Refreshing Old Yeast

[rjthomas21]

So I made a yeast starter about 6 weeks ago in preparation for a beer that I did not get around to brewing until this upcoming weekend. When I realized I wasn't going to be able to brew, I stored the yeast starter in my fridge and it has been there since the middle of April (I decanted it after letting it settle out).

Since I am brewing this weekend, I pulled the yeast out yesterday and made a 1L starter to get the yeast up and running. I'm trying to underpitch the yeast into the Saison I am brewing so I am trying to use the calculations from yeastcalc.com to figure out how much of my new starter to use and how much to put back in the fridge for the next brew.

So my question is, when on yeastcalc.com what do you think I should put in for the viability date? Should I put in the middle of April or yesterday since I pulled the stored yeast out and refreshed it? The 6 weeks makes a pretty large difference in the Viability % (90s to the 60s).

Let me know your thoughts, thanks!

 

[Toga]

Since you "refreshed" it put in yesterday. Keep in mind you just started a starter with a lot more cells than from a vial or smack pack.

 

[rjthomas21]

Thanks. When putting the info into yeastcalc.com, I am treating it as a stepped starter with my first step being the original 1.4L starter done 6 weeks ago and then the second step being yesterday's 1L starter.

That makes me wonder if I should use the date in April as the viability date so that it accounts for some cell death. Yeastcalc shows a Viability % of 68% when I use April as the production date. I imagine that % represents the % of viable cells left in a smack pack/test tube. Would that still be representative of what is alive in my sealed mason jar (after the first starter)? In other words, should I expect that only 68% of my 6 week old starter is viable yeast cells?