Getting Yeast From the Bottle

Many, if not most, of the distinctive beers brewed in Belgium owe a great part of their uniqueness to yeast strain. Homebrewers can capture some of these characteristics by culturing yeast from bottles of Belgian beers containing yeast. One of the most important steps of this process is finding fresh samples of the beer from which you wish to grow the yeast. You do not need a six-pack of beer to do this.

I rely heavily on sensory evaluation to assess the freshness of imports. Bottle-conditioned beers should have little autolyzed yeast character. If the beer smells like old, decaying yeast fetched from the bottom of some forgotten carboy, chances are the yeast has begun to die and decay. Although there are probably some living yeast cells in the bottom of the bottle, it is also likely that some bacteria are mixed in with the yeast and may be increasing in population due to the nutrient-rich goo leaking from the decaying yeast.

Yeast from the bottom of bottles can be propagated by simply decanting the beer from the yeast in the bottom and adding fresh, aerated wort and an airlock to the bottle and letting the yeast grow. If the bottle is old, this simple process may also propagate bacteria. The ensuing mixture of yeast and bacteria will not work for brewing Belgian ales, even if the style (such as a lambic) ordinarily relies on bacteria for some part of its flavor profile.

Belgian brands such as Chimay and Orval are fermented with yeast and have no bacterial phase. Such beers require a clean yeast for pitching. Very good homebrews can be made if fresh bottles of these beers are available in your local market. Assuming you can get fresh samples, begin by carefully pouring the beer off of the yeast sediment. This step is important because Belgian beers are a bit pricey and it’s a shame to let excellent beer go to waste.

Next, swirl the sediment on the bottom of the bottle and transfer it to a clean bottle containing about three ounces of boiled, cooled, normal-gravity (about 1.048), hopped wort. It is important for yeast to have air available during propagation. A cotton ball sprayed with rubbing alcohol serves as a good stuffing for the bottle during propagation as it allows air into the bottle while trapping microbes from the air that may find their way into your propagator. The bottle should be placed in a warm (70° to 75° F), clean environment to get the yeast started.

If the yeast is reasonably fresh, you should see signs of fermentation in two to three days. Once the fermentation kicks in, transfer the contents of the bottle to a large container with about a quart of wort. This should be a large enough starter to pitch a five-gallon batch.

Some brewers will add the entire starter. Others will allow the yeast to settle, discard some of the excess beer above the yeast, and use the yeast sediment as their yeast for pitching. Both methods work, but I prefer the latter method because it doesn’t dilute the wort from the batch of beer you are brewing as much as the first method.

I always taste the beer from my propagation before deciding to brew because the propagation may taste off due to contamination. This is true of any yeast propagation, whether from a lab culture or a bottle. Only decide to brew if you are satisfied with your yeast starter. There are much better ways to grow yeast from a bottle than the method I have outlined, but these methods require access to microbiological plating methods used to isolate a pure colony of yeast. Although these methods can be used at home, most homebrewers choose simpler techniques.

An alternative to culturing yeast from the bottle of Belgian ale is to simply buy a Belgian ale yeast from a yeast supply lab. Most yeast labs, especially those specializing in liquid yeast, stock more than one Belgian ale strain. Since yeast labs are typically operated by brewers, their staff can usually assist in selecting a strain to fit the style.

I like a good challenge and enjoy working with yeast. However, if you simply want to brew a good Belgian ale and don’t want to worry about growing yeast from a bottle, check with your local homebrew supply store or a liquid yeast supply company for their selection of Belgian yeast strains.

 

 

Response by Ashton Lewis.