THE ACTUAL TRUTH ABOUT YEAST: The Brett Episode; with Kevin Lane of Fermentis

Here is the next episode in the yeast series.  This one is long but awesome.  Espcecially if you are a sour or wild beer brewer.   Kevin has so much good information to share.  I know this one is long, but if you are serious about making Brett sour beers, it is a must read.  Fermentis

Sour beer brewing is less challenging than you may imagine, but takes far more cleaning, sanitizing, and planning than you could ever concieve.  If you are a new brewer, this probably isn't for you.  If you are more experienced, well then give these articles a read.  Sour brewing is rewarding, and you can make world class beer at home.  Much of this information is covered in our other posts on the subject.  Episode 1, Episode 2, Episode 3, Episode 4

What is Brettanomyces?

Brettanomyces isn't just another kind of Saccharomyces.  It is an entirely
different species of yeast.  Full size available ath the end of the post.

Brettanomyces (Brett for short) is another genus of yeast, not just a species difference like ale (Saccharomyces cerevisiae) and lager (Saccharomyces pastorianus). The genus itself is considered to be a wild yeast strain, but all yeasts were at one point in time wild; brewers from a couple of centuries ago thought fermentation was magical (sometimes I still think it is). Brettanomyces species have been cultured and are now produced in “pure” culture for use in brewing and other applications. Brettanomyces species are very different from Saccharomyces species, however one of the major differences is in sporification. The literal translation of Brettanomyces is actually “British fungus”. One of my favorite things about Brettanomyces is that people describe some of the flavor impact as “horse blanket” which refers to an interesting flavor component… the reason that people are taken back the first time they experience Brett beers.

What makes it different from ale or lager yeast?

There is a lot that makes Brett different from ale and lager yeast: the genus and species for one, the potential flavor compound production, the fermentation activities and the formation of a pellicle, just to list a few. What is important to know is that it is a very different organism and does not ferment the way that brewers are accustomed to, with ale and lagers. Brett have the ability to ferment out most of the carbohydrates that traditional brewer’s yeast leave behind; some even have the ability to ferment larger carbohydrates beyond tri-saccharides, like maltotriose. Another key to understanding and using Brett is that the flavor impact is greatly influenced by the time of use and stress factors.

Are there different kinds of Brettanomyces?

There certainly are different kinds of Brett. It is a completely different genus. Some Brett have been isolated from different regions of the world and some have been isolated from different industries: beer, wine and other industries (we won’t go into this). For both beer and wine, Brett is viewed, for the most part, as an infection. Some beer styles need Brett for the beer to fit into that style category (Lambic and gueuze come to mind) and can actually improve the flavor slightly in wines (research the impact on red wine production, if you are interested). The most common strains of Brettanomyces are anomalus, bruxellensis, claussenii, custersianus, naardenensis, and nanus. Each species will present different characteristics and flavor impact on the beer (or wine) and will have a different preferential fermentation environment (think S. cerevisiae vs. S. pastorianus).

What are the flavors produced by Brett yeast?  

There are many flavors that are produced by Brett, some that are the same/similar to Saccharomyces and others that are unique to the Brettanomyces genus. I have been fortunate enough to use Brett in both primary fermentation and as a secondary fermentation and the flavors produced are extremely different in each. The major sensory compounds associate with Brett fermentation, weather primary or secondary, would be 4-ethylphenol (horse blanket component mentioned earlier), 4-ethylfuaiacol (4-EG, similar to 4-VG phenolics) and isovaleric acid (smells like old, aged cheese).

Why is Brett called wild?

Brett is called “wild” because of the impact on beer that was primarily fermented with Saccharomyces and Brettanomyces ability to survive and ferment carbohydrates that are usually remaining after the Saccharomyces has finished. Again, I have to remind everyone that cerevisiae and pastorianus were once wild yeast but are now isolated and produced so they are more pure strains, however humans are doing this with Brett, so I can’t use that to explain why it is called wild.
Another reason for Brett being called wild, is due to the flavor implications. Beers that contain Brett won’t necessarily have a “horse blanket” or “aged cheese” flavor, but it is possible to detect those flavors if the Brett has been stressed. Actually, all Brett beers (meaning primary fermentation done without Saccharomyces) have a very nice, fruity character, similar but not the same as Saccharomyces beers. Of course, there is still some background notes of the “off flavors” produced by Brett, but the beers could be mistaken for Saccharomyces beers, by the untrained pallet. Getting back to the question, I think another reason for Brett being called “wild” is because they are present in the air and on the skins of fruit. Again, I have to go back to the fact that this is how humans started pure Saccharomyces cultures, but there is less commercialized Brett today (not to say that it will always be this way). Traditional lambic producers will use “coolships” (koelschips) for cultivating natural yeast and bacteria that are in the air during certain times of the year and with certain weather/environmental conditions. This allows any natural, or “wild”, yeast and bacteria to land in and grow in the cooling wort. If you ever have the chance to see one (there are a few in the US), it really is a sight to see!

Does temperature of fermentation impact Brett fermentation like it does ales and lagers?

Yes, temperature definitely affects the Brett. It is always important to know that any microorganism that is used in beer, wine, or any other “fermentation” such as bread making or cheese making will be susceptible to the environmental conditions such as temperature. Generally, Brett will have similar reactions to temperature as our friends, Saccharomyces.

So will Brett perform well at lower temperatures?

Brett will ferment at lower temperatures. Just how low… that is dependent on the species and strain (again, think ales and lagers). Depending on the species and strain, Brett will produce a cleaner flavored beer at lower temperatures, generally speaking.

So it will ferment, but it won’t put off some of the same flavors?

Exactly! Many flavors produced are environmentally influenced. An easy way to understand this is by comparing to ale or lager yeast (I seem to be saying this a lot, but for those who haven’t made Brett beers, it is an easy comparison to understand). If you are making an ale and you split the wort into two fermenters and ferment one at room temperature and ferment the other in a car, in direct sunlight in the South (like here in TX, in the summer), the resulting beer will be two completely different flavors. All other things the same, by only changing one environmental condition (ex. temperature, pitch rate, fermenter size/dimensions, ect) you will change the beer. This is the primary reason for having temperature control on fermentations. If you don’t have temperature control, your beer will be different every single time, with all  other things identical.

So, Brett produces esters, just different esters than lager or ale yeast?

Brett produces esters: some are the same as lager or ale yeast, but others are very different. Here, I will change the comparison. If you use two different varieties of hops in the same recipe, all other things the same, are you expecting the exact same beer? Answer is “no”. OK, this is different because hops aren’t living organisms in beer, but I hope that you can make the connection. As for the ester production, the rate at which and to some extent the esters produced are dependent on the stresses. Temperature is definitely a stress inducing condition as well as many others.

The reason I use hops as an example is because you usually aren’t looking for the same flavor profile as a Saccharomyces fermentation, when you use Brett. I mentioned some of the flavors above in a different answer, but Brett are able to produce compounds that Saccharomyces aren’t able to produce. This includes esters, phenols, organic acids released and a number of other compounds.

So stress and temperature have an impact, but what about pitch rate?

Pitch rate is an interesting topic. As explained earlier, the coolship method of cooling/inoculating wort was the primary way to get Brett into beer. Once modern laboratory practices were introduced, labs began collecting strains and keeping pure cultures. Another way that Brett is introduced into beer is by using oak barrels, which will harbor different yeast and bacteria, depending on the liquid that was kept in them. So, for both the coolship and barrel inoculation, the pitch rate isnot known.

For the use of modern, pure culture inoculation, the brewer is able to pitch at the rate that they want. Of course, just like with traditional Saccharomyces cultures, the pitch rate will affect the compound development during fermentation (both primary and secondary). General guidelines are that if you pitch low, there will be more stress and you will get a wider variety of yeast flavors.

Brett has a reputation for being a very aggressive fermenter, what is meant by that?

The aggressive nature of Brett fermentation can be described a couple of ways. As stated before, Brett can ferment “more completely”, meaning the sugars left behind by Saccharomyces in the same wort. Additionally, Brett forms the pellicle on top of the beer which limits the beer contact with oxygen and keeps the fermentation completely anaerobic. The pellicle will also keep other organisms from entering in a non-sealed container, like an oak barrel (for those who don’t know, oak barrels breathe, think the angels cut in whiskey production). A third way that Brett is aggressive is the speed of multiplication and culturing in either aerobic or anaerobic (the anaerobic cell multiplying is much more aggressive than that of Saccharomyces).

So Brett will attenuate a beer lower than normal ale and lager yeast?

Correct! This is what I mean when I say that Brett will ferment the sugars (carbohydrates) remaining after the Saccharomyces fermentation. Simply speaking, the more sugar that is fermented, the higher the attenuation.

Are there risks involved in using Brettanomyces?

There are huge risks involved in using Brett. When I was brewing professionally, I had three main enemies: lacto, pedio and Brett. If you ever visit production breweries using these organisms and they have a separate room or even building for their barrel aging, this is one of the major reasons why. When you introduce one of these organisms into the brewery (or your homebrewing system), it is very hard to get rid of completely. Once it is in your system, you have to do everything you can to get it out. Lacto, pedio and Brett like to be “that guy” who doesn’t get the point when you try to get rid of him.

Even with strict cleaning procedures, harsh sanitizing procedures and attention paid to all of your equipment, those organisms can hide in soft parts, like gaskets, buckets, cracks, scratches and any other surface or impurity in your system that is difficult to clean. The biggest problem with those organisms is that they will show their ugly/pretty face (depending on your opinion) until you get rid of them completely. They show because, like mentioned before, they ferment things that Saccharomyces do not. So, when you brew your next batch and use a cerevisiae, the cerevisiae finishes the sugar fermentation that it can and then the “wild” organisms finish what’s left.

So what special steps does a home brewer need to take when using Brett?

To be honest (and what I do) is keep it separate. I have a separate fermentation area with separate fermenters. I have a separate bottling bucket and a separate syphon. I KEEP IT SEPARATE. It is the easiest and best way to control those “infections” at home. It costs a little bit more to have separate equipment, but I am confident that I can still produce a clean, uninfected Saccharomyces beer and not have a Brett or lacto or pedio infection!

So guys, as we discussed in our Funkadelic mastery series, you really have to have separate gear if you are using any of the wild yeasts.   

Are there any special considerations when packaging or bottling a Brett Beer?  

First of all, know that there is the possibility of a pellicle, so if you syphon or when you are transferring, you may move some of that crusty, grey, mold-like cap to a different container. Know that if you don’t filter (I don’t and most homebrewers don’t) that the Brett will still be in the beer and will continue to develop flavors. Know that Brett can ferment more carbohydrates than Saccharomyces, so if you use speise (wort made for priming)  or extract or anything of the like, typical calculators will not work. You will need less of any of those than with traditional bottling.

Is wort composition is important?

Wort composition is always important. I think I have said it in previous Q & A’s, but the brewers main jobs are cleaning, sanitizing and preparing the environment for the yeast to be successful in the way that the brewer wants. Your entire job as a brewer is to make the environment that is perfect for the yeast, for the beer that you want. That being said, you have to figure out what you are looking for from the yeast and then brew to produce that environment.

Are mash temperatures then also important?  

Always, always, always important. If you mash in at 212dF you will only have the carbohydrates available that are in whole kernel malt. If you mash in at 173dF you will only have the carbohydrates available in whole kernel malt. If you mash at 100dF or 120dF or 151dF or any temperature below 172dF, you will have enzymatic activity from the natural enzymes present in malt (if the malts have diastatic power). I suppose that you could produce a beer by adding enzymes to the wort after that, but most homebrewers don’t have any glucoamylase at home…

We've heard that Brett can have weird reactions with Polyphenols and with Ferulic Acids, can you elaborate on this?

Polyphenols are the precursors for the volatile phenols that Brett produce to make the “Brett” odor. If the wort is lacking the right polyphenols, the Brett cannot change the composition and create those great/horrible odors (again, depends on how you look at it). The Ferulic Acid story is a little different. Brett doesn’t use the Ferulic acid directly to create its fantastic/disgusting (your opinion) flavors. Rather, Brett takes the 4-VG that Saccharomyces produces from Ferulic acid and converts it to 4-EG, one of the, simply put, Brett characters: horse-blanket. 

What general advice would you give new and intermediate brewers about brewing an a Brett Beer?

Buy fire proof equipment, so that when you are done with your Brett beer, you can pour gasoline over everything and start it on fire!!!  I am just kidding… I don’t even know if that would get rid of all of the Brett!!!

Ok, jokes aside:

(Kevin was joking, but many home brewers who brew Brett or other wild beers, myself included; use an entirely different set up, and minimize soft parts as much as possible.  As little tubing as possible, as few rubber gaskets as possible.  You have to look at your whole system. We have an auto syphon for clean beer, for brett, and for lactobascilus.  We have separate tubing for separate wild fermentations.   It never, ever ever gets used for anything but wild beers, and is stored in a different part of the basement.   The number one most important thing you can do is never touch any of your wild gear while you are brewing clean beers, and wash and sanitize your hands a lot, Star San does not kill yeast, keep a 10/1 bleach to water spray bottle handy if you brew sours!)

I think the best advice I could give would be to be very thorough with everything involved. There is a reason that most (possibly all) homebrewers don’t start with making Brett beers (at least on purpose!). Generally, brewers can clean and sanitize well enough to get rid of the Brett, but if you can’t you could end up having some “funky” beers or bottles exploding due to over carbonation. Using Brett in your brewery is similar to trying anything new. You have to understand it, apply your understnading, and then experiment with it. Some people do not like the flavors/aromas, others love that character. Some people like super hoppy beer and others hate it. It always comes down to what you want and the best explanation of homebrewing: you do what you want. Brett is slightly different because it could have a lasting impression on other beers, but still, just do what you want in your homebrewing and have fun doing it!


Additional Resources for sour beer
Themadfermentationist.com - Michael Tonsmeier's amazing site about sour beer.
Milk the Funk 
Sourbeerblog.com - really gets into the science of sour beers. great starting place.

THE ACTUAL TRUTH ABOUT YEAST: Volume 3: Lager yeast, with Kevin Lane of Fermentis.

the world's most popular lager
yeast. Good ol' 34/70

Part 3 in our on going series about the little bugs we all love.  This time we are focused on lager yeast with Kevin Lane of Fermentis.  And this one is great.   In our next installment we will be talking all about sours.... yum!

What is lager yeast?  

Lager yeast is a yeast that is generally used for producing cool fermentations (to be discussed later).  It is often referred to as a bottom fermenting yeast, due to the fact that it ferments from the bottom of the tank rather than the top, as ale yeast does.  Lager beer is also, typically, stored cold (lagered) for a period of time before being packaged/sold to the consumer or consumed. 

The species itself, Saccharomyces pastorianus, is believed to be a descendent/hybrid of Saccharomyces eubayanus.  Lager yeast has been named multiple names in the past, most recentlySaccharomyces carlsbergenesis, after the Carlsberg brewery, but is now defunct nomenclature.   

What makes it different from ale yeast?

The easiest way to explain the difference (which isn’t easy at all) is that it is genetically different.  So much so, that it is categorized as a different species of yeast Saccharomyces pastorianus. The brewer typically doesn’t think about that when brewing, but that is the real difference.  The genetic difference influences the brewer to use lager yeast in cooler fermentations and for certain styles of beer, where you are looking (generally) for less flavor impact coming from the yeast.  Lager yeast strains are very similar to one another and do not produce as wide a flavor range as ale strains do (think English ales vs Belgian ales).  Typically, lager yeast will attenuate fairly well and produce a very clean, crisp beer.

What is meant by bottom cropping?

Bottom cropping is a term that has been created to explain the process of collecting the yeast from the bottom of the tank.  Since lager yeast ferment at the bottom, you have a higher likelihood that you will be collecting healthy yeast from the bottom.  This is not to say that you cannot do the same with ale yeast; you certainly can, you just run a higher risk of collecting less healthy yeast cultures.  In ale yeast re-pitching, brewers traditionally would top crop and collect the krausen.  Thus, when lager beer production really picked up… the brewers came up with a new term and a new way to collect.

Why can lager yeast perform at lower temperatures?

Why not?

… I am kidding. 

Lager yeast produce the flavors that the brewers want at lower temperatures because of the genetics.  It is difficult to explain because people have talked about the characteristics of the yeast as what they do for the brewer, not what they do as an organism.  I think I may have stated this before but I will repeat… yeast don’t ferment wort to make beer, they don’t ferment must to make wine and they don’t ferment apply juice to make hard cider nor do they ferment mash to make the base for distillates.  All that yeast is doing is attempting to survive and reproduce so that their genetics are passed on to their daughters and subsequent generations. 

So, to get back to your question, yeast perform (the way the brewer wants it to) in certain environmental conditions, simply because of the genetics

Will Lager yeast work at higher temperatures?

It depends.  Some of the strains will work at higher temperatures and others will struggle.  I guess the real answer is yes, they will.  But the more complete answer is, yes, they will but they may not successfully finish the fermentation and could produce some flavors that are unwanted. 

Some yeast strains are capable of the same fermentation characteristics at lager (low) and ale (high) temperatures.  There is a lot of research that Fermentis is currently involved with, to bring these answers to you more definitively.

So it will ferment, but it will put off some off flavors?

Yes, the yeast will ferment.  There is a higher possibility for the yeast to produce unwanted flavors.

What are the flavors produced by lager yeast?  

Lager yeast will produce a lot of the same flavors that ale strains will, just in lesser amounts.  Typically, lager yeast will produce the same ester profile as ale strains, just in low enough concentrations that humans either don’t detect it (below the flavor threshold) or just slightly detect it.  Typically, lager yeast are POF- (phenolic off flavor negative) and will not produce the flavor complexities that are common in some Belgian and German beers. 

Typical ester production would include ethyl acetate (apple), isoamyl actetate (banana), ethyl hexanoate (tropical fruit), etc.

 So it still produces esters, just different esters than ale yeast?

ester forms naturally in fermentation.

The difference in the ester production isn’t the molecules that the yeast are producing but rather the concentrations and ratios of one to the others.  This will develop the differing characteristics in the beers and in a way the styles that lager yeast is used in.  Due to the fact that esters are combinations of organic acids and alcohols, the elevated levels in ales could also be perceived as a harsher beer, compared to the delicate profile of lagers.

What causes lager yeast to produce more or less of these esters?

The best way to think about this is the principle of mass conservation: nothing can ever be created or destroyed. The reason I say that is the best way to think about it is because esters are produced from different alcohols and organic acids.  If the yeast is in cooler temperatures and there is a higher pitch rate (general characteristics of lager production), the yeast will be less stressed and thus produce less of the variety of alcohols and acids.  With less of the “building blocks” available, less of the esters will be produced.

So stress and temperature have an impact, but what about pitch rate?

Pitch rate can be thought of as another environmental condition, in a way.  If there is a higher concentration of cells in the wort at pitching, the yeast will be less stressed to reproduce to build the correct concentrations.  Essentially, all of the flavors and all of the characteristics of the yeast come back to stress levels. 

If a brewer wants to make extremely "clean" lager with very little ester, what advice would you give him or her?

There are a couple of things the brewer can do, but I don’t know the application ability.  There are a couple of things that are easy to apply to make beer more “clean”, as well.  The easy applications are lower temperatures and higher pitch rates.  If the brewer has temperature control and are able to ferment in the upper 40’s, the lager yeast will produce a very neutral flavor.  Likewise, the brewer can also pitch at elevated pitch rates, nearing 200g/hL or roughly 4 x 11.5g sachets of Fermentis lager yeast (some other producers have differing viability and pitch rates, so I can’t speak for them).

Practically speaking if you want to make lagers, you have
to be able to control fermentation temperatures. 

The difficult aspects to change about the fermentation would be to increase the back pressure on the fermenter.  This can be done with most any pressure release valves connected to the fermenters blow off port.  The other important thing to remember is you don’t want to build a “bomb”, so you need to make sure your fermenter is capable of holding back pressure.  Not easily done, but will increase the neutrality.

   

So practically, to make a great lager you need to ferment cold?

To make a great lager, it is strongly recommended to ferment cold.  It doesn’t mean that you can’t make a great lager at elevated temperatures, but it is much easier to do so at lower temps.  Yeast will act according to what you do to them.  If brewers know that lager type flavors are produced (or not produced) at lower temperatures, then I would suggest that you apply that to the lager fermentation.

Are there sugars that lager yeast can process that ale yeast cannot process?

No… well… it depends on what strains you are comparing.  Lager yeast typically will ferment maltotriose to near completion.  Some ale strains will ferment maltotriose to completion while others will hardly touch it, if at all.  The important thing for the brewer is to understand the capabilities of the yeast they are using and apply the correct environment to allow the yeast to produce the beer that the brewer wants.

 So wort composition is important?

Wort composition is always important.  I cannot say it enough, “Brewers don’t actually make beer.  They make wort.  Yeast make beer.  If yeast don’t have what they need, they won’t do what you expect.”

 What unwanted off flavors can lager yeast produce?   and how do you limit them?

The most common off flavors are sulfurs, meaty notes and other internal yeast component release.  Most of these are caused by time and temperature, but can also be caused by lack of nutrition, in some cases.  If you are attempting to make an American Light Lager (very difficult), there is a need to supplement nutrition for the adjunct addition.  Adjuncts will not bring any nutritional components other than carbohydrates (food).  Yeast will need the mineral and vitamin cocktail that malt brings to the table (plus a little Zn and Mn). 

What general advice would you give new and intermediate brewers about brewing a lager?

General advice: make mistakes and learn.  It is a much different practice brewing lagers and the best results come from paying complete attention to the brew.  Since I spent 5 years of my life as a Pilot Brewer at one of the big guys, I have a bit of experience with lager brewing.  I can say that it is a very difficult range of beer styles to master.  The fermentation is one aspect of it that, in particular, needs to be done right.