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Wyeast - refrigerate ASAP

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How are you checking yeast health?  From what I've read, the methylene blue stain is not accurate below 95% viability.


--- Quote from: narvin on December 30, 2012, 03:26:18 AM ---How are you checking yeast health?  From what I've read, the methylene blue stain is not accurate below 95% viability.

--- End quote ---
I've read that too.  It is "not accurate" to some level.  Even the American Society of Brewing Chemists calls it not accurate.

If by "not accurate" you mean that it is not exact then I agree.  There is some error, but that error can be determined so that the accuracy is known.

It is very dependent on the strain and how much Methythele Blue that is used.  WLP004 and WLP566 stain just fine with 0.03% MB, but EC-1118, and WLP650 are better with 0.06% and 0.1% respectively.  It's also very dependent on the operator.  MB staining is very difficult to use on some strains, and there doesn't seem to be one concentration that works for every strain.  If you use too much it will actually start to kill some of the weaker yeast cells.  The method isn't perfect, but it has it's place.

I have a blog post on this coming up. 

Update:  The starter, after a couple of days, still looks fairly anemic.  It started to settle out overnight, so I put it in fridge when I got up.  Since I had planned today to be a brew day, I'm just going to go ahead with the plan.  I will decant the starter and just pitch it.  We'll see what happens.  It will be a good learning experience nonetheless.

The lag phase can be pretty long, especially if the yeast has come out of stressful conditions.  You aren't going to see much activity until the exponential growth phase.  Here is some observations I recorded recently when propagating some low viability yeast directly following a fermentation.  It took about 12 hours to start, but 2 days would not be uncommon.

Your plan to stay the course sounds good.  You will want to aerate well.  Pouring the wort between two buckets or a kettle until the foam is threatening to come out of the bucket will ensure that you are at the saturation point of O2.  That will yield 8-9 ppm of O2 which should be plenty unless your OG is above about 1.050

Very pleased with the way things worked out.  After pitching the starter on Sunday, nothing was happening for the first 24 hours or so.  Then I checked and it had really taken off.  A beautiful krausen has developed, and the activity is what I would expect.  Looks like things are on track.


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