stickyfinger
Well-Known Member
Hi, I am going to repost a thread I started at theelectricbrewery.com, just to get some more feedback. (I'm not sure how many people use the other forum.)...
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.
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.