Culturing Yeast

[spankymac]

I've noticed in several posts that some folks will use the trub from a secondary fermentation to culture yeast for the next batch. I've never done this, but I'm very curious about how it's done. Can the resulting culture be measured precisely so as not to over-pitch when brewing? How's it done? What do you store the cultures in, and where?

[Theakston]

I've never used trub from a secondary fermentation but have often successfully used yeast from the primary fermentation. By the time you hit secondary fermentation most of the yeast will be dead, killed by all the lovely alcohol you have made. The yeast left at that stage is not in great condition.

The only problem with using trub from primary is that there is a lot of it and there are is a lot of other sediment also. Better still to take the fresh stuff off the "head" during the early stage of fermentation when the head is strong and threatening to come out the top of the vessel ( you often need to skim then anyway). This is yeast on steroids.

Keep it in an airtight sterile container in the fridge and it should last up to a month, but sooner is better.

You only need about a quarter cup of the stuff. But you can't really pitch to much -- the advantage of a lot of yeast it it will get a hold really early -- well before any bacteria could get hold of the wort. using trub / foam is a bit like using a "starter" in this way.

I would only recommend this approach for ales. Lager yeast is too finicky.

I would not use too many generations of the same yeast either, although that is what commercial brewers do. Commercial brewers can control how the yeast develops into it's own unique clone. We generally can't control this process and we would get something less like the good yeast we started with and getting worse each time. Use it once, twice maybe then get some new yeast.

[spankymac]

Theakston,

Thanks for the reply. I may give this a try in the next brewing cycle.