THE ACTUAL TRUTH ABOUT YEAST: Volume 2 Ale Yeast with Kevin Lane of Fermentis

Today we continue our series with Kevin Lane of Fermentis, and we are focused on Ale yeast.   We will be taking a basic look at Ale yeast biology, understanding some of the terms you hear associated with ale yeast, and talking about how to get the flavors you want from ale yeast.  Any thing in italics I added, or clarified.  

We will gain an understanding that temperature, pH, pitch rate, and wort composition are tools you can use to make the beer you want.  And this is a very important point.  Too often now on home brewing forums I hear guys espousing "rules" ... "you have to do this"  or "you must do that"   To me, it is clear that these guys do not want to understand, they want to follow a set of rules that will make them successful.  Unfortunately, true success requires understanding.   My old mentor used to say "Recipes are for people who can't, or wont understand"  I finally get what he meant.  He would check gravities during the mash, and add base grain.  He would check color against a chart and cap his mash with crystal grains.  He would even check pH and see if it was optimum for the fermentation phase.  All because he understood the process and enough of the microbiology to make the adjustments. 

Yes this is a long post,  but read it. 

This is the stuff you actually need to know!

And always remember,  Brewers make wort, yeast makes beer!

What is ale yeast?  What makes it different from lager yeast?

Ale yeast is defined as top fermenting yeast.  Ale yeast (saccharomyces cerevisiae)  is a different species from lager yeast (saccharomyces carlsbergensis (former} orpastorianus {current}). Ale yeast, also prefers to ferment at warmer (usually ambient) temperatures, whereas lager yeast prefers to ferment at cooler temperatures.  The yeasts don’t actually prefer one over the other, they just produce better flavors/aromas and may ferment “better” in human terms.  Ale yeast, additionally, has a much larger variety of flavor and aroma production, as lager yeast has been selected by humans for centuries and has been (intentionally)  limited in the genetic differences.  There are a large number of different ale yeasts available in the market: American, English, German, Belgian, French, etc.

So top cropping versus bottom cropping? (Taking yeast from active fermentation)

When you choose whether to top crop or bottom crop, you are selecting different phenotypes (genetic differences).  If you top crop, you will be selecting the yeast that is more likely to form branched groups of cells that get stuck in the krausen during fermentation.  Traditionally, German ales have been top cropped for many styles, but the most common is hefeweizens.  If you were to top crop and bottom crop from the same batch of beer (separately) and repitch into the next batch (separately), you would likely see a difference in flavor/aroma production.

Why can ale yeast perform at higher temperatures?

Ale yeast performs better at higher temperatures.  That isn’t to say that you can’t use lager yeast at higher temperatures (ex. W-34/70 at warmer temperatures); you can, there is just higher potential for off flavor development (sulfurs, meaty notes, cider type flavors, etc).  Ale yeast are and have been naturally occurring yeast strains in regions that have warmer typical temperatures.  There are different stories about lager yeast and where that genus species came from, but my understanding is that lager yeast is a decedent from a cross between wine yeast (beyanus) and ale brewing yeast.  Wines are typically produced in coastal regions where the overnight temperatures drop to a fairly cool temperature with moderate humidity, so I could understand how lager yeasts could be a decedent of saccharomyces beyanus (wine yeast). Wine is also typically fermented at cooler temperatures when compared to ale yeast, so the cross between the two species is understandable: the maltose and maltotriose fermentation coming from the cerevisiae and the affinity for cooler temperatures from beyanus.

Back to the question, ale yeast performs better at higher temperature because that is how the environment was that the yeast came from.  Again, it’s not to say that ale yeasts definitely can’t ferment at cooler temperatures, they can, just might be slower and produce more neutral beer (ex. K-97 at cooler temperatures).

What impact, in general, does temperature have on fermentation and production of flavors?

Fermentation temperature is an “environmental condition” similar to OG, pH, pressure, pitch rate, etc.  In general, warmer temperatures will increase fermentation speed, increase ester production, and increase overall yeast flavors.  At cooler temperatures, yeast produce a more neutral beer, in general. 

This image shows the Safbrew WB-06 speed of fermentation (drop in degrees Plato) over time at three different fermentation temperatures: 16, 20, and 24°C (60.8, 68 and 75.2°F).  As you can see, the 16°C fermentation takes 6 days longer than the 24°C!

What I think is interesting is that different strains perform different ways.  Here is an image of how one of the Fermentis strains, Safbrew WB-06, performs in cooler temperatures, where it produces more isoamyl acetate (banana flavor).

Unfortunately (and fortunately for us as brewers), there are these differences between strains, where some will produce more of a certain chemical at lower temperatures, where others will produce more at higher temperatures.  Generally speaking though, yeast will produce more flavor compounds at higher temperatures.

What are the flavors produced by ale yeast?  

Ale yeast produce a wide variety of flavor and aroma compounds.  It is important to remember that the yeast is producing these compounds to develop the aroma and flavor in beer, they are simply just living in the environment that the brewer puts them into and most flavor and aroma compounds can be related to the stress of the yeast.  If you read the first installment of this Q&A with David and I and you took the time to look at that HUGE pdf image that I had him put in, you will see hundreds of compounds produced and altered by the yeast.  Each of those will have a different flavor and aroma and more importantly, a different human threshold.

The main flavors that brewers care/think about are phenolics (covered in the last installment of this), alcohols, and esters. 

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

Esters are generally created in stressful environments.  Esters are actually a compound that is formed by the yeast or simply by accidently being bound in the aging beer.  It is the combination of different alcohols and carboxylic acids.  More esters are generally produced in warm fermentations, wort with low dissolved oxygen (Acetal CoA can be in excess in low O2 environments), lower pitch rates (more cell growth), and tall thin fermenters.  Generally, less esters are produced with an increased fermenter pressure.  It is also important to understand the different human threshold levels (ex. isoamyl acetate has a human threshold of 1.4ppm while ethyl acetate has a human threshold of 33ppm).

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

In general, if you want to create a more neutral beer (low ester), you would over pitch slightly, keep the fermentation cooler than usual and if possible, keep some back pressure on the fermentation (not easy for home brewers, I know).  In addition, strain selection is important.  If a strain is more likely to produce esters in comparison to another, obviously, choose the low ester producer.  The same can be said about higher (superior) alcohols.

  

If a brewer wants to enhance these flavors (esters) what advice would you give?

Basically… the opposite of what I said above.  Choose a strain that is known to produce a lot of esters and higher (superior) alcohols.  Ferment warm, with a low pitch rate and little back pressure.

You have all been told that esters are bad, esters are neither bad or good, they are a tool for you to shape and create the beer you want.  Some fruity ale esters are important in many English beers, and in american , IPA, DIPAs, Belgians, and German Wheat beers

Ale yeast can also produce Phenolic flavors... Belgian flavors how does a brewer enhance these flavors?

The best ways to increase the phenolic flavor in beer is ingredient selection and strain selection.  In order for the yeast to produce phenolic flavors, they need the precursors (ex. ferrulic acid for 4-vinyl-guaiacol {4-VG}) and the yeast need the POF+ (phenolic off flavor positive) phenotype.  Some strains have that and others do not.

The malts that are highest in ferrulic acid are wheat malts.  In addition to the malt having that compound, the brewer can use step mashing to promote the extraction from the ingredients.  The rest that you will want for the ferrulic acid would be somewhere around 109-113°F.

So practically, to make a great abbey style ale, you need some wheat and you need to step mash?

Yes, and you need a yeast that has the POF+ phenotype.  Now, I have to make a comment that maltsters, currently, are doing a great job at modifying the malt, so the step mash isn’t completely necessary… it just is if you want to increase the phenolic expression by the yeast.

Are there specific sugars that ale yeast doesn't digest?   And how can brewers know what malts are high in these sugars?   

There is a specific group of sugars that ale yeast (typically) won’t ferment: dextrins.  Dextrins are a group of complex carbohydrates that most yeast are unable to pass across their membranes.  There are malts that are named specifically dextrin malt.  Some are hidden in the name (ex. "Carapils"). 

So wort composition is important?

Wort compositions is very important. 

When looking at the visualization above, it is easy to see that there is a portion of the mash that is not fermentable.  This depiction also includes the proteins and other compounds, but the idea is there,  generally for malt derived wort, only 70% of what you are extracting during your mash and lauter is fermentable.  The dextrins can be made fermentable with enzyme additions, but that isn’t something that most homebrewers are looking into doing. 

Do you think there is too much focus by the majority of brewers on limiting ester flavors"?  in other words do you think many brewers now think of any esters flavors in beer?

I think that it depends on the beer style you are trying to make.  Obviously, there are certain styles that you don’t want esters in, but there are others that you want a lot of esters in (Belgian styles usually have higher amounts of esters).  What I have been promoting in the last decade is, it doesn’t matter if your beer fits a certain style guideline or if it doesn’t.  usually, you are making the beer for yourself and your friends and in that way, you should make whatever type of beer you want to: low or high ester amounts.  If you are looking to enter a competition, then I would say, try to follow what the BJCP says; after all, the BJCP was created for homebrew competitions and it clearly states that in the opening of the document.

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

There are simply too many to list and how to limit them all. 

I will cover the big ones here but most can be limited by thinking about the stress level of the yeast:

Cidery notes – generally can be explained as a lack of yeast nutrition due to adjunct addition – avoid by decreasing the amount of adjunct or addition of a complex yeast nutrient (not just DAP) (Diammonium Phosphate)

Excess sulfur – generally due to autolysis – avoid by moving the beer to secondary after fermentation slows/ends

Meaty notes – partially or fully autolyzed yeast – avoid by moving the beer to secondary after fermentation slows/ends or make sure the alcohol level isn’t too high (alcohol degrades cells)

Aldehydes – produced naturally during fermentation and are later reabsorbed by yeast – allow the beer to be in contact with yeast for more time

Diacetyl (vicinal diketones {VDK}) – produced naturally during the growth phase by yeast due to the lack of Valine and Isoleucine (amino acids) and is a byproduct of the yeast synthesis of these two amino acids.  Yeast will naturally absorb and assimilate this after the sugar fermentation, however it is also produced by bacteria and if you have an infection, the yeast will never be able to assimilate it all.

Soapy notes – fatty acid degradation and dead or inactive yeast degradation – avoid by moving the beer off the yeast, especially if it is a high alcohol environment

Note:  Having the yeast in contact with the beer for long periods of time is rarely a problem in home brewing.   In home brewing we are generally not dealing with amounts of yeast that can harm our beer.  But when you are brewing a huge OG beer, or adding fruit, wood, spices etc... you might consider secondary fermentation.

What general advice would you give new and intermediate brewers about brewing an ale?

Ale fermentation is the most common for home brewers because it doesn’t necessarily require any extra equipment for cooling the fermentation.  Remember that yeast do produce heat as a byproduct of fermentation, so fermenters will heat up in high fermentation.  In general, ales are more forgiving, so the brewer doesn’t need to have an exact fermentation temperature.  Additionally, understand that there are a lot more flavors in beer than just the yeast.  Malts, hops, water and adjuncts all contribute something to the flavor of the beer and understanding all of those as well will help you make the best beer you have ever made.  Yeast is the most complex part of the beer, because it is (usually) the one living part of the beer; the hops have been harvested off the bine and the barley has been harvested and malted.  For brewing ales, I always suggest to start with the suppliers guidelines and then experiment from there as it will give you a baseline and starting point (ex. Fermentis produces the 11.5g sachets for 5 US gallons of beer, but you could always use more or less to find out what happens).  We also recommend a temperature range, but you can ferment above or below that.  That is the exciting part of homebrewing to me… you can do whatever you want and make it completely your own!

THE ACTUAL TRUTH ABOUT YEAST: Volume 1 with Kevin Lane of Fermentis

Brewers make wort,
Yeast makes Beer!

The old adage is that "brewers make wort, yeast makes beer" and that is true.  Despite all of your best efforts you can not make beer with out the help of these miraculous little critters.   Of all of the things we deal with as brewers, mashing, hop additions, water chemistry,  chilling and dreaded off flavors,  yeast is perhaps the least understood, and the most researched.

In truth you don't really have to understand yeast to make great beer.  In truth you could never fully understand yeast.   You can literally study it for your entire life and never learn all there is to know. Heck, they offer PhD's in yeast studies.   What did you think a PhD in microbiology was?

But to become a great brewer, to consistently make world class beer, you need to know at least the basics about yeast.  So, I am teaming up with Kevin Lane of Fermentis.  To do a three or four part series on yeast.   The series will be presented as a question and answer format.   It will have straight answers on yeast.  Yes, it is from one of my trusted sponsors.   Yes, it may have a decidedly "dry" yeast slant.  But It will also have loads of good information.  The first question and answer is called, "yeast basics".

Remember, a big aim here at Counterbrew is to dispel some of the common wisdom (read as misinformation) about home brew.  With the growth of the internet, you can easily source all kinds of good information about home brewing.   There are hundreds of articles available for free online that are credible and educational.  Unfortunately, there is also so much bad information about brewing out there. Much of that bad information is released by good, intelligent, caring people who are trying to show you all a "best practice".  Not a Law of Brewing.  Here are some examples of questionable information.

• The need to heavily aerate or oxygenate your wort.- they don't need as much as you think.  You don't need 60 seconds of pure o2. 
• The need to ferment lagers under 50 F (10 C) - I've used 34/70 for years at 62 F (16.66 C) No off flavors and several awards.
• The need to pitch a huge volume of yeast every time - sometimes you want stressed yeast. yes sometimes you want more off flavors.

So, to dispel some of the mis-information.   We go straight to the source, Kevin Lane,  Technical Sales Manager of Fermentis.   Anything I added is italicized. 

What is yeast?

Louis Pasture the actual father of
modern brewing.

Yeast is a microorganism that is part of the Kingdom Fungi.  The Kingdom Fungi is a group of Eukaryotic organisms (membrane protected organelles) that have the ability to function as a unicellular organism.  Yeast are not plants and are not animals or bacteria.  They are similar to animals in the means of digesting food by absorbing and breaking down food to receive energy.  Brewer’s yeast was discovered in 1876 (Louis Pasteur) and has been applied to brewing beer as a pure yeast strain selection since 1883.

What does yeast do?

Yeast survive.  Their entire reason for doing what they do is to survive and to create new generations to succeed themselves!  In their attempt to survive, they consume food (sugars) for energy and grow in population (by digesting proteins and amino acids as well as trace components).  Their digestion of sugars creates alcohol, CO2, heat and other trace chemicals that we recognize as flavors and aromas. (trace chemicals are a small % of output, but huge impact on the flavor of your beer)

Why does yeast do what it does?

Yeast ferment (digest) to provide energy for themselves.  The chemistry is very complex and the metabolic pathways for nearly every chemical the yeast produce has been mapped out.  The easiest way to describe what the yeast is doing is by analyzing the ATP synthesis via their metabolic pathways.  The real answer to why yeast does what they do is very simple: they live!  They are living, breathing (in aerobic environments), eating and sexing (asexual) machines! (fungi not really machines)

What is a metabolic pathway?

A metabolic pathway is the means by which an organism metabolizes (processes) chemicals.  For yeast, the metabolic pathways describe the breakdown of sugars, proteins and any other chemical compound that they transfer through their cell wall and digest.  If you google yeast metabolism, you will find many visual diagrams, showing the many metabolic pathways

This is one of my favorite chemical pathway maps to show people.  I received it from a good friend, Alex Combe, who I worked with in the pilot brewery at MillerCoors.  It really shows how complex yeast are and how many different pathways they control for the production of different components.  (very sciency and complex but if you want a pdf, let me know)

So yeast converts sugar to Alcohol, and CO2, and creates a range of other by products.  What are these other by products?

Do you really know how to prepare
a wort for real Belgian flavors?

The other by-products are any of the intermediates in the diagram of the biochemical pathways.  It can be said that most of the intermediates are only present for a short period of time, while the yeast are going through the biochemical pathways, but they are still present and therefore can be released from the cell, due to many factors.  The main by products that we are brewers are concerned with impart flavor and aroma to the beer.  With that said, the main focus is usually on esters and off flavors.  It is important to note that certain flavor and aroma compounds (ex. 4VG {phenolic}) are only possible if the wort supplies the precursor (in 4VG production, the precursor is ferulic acid) and the yeast need to have the genentics to produce the compound (again with 4VG, the yeast need to carry the POF+ gene {phenolic off flavor positive}). (very important points made here, hop you all caught them... if you want a phenolic spicy Belgian beer better make sure you get ferulic acid in your wort... here's a hint you have to step mash!)

So the other by products of fermentation contribute a lot to the flavor of a beer. How can home brewers increase or decrease these by products?

There are many factors that can contribute to increased or decreased expression of the by products.  There are simply too many to list and there are still some unknown factors that yeast producers/providers and Universities are investigating.  The major contributors are: pitch rate, fermentation temperature, OG, pH, fermenter design (tall, narrow vs. short, wide), open fermentation, etc.  The key to remember is that if you change one of those parameters, there is a chance that the yeast will perform differently.  In the yeast world, we refer to these as environmental conditions and the brewer is there to attempt to create the environment that the yeast will perform best in.  Most of the parameters come down to stressing the yeast (ex. if you under vs over pitch, if it is a cool environment or a hot environment.  A metaphor could be made that yeast are very much like humans, in these regards: if you are stressed, bad words come out of your mouth (at least they do out of mine).

There is a lot of emphasis on the role of oxygen right now in home brewing, can you talk about that?

This is a very interesting topic.  There is a lot of confusion in home brewing as to the needs and demands from yeast.  Yeast need oxygen to produce sterols that are part of the cell.  They need oxygen to reproduce and to live a healthy life.

That being said…

I can only speak for Fermentis and that is what my intention is here.  Our yeast are produced in fully aerobic environments that have sugar and nutrients dosing.  We propagate our yeast with the idea that we want the yeast to be as healthy as possible, when the brewer (whether home, craft or industrial) purchases it.  We move immediately from propagation to the drying process, which is quite extensive (5 stages and each strain has a different recipe to make sure it remains in peak condition).  With that, our dried, packaged yeast has enough sterols and oxygen demanding components to reproduce 10 times without any oxygen present in the wort!  We have performed trials to analyze this and have the results.  Does that mean you should try to make oxygen deprived wort?  No.  Does that mean that you don’t need to be concerned about the oxygen?  To some extent.  The idea that I want to get across here is that Fermentis provides you with a “safety blanket”.  The yeast is already able to reproduce 10 fold, so there isn’t a need to be pumping a bunch of oxygen into your fermenter or being concerned about the DO levels.  (basically quit stressing about Dissolved Oxygen, Shake it up, hit it with a little o2, use an aquarium pump, but don't obsess over the dissolved oxygen it will be fine RDWHAHB  I should point out to you skeptics that Brulosophy has tested this misnomer.)

There is also a lot of emphasis in home brewing on proper pitch rate of yeast,  how can a home brewer know they are pitching the right amount of yeast?   Does Fermentis offer a calculator?   Does Fermentis have a viable cells per sachet list or resource? 

Wort Rehydration of Fermentis
t598 and s33

Another very good, but difficult question to answer.  The difficulty isn’t in the later questions; the difficulty is in the first question regarding “proper pitch rate”.  I would like to remind you that yeast is not an ingredient, it is a living organism.  With it being a living organism (and I will reference back to the question about by products), if you put the yeast into a different environment, they will act differently.  Is there a proper pitch rate?  My answer is no.  The beauty of brewing is that you can change the flavor every time you brew and end up with different beers based on a few changes.  The end results are up to the brewer’s opinion of what they want.  If everyone reading this were to try the same 20 beers and list them from best to worst, we would likely all have a different order.  Some beer drinkers like IPAs, some like Stouts, some like phenolic flavors and some hate phenolic flavors.  It is important to remember that you as a home brewer, are able to create the beer that you want and that you think is the “bees knees”.

Back to the question, Fermentis recommends a pitch rate range: for ales we recommend 50-80g/hL(grams/hectoliter)  and for lagers 80-120g/hL.  Remember that a standard home brew batch of beer is just shy of 20L so we recommend 10-16g for ales and 16-24g for lagers.  Does this mean that you need to stay within those recommendations?  No, you get to do what you want! (important point here,  you might pitch more or less yeast depending on what you are trying to accomplish)

The other tricky thing about this topic is that people have been hypnotized by liquid yeast, to the point that they always want to know cell count.  For liquid, that is the best way for you to measure the amount of yeast you are adding.  For dry yeast, we recommend a biomass pitch rate (weight/volume).  If you read the bottom of our technical data sheets, we state that if you pitch at 100g/hL, you will achieve 6 mc/mL.  That pitch rate is above the recommended rate for ale’s but the reason is as I stated before, our production procedures and the health of our yeast in the package.  We do not have a list of the viable cells per sachet, but we have done time trials and have found that annually you will lose about 5% of the viability if the sachet is stored in a refrigerator and 10% if the sachet is stored at ambient temperature!!!  Our yeast now has a three year best before date.  

Can brewers reuse yeast?  There is lots of talk about washing or rinsing yeast and using it again and again.  

Can brewers reuse yeast?  Good question.  Simple answer is yes.  I always remind people that dry yeast is yeast, we have just processed it so that it is shelf stable and the brewer doesn’t have to worry about doing a starter a day or two ahead of when they want to use it.  The difficult answer is “yes, but be careful”.  Remember that yeast is living and that every time yeast reproduces (buds) and creates new cells, there is a possibility of genetic mutation.  These mutations can happen 10-20 times in one fermentation and can lead to a colony of yeast that is genetically different than what you started with.  The “be careful” part of my response is related to this fact.  Additionally, every time you reuse yeast, you introduce the possibility of introducing an infection: bacterial or wild yeast.  With all of that said, you can reuse yeast and our company recommends 4-6 generations at the most. (my personal suggestion is no more than 3 times and handle it as little as possible, Ill post again soon about pitching onto yeast cakes in progressive OG beers)  When reusing yeast, you have to do it knowing that you may end up with different fermentation kinetics and the possibility of different flavors coming from the yeast.  This could be a good thing or it could be a really bad thing.  If you want consistent beers every time, it is best practice to start with a new package.  Remember that when commercial breweries reuse yeast, they have a team dedicated to yeast handling and they have the ability to acid wash the yeast (homebrewers can too, but it is a lengthy, difficult process) to kill bacteria and yeast that aren’t capable of surviving the acidic environment.

If a brewer re uses yeast, how many times can they use it before it mutates?   

It depends on the environmental conditions and the strain its self.  Some strains mutate faster and others slower over the course of fermentation and growth phases.  It is hard to say how many times, because some strains will mutate the first time and others won’t for multiple generations.

What is the importance of temperature controlled fermentation?   Which is more important control or consistent temperatures?

Temperature controlled fermentation is similar to using a new yeast package every time.  The control is for consistent results for duplicating the beer.  It would be the same as asking, “what is the importance of using the same amount of malts in the recipe” or “the same amount of hops at the same times”.  If you change the fermentation parameters, you will change the outcome.  Sometimes, you won’t see a difference, but other times you will.  Both control and consistent temperatures are the same.  Neither is more important, they both play a role in fermentation. (get a fermentation chamber, or two)

Best advice for new and intermediate brewers?  Sanitation, Fermentation, Oxygen, Dry yeast?

Best advice I can give is…

Remember that as a brewer, you aren’t making beer.  You are attempting to make the “right environment” for the yeast to produce the beer you are wanting.  You are only able to control the wort before the yeast goes in.  Once the yeast is pitched, the yeast do the work.  REMEMBER this!  Everything you do in cleaning, sanitizing, brewing, fermentation controls and parameters… all of that is for the yeast.  Brewers are essentially glorified cleaners and “pet” caretakers.  Humans don’t make beer, ONLY YEAST CAN (with the exception of GMO organisms, but that is a very different conversation)!

Great stuff from Kevin Lane.  And there is more to come sports fans, so check back as we continue this series on The Actual Truth about yeast!

Prost!