This past week I was met with an inevitable challenge: I wanted to brew a Northern English Brown, but the only appropriate yeast that I had on hand was old. Its manufacture date in early April left it with an estimated viability of ~10%, according to mrmalty.com. Obviously, I would need to make a starter at the least, and take that starter through a few steps at best.
Not yet having a copy of Yeast by Jamil Z. and Chris W., the best source of information I could find on starter stepping was BillyBroas' well-crafted and informative post and video on the topic. He uses tabulated data from Yeast to calculate what a starter's estimated final cell count will be based on starter size and initial cell count. Unfortunately, the cell counts that he addresses start at 100B, and I had only ~10B on hand. While Mr. Malty is good for estimating total required yeast, I find that it becomes cumbersome with very low initial cell counts.
Thus, I decided to automate BillyBroas' method in an Excel sheet, and add some math (linear interpolation) to accommodate different starter sizes and varying cell counts.
Starter Stepping Caclulator
Please feel free to use it, and give any feedback. Of course, the numbers that it produces are just estimates, and YMMV. The interface is still a bit lacking of polish, but it seems to get the job done.
Citation: data from Data from Chris White and Jamil Zainasheff, Yeast: The Practical Guide to Beer Fermentation. Boulder: Brewers Publications, 2009.
Not yet having a copy of Yeast by Jamil Z. and Chris W., the best source of information I could find on starter stepping was BillyBroas' well-crafted and informative post and video on the topic. He uses tabulated data from Yeast to calculate what a starter's estimated final cell count will be based on starter size and initial cell count. Unfortunately, the cell counts that he addresses start at 100B, and I had only ~10B on hand. While Mr. Malty is good for estimating total required yeast, I find that it becomes cumbersome with very low initial cell counts.
Thus, I decided to automate BillyBroas' method in an Excel sheet, and add some math (linear interpolation) to accommodate different starter sizes and varying cell counts.
Starter Stepping Caclulator
Please feel free to use it, and give any feedback. Of course, the numbers that it produces are just estimates, and YMMV. The interface is still a bit lacking of polish, but it seems to get the job done.
Citation: data from Data from Chris White and Jamil Zainasheff, Yeast: The Practical Guide to Beer Fermentation. Boulder: Brewers Publications, 2009.