4/7/2024 0 Comments Beersmith 2 vs 3To generalize the above graph, we need to use it with larger or smaller starters and batch sizes. ![]() The above graph is great if you always pitch a 100 billion cell starter and are always brewing a 5.25 gallon batch, but often this is not the case. This means that in most cases, you will not achieve a growth rate above 3.0 for your starter unless you use a multi-stage starter. Since you don’t want your starter to be so huge it is a major fraction of your beer, the practical range most home brewers operate in is really on the left end of this graph – typically 1-4 liters for a five gallon batch. However, if we factor in viability (the aging of the yeast which was also covered in part 1), a larger starter of 2-3 liters is needed, since we won’t be starting with a fully viable 100 billion cell yeast package. So using the graph at the right, a 100 billion cell packet pitched into a starter of just over a liter would be sufficient for this beer. A sample 5.25 gallon ale at 1.048 gravity needed about 177 billion yeast cells. In part 1, I covered how to calculate the ideal number of cells needed for an average batch of beer. However, a 20 liter starter is essentially no starter at all if your batch of beer is only 20 liters. What this shows is that 100 billion cells pitched into a 2 liter starter will only grow to a bit over 200 billion cells (growth rate of 2.05), while the same 100 billion cells in a 20 liter (5+ gallon) starter will grow to about 600 billion cells (growth rate of 6.0). This is extracted from “Yeast, A Practical Guide” by Chris White and Jamil Zainasheff. In fact if we pitch a typical liquid yeast package (vial or large smack pack) of 100 billion cells into starters of varying size we get the graph to the right. ![]() The growth rate of the yeast (number of ending cells divided by the number of starting cells) varies depending on the pitching rate of the yeast. I ended part 1 on yeast starters explaining that all liquid starters are not created equally. This week, I’ll finish the detailed calculations for liquid yeast as well as provide a summary on how to do the entire end-to-end calculation. In part 1 of this in-depth series on yeast, I covered how you can calculate the required pitching rate (number of yeast cells needed) for a given batch of beer, understanding the viability of yeast over time, and also how to hydrate and use dry yeast. Follow week, I take a look at how to calculate the appropriate starter size for home brewing beer with liquid yeast.
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