Following a discussion opin another thread about dry yeast dating, I contacted a friend at Lallemnd. Here’s his reply. BTW, I asked him for a copy of the chart he mentions and will post it here when I get it.
Best By date is the point where you start to see a reduction in the performance of the yeast. The lab geeks have figured this out so they call it probably way before they should. Treated well……that sachet will still perform for years. Strains are different too……some have a shorter life than others….I have a chert somewhere…I can send to ya.
So when I’m using the software to figure pitch rate I usually put the package date and the yeast variety (I.E. BRY-97) to determine viability and the resulting number of sachets to use. If the best by date for example says March 2023 what would you recommend I use for the package date? Thank you.
Yeast are not automatons. They are living organisms whose behavior is dictated by genetics. No two yeast strains behave exactly the same way when pitched into identical wort. Plus, some yeast strains remain viable longer than others. That is why yeast calculators are one step above worthless. One can use rules of thumb when pitching a new yeast culture, but one is kidding oneself if he/she believes that the precision offered by a yeast calculator is anything more than fiction.