Wild Yeast Pitch Rates

Pitching rates for wild yeast and bacteria are really all over the place.

Brettanomyces species can be used in place of Saccharomyces species for the primary fermentation of wort into beer. Brettanomyces has become a very popular “wild” yeast in certain brewing circles and imparts an interesting aroma and flavor to a wide range of beer styles. When used as the primary yeast strain the flavor contribution is more up front and immediate compared to when Brett is added to beer during aging, where the aroma notes develop slowly over time. If you are looking for numbers, the range in pitching rate varies from about 250,000 cells/mL to over 10 million cells/mL, depending on how the yeast is going to be used.

If you want to use Brett for the first time, I would use it after primary fermentation is complete and add for bottle conditioning. This yeast is a “super-attenuator” and ferments sugars that ale and lager yeast cannot. This means that these beers have the potential to be bottle bombs. Heavy bottles, like champagne bottles, are recommended. Pitch with about 1 million cells per mL to give your beer a good shot of developing the aroma that is expected.

Bacteria, such as Lactobacillus species and Pediococcus species are completely different, for two big reasons. The first thing separating these bugs from yeast is that they are sensitive to hop acids, and in some cases alcohol strength. This means that souring beers that are highly hopped and high in alcohol can be a real challenge. Even moderately hopped beers can give lactic acid bacteria the cold shoulder and will not turn sour. This is really frustrating when you are intentionally trying to do something that many brewers curse when it happens on its own. I have been in that boat!

The other thing about these bacteria that set them apart from yeast is that it does not take many cells to affect change. A few hundred cells/mL in the proper setting can grow into a population large enough to have obvious flavor contributions. In comparison to yeast cell densities, bacterial densities are usually much lower. A lager beer that has been thoroughly spoiled by lactic acid bacteria may have only 5,000 cells/mL of the culprit. The interesting thing about bacteria is that they can grow very well by feeding on amino acids associated with autolyzed yeast cells, especially in anaerobic environments. This means that the bottom of a beer tank is a pretty ideal propagation container for bacteria, and beers often sour when held for prolonged time periods with yeast present.

The take home message here is that the answer to your question depends on what you want to accomplish by adding these sorts of organisms and how quickly you want results. Most beers produced with these types of cultures are not produced overnight and it is very important to be patient.

Response by Ashton Lewis.