One of my biggest surprises as a homebrew beginner was learning just how much influence yeast exerts on the flavor and aroma of beer. Malt, hops, and water are clearly products of the land, but yeast is just a microbe. But, as so often happens, big things come in small packages, and it turns out that often yeast is the defining feature of a brewery’s signature beer.
While commercial yeast labs such as Wyeast, White Labs, GigaYeast, East Coast Yeast, and The Yeast Bay offer more microorganisms than you can shake a stick at, certain strains simply aren’t available commercially. That’s why some homebrewers get a kick out of building up a yeast population from the dregs at the bottom of a bottle-conditioned commercial beer.
Unpasteurized, bottle-conditioned commercial beers may or may not contain the primary yeast strain used for fermentation. Many examples are filtered or centrifuged before packaging and then re-dosed with a neutral ale, lager, or wine strain for packaging. This helps ensure consistent carbonation and can protect a brewery’s proprietary culture. Other brewers, however, are content to ship beer that includes a full complement of their own brewing microbes.
A few breweries whose lineups feature one or more products with harvestable yeast strains, bugs, and blends include
- The Alchemist (Heady Topper): Conan yeast strain
- Bell’s Brewery: House yeast strain
- Brasserie d’Orval: House yeast strain and Brettanomyces
- Brasserie Cantillon: House lambic and gueuze bug blends
- Crooked Stave Artisan Beer Project: Various house “CMY” yeast strains, including numerous Brettanomyces variants, plus bacteria in varying amounts
- Rogue Ales: Pacman yeast (also occasionally available as Wyeast 1764)
- Russian River Brewing: Various blends of house yeast strains, Brettanomyces, and bacteria
If you want to build up a culture from the dregs of one of these beers, simply drink one or more bottles of the beer and pour the last bit of sediment into a small amount (3.5–7 oz/100–200 ml is plenty) of cool wort, just as you would with any other starter. Let the yeast ferment out, then pitch this into a larger quantity of wort (17 oz/500 ml, say), and repeat the process with increasingly larger volumes until you’ve built up a nice colony.
This incremental starter method works best for “normal” ale and lager yeast strains. To use _Brett, _bacteria, and blend, it’s better to simply dump the dregs from a few bottles into beer that you’ve already fermented and are ready to sour. Building numerous starters of these microorganisms can throw off the relative proportions of these finicky microbes, and only a small amount is needed anyway.