Yeast Attenuation
About our Attenuation values
The stated attenuation value is dependent on the type of wort brewed and represents an average.
Depending on the fermentability of the wort that is produced, the yeast attenuation values you measure may fall outside this range.
About Attenuation
To many brewers, yeast attenuation is a bit of a mysterious black box. Yeast producers provide wide ranges in their product specs. Even more confusingly, sometimes the yeast in your fermentation performs above or below that range. That is understandably frustrating, and leads to a lot of troubleshooting conversations here at Escarpment Labs!
Key factors in beer attenuation
Mashing is the primary control we have for attenuation because mashing determines the types of sugars we make available for our yeast to ferment.
In the mash, both pH and mash thickness can have a big impact on enzyme activity, and both can impact your fermentability. In general, the amylase enzymes (alpha and beta amylase) are most active around pH of 5.5. To increase fermentability, consider adjusting mash pH closer to 5.5 if you are currently targeting a pH (room temperature measurement) of 5.2 or lower. Thinner mashes also favour higher fermentability due to higher amylase enzyme activity. If you want to make a dryer beer with a lower attenuation yeast, we recommend increasing your mash pH and decreasing your mash thickness.
Info on pH and mashing: Braukaiser
Info on mash thickness and attenuation: Braukaiser
Malting is also important. Some malts are higher in unfermentable melanoidins than others.
Yeast genetics are also critical. Some yeasts ferment some malt sugars poorly and will never be highly attenuative without help. Simply put, some yeasts don't have the required machinery to ferment some malt sugars. On the other hand, some yeasts are diastatic and will ferment nearly all available sugars and dextrins.
Yeast health and fermentation consistency is the final critical factor. Unhealthy yeast is at risk of stalling (incomplete ferment), especially when it is trying to get through the last of the sugar in the wort - maltotriose. Insufficient wort oxygenation is a common cause of stalled ferments. Temperature swings can also impact attenuation since cold temperatures can make yeast flocculate prematurely.
More on Attenuation Ranges
At Escarpment Labs (and most yeast producers), the yeast products come with a stated attenuation range. In general, the range tends to be plus or minus 5% from the average attenuation observed in the average wort. This means that a strain with an average attenuation of 75% in the lab will typically be sold with a stated range of 70-80%. It doesn't mean that this yeast will only attenuate between 70-80%. Mashing and yeast health can influence attenuation below or above this range.
Over the last few years, we have recorded attenuation ranges for every single batch of our yeast in various wort streams. This has helped us understand the typical attenuation ranges of our yeasts better. Periodically we update the attenuation ranges of our strains to reflect the data we are recording.
Additional Resources: