF for mashout and recirculated as usual. First runnings at 1.063. Second runnings at 1.018. Collected a total of 5.9 gallons at 1.034. Boiled for 60 minutes:

0.5 oz of Centennial at 60 minutes.
0.5 oz of Centennial at 0 minutes (flameout).
Whirlfloc and yeast nutrient at 15 minutes.
Cooled to 62ºF and pitched the amount of yeast noted above. I did not oxygenate the wort in any sample. Fermented cool (62ºF) until fermentation slowed then slowly ramped up to 70ºF.

On December 14th the class is scheduled and I will post the results, including flavor and fermentation profiles. I’m also thinking of polling the students to see how each beer scored."

http://sciencebrewer.com/2011/11/29/pitching-rate-experiment/

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I'm still new to brewing and haven't put too much thought into this, should be very interesting!

Two Beer or not Two Beer

Subscribed...

yep... I wanna know

Cool! Subscribed. .1/mL/plato seems like a pretty significant underpitch.

i'll take notes and come back with any impressions. thanks for the interest!

Very curious about the over pitch, especially with a neutral 1056... As started before, .1 is a but extreme for an underpitch... But we ll see! Subscribe!

Subscibed, definitely curious to see what differences come about in this one!

I'm curious to hear your results.

I tip my hat to you sir. Eagerly awaiting the results.

subscribed as well!

A previous study on pitching rates:

http://www.scientificsocieties.com/jib/papers/1993/1993_99_4_341.pdf

Interested to see your results.

count me in; subscribed

Subscribed!

looking forward to seeing the results as well.

As an admitted but not unwashed underpitcher, I am all in on this one.

I would like to thank you for submitting your body for the good of science....

I read that article recently, and actually believe in over-pitching to speed up primary... however, I may change my stance...

As with everything in life, you must "strike a balance"... SUBSCRIBED!

/subscribed. Sweet!

Hello and firstly thank you for this experiment and sharing your findings.
Could you please explain how you measure the amount of yeast cells?
If a smack pack contains 1billion cells and you create a starter, how do you know when the culture will have stepped up to for example approx. 1.3 billion?
Or if I create a 2 litre starter and added the smack pack what would the cell count be?

Yeah definitely need to subscribe to this one.

Subbed... and horny.

Hi Everyone!

Jason here, and I am the one actually doing the experiment. Glad everyone is interested in this! Currently the bottles are priming and should be ready when I poll the class by the 14th. I'll post the results soon after.

I did taste them out of the primary and they were each different. With the control pitch I thought, "ok tastes like a run of the mill blonde ale. Not bad."
The other two I went "meh..." Of course this is all very unscientific and not blinded. Before I poll the class I'll have my wife blind the samples and critique the brews. As a side note this is the first time I brewed in 1 gallon jugs and I did not use oxygen (decided to leave this variable for another day). The base beer may not be the best beer i have brewed, but hopefully the samples will be different from one another.

Thanks everyone! Feel free to post comments here. I'm more active on BA but this should change!

J

BeerMbob said:

Hello and firstly thank you for this experiment and sharing your findings.
Could you please explain how you measure the amount of yeast cells?
If a smack pack contains 1billion cells and you create a starter, how do you know when the culture will have stepped up to for example approx. 1.3 billion?
Or if I create a 2 litre starter and added the smack pack what would the cell count be?

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So I counted the cells with a hematocytometer in the lab. Wyeast packs usually have around 100 billion or so, give or take. For the experiment I made a simple one liter starter from a very small amount of cells. About 1 million. I freeze them down and store them in aliquots at -80C so I don't have to buy smack packs

Do you have access to a ViCell in your lab in will give your far more accurate viability counts

j1laskey said:

Do you have access to a ViCell in your lab in will give your far more accurate viability counts

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We have something similar in the lab but its optimized for mammalian cell culture. However, I feel something like this is unnecessary. Counting in a chamber slide, if done correctly, can be extremely accurate. I have done trypan blue staining, but only for bottle dregs. My yeast that I grow in the lab are foten 95-98% viable since they are continuously stirred and stepped up appropriately.

J

phattysbox said:

Hi Everyone!

Jason here, and I am the one actually doing the experiment. Glad everyone is interested in this! Currently the bottles are priming and should be ready when I poll the class by the 14th. I'll post the results soon after.

I did taste them out of the primary and they were each different. With the control pitch I thought, "ok tastes like a run of the mill blonde ale. Not bad."
The other two I went "meh..." Of course this is all very unscientific and not blinded. Before I poll the class I'll have my wife blind the samples and critique the brews. As a side note this is the first time I brewed in 1 gallon jugs and I did not use oxygen (decided to leave this variable for another day). The base beer may not be the best beer i have brewed, but hopefully the samples will be different from one another.

Thanks everyone! Feel free to post comments here. I'm more active on BA but this should change!

J

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Thanks for sharing your experiment with us!

phattysbox said:

Hi Everyone!

Jason here, and I am the one actually doing the experiment. Glad everyone is interested in this! Currently the bottles are priming and should be ready when I poll the class by the 14th. I'll post the results soon after.

I did taste them out of the primary and they were each different. With the control pitch I thought, "ok tastes like a run of the mill blonde ale. Not bad."
The other two I went "meh..." Of course this is all very unscientific and not blinded. Before I poll the class I'll have my wife blind the samples and critique the brews. As a side note this is the first time I brewed in 1 gallon jugs and I did not use oxygen (decided to leave this variable for another day). The base beer may not be the best beer i have brewed, but hopefully the samples will be different from one another.

Thanks everyone! Feel free to post comments here. I'm more active on BA but this should change!

J

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Uhhhh wow, world is a small place! Looking forward to your class, see you on the 14th!

sub'd

Hmmm, by not oxygenating, you're restricting growth. So not only are you under pitching, you're also not giving the right conditions for a normal fermentation by liquid yeast, so problems that occur from this maybe mistaken for under pitching.

You'd have been better off using dry yeast (S-05) if you didn't want to oxygenate IMO

ChillWill said:

Hmmm, by not oxygenating, you're restricting growth. So not only are you under pitching, you're also not giving the right conditions for a normal fermentation by liquid yeast, so problems that occur from this maybe mistaken for under pitching.

You'd have been better off using dry yeast (S-05) if you didn't want to oxygenate IMO

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Maybe he just meant he didn't add oxygen with an oxygen tank, instead he could have shock it around to get oxygen in it. That's my guess.

Two Beer or not Two Beer

ChillWill said:

Hmmm, by not oxygenating, you're restricting growth. So not only are you under pitching, you're also not giving the right conditions for a normal fermentation by liquid yeast, so problems that occur from this maybe mistaken for under pitching.

You'd have been better off using dry yeast (S-05) if you didn't want to oxygenate IMO

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I'll have to disagree.

My whirlpool step is quite vigorous (20 minutes) and there is more than enough gas exchange to maintain a minimal amount of oxygen for the yeast to do their job. Also, their is plenty of gas exchange when the wort hits the fermenting vessel. Moreover, the liquid yeast was made in my lab with two stepped starters under continuous stirring for close to a week. The yeast had plenty of oxygen from this so using US-05 would have made no difference.

I left oxygenating with pure O2 out because most novice homebrewers do not take this into account. Also, 1056 is such a clean strain adding oxygen could have removed any sort of off-flavor profiles. The point of the experiment is to compare under and over pitching rates to a control. Whether I added pure O2 is irrelevant.

Having said all of this - you are right, it is best to add oxygen when brewing a batch of beer and calls for another experiment where this is the sole variable. I could have one sample with no oxygen added, a control amount, and much higher amount. Or I could even titrate the amount to see what level of O2 produces the best result.

Something for the next class eh?

J

I feel like I should be paying for this class. Even though I live on the West Coast. Thanks for taking the time, James!

Ah I see. When you said you didn't oxygenate, I took this as you didn't do anything to get oxygen into the wort. But it sounds like you do have some going into it.

You have my permission to carry on with the experiment... lol.

Two things

1)Cool experiment I love the science side to brewing

2) That article that someone linked back on page two about high gravity brewing is disturbing. I new mass beer makers used adjuncts to make their beer cheap but brewing heavy beer and the watering it down is just plan evil.

Clem

Clementine said:

...but brewing heavy beer and the watering it down is just plan evil.

Clem

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why?

Clementine said:

2) That article that someone linked back on page two about high gravity brewing is disturbing.

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I thought an interesting result from the article was diacetyl production was signicantly reduced in worts with higher OGs regardless of pitching rate. So diacetyl rests should especially be a priority for beers with lower OG.

broadbill said:

why?

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Words fail me on this but it is sort of if you want to make a beer a certain strength make it that way don't f&*( with it. Why don't home brewers and craft breweries do the same thing. Cause we are here to make great beer, not money.

Clem

Don't take this one OT please