Understanding a Beer Yeast Data Sheet

This week I take a look at the key components of a brewing yeast data sheet and how to apply them when brewing beer.

Yeast Data Sheets

With the explosion of information available to home brewers, many yeast labs are now providing detailed data on the performance of their yeast strains. Virtually all yeast labs provide the basic data on their yeast strains, but I will also cover more advanced data you can often find from many labs with a bit more digging.

Basic Yeast Data

Here’s a summary of the basic yeast parameters that virtually all labs provide:

• Attenuation – Typically listed as apparent attenuation, this parameter provides the percent of the sugars or gravity points you can expect to ferment into alcohol. High attenuation yeasts will generally ferment more sugars leaving a drier, less malty finish.
• Temperature Range – This is the recommended temperature range for fermentation. Fermenting within this range will result in the best performance in terms of fermentation and also flavor. Fermenting too hot can result in off flavors including esters and fusel alcohols, while fermenting too cold can result in poor yeast performance.
• Flocculation – A measure of how quickly the yeast drops out of solution after completing fermentation. High flocculation yeasts generally will mature and drop out more quickly while low flocculation yeasts can require an extended maturation period.
• Alcohol Tolerance – A measure of how much alcohol by volume the yeast can tolerate. Many beer yeasts have low alcohol tolerance in the 5-10% range that make them unsuitable for very high gravity beers, so you need to pay attention to this parameter if brewing a high gravity beverage.

Advanced Yeast Data

While this data can be more difficult to find, many of the top labs have it available if you ask. Typically this data is collected by brewing an in-style beer and measuring yeast performance and byproducts from the fermentation.

• Isoamyl Alcohol/Acetate – A commonly produced ester in beer which has a flavor like pear blossoms or bananas in small quantities. This is an indicator of overall ester profile for the yeast.
• Acetaldehyde – An intermediate compound produced during fermentation with a flavor and aroma of green apples.
• Ethyl Acetate – A strong common ester in beer which will have a fruity flavor in small quantities but can take on a solvent flavor at higher levels.
• 2.3 Pentainedione – A Vicinel Diketone (VDK like diactyl) which gives a honey like flavor but has a lower flavor threshold. Can be reduced by using a diacetyl rest.
• Diacetyl – Another VDK that has a buttery/popcorn flavor in the finished beer. Can be reduced by using a diacetyl rest.
• 1-Propanol – A higher order fusel alcohol that gives off a strong alcoholic odor or solvent like flavor (like moonshine).
• Ethanol – Simply the alcohol by volume for the test batch
• Hours to 50% – a measure of the time it takes to reach 50% completion in the fermentation. A measure of how quickly the yeast ferments out.

Comparing Yeasts

The above data can be used to compare yeast strain performance. This includes simple comparison of parameters like attenuation and more advanced comparisons such as selecting yeasts based on ester profiles. In my advanced Designing Beer course we walk through several of these comparisons to help students understand the significant differences between similar yeast strains. If you do this analysis ahead of time, you can make more intelligent yeast strain selections before you brew.

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