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Yeast Viability


Beerlust

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Hi guys.

 

Over the last 3 or so years I've spent an enormous amount of time dedicated to improving my knowledge of hops (in particular), & to a lesser degree, my knowledge of certain malt grains along the way. One area of brewing I've spent far less time with is yeasts. Don't get me wrong, I've certainly brewed with a fairly decent spectrum of yeasts for a home brewer, but I admit I haven't put anywhere near the amount of time into understanding this area as I have the other two. innocent

 

Over the last 6 months or so, I've centered my brews predominantly around trying to learn more about yeast. I admit, a handful of my brews in this time-frame have not been as successful as I would of hoped, but I'm learning more & more by being more daring in this area of my brewing.

 

(Get to the point Anthony! rolleyes)

 

I recently posted a (hopefully helpful) comment in "Martyn's Fermentis W-34/70" thread. After posting that comment, given my current interest in expanding my knowledge of yeasts, I did a bit of online reading, & also a bit of searching across the Coopers website.

 

I found the following quote from a few years ago by PB2 (whom I respect greatly) regarding yeast viability, & that drew reference to the Mr. Malty Yeast Calculator.

 

...Can you be sure that the calculator is accurate?? Our laboratory tests on dry yeast show that viability of lager strains are generally lower than ale. Yet the calculator assumes the same viability, regardless of the strain

Also, the rate at which viability drops with age is exaggerated.

 

Mind you, it's probably not such a bad thing, if all the errors/assumptions suggest pitching more yeast rather than less.

 

The vast majority of beer, made in Australian homes, starts at 10P (1040) or less. But yes, if fermenting a high gravity brew it's a good idea to pitch at a higher rate, either by simply adding more yeast or stepping up the yeast supplied.

 

As usual it's great advice from PB2. I am personally interested in the quote (I highlighted) about viability difference(s) between ale & lager yeasts. From a completely innocent & novice position, I would really like to understand why this is so in an effort to improve my brewing, & further my understanding of yeast(s).

 

All thoughts welcomed (particularly PB2). cool

 

P.S. In respect to my quoted comments of PB2, & to put them in the context they were originally stated, the full thread can be found HERE.

 

Cheers,

 

Anthony.

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I think the main contributor to this is:

The spray drying process exposes the yeast to higher temperatures (how high and for how long, not sure). Lager strains are more sensitive than ale strains to high temp's and so the viability immediately after drying is lower.

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I don't want to give anyone the impression I'm a geek. OK, I am a geek. But not a knowledgable one. I've been using my time away from the FVs to do a bit of reading, and given that I have done several uni courses in microbiology and biochemistry etc, this paper caught my eye. Actually, I was trying to discover whether it is feasible to dehydrate yeast on a small scale at home, and it is (if you have a zillion dollars).

 

Yet this paper discusses the viability following the dehydration of Fermentis W-34/70 yeast under different conditions. I probably nearly understood between 33% and 50% of it, but the bits I understood were quite interesting.

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Thanks for the replies on this topic, both PB2 & Sir Les. My apologies for the delay in acknowledging your posts.

 

I admit I didn't read the entire paper Sir Les, as it is quite technical & a lot to digest. What I did skim over was quite interesting though.

 

Cheers,

 

Anthony.

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