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dry yeast cell counts and viability

 
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stickyfinger




Joined: 04 May 2014
Posts: 176
Location: hudson valley, NY


PostLink    Posted: Tue May 06, 2014 7:40 pm    Post subject: dry yeast cell counts and viability Reply with quote


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I've been thinking about dry yeast lately, and I've been using the mrmalty.com calculator to determine pitch rates for liquid and dry yeast. Jamil says on his site that dry yeast has 20 billion cells/gram. I've been talking to someone from Fermentis about their dry yeast, because I kept reading that they guarantee 6 billion cells/gram up to two years from production (expiration date.)

I've reaped some very interesting information from the person at Fermentis, if it is all true. I assume this would only apply to Fermentis yeast, though, it MAY apply to other dry yeast.

1) The viability of dry yeast stored in the fridge (+4 degrees C) or the freezer (-4 degrees C) is the SAME.

2) There will be a minimum of 6 billion viable cells per gram up to the best before date on the package of yeast.

3) A 10% loss of viability over the two year storage (if the yeast is stored correctly) would be considered extremely high by Fermentis. So, you are looking at 90%+ viability over the entire useful life of the yeast sachet.

4) Fermentis does not see "any difference" in performance of the yeast with a 10% difference in viability (not sure what they have fermented, but probably a wide range of gravities, etc.)

5) Using the classic methylene blue method for measuring viability in active dry yeast cells will result in very inaccurate results, as they have disorganized membranes and lower capability for pumping out the stain (this would seem to indicate to me that the yeast count would be in fact much higher than results determined using the methylene blue method.)

That is basically the summation of the interesting information I have gleaned. Has anyone (besides Jamil) recently done a methylene blue yeast viability test on a package of dry yeast? If not, maybe I will take it upon myself to do that a few times to see what kinds of counts I am getting and then see if I can use another method appropriate for dry yeast and see what that gives. I had assumed I could just rehydrate the yeast and then do a test on the yeast once it is in good shape with the methylene blue test. I should confirm with Fermentis if this is appropriate.

I specifically asked Fermentis how many cells should be in the sachet, and they keep saying 6 billion, but they never really confirmed that number. they said "if we give you 6 billion cells per gram", so maybe they in fact are giving 20 billion per gram but don't want to say any more than 6 billion for liability or bad storage or something?

I don't have enough experience with dry yeast to know whether the 6 billion number even makes sense in terms of the degree of attenuation experienced with the yeast.

I know some of you probably don't care much what the counts are, but I am just curious and would like to pitch consistently.
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Jerz




Joined: 17 Nov 2013
Posts: 235
Location: Canton, Georgia

Drinking: Rye IPA (brewed a year and a half ago)

Working on: ESB


PostLink    Posted: Tue May 06, 2014 11:19 pm    Post subject: Reply with quote

Here's my experience with dry yeast... It exploded and hit the ceiling 16 hours after two packets were pitched... (sorry I know it's not scientific data... Very Happy)


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Jerz
Head Brewer and #1 Consumer
2dogsBrewing - Canton, GA
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stickyfinger




Joined: 04 May 2014
Posts: 176
Location: hudson valley, NY


PostLink    Posted: Tue May 06, 2014 11:38 pm    Post subject: Reply with quote

Wow, what a mess!! Your wife (if you have one) must have wanted to kill you! That's bound to happen if you ferment without temp. control!!! Also, if you add 5-10 drops of anti-foam, you won't have that anymore.
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Jerz




Joined: 17 Nov 2013
Posts: 235
Location: Canton, Georgia

Drinking: Rye IPA (brewed a year and a half ago)

Working on: ESB


PostLink    Posted: Wed May 07, 2014 12:58 am    Post subject: Reply with quote

Yeah... well... I had to get a divorce so I could start brewing again.... Yup... fermentation is now taking place in the basement and I'm working on my fermentation keezer so should have it ready within a couple weeks...

I'm just glad that I was only about fifteen feet away when this happened so I was able to clean it up pretty quick.

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Jerz
Head Brewer and #1 Consumer
2dogsBrewing - Canton, GA
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stickyfinger




Joined: 04 May 2014
Posts: 176
Location: hudson valley, NY


PostLink    Posted: Wed May 07, 2014 2:30 am    Post subject: Reply with quote

Ha!! I hope you're joking!! You'll be very pleased with fermenting in a fridge. You can really dial in the temps and make awesome beer. I made great beer when I just fermented at room temp, but it's a lot more consistent with temp. control, and not that expensive. I have 3 mini-fridge/freezers in my basement that work very well. I was a little scared bending down the cooling element from the top, but it didn't break!!

What a mess! I remember one time I had a couple hefeweizens out at room temp, and I woke up the next morning to find a yeast mess all over my wall. The top had blown off and sprayed yeast all over my walls!!!
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huaco




Joined: 05 Apr 2012
Posts: 1506
Location: Burleson Texas


PostLink    Posted: Wed May 07, 2014 12:52 pm    Post subject: Reply with quote

Great info. Thanks for sharing.
Is this typical of all dry yeast I.e. Mangrove Jack's... I've been very happy using dry yeast.
And yes, though it was using liquid yeast,I had a weizen blow through 3 gallons of head space and still pushed out over a gallon of krausen all over the floor of my fermentation chamber. That was a semi-open fermentation with no head pressure and it still went crazy like that.
I've learned to respect weizen yeast and now give them a full 1/3 volume head space.
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stickyfinger




Joined: 04 May 2014
Posts: 176
Location: hudson valley, NY


PostLink    Posted: Thu May 08, 2014 11:23 am    Post subject: Reply with quote

huaco wrote:
Great info. Thanks for sharing.
Is this typical of all dry yeast I.e. Mangrove Jack's... I've been very happy using dry yeast.
And yes, though it was using liquid yeast,I had a weizen blow through 3 gallons of head space and still pushed out over a gallon of krausen all over the floor of my fermentation chamber. That was a semi-open fermentation with no head pressure and it still went crazy like that.
I've learned to respect weizen yeast and now give them a full 1/3 volume head space.



I recently found (and was directed to) this site by Sean Terrill:

http://seanterrill.com/2011/04/01/dry-yeast-viability/

He seems to confirm Jami's yeast pitching rate calculator and the 20 billion cells per gram estimate for fresh dry yeast. I'm wondering if Fermentis is just telling us 6 billion cells to make sure that they are always covered?
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stickyfinger




Joined: 04 May 2014
Posts: 176
Location: hudson valley, NY


PostLink    Posted: Tue Jul 15, 2014 7:49 pm    Post subject: Jamil discussing dry yeast on BN show - Munich Dunkel Reply with quote

Just an FYI on this topic that I stumbled upon today. I happened to be listening to a Brewing Network podcast on Munich Dunkel (from years ago) where Jamil talks about how he does his Dunkel. Anyway, he has a segment where he discusses dry yeast (S-23 was all there was for lagers then I think.) He confirms that Clayton Cone said dry yeast has 20 billion cells/gram. He also says all of the tests he has done (i.e. cell counts after proper rehydration) show around 20 billion cells/gram. He offers the explanation that the yeast makers probably hedge their bets to account for poor storage and poor pitching technique (i.e. sprinkling on wort without rehydration) when giving the value of 6 billion cells/gram.
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skelley




Joined: 24 Feb 2012
Posts: 210
Location: brookfield, wisconsin


PostLink    Posted: Thu Jul 24, 2014 3:22 pm    Post subject: Reply with quote

What are peoples thoughts on dry yeast versus liquid yeast? I have only used the slap packs and have been very happy but I don't build starters and simply buy enough packs to get the appropriate yeast counts for the gravity of the beer I am brewing.

-Do you use starters with dry yeast or simply rehydrate the appropriate amount?

-do you use the 6 billion or 20 billion number per gram?
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stickyfinger




Joined: 04 May 2014
Posts: 176
Location: hudson valley, NY


PostLink    Posted: Thu Jul 24, 2014 6:42 pm    Post subject: Reply with quote

I assume 20 billion and have gotten excellent fermentations (though I use the mrmalty.com pitching rate calculator to estimate viability.) Most recommend not making a starter with dry yeast, as it is engineered to be ready to go upon rehydration and a starter may actually hurt its performance. Just don't sprinkle the yeast without rehydrating unless you assume 50% of the viable yeast dying upon hitting the wort. You can use rehydration aids like Go-Ferm if you want.

I've used US-05, S-23, T-58, Nottingham and W-34/70. The US-05 makes a beer very similar to WLP001. The S-23 wasn't my favorite lager character. I wouldn't recommend it based my fading memory of its performance. T-58 makes a very nice Belgian-style ale. I'm not sure what yeast to compare it with, but it has a lot of phenolic character and makes a dry beer. Nottingham is super fast and clean but can make a beer that seems a little one-dimensional in my opinion, though I haven't used it much. I just used W-34/70 for the first time a few months ago, and it made a fantastic lager!

I like liquid yeasts a lot and starters aren't really a pain for me at all, but I like the fact that I can buy some fresh dry yeast and store it for maybe even a year and still have 50% viability if I need it in a pinch. With liquid yeast you are always fighting the rapid viability drop, even with cold storage. The variety is pretty incredible with liquid yeasts though. I think a lot of people probably just use US-05 and W-34/70 for American/hoppy beers and lagers, respectively since they work in so many styles and are easier to store and still have an adequate pitching rate.
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