The following article was printed in the winter 2003 issue of Craft Beer Quarterly. 

By Chris White
President, White Labs Inc.

  Why use different yeast strains?  Well, why make craft beers? The reason is simple — flavor.

Too often, when the discussion turns to using multiple yeast strains, we worry about performance. What will happen after a few generations, we ask. Questions like this need not be our main concern, however. Most craft breweries have conical fermentors, and don’t use yeast that many times. We should be talking about the flavor impacts, and how the flavors would best match the beer styles being produced. Here are some of the reasons why craft brewers should consider using multiple strains:

— The major brewers in the world do not use multiple yeast strains, but they are making clean lager beer. It makes sense for these large brewers to minimize flavor contributions from yeast. But craft brewers are making flavorful ales, wheat beers, Belgian beers, and strong beers. We want to add flavor and interest to our beers. One of the most effective ways to do this is through the use of multiple yeast strains.

— As the numbers of craft breweries grow, so does the need to differentiate your products. Consumers are more sophisticated, and I think would appreciate a beer with more flavor, or a different character, than they have experienced in the past — one they can only get with your yeast. By combining yeast, you can create a yeast profile that is not only secret, but produces a unique signature flavor.

— Brewers yeast can live happily together. They do not have a competitive nature, or a kill factor as in other strains, including some wine strains.Here are a few questions that have been directed my way regarding multiple yeast strains:

Q: I thought we shouldn’t care about performance?

A: You should not let it stop you from doing this, but you still should know what to expect and how to work with different strains, and that will help to know what to mix.

Q: Do I add the strains in the beginning or staggered?

A: Depends what you want. When yeast is pitched into beer, it starts to grow, entering into a log phase of growth after a few hours. This is when the bulk of the flavor compounds are produced. 12-36 hours into the fermentation. Therefore, if your goal is flavor, you need to add the multiple strains early on, preferably together. Note that if you just want another strain for bottling, or to complete attenuation, go ahead and add later. Very little flavor contribution happens here, unless the beer undergoes prolonged ageing. 

Q Do I need extra oxygen?

A: No, pitch the same total amount you normally would (7-8 million would be best for most ales), and oxygenate the same.  However, each strain has some different optimums, so if you are using a strain you are unfamiliar with, you might want to hedge your bet and add more. 

Q: Won’t it be hard to collect the yeast?

A: Yes and no.  It will be hard to collect the same percentage every time, but we don’t use yeast that much anyway. It won’t change that much over 5 to 10 generations. And if you only go 3 or 4, it is not that much extra of a cost if you get your target results.