Blending Brewing Yeast Strains in Beer

This week I take a look at yeast blends and how you can blend yeast to achieve a unique flavor profile in your finished beer.

Why Blend Yeast?

In the last few years, hop blends have become very popular with home and professional brewers. By blending your hops you can not only get unique flavors and aroma but you can also insulate yourself somewhat from season to season variations in hop quality.

But what about yeast? Can I blend two yeast strains to create something new and unique? What happens to the flavor and other characteristics when I blend more than one yeast strain?

I discussed this in a recent podcast with White Labs founder Dr Chris White. Chris has not only done a lot of work with yeast blends but he sells a number of blended yeasts as separate products for use in beer. In fact Chris recently re-launched his “FrankenYeast” blend which is basically a blend of the 96 major yeast strains that White labs makes.

What Happens When you Blend Yeast Strains?

Here are some rules of thumb for blending yeast:

• Attenuation: The yeast strain with the highest attenuation will dominate the blend, so if you mix a low attenuating English yeast with a high attenuation California Ale yeast you will finish with a high attenuation and gravity consistent with the California strain. So basically you can take the highest yeast attenuation in the blend and assume that will be the result.
• Phenolics Dominate: If you mix a phenolic yeast (like a Belgian yeast) with a non-phenolic yeast, the finished beer will still have phenolics in it. Therefore the phenolic flavor is dominant and won’t necessarily blend like you might expect.
• Sour Yeast/Bacteria Dominate: If you add a bacteria (bug) like Lactobacillus or Pediococcus, not surprisingly it will dominate and sour your beer even if added in small quantities. Similarly if you add a sour positive yeast like a wild yeast, it too will dominate and produce a sour finish in the beer.
• Kveik Yeasts Dominate: I’ve been told that Kveik yeasts can be aggressive and can often dominate a mix with other yeast. I suspect this is due to fact that these yeasts complete fermentation very fast and can operate at high temperature.
• Alcohol Tolerance: If you are working with very high gravity wort or wine/mead must, alcohol tolerance does come into play. However it generally is a large factor only near the end of fermentation when the limit is reached on one or more strains. So for the bulk of the fermentation, all of the yeasts in the blend will be active. Lower alcohol tolerant yeasts will tend to shut down near the end of fermentation as each of their limits is reached, but typically the highest alcohol tolerant strain will continue to act until their limit is reached.
• Temperature: The yeast temperature range is still a factor if we want to blend something like an ale and lager yeast. If we ferment the blend at ale temperatures, for instance, we can expect the lager yeast will throw off some esters and fusel alcohols as well as possibly other off flavors if it is fermented warm.
• Other Flavors Average: Other compounds like esters, alcoholic, diacetyl, sour/acidic, sulfur and yeasty flavors will tend to average out for the blend. For example an estery English yeast mixed with a neutral California Ale yeast in equal proportions will create a beer that has some esters in it but not as much as you would get using the English yeast alone. So, in general, the flavors tend to average out to be approximately the weighted average for each yeast used.

Reading Yeast Data Sheets

How can you better define the results of the finished blend? Many of the better yeast labs publish detailed yeast data on their strains. Ideally the following data should be listed for your yeast:

• Alcohol Tolerance: Shows the maximum alcohol percentage the yeast can tolerate before shutting down.
• Attenuation: The average apparent attenuation (percent of sugars consumed) before fermentation completes
• Temperature: The temperature range where the yeast performs best
• Isoamyl Alcohol/Acetate: The primary ester in beer, and a measure of ester production for the beer.
• Acetaldehyde: A green apple tasting flavor produced during fermentation
• Ethyl Acetate: The strongest of the common esters with flavors like fruits, pears and even solvent if the level is too high
• Pentainedione – A VDK like diacetyl which gives a honey like flavor but is easily detectible in the beer.
• Diacetyl: A buttery popcorn like flavor common in many English ale strains
• 1 Propanol – A fusel alchol that gives off alcoholic odor and a strong solvent like flavor
• Ethanol – Another name for alcohol
• Hours to 50% – The number of hours required to reach 50% completion in the fermentation

So if you are flying blind or using new yeast strains, and can find the detailed yeast data listed above you can get a very good idea of how two yeasts might blend by averaging the values above (with the exception of Alcohol Tolerance, Attenuation and Temperature).

I hope you enjoyed this weeks article on blending yeasts. Thanks for joining me on the BeerSmith Home Brewing Blog. Be sure to sign up for my newsletter or my podcast (also on itunes…and youtube…and streaming radio station) for more great tips on homebrewing.