# Another yeast pitch rate question

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#### hilljack13

##### That's what she said!
HBT Supporter
I was randomly looking at yeast pitch rates since I am trying to do some 1 gal batches. Need to figure out how many grams to use out of the pack. So according to Fermentis, 34/70 is >6*10^9 cfu/g.

If I did the math right, that is only 6 billon/g. In the BrewFather calculator I need to use 2 packs of this for 1 gal!!??!! I must be doing something wrong. I had used only 6g in my previous test batches, but that was my own math, and fermentation went to 1.008-1.0010 as expected.

Easier than that: 2 packs works for 5 gallons, so I'd use 1/2 a pack for 1 gallon.

For
I am trying to do some 1 gal batches.
For most Lallemand and Fermentis strains at OG 52 in 1.25 gal, I typically pitch 1/4 the sachet.

With some Lallemand strains (e.g. New England) their pitch rate calculator recommends a higher pitch rate - so I'll pitch 1/2 the sachet.

eta (see below): these are for ale strains, not lager strains.

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The problem with trying to calculate pitch rates for dry yeast is that you don't really know how many cells per gram you're getting. For all we know, that ">" could mean 6.1 x 10^9 or 61 x 10^9.

For most Lallemand and Fermentis strains at OG 52 in 1.25 gal, I typically pitch 1/4 the sachet.

With some Lallemand strains (e.g. New England) their pitch rate calculator recommends a higher pitch rate - so I'll pitch 1/2 the sachet.
1/4 for a 1G lager? He mentioned 34/70. For an ale I'd go 1/4. For a lager I'd go 1/2.

1/4 for a 1G lager? He mentioned 34/70. For an ale I'd go 1/4. For a lager I'd go 1/2.
Agreed.

Cool. I'll stick to my 6g. I have a 500g pack I'm pulling from.

The dosage they recommend is between 80 to 120 grams per hectoliter.

Dosage / Temperature
80 to 120 g/hl at ideally 12°C – 18°C (53.6-64.4°F).
SafLager™ W-34/70 technical features

There are 26.4 US gallons in a hectoliter. So at the lowest dosage of 80 grams per 26.4 US gallons, you'd only use 3.03 grams for 1 gallon of wort.

At their highest recommended dosage of 120 grams per 26.4 US gallons, you'd use 4.55 grams for one gallon of wort.

The >6*10^9 cfu/g that you quoted is how many viable yeast are in a gram of yeast from that pack of yeast you have.

If you are figuring your dosage based on the number of billion viable cells you want to pitch, then you'll have to tell us what made you think you needed to pitch more viable cells than their recommended dosage works out to.

Not that it's going to make any difference. A full 10 or 11 gram pack of yeast in one gallon won't really hurt anything but your wallet if you do a gallon of beer a week for a few years.

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If you are figuring your dosage based on the number of billion viable cells you want to pitch, then you'll have to tell us what made you think you needed to pitch more viable cells than their recommended dosage works out to.
I was just guessing previously. I took 11.5g/5gal batch and just used1/5. This was for Ales. I just added more since it was a lager. I was a bit curious so started playing around and saw the viable cfu/g formula, which made me even more curious.

Well for one thing, 6.0 *10^9 or 6.0 *10E9 is 60,000,000,000 not 6,000,000,000.

In real life, there's closer to 15-20 billion cells per gram.

I'd use at most 1/4 pack to make 1 gallon lager at cold temperatures.

And if fermenting a lager warmer, in say the mid-60s F (which a lot of people do these days, including myself), I'd use no more than 1/8 pack for 1 gallon. That's plenty. Save the remainder in your refrigerator to make 7 more batches later. Dry yeast lasts forever too. Even after opening, it will last for around 10 years.

Well for one thing, 6.0 *10^9 or 6.0 *10E9 is 60,000,000,000 not 6,000,000,000.
How?

6*10E9
6*1,000,000,000
6,000,000,000.

Yours has 10 zeros?

And if fermenting a lager warmer, in say the mid-60s F
Going off topic...have you happen to ferment 34/70 over 60-65F? My last batch was very off tasting.

How?

6*10E9
6*1,000,000,000
6,000,000,000.

Yours has 10 zeros?
ten to the ninth power is 10,000,000,000 isn't it?

multiplied by 6 is 60,000,000,000.

No?

Going off topic...have you happen to ferment 34/70 over 60-65F? My last batch was very off tasting.
I have not tried W-34/70 warm. But Brulosophy loves using W-34/70 warm for some reason. W-34/70 is not my favorite lager yeast. I have successfully used S-189, Diamond, and WLP833 in the mid-60s. These turn out quite good, perhaps not perfectly clean but possibly good enough depending on how picky you are. WLP833 fermented at 60 F turned out wonderfully clean in a recent batch vs. S-189 at 60 F which has slight berry esters. I am starting to lean more towards liquid yeasts to make the very best lagers, not completely impressed by any dry yeasts although Diamond and S-189 are both quite good, they're not as good as liquid yeasts. And in any case, it seems like we can get away with fermenting lagers a little bit warmer than traditionalists would have us believe. I'm going to keep on playing with various lager yeasts in the low to mid 60s for at least a few years to come. I've tried all the dried yeasts, now it's time to try all the liquids. That's where I'm at.

Hmmm...... maybe you are correct.

When I put the 6 X 10E9 in my calculator I get 60,000,000,000. But maybe 6 x 10E9 isn't the same as 6 x 10^9.

Maybe I need a math refresher. Another online calculator gives me 6,000,000,000.

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I hate math...

HA...I think we have settled this now. If I need to rack my brain this hard on math I quit! Not really.

6*10^9 does NOT equal 6*10E9

6*10^9 DOES equal 6E9

See the difference? By entering an additional " *10 " to the "E" notation, you have multiplied by an extra 10.

In a calculator, you should be entering "6*10^9" or "6 EXP 9". The 6E9 is a shorthand notation used by engineers and chemists, which may or may not translate well to being used in a calculator, depending on the model of calculator you are using. (I use a Casio, where the "EXP" button is the "E" for that notation.)

I guess I know this stuff because... I'm a chemical engineer and have worked both as an engineer and a chemist.

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You know how many cells you need?

Yeah, I had to go back and do some reading last night to get me somewhat re-educated. I was not using the EXP key on the calculator correctly. The EXP key assumes 10 and exponentiates that. So instead of pressing the keys
6
x
10
exp
9
=

I should have just pressed the keys

6
exp
9
=

Dealing with negative scientific notation, I know I just move the decimal that many places left. And when a positive number that many to the right. But this time I grabbed a calculator, used it incorrectly and that started my demise.

Probably a good thing I'm retired.

6*10^9 does NOT equal 6*10E9

6*10^9 DOES equal 6E9

See the difference? By entering an additional " *10 " to the "E" notation, you have multiplied by an extra 10.

In a calculator, you should be entering "6*10^9" or "6 EXP 9". The 6E9 is a shorthand notation used by engineers and chemists, which may or may not translate well to being used in a calculator, depending on the model of calculator you are using. (I use a Casio, where the "EXP" button is the "E" for that notation.)

I guess I know this stuff because... I'm a chemical engineer and have worked both as an engineer and a chemist.
Oh, you figured out what I was doing wrong! Would have saved me some searching if I'd come back and read that.

Somewhat off-topic yet somewhat related, what is the proper procedure for storing 1/2 to 3/4 of an opened yeast sachet?

Still though on the OP's issue, why is the Brewfather calculating so many cells to pitch? 91 billion.

In fact why does Brewer's Friend come up with 91 billion cells for a 1.25 gallons of wort the OP was pitching to?

Not to mention that Brewfather says it takes 19 grams to reach that many and Brewer's Friend says 15.1 to get there.

So why the large pitch over the max dosage Fermentis recommends of 4.55 grams or 27.3 billion cells?

I guess a lot of this gets answered in this link from Brewer's Friend on their pitch calculator
https://www.brewersfriend.com/2012/11/07/yeast-pitch-rates-explained/

The 4.55 grams max dose that Fermentis recomends seems to work out to a 0.35 (million cells / ml/ degree Plato) pitch rate if I did the math correctly. Which obviously from earlier posts should not be trusted!

So does that mean those of us that use dry yeast should should all be buying the 500 gram packs of yeast? Or do we assume the yeast makers are hedging their numbers to be safe and telling us a low number of viable yeast when in most cases it's double that or more, but they can't take the liability of getting any one pack being wrong for any of a number of reasons and someone just happening to check the actual count for that pack?

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Somewhat off-topic yet somewhat related, what is the proper procedure for storing 1/2 to 3/4 of an opened yeast sachet?
I just push the air out of the pack and fold a piece of tape over the cut end and put in the fridge. My bread yeast comes in a jar that I keep in the fridge and is opened and closed many times during the time it takes to be used up. And it seems to be good even a year after the use by date.

So for dry beer yeast, I'm sure anything the maker says is very conservative too. Like this statement from Fermentis.

For the 500g sachets, we don’t recommend to re-use open sachet. However, for a sachet where the air has been flushed and firmly closed, we have experienced that the sachet can be stored for one week in a refrigeration temperatures and still be fine for use. Be aware that after storage, the yeast sachet need to be kept at ambient temperature until the yeast comes back at ambient temperature.This process works only one time. Indeed, when you take the sachet out of the fridge and come back to ambient temperature, you will have some humidity formed by the change that you won’t be able to remove. Humidity is the second enemy of active dry yeast, after the air.

While they make it sound like only a week, I've used opened and resealed packets over 6 months later. So obviously YMMV and your own preference and opinion will be in play. And remember, Fermentis and other maker's are also talking to commercial brewer's where the standards have to be higher. Many times for other reasons than we'd expect.

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I just push the air out of the pack and fold a piece of tape over the cut end and put in the fridge. My bread yeast comes in a jar that I keep in the fridge and is opened and closed many times during the time it takes to be used up. And it seems to be good even a year after the use by date.

So for dry beer yeast, I'm sure anything the maker says is very conservative too. Like this statement from Fermentis.

While they make it sound like only a week, I've used opened and resealed packets over 6 months later. So obviously YMMV and your own preference and opinion will be in play. And remember, Fermentis and other maker's are also talking to commercial brewer's where the standards have to be higher. Many times for other reasons than we'd expect.
I have the 500g big boy pack. It's been open over 30 days, but I put it in a ziplock and get as much air out as I can, then to the fridge it goes. However, I just received my food sealer. I ordered a bunch of small bags that just happen to be the same size of a 11.5g sachet. I measured and sealed ~40 sachets last night!

So does that mean those of us that use dry yeast should should all be buying the 500 gram packs of yeast?
I've been pitching one pack into five gallons of medium gravity wort forever and getting good fermentations and good beers. I use two packs for high gravity brews. I'm sure there are plenty of people who would say that we're all underpitching, but if we aren't actually observing any of the ill effects typically associated with underpitching then maybe we aren't actually underpitching.
Or do we assume the yeast makers are hedging their numbers to be safe and telling us a low number of viable yeast when in most cases it's double that or more
Yes. If they say >6 billion cells per gram, then anything over 6.01 billion passes. But if they're routinely packaging >12 billion per gram and decide to make that the specification, then when one batch comes out at 11.9 billion they have to fail it.

I guess it's time to measure a gram and start counting all those billions!

Yeah, if one assumes they are understating their cell count to only a 1/3 or 1/4 of what the actual typical count is, then the pitch rates of 1 to 1.5 million cells/ml/degree Plato seems to work out for their recommended dosage of 80 to 120 g/hl and the suggested cell count of Brewfather and Brewer's Friend.

Somewhat off-topic yet somewhat related, what is the proper procedure for storing 1/2 to 3/4 of an opened yeast sachet?
I just fold over the corner, tape it, put it in the refrigerator. Lasts pretty much forever.

do we assume the yeast makers are hedging their numbers to be safe and telling us a low number of viable yeast when in most cases it's double that or more, but they can't take the liability of getting any one pack being wrong for any of a number of reasons and someone just happening to check the actual count for that pack?
YES, THIS. ^^^^

A couple of references:

In How to Brew, E4, Palmer states that "a good rule of thumb is that dry yeast has about 10 billion cells per gram".

Yeast, by Zainasheff and White, states "Most dry yeast contains about 7 billion to 20 billion cells per gram"

Edit: For those who want to read more, the How to Brew reference was from page 109, and there is more discussion in Chapter 7. The Yeast reference was from page 124.

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