I thought I would post a bit on the yeast that are responsible for the wonderful beverages we all enjoy so much. Above is a false-colored scanning electron micrograph of a Saccharomyces cerevisiae cell. This strain of yeast is called baker’s or brewer’s yeast and is responsible for the majority of yeasty baked goods and ales that we eat and drink. The organism’s name means “sugar fungus of beer,” this is because yeast is a member of the kingdom Fungi:

Kingdom:     Fungi
Phylum:     Ascomycota
Subphylum:     Saccharomycotina
Class:     Saccharomycetes
Order:     Saccharomycetales
Family:     Saccharomycetaceae
Genus:     Saccharomyces

Its phylogeny reveals that it is the founding member of the yeast.

The cell is an oval-shape and they divide by a budding process (they are also called budding yeast). You can see the bud-scars in blue at one end of the yeast cell. When a cell divides, the yeast’s cell wall is modified to allow a bud to form. When it has copied its DNA and divided up its cellular organelles (microbial guts if you will), the two cells separate, and the cell wall is left with a characteristic scar. I have posted another electron micrograph below that shows dividing Saccharomyces cerevisiae.

Intermediate budding cells are sometimes called “schmoos” because their resemblance to a cartoon character. The Saccharomyces sp. are distinct both morphologically and genetically from the Schizosaccharomyces sp. which divide by fission. I have included a picture below:

As you can see, these little guys not only divide differently, but they look very different as well. The cells are rod shaped and the division plane (the welt-like scar that looks like a ring near the end of the cell) is asymmetrically located. The genetic difference between the Saccharomyces and the Schizosaccharomyces is also substantive. The following information is copied from the wikipedia entry for Schizosaccharomyces pombe, the architype of the Schizosaccharomyces.

• S. cerevisiae has ~ 5600 open reading frames, Sch. pombe has ~ 4800 open reading frames
• S. cerevisiae has 16 chromosomes, Sch. pombe has 3
• S. cerevisiae is usually diploid while Sch. pombe is usually haploid

Open reading frames = genes, diploid = two copies of every chromosome, haploid = one copy of every chromosome. Schizosaccharomyces pombe is used extensively as a research tool to understand basic biological processes like cell division, DNA replication, DNA repair, etc. Schizosaccharomyces, to my knowledge is not made to make beer, wine, or any other fermented beverage.

This is all well and good, but you may ask, “what is the difference between ale yeasts and lager yeasts?” I have mentioned before that we are making lager, which require a different kind of yeast. The yeast used in today’s lagers is called Saccharomyces uvarum and is a relative of Saccharomyces cerevisiae. Its name means sugar fungus of grapes. Unlike the other two yeast species I’ve mentioned in this post, S. uvarum is allopolyploid which means that it has multiple chromosomes from two or more different species. This is not at all unusual for fungi. The mushrooms you see in the wild are the reproductive organs of the fungus that grows in the soil. The fungus itself is a web of very long chains of cells called a mycelium. The chains are called hypha (sing. pl. hyphae) and are one or a few cells thick and are surrounded by a thick cell wall; each cell is separated from the other by a loose septum. This allows for the exchange of organelles or genetic material between cells. Genetic exchange can occur not only between hyphae in the same fungus, but between hyphae in distinct species of fungi. The human equivalent would be if you not only had a copy of your mom’s and your dad’s chromosomes, but also of your friends, neighbors and acquaintances. As you can imagine, this can lead to significant genetic diversity.

A Penicillium hypha.

In the case of S. uvarum, the two species are believed to be S. cerevisiae and S. monacensis. These strains of yeast and similar strains were isolated in brewing laboratories. They produced a light, crisp and pale beer when fermented at lower temperature and lagered for long periods. Saccharomyces pastorianus (once known as S. carlsbergensis because it was isolated in 1883 by Emil Christian Hansen in the Danish Carlsberg brewery) is a yeast hybrid that produces lagers much in the same way as S. uvarum.

I have seen the names and the strains of some lager yeasts used interchangeably, and data on the origin of any one yeast strain is, on average, non-existent. Which leads to the question, “What yeast is fermenting my beer?”

If your beer is an ale, then it is a S. cerevisiae strain that has, at some point in the distant past been isolated and purified and used by one abbey or brewery to produce a characteristic flavor profile. Within the S. cerevisiae there is great genetic diversity, and any given strain is indeed distinct as has different biosynthetic potential, resulting in higher or lower esters, fusel alcohols, ethanol, residual sugars, etc. If your beer is a lager, then the yeast you are using is far more similar to other lager yeasts used around the world. Lager yeasts likely arose as a spontaneous hybrid between S. cerevisiae and another Saccharomyces species, was isolated in the brewing process, and was finally widely disseminated. Whether they are called S. uvarum or by another name, they are hybrids capable of fermenting the sugars to a greater degree and producing a more refined beer.
In any case, these organisms are a wildly successful evolutionary development. It is estimated that fewer than 1% of all yeast species have been identified and characterized. The budding yeast’s impact on civilization is monumental as a way to produce or refine food. You eat yeast or yeast products whenever you have bread, beer, wine, vegemite, cider, or nearly any grape. Yeast extract is used extensively in laboratories as growth media and as dietary supplements. They are used in conjunction with acetobacteria to produce other types of foodstuffs and teas as well. Yeast have also been used in bioremediation to remove hydrocarbons and other effluents from wastewater. Transgenic yeast are used in industrial ethanol production from cellulose. Go to the store, and you can see them growing on grapes as a white film. Have a few grapes, or a lager, or a vegemite sandwich and consider where we would be without the tireless yeast.

Val and I went out to Long Grove this weekend to brew the second batch of Kerntoberfest bier: the Helles. A Helles is a pale lager of bavarian origin with a clean, crisp but malty flavor. This style is meant to be drunk in a biergarten from a stein. I have included at the end of this post an ingredient list.

The brewing process begins the night before with a starter culture. The bavarian lager yeast comes in what is called a “smack pack.” This is a pouch with approximately 100 billion yeast cells inside along with a small pouch filled with nutrients. When you are ready to brew, you simply pop the little pouch on the inside and release its goodies for the yeast to eat. Within a few hours the package has swelled like a balloon. Good technique dictates that these activated yeast cells be pitched into a starter culture the night before and allowed to grow in aerobic conditions so as to become greater in number and acclimated to growing in wort. This ensures a vigorous and quick fermentation, virtually eliminating the chance for anything else to grow in the wort.

A “smack pack.”

I created a 1 L starter culture at approximately the same gravity (sugar concentration) as the wort is to be. This culture was allowed to grow overnight at room temperature. The sugar was boiled inside the flask on the stovetop and allowed to cool to room temperature. The “smacked” yeast had swelled the smack pack nicely and began active growth and fermentation within hours once pitched into the starter.
The next day ….

I racked the Mutterswald Marzen from the primary fermenter to a secondary fermenter. The secondary fermenter is a smaller glass carboy with an airlock that is to be stored at 4C for the next few weeks. This cold storage period or “lagern” is the process from which lager derives its name. Over the next few weeks, the beer will condition in the fridge as volatile alcohols and compounds evaporate and the cold causes many other molecules to fall out of solution and sediment. Here is a photo of the Marzen after primary fermentation:

You can clearly see the residue of hops and sugars that is the high-water mark for fermentation. There are very few bubbles at the top of the beer now (it is in fact no longer wort - and has become beer) and this is also the case in the secondary fermenter. There will be no signs of active fermentation any longer.

Having racked the Mutterswald Marzen and scrubbed the residue from the side of the carboy (at great pain by Val using a coat hanger and a dish rag as the carboy brush was left at home), we sanitized and prepared the kettle for brewing. When we brewed the last batch - the water took nearly two hours to come to a boil. Thankfully, Dad was willing to spring for a propane burner in order to carry the brewing process outside and greatly increase its speed.

We added approximately 6 gallons of soft water to the kettle and 1 tablespoon of Burton’s Brewer’s Salts (to harden the water with essential ions) and brought this to a boil using nearly 200,000 BTUs from the propane burner. Once the water reached a rolling boil, we added the following ingredients:

6.6 lbs Northwestern Extra Light Gold Malt Syrup

1 lb Northwestern Gold Dry Malt Extract

1.5 oz (3% a.a.) Hallertau German Hops Leaves (60 min)

1.5 oz (3% a.a.) Hallertau German Hops Leaves (2 min)

A thunderstorm threatened and we had to move the burner and kettle within the shelter of the garage, but other than that, all went well during the boil.

In the end, the pitchfork was unnecessary

The wort was rapidly cooled to fermentation temperatures with the help of a copper wort chiller and the hose. We racked from the kettle to the fermenter.

About two minutes after Dad took this photo, things started to go wrong. First the racking cane clogged with hops leaves, and in the process of shaking them off into the wort, the end of the siphon came off and I was left with a useless tube unable to siphon. Instead, I had to pour the rest of the wort into the fermenter very carefully. Next, as I tried to cap the fermenter with the rubber stopper, the stopper fell right through and into the wort.

Many expletives followed. We covered the fermenter with a bit of foil and dragged out a large lathe-like grinder from grandpa’s building in order to shape a larger stopper down to size. This could have gone far worse, and in the end I was left with a passable stopper. To be sure that we formed a seal, however, we wrapped the top of the fermenter in saran wrap and duct taped the whole bundle down. The final solution is ghetto, but effective:

I called later at night when I was headed home from the lab and Mom told me there was foam at the top, indicating fermentation had already begun.

Dad sent me this photo this morning:

As you can see, things have taken off nicely despite all the worry. If you look above at the picture of Val racking the wort into the fermenter you can see a tall cylinder filled with wort. We allowed the sediment to fall out and took the starting gravity. The value was 1.050. This is a little lighter than the Marzen, as it should be, but will still produce a delightful beer with about 4.5 - 5% a.b.v.

I should also mention that we had a taste of the Marzen as we racked it to secondary and it was light, malty and delicious. Dad, Mom or Garrett should post what they thought of the “green” beer in the comments.

I hope to update kerntoberfest.com with another post about where and how to order your t-shirts in the coming days.

-Justin

Fermentation is a biochemical process evolved to produce energy from the oxidation of carbohydrate bonds in the absence of free oxygen. All organisms that require oxygen for growth are only capable of glycolysis, a process that converts sugars into ATP (energy), water, carbon dioxide and heat. This method of metabolism is very efficient, but requires diatomic oxygen as the final electron acceptor. In anaerobic conditions, there is no free oxygen and, if an organism is to turn sugars into energy, a different pathway of carbohydrate metabolism is required.

This pathway is called fermentation.

Here is a vastly simplified view of the fermentation pathway. There are numerous cofactors, enzymes and steps left out. Most notably, the stoichiometry is missing - the cell begins with one molecule of glucose and turns it into a handful of ATP molecules (synonymous with energy) and ends up with 2 molecules of ethanol and 2 molecules of carbon dioxide.

But let’s back up a moment and discuss brewing and malt, and then we will return to fermentation. If you read the post below, you know that I added 7.6 pounds of malt extract to boiling water. So, you may ask, what exactly is malt? Malt is barley that has been treated by a maltster. The process of “malting” is very complex and is something I will only touch upon. A maltster receives barley corns from a farmer. He then washes the barley in warm water and the barley sense they are in a wet, warm environment ripe for growth. Consequently, the barley corns (which are the seeds) begin to germinate and grow into little sprouts. As they germinate they begin to coordinately change their many complex carbohydrates into simple sugars for the budding plant to eat. At this point, the maltster kilns the buds at a high temperature. Kilning stops the barley from growing and eating its sugars, and drys the seed, preserving many of the sugar-generating enzymes for later use. The malted barely is then shipped to a brewer. The brewer “mashes” the barley by gently grinding it and then soaking it in hot water to release all of the simple sugars, and to activate the remaining enzymes to release even more simple sugars. This “hot liquor” is then filtered and boiled into wort. The predominate sugar in this mixture is maltose (named, of course, after malt itself), which is a disaccharide of D-glucose. This is important, because D-glucose is the sugar from which both fermentation and glycolysis produce energy most efficiently.

Maltose: or 4-O-α-D-Glucopyranosyl-D-glucose. Sugars, and their linkages, are numbered on each carbon. Do you see the single oxygens on the above chemical drawing? There two glucose molecules (they look like the little bow-ties), each of which has its own single oxygen (as it exists above, this is called an ether - and if you were to remove the rest of the molecules and only have carbon-oxygen-carbon you would have ether).

Each carbon is numbered in the clockwise direction, starting with the carbon after the ether. If you were to count on the above drawing, you would see that carbon 1 of the left glucose is bound to carbon 4 of the right glucose. Therefore, we call the bond a 1-4 glycosidic bond. If you read the detailed name of the maltose molecule above, you will also notice an α, this is because sugar molecules can be either α or β. Take a look at the -OHs on the very right and the two at the top of each molecule in the above figure. They are all pointing up, therefore we call this α. If the -OH on the very right were pointing down and the two at the top pointing up, we would call it β. The difference between “D” and “L” glucose has to do with the positioning of each of the four different atoms bonded to the 1 carbon, and because throughout biology, glucose is D-glucose, I won’t go into it here. So enough ranting about chemical nomenclature you say - what does it all mean?

What it means is - the wort that we made on Sunday was loaded with maltose, and we dumped in 100s of billions of yeast cells. What they are now doing is chewing up the maltose, producing ethanol, carbon dioxide, and heat. So, you ask, how much maltose was there in the beginning? I measured the worts original gravity (OG) as 1.062, which converts into 15.65°Bx or 15.65 grams of dissolved sugar per 100 grams of water. The carboy contains at least 5 gallons of liquid, or about 19000 mL. This means there is approximately 3 kg of dissolved maltose. All well and good, but what does this mean for the final beer? Well that depends on what the final gravity of the beer is after fermentation is complete. We can use the information I posted in the first kerntoberfest.com post about the yeast I pitched to estimate what our Mutterswald Marzen should be like at the end of fermentation. I estimate our final gravity will be 1.012 based on the yeast’s average ability to chew up sugar (expressed as a % attenuation). This would mean the beer would contain 6.6% (v/v) alcohol. This also means that the fermentation will yield 383 L of carbon dioxide (watch out carbon budget).

I’ll stop pontificating here and show you the active fermentation of the Mutterswald Marzen. It took only 36 hours before a vigorous fermentation began:

Dad snapped this photo Monday night.

And here it is Tuesday morning. As you can see by the layer of foam at the top - we have an active, healthy fermentation. If you look at the photo of the carboy in the post below, you will see some bubbles at the top - but these are the result of vigorous shaking, and within a few hours the top of the wort was glassy smooth. We are witnessing a process that is as old as agriculture itself, and a staple of humanity since the dawn of civilization. A bier is born.

Brewing is all about preparation. When you are well prepared, then making beer is simply a coordination of cleaning, sanitizing, boiling, siphoning, and pitching. Over the weekend, both my fermenter (a 6.5 gallon glass carboy - borrowed from Garrett) and my yeast starter (a glass flask) broke while I was sterilizing them in the oven. In my frenzy to find replacements one day before I was to brew the Mutterswald Marzen, I found an excellent homebrew shop called Perfect Brewing in Mount Prospect, IL. The shop is a small space inside a larger warehouse that is simply packed with homebrewing goodies. The ingredients and equipment to be used in subsequent Kernbrau brewing are sure to come from Perfect Brewing.

By 3:00 PM, Val and I were in the Mutterswald with a new carboy, some extra yeast, iodine, and brewing salts. Chateau LG’s stove had a very difficult time bringing 5.5 gallons of sugary wort (pronounced wert) to a boil, and perhaps a propane burner will make things easier on us and the stove in the future.

As the water in Chateau LG is extensively filtered, we added some brewing salts as the water heated (these are mostly Calcium and Potassium salts) which are necessary for the yeast as well as for the final flavor to progress properly. At 150F - 170F, we steeped 1 lb of US 2 row Crystal Malt 30 Lovibond in a muslin bag for 15 minutes. Lovibond is a color scale used to describe malt colorings. The scale ranges from 0L (clear) to 600L (nearly opaque black), a malt’s color depends on how long and at what temperature it was kilned. A 30L crystal malt will impart a very subtle orange hue to the beer as well as provide some of the more complex sugars, proteins and tannins that are not present in malt extract, but add immensely to the flavor.

When the kettle came to a boil we added 6.6 lbs of BierKeller malt extract (1/2 amber and 1/2 pale) and 1 lb of Munton’s light dry malt. The solution was then allowed to reach boiling once more. Boiling the wort serves many purposes. Perhaps the most important is that it sterilizes all the ingredients, allowing for fermentation by yeast unfettered by nasty bacterial growth. Boiling also causes many proteins and larger chains of sugars to fall out of solution, clearing the malt extract of bitter or unsavory compounds. A clear wort is described as “bright.” Finally, when you add hops to boiling liquid, a class of molecules called humulones in the hops leaves isomerize to form very bitter flavors necessary to balance the intense sweetness of malt.

2 oz of Tettnang (US grown) hops at 3.5% alpha acid (a measure of humulone concentration) were added at the beginning of the boil, and the mixture was allowed to stew at boiling for 60 minutes.

15 minutes until the end of the boil, Val and I place the wort chiller into the brewkettle to sterilize its surface. Chilling a wort rapidly clears it of still more insoluble compounds, making the final product even brighter.

You can see the leads of tubing connecting to the ends of a copper tube. The tube is coiled into a cylinder and submerged in the hot liquid. This allows for very efficient heat transfer.
When the boil is finished, very cold water is run through the wort chiller and the wort is gently moved around the coils until it reaches a cool 60F. All the insoluble material is then allowed to sediment out of the wort by allowing it to sit for 15 minutes. In order to remove the bright wort from the trub (pronounced troob - this is all the insoluble gunk at the bottom of the kettle), we siphon into a fermenter.

You can see the form of the wort chiller in the sink to the right in the above photo. Perhaps you can also see how Val is holding the edge of the siphon against the glass so as to allow the wort plenty of access to oxygen. A well oxygenated wort is essential for a vigorous fermentation. After siphoning is complete, we shake the fermenter a bit to work in as much oxygen as we can manage. Next, we add Saccharomyces uvarum wort (dumping yeast into wort is called “pitching” because it makes it sound far more complicated than it really is) and cap the fermenter with a rubber stopper and an airlock.

The wort is then transported carefully to the temperature-controlled refridgerator in which it will now ferment.

The refrigerator has been emptied of all other contents and a small box that controls the temperature has been attached so as to keep the inside of the fridge a cool 52F.
Now we simply wait for fermentation to begin. I will post photos when the yeast begin to take off. Ale yeasts typically take an hour when they have been properly prepared, lager yeasts take longer - but we still expect to see activity within 24-48 hours..

I spent some of what I call “incubation time” (the time it takes for things to grow, stain, etc.) in the lab designing the above decal.  I want to assess the interest that everyone has in purchasing apparel with this logo.  The more people who want a sweatshirt with this sweet art work (”Kerntoberfest, Where the Sausage and Beer flow like wine.”), the lower the price will be.  Tell me what you think and if you are interested.

Welcome to Kerntoberfest.com - your passport to all things related to the first annual Kerntoberfest. Drop by frequently, as this page will contain constant updates on all aspects of this wonderful fest. Leave a few comments and don your lederhosen!

Val and I drove out to Long Grove today, arriving before Mom and Dad had finished their morning ritual. Although this is far earlier than I would consider stirring on a Saturday, the promise of homebrewing was motivation enough. We headed out to the Brewer’s Coop, a homebrew shop run by the Two Brothers Brewing Company in Warrenville, IL.

I bought a temperature controller for the refrigerator and the ingredients listed below (and of course we couldn’t leave without some of their excellent beer!). The temperature controller was expensive, but necessary as Saccharomyces uvarum (lager yeast) requires fermentation temperatures in the low 50’s. Not even the coolest basement in the Illinois summer will do, and a refrigerator modified to hold a steady 52F is required. This is not a problem when you know a couple of empty nesters with three! The first lager we will brew is a Märzen, a style of beer synonymous with Oktoberfest traditionally laid down in March (at the end of the brewing season). These beers are deep orange in color and stronger than your average lager (about 5.5% ABV). See the Märzen link for the wikipedia entry.

This is a custom Kernbräu recipe for an Oktoberfest Märzen that is to be served at the first annual Kerntoberfest. As I go through the brewing process, I will post photos and explain what I am doing or (more importantly) what the yeast is doing. As we need to set a date for this grand festival - I suggest all those in attendance being to chime in on the comments in order to hammer out a date. I am also looking to Garrett to post some of his custom sausage recipes and Jara to post about her contributions. Prost!