Pitching Rates For Dry Yeast

[micblair]

According to Fermentis, the number of viable cells at packaging is >6x109/g, or 69 billion cells per 11.5g pack (US-05). Their dosage rate suggests a range between 50-80g/hl. If we're conservative thats 65g/100L or 1/5th that for a standard 20L batch (13 g of dried yeast), bearing in mind Fermentis don't provide a wort strength when publishing these values.

Maintaining this conservative approach, and opting for a pitching rate of 1x106 cells mL-1degree-1 plato (over 0.75x106 cells mL-1 for an ale), then we require 1x106 x 20,000 mL x 12.5 degrees plato = 250 x109 cells, for a 1.050 OG wort. Apparently under-pitching by more than 1.5 packs!

Whilst the technical document for US-05 (http://www.fermentis.com/wp-content/uploads/2012/02/SFA_US05.pdf) suggests a viable cell count of >6x109/g, I find it difficult to believe that this number could be more than twice this, as most other manufacturers will state values less than or equivalent to this range, i.e. Danstar ≥5x109/g viable cells.

But as we all know, 1 packet of US-05 is perfectly capable of producing excellent beer, even when apparently under-pitched by 170 billion cells!

 

[verysupple]

You've had the same thought process I had a while ago. My research at the time found multiple respectable sources stating that the number of viable cells / g in a pack of well handled, reasonably young dried yeast was ~20 billion. This is quite a lot higher than the guaranteed 5 - 6 billion as you stated. But I tend to believe the claims of higher cell counts when you take into account the endless anecdotal evidence (weak evidence I know, but strengthened by...) and the fact that those figures came from scientists with microscopes (I like to believe they have beards and walk around with 4-colour pens in the breast pockets of their lab coats exclaiming "Fascinating! That is so remarkable!").

Anyhoos, I digress. The point is, it's reasonably well accepted that the real number is more like 20 billion / g.

EDIT: Grammar

 

[micblair]

Anyhoos, I digress. The point is, it's reasonably well accepted that the real number is more like 20 billion / g.

Shouldn't we be trusting the manufacturer's specification to be accurate, particularly when it comes to something as rudimental as controlling the number of viable yeast cells lyophilised into a 11.5g packet? It's not like we make the same dispensation for any other manufactured product on the market, right?

 

[verysupple]

I believe the manufacturer's 100%. They say (as you quoted) Fermentis: >6 billion / g, and Danstar: >5 billion. 20 is greater than both 5 and 6, is it not? Besides, I'm sure if the aforementioned scientists are intelligent enough to use a microscope without breaking it, and someone is willing to pay them money to conduct their work and write about it, then they're intelligent enough to count in integer increments up to quite large numbers.

I'm pretty sure the lower limit numbers they put on the pack or in the documentation are guaranteed minimum. Like, if the pack has been handled properly it will have that many cells even if it's quite old (Fermentis say the shelf life is 2 years). Kind of like how Coke fill their cans and bottles slightly more than they volume printed on the packaging because the tolerances allowed are smaller than the tolerances of their machinery - they need to guarantee a minimum amount so that people don't get narky if they're a bit short.

EDIT: Couldn't resist adding an example.

 

[HBHB]

I take the highly scientific approach to this and toss in 1 packet of dried yeast for "average" ales, 2 packets for "average" lagers, whip a bucket load of air in and hope for the best given the yeast packets have been stored exceptionally well, rehydrated etc.

When it comes to bigger beers, like 1.060-1.100 i pitch 2 packs. Sometimes on bold stuff like IIPA+ i'll oxygenate and repeat in the morning.

Appears to work, most are even enjoyable (most).

What i don't do is lay awake at night worrying about whether an airlock is bubbling or if i pitched enough.

If you pitch enough and do it at the right temperature, it'll be fine, if you underpitch a little, it'll be fine, if you overpitch by a bucketload, it'll be fine, if there's 2g less dissolved oxygen than the theoretical ideal, it'll be fine.

Read the packets and go with what the scientists decided that individual yeast was best at......it'll be fine.

 

[verysupple]

Read the packets and go with what the scientists decided that individual yeast was best at......it'll be fine.

Yup, pretty much. I mean, Fermentis and Danstar both seem to think that one pack is enough for an "average" batch (I presume to be ~20 L at <1.060) which suggests they think there is actually much more than 5 - 6 billion cells / g.

 

[micblair]

Sorry guys, this topic has already been loosely discussed here: http://aussiehomebrewer.com/topic/67553-dry-yeast-cell-count/, (you do have to wade through a fair bit of anti-Zainasheff-White-pro-liquid yeast propaganda before arriving at any useful information).

I was going to say I think we should be happy settling for the manufacturer's recommendations (10-16g of yeast per 20L batch, see below), however Fermentis go and further confuse things on their craftbrewing blog by recommending 150g/hl for an IPA of OG 1.060 (30g/20L, 180 billion cells @ 6 billion cells/g) http://www.brewwithfermentis.com/fermentis-recipes/india-pale-ale-recipe/, which coincidentally is 1x106 cells mL-1degree-1 plato.



ALE YEAST
TARGET CELL COUNT IN WORT: 4-6E+06 cells/ml
FERMENTIS YEAST DOSAGE: 50-80g/hl

LAGER YEAST*
TARGET CELL COUNT IN WORT8-12E+06 cells/ml

FERMENTIS YEAST DOSAGE:80-120g/hl

* At 12-15C.

From: http://www.brewwithfermentis.com/tips-tricks/cells-at-pitching/

 

[hellbent]

WOW!! :huh: .....knew I shoulda studied science in my last year at school ....trouble is they didn't do science in the fifth grade :unsure:

 

[verysupple]

I was going to say I think we should be happy settling for the manufacturer's recommendations (10-16g of yeast per 20L batch, see below), however Fermentis go and further confuse things on their craftbrewing blog by recommending 150g/hl for an IPA of OG 1.060 (30g/20L, 180 billion cells @ 6 billion cells/g) http://www.brewwithfermentis.com/fermentis-recipes/india-pale-ale-recipe/,

I don't think that's a confusing concept for most people. All they're saying is that not all styles are best with the same pitching rate. That's not groundbreaking news. Here's a good link that talks about it if you're interested. http://byo.com/stories/item/1717-yeast-pitching-rates-advance-homebrewing

 

[verysupple]

Sorry guys, this topic has already been loosely discussed here: http://aussiehomebrewer.com/topic/67553-dry-yeast-cell-count/, (you do have to wade through a fair bit of anti-Zainasheff-White-pro-liquid yeast propaganda before arriving at any useful information).

I have actually read that thread and nobody seemed to realise that the numbers on the dry yeast packs and spec. sheets are minimum values. ">" and "<" are very important characters, they're not just used for making angry faces in forums and in chat. At least the OP here noticed those extra little characters.

 

[micblair]

Well I dunno, I think if they are going to quote a minimum, they should be prepared to define a range. I think as numerous people have pointed out, that there is quite a big difference between 6 billion and 20 billion cells/g. At least Danstar/Lallemand are slightly more articulate by using the greater than or equal to symbol ' ≥' in there technical sheets.

I think we should get hung up on the semantics here, and take a conservative approach. If there's no range, then we should be prudent homebrewers/scientist and accept the lowest quoted value, i.e. 6 billions cells/g, and not a range that might as well be a whole order of magnitude.

 

[verysupple]

Well I dunno, I think if they are going to quote a minimum, they should be prepared to define a range. I think as numerous people have pointed out, that there is quite a big difference between 6 billion and 20 billion cells/g. At least Danstar/Lallemand are slightly more articulate by using the greater than or equal to symbol ' ≥' in there technical sheets.

I think we should get hung up on the semantics here, and take a conservative approach. If there's no range, then we should be prudent homebrewers/scientist and accept the lowest quoted value, i.e. 6 billions cells/g, and not a range that might as well be a whole order of magnitude.

You could also take the attitude suggested by Danstar and just try different pitching rates and see what gives you the result you want.

A brewer may experiment with pitching rate to achieve a desired beer style or to suit processing conditions.

Note that this approach doesn't actually require you to know the number of cells pitched. You just adjust the weight of dry yeast pitched per volume either up or down.