Quantcast

Dry Yeast Cell Count

Aussie Home Brewer

Help Support Aussie Home Brewer:

dabre4

Well-Known Member
Joined
11/6/07
Messages
137
Reaction score
4
I am going to do a high gravity brew this weekend (OG = 1.106). I normally use liquid yeast and build up starters according to the calculated viability of the pack by the manufactured date. For this brew I am going to use S05 as I figured it will be easier and cheaper to get the required pitching rates then from liquid yeasts. I have a bit of confusion about the number of "viable" cells there are in a pack of dry yeast. In the past, and going by Mr Malty, I have figured that there are around 20 billion yeast cells per gram of dry yeast, so in a 11.5 g pack around 230 billion cells. However, I found the spec sheet on S05 from the fermentis website, see here. This states that there are 6 x 10^9 (6 billion) cells per gram. This would mean there are only around 69 billion cells in a 11.5 gram pack, that's much less then the supposed 100 billion in a fresh pack of liquid yeast. So what is correct? What fermentis are quoting seems too low, as too my knowledge the 11.5 g packs of dry yeast are meant to have much more yeast then the liquid. Unless of course I am reading this wrong.

Cheers
 

Steve@PMF82

Simplicity is perfection
Joined
13/11/10
Messages
883
Reaction score
3
I am not sure about exact cell counts. I would think what you end up with would have a lot to do with how you prepare and pitch your dry yeast, also how old the pack is and how it has been stored.

For a beer that big, personally i would be looking at 1.5 to 2g of dry yeast / L rehydrated according to fermentis instructions.
 

MHB

Well-Known Member
Joined
1/10/05
Messages
5,993
Reaction score
3,435
Location
Newcastle
Personally I would trust the manufacturer, what incentive is there for them to quote a number 2/3 or more lower than is actually in the pack?
Realistically that will be a minimum number for a packet at the end of its shelf life, under recommended storage conditions. From my reading dry yeast will lose about 20% of its viability/year at 20oC and only about 4% at 4oC, so very young very well looked after yeast could be giving a cell count in the order of around 1*10^10 (10*10^9 or 10 Billion) still half of what Jamil says he sees.
If you look at the tech sheets for both Danstar and Mauri (the other two makers of dry yeast widely available in Australia) you will see cell counts compatible with those made by Fermentis.
This is just one of the reasons I view Mr Malty and the Yeast Book with just a touch of caution (well outright scepticism in places)
For a beer that big I would be thinking Active Starter rather than just about the pitch rate
Mark

I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration I will not.........
m
 

dabre4

Well-Known Member
Joined
11/6/07
Messages
137
Reaction score
4
Interesting. I wonder where this perceived 20 billion/g has come from. I've already bought the packs, if I knew they were only 69 billion per pack I would have just got some 1056 and built it up in a starter. Lesson learnt.
 

Wolfy

Well-Known Member
Joined
18/12/08
Messages
3,872
Reaction score
64
Location
Melbourne

I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration; I will not talk about yeast rehydration I will not.........
m
Maybe the manufacturer quoted numbers assume you will sprinkle the yeast directly, while MrMalty's calculations assume you will hydrate, then going on JZ/JP's assertion that 1/2 the cells die when sprinkled directly, you end up with the same number of viable cells in both situations. ;)

But as MHB said, there is no reason or logic for the manufacturer to seriously under-estimate the number of yeast cells they provide in a packet, and one would assume they have a good idea of what they put into what they make.
 

felten

Homebrew Conjecturist
Joined
13/5/09
Messages
2,536
Reaction score
45
The best way to get an answer dry yeast part of the mr. malty calculator is to contact Jamil and ask him. A lot of people use the calc verbatim, and if they were underpitching by 3/4 I would have thought it would have been brought up by now.

IIRC he measured the cell count himself and confirmed the number with other people who had done measurements as well to arrive at 20 billion per gram.

http://www.mrmalty.com/pitching.php#s3
 

dabre4

Well-Known Member
Joined
11/6/07
Messages
137
Reaction score
4
Cheers. So according to Jamil:

"Recently there have been other numbers mentioned for cells/gram of dry yeast and folks have asked me why I believe there are 20 billion cells. I've actually done cell counts on dry yeast and they're always 20 billion per gram +/- less than a billion. Dr. Clayton Cone has also stated that there are 20 billion per gram, and other folks I trust tell me that 20 billion is correct."

Based in this I will go on assuming they are 20 billion/g. Still, I can't see any sense in the manufacture grossly underestimating the amount if yeast per pack. It must be to cover their arse in the cases where their yeast is mistreated and not re-hydrated correctly. In saying that though Wyeast claim 100 billion and I know for a fact that even fresh packs don't have that many viable cells.
 

hoppy2B

Well-Known Member
Joined
31/7/11
Messages
1,647
Reaction score
179
Yeast nutrition would have to be way more important than pitching rate.
 

hoppy2B

Well-Known Member
Joined
31/7/11
Messages
1,647
Reaction score
179
If you're going for esters for the purpose of creating a brew worth aging then low pitch rate is actually meant to be better. The actual type of esters you are producing is also dependent on the quality of the nutrient available.
I'd be selecting something other than us05.
 

hoppy2B

Well-Known Member
Joined
31/7/11
Messages
1,647
Reaction score
179
Or in lay terms, you can't make good beer from shit wort using good yeast. :lol:
 

MHB

Well-Known Member
Joined
1/10/05
Messages
5,993
Reaction score
3,435
Location
Newcastle
Beginning to wonder if I am the only one who sees something wrong with the guy who co-authored a book with a manufacturer of liquid yeast being totally at odds with the three big manufacturers (all much bigger than Whitelabs) and their paid professional yeast experts.
Considering the scant mention of dry yeast given in Yeast: The Practical Guide to Beer Fermentation (Brewing Elements) you would be left in no doubt as to the bias of the authors.
And yet we are asked to take Jamils word for how many yeasts are in a packet and the best way to handle that yeast.
Like I said isnt anyone just a little cynical arent there any faint tinkling of alarm bells in the distance?
The idea that you must rehydrate yeast reference Chris White/Jamil
That half your yeast will die if you dont same/same
That you get 3-4 times as many yeast cells as the maker claims think about it.
I guess if you use dry yeast and you follow Mr Maltys advice and dont get the results you wanted you should have brought a liquid culture in the first place dont worry you will know better next time seriously?

I both use and sell both dry and liquid cultures, both have their place but I never bother with Mr Malty, I really think he cant count and I am quite capable of working out from the manufacturers cell counts how much yeast I need in a brew.
Mark
 

Wolfy

Well-Known Member
Joined
18/12/08
Messages
3,872
Reaction score
64
Location
Melbourne
@Doog we don't really get 'fresh' packs of yeast here, we only get those that are shipped internationally that are often weeks or months past being 'fresh'.

@MHB, I think dried yeast gets mentioned once or twice in the 'Yeast' book, one is in a small little box at the bottom of the page - it's hard not to notice the bias.

However, every yeast information .pdf file I have downloaded from Danstar/Fermentis (I've never had need to visit/review Mauri's website/documentation) outlines detailed rehydration procedures and either cell count and/or pitching quantity information - which one would presume should be trusted.
 

MHB

Well-Known Member
Joined
1/10/05
Messages
5,993
Reaction score
3,435
Location
Newcastle
I am trying to avoid getting into another discussion about rehydration but will repeat what I have said many times in the past namely Follow the manufacturers instructions, exactly.
The advice offered by many here and in other media very rarely goes anywhere near being complete and is often at odds with what the maker recommends. Please note that Fermentis dont just recommend rehydration, equal weight is given to just sprinkling into the wort (with recommended temperatures), they offer two equally effective alternatives.

I did a bit more reading last night, from what I can gather if you want a real viable yeast count you dilute a sample plate it out and count the colonies, this is I suspect how the manufacturers reach the number they state. It is pretty well known that at least half of the cells die during freeze drying, they probably rehydrate pretty well and look just like live cells under a microscope they are still dead.
Put that with Jamils cell count and the back of an envelope numbers posted above, its quite possible that if you rehydrate some dry yeast and do a quick count you are seeing 20Billion cells, just not 20Billion live ones.
Mark
 

hoppy2B

Well-Known Member
Joined
31/7/11
Messages
1,647
Reaction score
179
I wouldn't be overly fanatical about following the instructions from yeast manufacturers. Its in their interest to tell you to chuck out a packet of yeast if more than 7 days have elapsed since you opened it. That way you go out and buy more yeast. The same thing with pitching rates etc. Not saying that you shouldn't pitch a good amount of yeast, just that all their instructions seem to be aimed at getting you to use as much of their yeast as possible. :angry:
 

hoppy2B

Well-Known Member
Joined
31/7/11
Messages
1,647
Reaction score
179
I'd rather pitch a smaller than average amount of yeast into a great wort than pitch a 'scientifically' calculated amount of yeast into a shit wort. :lol:
 

MHB

Well-Known Member
Joined
1/10/05
Messages
5,993
Reaction score
3,435
Location
Newcastle
I think the point of brewing is to pitch the right amount of yeast into the best wort I can make!
When did making crap wort come into the discussion, just looking up this page Im seeing something like 5 totally irrelevant OT posts by Hoppy2B intruding into an otherwise interesting discussion.
Mark
 

hoppy2B

Well-Known Member
Joined
31/7/11
Messages
1,647
Reaction score
179
You're entitled to your opinion MHB..... I don't agree with it. :lol:
 

manticle

Standing up for the Aussie Bottler
Joined
27/9/08
Messages
25,707
Reaction score
6,120
Location
Glenorchy, TAS
Your opinion, based on something tangible like your experience or research or a combination of both, clearly outlined and explained would be very welcome.

The problem is that you seem to make statements, phrased as being factual, that have little obvious basis in either of those.

If you have some justification for statements such as

Yeast nutrition would have to be way more important than pitching rate.
OR

If you're going for esters for the purpose of creating a brew worth aging then low pitch rate is actually meant to be better. The actual type of esters you are producing is also dependent on the quality of the nutrient available.
then let people know. Who says it's meant to be better? Why is it meant to be better? I've heard of low pitch creating esters but not about a blanket 'better for aging beers'. I age a few beers - I'd like to know who said so and why.

Not saying you're wrong - I just have no reason to think you're right and you're not giving me any.

This is a place where people (most people hopefully, myself included) learn new things. I can speak only for myself but I see people learning best from those who seem to know what they're talking about and are happy to share their knowledge and resources.
 
Top