At least 10 trillion1 yeast cells are made, do their work and die.
This happens, every single week, in our brewery.
And we are only a very tiny brewery.
They do this, selflessly, so you have beer to drink.
Makes you think it does.
We used to use dried yeast from Fermentis. Good stuff it is too. We still use it when we want a yeast that has a different character. Fermentis yeast does the same thing every time with generally a very good consistent fermentation. There can be a little bit of snobbyness in the brewing community that suggests that a brewer is somewhat inferior for using dried yeast. I disagree, although that isn't really the point I'm trying to get to.
Cost is the main driver. A pack of dried yeast each brew gets expensive. A good clean brewery is as good a yeast production facility as you need for most purposes.
Hardknott now has its own house yeast. However, most of our yeast knowledge has been supplied by BrewLab and conversations with other brewers who are also BrewLab trained. The strong advice is that to ward off bacterial infection, that might ruin that house yeast, regular acid washing2 is required.
Mentioning this on twitter generated an interesting reponse. Many brewers I love and respect, including Eddie Gaedd, Dominic Dirscoll and the lordship himself, John Keeling, are very much against acid washing. As far as I can determine the argument goes along the lines that it does damage yeast and a good brewer shouldn't get bacteria in the yeast anyway.
Other brewers have stated, including my close neighbour and fine chap Ian at Coniston Brewing Co, that acid washing before every single pitching of the yeast is great.
The problem is that if I do get a yeast infection3 it might take a while to find out, as I have no in-house facilities to check for contamination, other than our palates. By the time I know I have a problem I would have to wait a couple of weeks for a new batch of pitchable yeast to be cultivated. I would in the interim have to choose to stop production, or continue and make infected beer. Either that or negate the advantage of the cost saving by regular micro-audits or premature routine recall. The argument goes, if done regularly the yeast get used to acid washing and it saves cost in the long run. The small reduction in viability can be compensated by upping the pitching rate.
I know of larger breweries who might only pitch-on their yeast for as few as 6 generations before ordering a new cultivation as routine. With in house laboratories to check for problems and to re-cultivate this is not a cost issue.
I don't know what makes the most sense. Obviously many, many good brewers make very good beer with many different types of yeast management systems.
I guess the results are in the taste of the beer.
In any event, yeast is great. Go yeasty beasties!
I point out that I am by no means a yeast expert. We bow to any advice or opinions other brewers might have to chip in here.
1generally, a trillion is 1x1012 or 1,000,000,000,000
As Doulas Adams would say, mind bogglingly big. There are about the same number of stars in our galaxy and about the same number of galaxies in the universe.
I'm guessing the number of yeast cells in the world that die every day to make beer is probably the same order of magnitude as the number of stars that exist, give or take an order of magnitude or two.
2No, acid washing is not the introduction of LSD, as one wag suggested. It simply involves reducing the PH of the yeast slurry to 2.1 at a low temperature just prior to pitching the yeast into the wort. This kills 99% of bacteria and nearly no yeast.
It is done by adding controlled amounts of a food grade acid like phosphoric and measuring carefully with a calibrated PH meter as you do.
3In my brewers yeast, before the reader jumps to any lewd conclusions.