How to Read a Beer Brewing Yeast Data Sheet

This week I take a look at how to read a yeast data sheet for brewing yeasts and how to better understand the flavors a given yeast might produce.

Yeast Data Sheets

Accurate yeast data can be hard to come by. Some of the better yeast labs publish detailed data on each strain, often collected by brewing a “typical” batch and then measuring specific compounds present in the finished beer. Others publish only the basic data such as recommended temperature range, average attenuation and a short description. A few yeast providers, like White Labs have begun publishing “Spider charts” (like the one here) – much like we see for many hops and malts which gives you a better idea of the typical flavor profile. However virtually every major yeast lab now provides at least their basic yeast bank online so you can easily look up their products and get some idea of what they are offering.

Basic Yeast Data

This is the type of data you can expect to see for the vast majority of yeast providers:

• Name and Product ID: Most yeasts are named for the style of beer they target, for example “California Ale Yeast” or “English Ale”, but they also have a ID number associated them such as WLP002 for White labs, or 1028 for a Wyeast London Ale. This helps narrow things down as some labs provide multiple strains for a single style such as “American Ale II” or “Whitbread II” which have different product numbers.
• Attenuation Range: The range listed is apparent attenuation, and gives you an idea of the percent of sugars fermented. Most brewers yeast will have apparent attenuation in the 68-85% range. Those with low attenuation will give you a higher finishing gravity with more body, maltiness and residual carbohydrates while those with high attenuation will finish cleaner and drier.
• Fermentation Temperature Range: This is the recommended fermentation temperature for this yeast strain. Within this temperature range you will typically get the best yeast performance and best overall flavor. If you ferment too cold, the fermentation may be slow, stall or not finish properly. Fermenting too hot can result in additional esters (fruity flavors) as well as fusel alcohols. Fermenting outside the range can also give you off flavors.
• Flocculation: A measure of how fast the yeast “drops out” of suspension after the fermentation is complete. A highly flocculant yeast will fall out rapidly, leaving your beer clear in just a few days, while a low flocculation yeast can stay in the finished beer for some time.
• Alcohol Tolerance: A measure of the percent of alcohol the yeast can tolerate before it shuts down. Many beer strains are not as tolerant as wine yeast and can only handle lower alcohol levels in the 6-10% range. If you attempt to make a high gravity beer or barley wine with a low to medium alcohol tolerance yeast, you will find that the fermentation often stalls leaving you with a very high finishing gravity and improper balance. So if you are working with a high gravity style, you need to select a yeast that can tolerate higher alcohol.
• Description: These vary tremendously, but the description will typically include something about the source or heritage of the yeast, styles it is used in and something about the flavor and character of the yeast strain.

Advanced Yeast Data

• Diacetyl (Buttery): A buttery popcorn-like flavor common in many English Ale strains. While desirable in English ales, high levels of diacetyl are not desirable in many continental and US beer styles.
• Phenolics (Pentainedione): Present in many Belgian yeast strains, phenolics produce a clove and spicy finish that is distinctive. To some it can take on a smoky flavor and at very high levels result in medicinal and band-aid flavors. Another good example is Bavarian Witbier yeast which has a distinctive clove character from phenolics produced. Pentainedione is loosely related to diacetyl, this compound has more of a honey like flavor that is easily picked up in the finished beer.
• Acetaldehyde (Green Apple): A green apple tasting flavor that is actually an intermediate compound created during fermentation. Most yeast strains will clean it up, but some yeast strains have higher residual levels than others leaving a slight green apple finish to the beer.
• Esters (Fruity, Isoamyl Alcohol, Ethyl Acetate): Sometimes listed separately, but these are all esters. Ethyl acetate is the strongest of common esters with a fruity pear like flavor and aroma. Isoamyl acetate is another form with a flavor more closely aligned with bananas or “circus peanuts” and is a major component in the banana flavor we get from Bavarian Witbier yeast. In extreme, very high levels of esters can give you a solvent flavor like nail polish or turpentine.
• Alcoholic (1-Propanol): These are both measures of higher level fusel alcohols you might associate with hard liquor. Fusel alcohols are produced by many strains if you ferment at a high temperature, though all yeast produce them to some degree.
• Ethanol (Regular Alcohol): This is just the normal alcohol produced by the yeast. So if you see this stat, it is typically the alcohol level of the sample beer produced to collect statistics.
• Hours to 50%: The number of hours for the yeast to ferment 50% of the fermentable sugars.
• STA1 Positive or Negative: This is a fairly new stat, but many labs have started publishing it. The STA1 gene is an indicator of a particular variant of saccharomyces cerevisiae (normal brewing yeast) called diastaticus which is common in wild yeast. Unfortunately the presence of this STA1 gene means that under certain environments the yeast can ferment residual carbohydrates that a normal cerevisae strain would not ferment, and also can do it over an extended period. This can result in instability in the finished beer, extended fermentations and even bottle bombs. So some labs have started genetically testing their strains to identify STA1 positive yeasts.

I hope you enjoyed this week’s article on yeast statistics. Thank you for joining me this week on the BeersSmith blog – please subscribe to the newsletter or listen to my video podcast for more great material on homebrewing.