You might see lots of breweries describing their beers along the lines of ‘fermented with our house culture’ or ‘using our mother culture’. But what does that mean in practice?
What do other people do?
For clean breweries, it’s generally pretty easy. When I (James) worked at a large cask brewery, we used the same strain of beer for all our beers, cropping it from one batch and inoculating the next, simple**. This is cheap, easily manageable and pretty consistent, ideal if you’re a busy, high throughput operation.
For mixed ferm breweries it gets a bit murkier. The idea of maintaining a mixed culture over time is actually trickier than you’d think (without some bugs dominating or disappearing). A couple of common approaches: either grow up the constituent bugs separately and then combine them in the fermenter (as I assume is being described here - but happy to be corrected), or maintain an ever present mother culture in tank that you draw from to inoculate each beer (like our good friends at Pastore)
Then there’s your truly wild or spontaneously fermented beers, where you’re not maintaining a specific culture at all, just praying to the brewing gods that the air will bring in the correct mix of microbes to produce your beers***.
So what do we do?
Our ‘lowland’ culture is a custom home-grown blend of French saison yeast and Brettanomyces, which we occasionally spike with a little mixed culture from a recent aged batch. This blend gives us what I think of as our signature style - dry, refreshing beers with a hint of funk.
Our ‘orchard’ culture is a little more variable. As we have our own orchard up in the hillside, which we use for the majority of our fruit additions, I (romantically!) like this to be the source of bugs too. We use a variety of techniques to collect microbial cultures from the orchard, from mini-coolship overnight camp-outs, to bringing fruit into the brewery and ageing beer on the skins. This culture may be reused from one beer to the next, or we may restart it fresh with a new batch of fruit. Perhaps a more spiritual ‘culture’ than an actually reliably similar collection of bugs :).
What’s used where?
You’ll find our lowland culture in our canned grisettes or petite saisons, along with some of our fresh fruited sours. Our orchard culture needs a lot longer to work its magic, but you’ll find it in our beers aged on fruit, our hedgerow pale and our forthcoming spontaneously fermented beers.
* See also here
** Some cleaning/acid washing/occasional regrowth from lab stocks required :)
*** Often “encouraged” by bits of inoculated wood hanging above your coolship