I haven’t really paid too much attention to the amount of yeast that I have been adding to my beer. Sounds strange, but the commonly available 11.5g sachets of yeast are designed for a 23L batch. Or at least that is what I thought. Up until now, I have just been adding one sachet to every batch. Simples!
However, it turns out that this amount of yeast is only just enough and that there are benefits to increasing the amount of yeast added to the wort. If there isn’t enough yeast cells in the wort, it can overwork the yeast producing off flavours. Increasing the amount of yeast reduces the amount of time required to ferment the beer.
There is a handy calculator here on Brewer’s Friend. This is the one that I have used for my calculations. I am sure that they are others around.
So using this, it looks as if a wort with an SG of 1.040 will require around 20g of Fermentis US-05 in a 23L batch. This isn’t an exact science since the number of yeast cells in a gramme can only be estimated. Looking at their website, Fermentis guarantee that US-05 (and SA-04 for that matter) have a minimum of 6B cells per gramme, but suggest that a more accurate estimate is in the order of 10B. As the calculations show, there is a big difference between 6-10B. I went with the 10B for my calculations.
The manufacturer’s packaging suggests a pitching rate of 50 to 80g per HL. HL is a 100 litres. Therefore, it is about 12.5 to 20g for a 25L batch. Looks like my calculation of 20g is about right.
Brew number 58 is a version of Deanhouse Blonde using 20g of US-05. Starting gravity 1.044. Let’s see what happens.
UPDATE: This brew cleared within 48 hours of being bottled, so the additional yeast hasn’t inadvertently affected the clarity of the beer. I’ll have to wait to see if it has affected the taste.