Yeast Entry #1: Time for a Revolution Part 1

I like video games.  I used to work in the video game industry, I still play them, and find them very relaxing; especially when enjoying them with a quality beer or mead.  Recently I have found myself indulging on a regular diet of wheat beers and Assassin’s Creed.  I know your asking yourself right now, why is this important, and truthfully it is not, however I figured I would share with you what caused my inspiration for this next entry.  I have been wanting to start a short series on yeast, but I came to the realization that to really talk about yeast, they should be grouped into certain categories and an adequate amount of time should be spent investigating and talking about each different category.  So….while playing Assassin’s Creed III, which for those unaware takes place during the Revolutionary War, I finally became motivated to begin this series, and more importantly had my starting point.

For those living under a rock, the Revolutionary War, in layman’s terms refers to the war that gained America its independence from the British Crown.  Thus, playing this game not only motivated me to start my yeast series, but gave me the group of yeast that I would first discuss, American Ale.

Before I begin discussing American Ale yeast strains, I think it is important to review a couple of key terms and concepts that relate to yeast, so that my rant makes a little bit more sense.

Yeast working hard

Yeast working hard

Flocculation:  When it comes to beer, brewers accept the fact that brewing is a mixture of art and science.  From an artisanal point of view we aim to create flavorful, balanced, and picturesque beers.  From a scientific perspective we attempt to concoct recipes that will deliver flavorful and balanced beers and we attempt to use ingredients that will aide in creating these tasty treats while also allowing them to “look good”.  The brewer’s term known as flocculation is a key concept when it comes to successfully accomplishing these goals.  Simply put, flocculation refers to the yeast cells, clumping together and falling to the bottom of the fermenter and out of suspension.  By falling out of suspension in large clumps, the yeast settles to the bottom of the fermenter leaving behind clear beer that can be siphoned or racked off off the flocculated yeast.  Clearly using a yeast strain that “flocs” well is a key component in having your beer appear clear and appealing.  While it is important to have good flocculation it is also important that your yeast strain’s flocculate properly.  If the yeast flocs out to early than you are in danger of having unfermented sugars remaining in your beer, resulting in an overly sweet beer.  If the yeast does not floc out properly, then the result will be a cloudy, hazy less appealing beverage. Thus, choosing a yeast that flocculates well and at the proper time is imperative.  Most lager yeast strains are classified as medium flocculators, while ale strains run the complete gammet.  As a general rule of thumb, most English strains are considered to have a high flocculation, while American strains tend to be in the medium range.  Most hefe and wheat strains have low flocculation, which is preferred for these beer styles which should appear cloudy and slightly chewy from the residual yeast in suspension.
While it is not truly necessary to understand the chemistry of flocculation, it is important to note, that while yeast plays a major role in a beer’s flavor, there are other major reasons why certain yeast strains are used for brewing.  Many “wild” yeast strains, or strains that are not used for brewing have such poor flocculation that they are almost impossible to use during the brewing process.  Again, a testament to how specialized brewing yeast strains truly are.

Attenuation:  While flocculation deals with a yeast strain’s ability to fall out of suspension, attenuation focuses on a yeast’s ability to eat fermentable sugars and create alcohol.  Put simply, the higher the attenuation, the more capable a specific yeast is at eating more sugars and turning them into alcohol, co2, and other enjoyable flavors.  Attenuation can be effected in multiple ways including, fermentation temp, gravity, yeast viability etc.  Because of the varying factors that can change a yeast strains attenuation from brew to brew, brewer’s generally look at a yeast strains attenuation via a “range”.  For the most part Brewer’s will see that most brewing strains have an attenuation somewhere in the range of 65-85%.

As brewers, having control over the attenuation range of the yeast strain that we are using in a particular beer is paramount.  While it is true that technically any yeast strain could be used for any beer, and still result in a tasty brew, from a stylistic perspective certain beer styles require specific amounts of dryness, or residual sweetness to be consider “true to style”.  Thus, having control over attenuation allows you to make sure your beer turns out true to form.  For example, an American Pale Ale is generally on the drier side of the beer spectrum.   Therefore selecting a yeast with a fairly high attenuation range, such as White Labs California Ale Yeast or their San Diego Super Yeast, will result in a drier beer that meets style specifications.  On the other hand if you were brewing something that needed more residual sweetness such as a brown ale, porter, stout etc, a yeast from the English region such as White Labs Irish Ale Yeast or their London Yeast would do the trick.

Finally while understanding the attenuation range of different yeast strains will help you brew true to style, it is also the only way you can really be completely sure that your beer is done fermenting.  Sure, the airlock, yeast flocculation, and a hydrometer reading can provide educated information that suggests that the fermentation is complete, however a check of apparent attenuation can turn these suggestions to fact.  In order to check apparent attenuation you must take an original gravity reading and a final gravity reading.  Using these two numbers the following formula will allow you to see your attenuation percentage.

[(OG-FG)/(OG-1)] x 100

This formula will provide you with your attenuation percentage which you can then check against the attenuation range of the yeast strain you chose.  If the numbers match up then you can assume that the yeast has done as much work as it can do, and that the beer is fully fermented.  While it may seem that this is an unnecessary step, it does help, especially with high gravity brewing, when the gravity may appear high, but the yeast has actually maxed out.

Regardless of if you check your attenuation, it is important to understand what it means when you are trying to select your yeast.

Optimum Fermentation Temperature:  This concept is fairly self-explanatory, but it is still worth going over.  Every yeast strain, regardless of dry or liquid has an optimal temperature range at which fermentation will occur.  This ideal range varies from yeast strain to yeast strain, and from style to style.  Furthermore, these so-called ranges can vary from a very wide, and therefore forgiving range, to a hyper-sensitive narrow range.  Because of this enormous amount of variety, different strains, and thus different beer styles, tend to ferment better in conditions ideal for that particular style and yeast.

In my opinion the important thing to realize here, is that these ranges are suggestions, albeit good suggestions.  That being said, if a yeast strain’s range tops out at 72 degrees, and you are sitting at 73, the beer will still ferment regardless of the fact that it is just outside the optimum range.  The next question that probably pops into your head is, if the beer ferments fine outside the range, then what is the point?  It is true, the beer will ferment, but yeast is a sensitive living organism, and its environment directly effects its ability to do its primary job, eating sugars, in a timely manner while maintaining the characteristics of that particular yeast strain and prohibiting the growth of any “off-flavors”.

Keeping all this in mind, I offer this advice on optimum temperature range…If you want your beer to contain the flavor profile specific to the yeast you are using, then it is quite imperative that you find a way to ferment in the optimum range.  If you fall outside of the range, the beer will ferment, however, more often than not you will either have off-flavors, or be missing flavors that highlight the profile of that specific yeast; and as we have all come to learn, yeast provides a significant amount of flavor and personality to a beer.

Fortunately for us as brewers, the majority of yeast manufacturers provide us with the optimum range for each yeast.  Better yet, there are so many yeast varieties available that it is almost impossible to find a yeast that won’t be ideal for your specific environment and temperature.

As a brewer the first step to matching your yeast and your brewing conditions, comes with identifying the temperature at which you plan to ferment.  The holy grail of fermentation is temperature control, having either a fermentation room, or fridge that is controlled with a temperature controller and is capable of maintaining a consistent temp.  For those of us not quite that fortunate, (and that is the majority of brewers out there) we must yield to mother nature and deal with the hand, and the temperature, she deals us.  If you fall into this group, I highly suggest tagging each of your fermenters with a liquid crystal thermometer, so that you can get as accurate and consistent of a reading as possible throughout the fermentation.  Based on the temperature you can then select a yeast strain that both matches your temperature and the style of beer you wish to brew.

Alcohol Tolerance:  The final term that is important to understand when trying to identify the proper yeast to use for a specific beer is the idea of alcohol tolerance.  Simply put, alcohol tolerance represents a yeasts capacity to survive, thrive and work in an environment with a certain percentage of alcohol.  Certain strains have a higher resiliency than others making them capable of functioning properly in the presence of high levels of alcohol.  Conversely, many strains top out and lose their functionality once a certain alcohol percentage is hit.  I often hear people say that they will simply, double the amount of yeast they use, or create a yeast starter in order to create a higher ABV beverage.  This is a common mistake made by brewers, and the fact of the matter is, simply adding more of a particular yeast strain does not change the yeast’s ability to ferment sugars into alcohol PAST the tolerance level of that specific yeast.  Each yeast strain is capable of producing a certain amount of alcohol before the yeast cells cease to work.  Adding extra yeast simply adds more yeast cells to the fermenting beverage resulting in a quicker fermentation, but not enhancing the amount of alcohol being made.  In fact when brewing high alcohol beers, it is important to know if the yeast maxed out during fermentation.  If it has “maxed out” then it may be necessary to add more yeast during bottling in order to carbonate your beer.

Based on the ingredients you are using to make your beer, you should be able to get a fairly good estimation of what the final alcohol percentage will be in your beer.  Using this estimated alcohol percentage you can then select a yeast strain that can handle that particular amount of fermentable sugars.  Conversely, if you are set on using a specific yeast strain, you can assess your ingredient list and alter it to make sure the yeast strain will be effective.  Different yeast companies express their yeast strain’s tolerance levels differently.  Wyeast tends to show specific alcohol tolerance’s a yeast can reach ultimately saying that the yeast will successfully ferment a beer “up to” the listed alcohol percentage.  White Labs uses a “low – very high” scale to explain the capabilities of each of their strains.  Strains listed with “low” alcohol tolerance can successful ferment beers between 2-5%.  Those listed as “medium” are ideal for beers between 5-10%, while the “medium-high” category ranges from 8-12%.  Yeast strains designated as “high” range 10-15%, and finally the “very-high” category, works for beers over 15%.  While a yeast designated as “high” will successful ferment out up to 15% as well as any percentage below that, if the beer you are brewing is estimated to reach above 15% you would absolutely need a yeast that has “very high” tolerance.  On a side note it is possible to blend two yeast strains, so that you can get the character of a specific yeast strain, while also getting the fermenting capabilities of another one.  While this does create a completely unique profile, it is another option available to brewers.

While yeast is a major catalyst in brewing, it is also very temperamental.  Having a quality understanding of these terms, and learning how to select the correct yeast based on the beer you want to create, the temperature and environment you have to work with, and the overall alcohol percentage you are trying to create is incredibly important to designing enjoyable, tasty and fully fermented beer.  I will add charts of yeast attenuation, flocculation, tolerance, and optimum fermentation range to the tools and references page on this blog, but again the major point of this entire ramble is to know your yeast before pitching it into your beer.  Understanding your yeast and the conditions that it is being used in can be the difference between good beer and great beer.

This first entry was supposed to focus on American Ale yeast strains, but clearly I got carried away with background information, and to be completely honest I am tired of typing right now.  Thus, the American Ale strains will be covered in the next yeast entry, and for now I am going to grab a beer, and watch this video….Cheers!

Categories: Beer

Leave a Reply