Yeast Overpitch/Underpitch Experiment From a Microbiologist

[emjay]

Don't take this one OT please

Hahaha... I opened a whole can of worms on a different one this morning. Although, people were basically just saying what I was originally getting at.

 

[broadbill]

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

Yeah, but it would theoretically cost just as much to make the high gravity wort and water it down compared to making the same amount of beer at with a lower OG.

Just because a big brewery does it doesn't make it evil.

 

[sheeshomatic]

Fantastic experiment! One question, however - Are you (or did you, I guess) allowing all 3 samples to attain their stable FG prior to bottling? If so, were they different?

 

[william_shakes_beer]

Subscribe. Guess I gotta start calcu;lating pitching rates next (sigh)

 

[JakeFegely]

subscribed. Thanks

 

[phattysbox]

Fantastic experiment! One question, however - Are you (or did you, I guess) allowing all 3 samples to attain their stable FG prior to bottling? If so, were they different?

More than just that! :cross:

I took measurements every 8-12 hours with refractometer and will plot gravity as a function of time.

Each sample was very different, and as predicted, the overptich reached terminal gravity faster than the other two. The underpitch was slower.

The interesting thing is - the under and over pitch had a lower gravity than the control. This was after multiple readings on successive days. Not sure what this means

 

[phattysbox]

More than just that! :cross:

I took measurements every 8-12 hours with refractometer and will plot gravity as a function of time.

Each sample was very different, and as predicted, the overptich reached terminal gravity faster than the other two. The underpitch was slower.

The interesting thing is - the under and over pitch had a lower gravity than the control. This was after multiple readings on successive days. Not sure what this means

Let me clarify. The under and over pitch had a lower final gravity. The kinetics of fermentation made sense however.

 

[sheeshomatic]

More than just that! :cross:

I took measurements every 8-12 hours with refractometer and will plot gravity as a function of time.

Each sample was very different, and as predicted, the overptich reached terminal gravity faster than the other two. The underpitch was slower.

The interesting thing is - the under and over pitch had a lower gravity than the control. This was after multiple readings on successive days. Not sure what this means

Now THAT I would not have guessed. I love science.

 

[insubordinateK]

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

Since you didn't test with trypan blue after freezing, did you step up the yeast in one batch, measure with the hemocytometer, then dilute to obtain different concentrations for the 3 batches?

Although if the kinetics made sense, then the dilutions were probably good.

 

[emjay]

Now THAT I would not have guessed. I love science.

Then you should know a result like that really needs to be consistently repeated before drawing any conclusions. I have my doubts that it can be, but it'll be really interesting if it is.

 

[phattysbox]

Since you didn't test with trypan blue after freezing, did you step up the yeast in one batch, measure with the hemocytometer, then dilute to obtain different concentrations for the 3 batches?

Although if the kinetics made sense, then the dilutions were probably good.

I didn't test with trypan blue actually.

I stepped in multiple batches. Went from a 500 ul frozen stock to 100 mls. Then the 100 mls stepped up to 1 liter. From this, I took 100 mls and stepped it even further to another 1 liter. I centrifuged 2 liters down to about 50 mls and counted the cells by dilution.

As for viability, stepping starters under constant aeration produces VERY healthy cells - almost 98-99%. I've tested for viability before but whenever I step with my frozen stock of 1056, I get great results.

I then split that 50 mls into the desired volumes that contained the correct numbers stated in my blog, and pitched three different vials.

Hope this makes sense...:rockin:

 

[phattysbox]

Then you should know a result like that really needs to be consistently repeated before drawing any conclusions. I have my doubts that it can be, but it'll be really interesting if it is.

EXACTLY...

Observation can only be proven true through repetition. Not sure when I can do that though with my limited time doing research in the lab. For now we have to leave it to speculation.

Any ideas?

 

[DannyD]

+1

 

[Yooper]

Let me clarify. The under and over pitch had a lower final gravity. The kinetics of fermentation made sense however.

I think it was about 2 years ago that there was a BYO/BBR collaboration that did the same type of experiment, although unscientific. They did three batches, one with an appropriate sized starter, one was with one vial of yeast, and one was overpitched. No cell counting was done, just a set volume of "a vial of yeast", "a XXXX-sized starter" and "XXX vials of yeast". (I can't remember the amounts).

The results showed that both the overpitched and underpitched beer had a lower FG, if I remember correctly.

We usually assume that an underpitched beer will stall out and have a higher FG but I've also heard of a lower FG. It must have something to do with stressed yeast and their metabolism.

 

[insubordinateK]

EXACTLY...

Observation can only be proven true through repetition. Not sure when I can do that though with my limited time doing research in the lab. For now we have to leave it to speculation.

Any ideas?

We can ask people to do their own experiment to obtain more replicates. I think a nice experimental design would be to take a 4 gallon batch and split into eight 0.5 gallon fermenters. 4 pitching rates 2 reps each

For set 1 - severely under pitch
For set 2 - under pitch
For set 3 - pitch "optimal" amount
For set 4 - severely over pitch

Take gravity every 4 hours for the first 24 hours of each one, then every 8 hours for the next 24 hours, then every 12 hours until completion. Since we all don't have hemocytometers, we could combine dry yeast packs until homogeneous and pitch by dry weight.

Then, I think we can start to make knowledge-based assumptions on the effect that pitching rate has with final gravity. If we use a "spicy" yeast such as T-58, we could assess flavor profiles as well.

 

[badhabit]

Subscribed

 

[dantheman13]

Subbed!

 

[year2beer]

We can ask people to do their own experiment to obtain more replicates. I think a nice experimental design would be to take a 4 gallon batch and split into eight 0.5 gallon fermenters. 4 pitching rates 2 reps each

For set 1 - severely under pitch
For set 2 - under pitch
For set 3 - pitch "optimal" amount
For set 4 - severely over pitch

Take gravity every 4 hours for the first 24 hours of each one, then every 8 hours for the next 24 hours, then every 12 hours until completion. Since we all don't have hemocytometers, we could combine dry yeast packs until homogeneous and pitch by dry weight.

Then, I think we can start to make knowledge-based assumptions on the effect that pitching rate has with final gravity. If we use a "spicy" yeast such as T-58, we could assess flavor profiles as well.

I don't think this is very easy with homebrewers... That's 20 gallons of homebrew-- maybe this can be shared across the forum?

 

[BBL_Brewer]

I'm wondering how you are going to take all those gravity readings with only .5 gal of beer to work with. Are you goind to keep dumping it back in? If so, contamination could easily throw off your results. Plus, getting up in the middle of the night to take 8 gravity readings is not on my list of things to do.

 

[bigbeergeek]

I don't think this is very easy with homebrewers... That's 20 gallons of homebrew-- maybe this can be shared across the forum?

Read the post again.

 

[bigbeergeek]

I'm wondering how you are going to take all those gravity readings with only .5 gal of beer to work with. Are you goind to keep dumping it back in? If so, contamination could easily throw off your results. Plus, getting up in the middle of the night to take 8 gravity readings is not on my list of things to do.

Refrac with alcohol-corrective software?

 

[emjay]

Refrac with alcohol-corrective software?

Was thinking the same thing. Since it's strictly comparative, you technically wouldn't even need to calculate SG (and thus correct for the presence of alcohol), but it definitely doesn't hurt.p

This would be perfect for my new digital bench refractometer... greater precision and far less room for human error than the small optical refracs that most homebrewers use should produce similarly advantageous results.

 

[Begin2Brew]

Subscribed, this should be cool..

 

[insubordinateK]

I don't think this is very easy with homebrewers... That's 20 gallons of homebrew-- maybe this can be shared across the forum?

Sorry if I wasn't clear. That's 4 gallons of home brew total for this experiment: 4 conditions replicated twice - each condition is 0.5 gallon batch. But the more people who can participate, the better for sure.

 

[insubordinateK]

I'm wondering how you are going to take all those gravity readings with only .5 gal of beer to work with. Are you goind to keep dumping it back in? If so, contamination could easily throw off your results. Plus, getting up in the middle of the night to take 8 gravity readings is not on my list of things to do.

I'm thinking regular hydrometer readings and return to fermenter. Before and between each reading, rinse the vessel with sterile water and/or sanitizer. Not really a big deal, you are right, we definitely want to avoid contamination and I think that will be an easy task.

Getting up in the middle of the night is a b#itch but it's for the greater good of the homebewing community man! And if one starts on say, Friday night, it would not be that bad for the working man.

I'm just trying to think what I could use as temporary fermenters. Wash and sanitized 1/2 gallon milk jugs? It might take awhile to collect 8 of these.

 

[insubordinateK]

Refrac with alcohol-corrective software?

I don't have experience with this but sounds like it would work.

 

[BBL_Brewer]

Getting up in the middle of the night is a b#itch but it's for the greater good of the homebewing community man! And if one starts on say, Friday night, it would not be that bad for the working man.

Nice of you to take one for the team

I'm just trying to think what I could use as temporary fermenters. Wash and sanitized 1/2 gallon milk jugs? It might take awhile to collect 8 of these.

I don't think 1/2 gallon jugs will work well for 1/2 gallon of beer. I'd go with gallon jugs and you still might have to worry about blow off.

 

[insubordinateK]

I don't think 1/2 gallon jugs will work well for 1/2 gallon of beer. I'd go with gallon jugs and you still might have to worry about blow off.

good point - christ, that is a lot of milk.

 

[CnnmnSchnpps]

I don't have experience with this but sounds like it would work.

If you have a refractometer BeerSmith does all the math for you

Worth the investment IMHO considering how many more readings you can take for each batch without wasting any appreciable qty of beer

Looking forward to the results!

Cheers
-D

 

[helibrewer]

I don't have experience with this but sounds like it would work.

Here's a link to the spreadsheet from MoreBeer.com: http://morebeer.com/public/beer/refractbeer.xls

I have been using this method exclusively for all of my wine and beer making, I rarely pick up a hydrometer any more. The key thing is to remember to enter the first refractometer reading in the top box BEFORE fermentation begins (prior to pitching).

After that a couple drops of wort is all it takes for a reading.

 

[Brew-Happy]

subscribed

 

[insubordinateK]

Here's a link to the spreadsheet from MoreBeer.com: http://morebeer.com/public/beer/refractbeer.xls

I have been using this method exclusively for all of my wine and beer making, I rarely pick up a hydrometer any more. The key thing is to remember to enter the first refractometer reading in the top box BEFORE fermentation begins (prior to pitching).

After that a couple drops of wort is all it takes for a reading.

Simple, easy, efficient. I like it.

Muchas Gracias

 

[sheeshomatic]

Here's a link to the spreadsheet from MoreBeer.com: http://morebeer.com/public/beer/refractbeer.xls

I have been using this method exclusively for all of my wine and beer making, I rarely pick up a hydrometer any more. The key thing is to remember to enter the first refractometer reading in the top box BEFORE fermentation begins (prior to pitching).

After that a couple drops of wort is all it takes for a reading.

Maybe I'm doing something wrong, but I think that spreadsheet is borked.

It doesn't matter what I put in for my starting gravity, the OG field ALWAYS sets to 1.004 and then the readings in the gravity fields below will always be 1.007 no matter what I put in for a gravity reading. I think there's something wrong with the formula in A8

 

[insubordinateK]

Maybe I'm doing something wrong, but I think that spreadsheet is borked.

It doesn't matter what I put in for my starting gravity, the OG field ALWAYS sets to 1.004 and then the readings in the gravity fields below will always be 1.007 no matter what I put in for a gravity reading. I think there's something wrong with the formula in A8

It seems to function fine for me. OG and gravity fields change appropriately.

A8 should be: =1.000019+0.003865613*(A7)+0.00001296425*(A7*A7)+0.00000005701128*(A7*A7*A7)

 

[sheeshomatic]

Never mind, I'm dumb. I was testing it by putting in specific gravity readings and it seems like it is in degrees Brix. Cancel all emergencies, we now resume our broadcast day.

 

[kickz28]

Subscribing

 

[daksin]

Hmm, I'm going to have to agree with ChillWill about the oxygenation issue- I'd rather the variable be eliminated by oxygenating all of the worts equally (to max dissolved O2) rather than by eliminating it by not aerating at all. That said, I defer to the expert and perhaps this condition will accentuate the differences between the different pitching rates.

Also: didn't know you could use trypan blue on yeast. I've only ever used it on mammalian cells before. Good to know.

 

[mightynintendo]

scribed

 

[Reno_eNVy]

Also: didn't know you could use trypan blue on yeast. I've only ever used it on mammalian cells before. Good to know.

Yup... IIRC (or if I'm confusing it with another dye process) it dyes dead yeast cells (i.e. no controll of what goes in or out) so you can get an idea of viability.

 

[weirdboy]

I thought it was methylene blue that was typically used for yeast.