BSU #3 - "The Fermentation, Worts and All" or "May I Draw your Attention to Attenuation"
We can't ever know how the first beer was brewed. It is likely that grain was stored in some vessel (a jar or bowl say), and water got into the container. We know (from my previous episode of BSU) that this would trigger the enzymatic process that would normally lead to fully malted grain. However, the grain-water mix likely was only a little sweet, and natural yeast got in, making early beer. It's worth noting that the person that drank this[1] was probably one of the first ever drunk people ever[2].
Some years later, and many of the processes (for example, malting, boiling, etc) that lead to a modern beer have been improved, and made far more complex, in the never-ending quest for the perfect brew. It should come as no surprise then that the process of fermentation has also been refined, and can now be done in different ways to achieve very different finished products.
The main three ways are:
These yeasts are regularly members of the Brettanomyces family (a beer made with a Brettanomyces yeast is called a "Brett beer"), and will produce sour flavours in the beer. While this may not be a flavour characteristic that many beers will want, it is certainly in vogue at the moment in craft beer! A classic example that has been continuously brewed for centuries are the lambic beers of Belgium. These wort of these beer are cooled in open vats, and never have yeast introduced by the brewers. Instead, they are fully naturally inoculated by wild yeasts, and then left to condition and age in wooden barrels for up to three years.
The presence, abundance and diversity of wild yeasts will vary from location to location. For this reason spontaneously fermented beers will have a sort of terroir[18], making for an even greater range of beers in this style!
[2] They probably also experienced the first ever hangover, and still decided to try and recreate the process of making beer. What a hero.
[3] In some places the "cool" method is known as the "3wordsBen" method. These places are my living room and in my dreams due to the fact that I am in fact not cool, and do maths for a living.
[4] Clumps together during the fermentation process. Think about it as the yeast having a meal, creating byproducts (alcohol and carbon dioxide) and then getting together in groups afterwards.
[5] There are of course some exceptions to these rules. Some breweries go outside of these temperature ranges, and the ones I've found tend to be Belgian. You keep doing you Belgium.
[6] But for some reason we're okay with other stupid words, like eggplant, which must have been named by a very confident liar that had never seen the colour or the shape of an egg, or the relative size of a chicken.
[7] A hazy New England Explanation if you will. Ha ha..........I'm so sorry.
[8] While trying to find the temperatures that these hybrid yeasts are fermented at, I discovered an interesting paper on yeast hybridisation in brewing. At this stage the effect on the phenotype "temperature tolerance" is "not yet clear". I think I may have found a new topic of research I'm interested in!
[9] Each example I could find was from a Belgian brewery, though this was not an exhaustive search. Again, Belgium marches to the beat of its own drum.
[10] Tasty little chemicals that produce the aromas in fruits.
[11] I brewed a pale ale with my friend once. Even after three weeks it was not fit for human consumption, but we drank it anyway. It tasted distinctly of sulphur and washing detergent. Still better than a Bud Light.
[12] It's a myth that English ales are served warm at room temperature. It's served at 10-14°C, which if that's room temperature for you, I'd encourage to google the word "heater"[13].
[13] Fun fact, Tasmanians call a "heater" a "heat pump". Aren't they adorable?
[14] It's the same reason you shouldn't add ice to a good whisky, as it robs the drink of some of the character the brewer/distiller intended you to experience. If you try a whisky neat, and it's terrible, by all means add some ice!
[15] "Lager" is the German word for "to store".
[16] In 1845 the Spaten brewery in Bavaria sent some of their yeasts to Carlsberg in Denmark. This pure lager yeast strain entered industrial production in 1884. Another little known brewery, Heineken, also started production of their own pure lager yeast strain, and between them supplied all cold fermenting lager yeasts to breweries in Europe.
[17] How the Patagonian yeast got to Europe I don't know, but I like to imagine a yeast version of Fievel Goes West.
[18] That is, the actual location of the brewery/maturation cellar plays a role in the flavours of the finished product. That is, if you brew and ferment a lambic beer in the exact same way in two distant places, they will likely taste quite different. For this reason, lambic beer producers rarely wish to move their facilities if possible.
[19] I'm not including water as a "drink" here, because it's really just the most boring possible beer. I'm worried about what that opinion says about me.
Some years later, and many of the processes (for example, malting, boiling, etc) that lead to a modern beer have been improved, and made far more complex, in the never-ending quest for the perfect brew. It should come as no surprise then that the process of fermentation has also been refined, and can now be done in different ways to achieve very different finished products.
The main three ways are:
- Warm.
- Cool[3].
- Wild or Spontaneous.
 |
| Figure 1: A graphical representation of the difference between warm-fermenting (ale) and cold-fermenting (lager) yeasts. |
However, let's take a small detour to quickly talk about the different "types" or "families" of beers. I promise this might get a little convoluted.
The two main types of beer are "ales" and "lagers". Now, we know a lager is a crisp and clear beer (not always) and that ales are thicker, and darker in colour (but not always). Okay, so it's not about the chacteristics of the beer, well then, it's about where in the brewing vessel the yeast does its work. See, lagers have yeasts that ferment at the bottom, and ales have yeasts that ferment at the top, right? Well, again not quite.
We now know that yeast is fully spread throughout the beer during fermentation. However, the yeast flocculates[4] and is simply collected (at the end of fermentation) for reuse from either the top and bottom. So instead, they're called "top-cropping" and "bottom-cropping" yeasts. Or at least they were, because now with modern brewing techniques, and the use of cylindro-conical (a cone-shaped bottom on a cylinder top), almost all[5] yeasts are collected at the bottom. So this terminology is no longer terribly accurate.
Okay. So far we had top and bottom fermenting yeasts, but we discovered that they don't ferment at the top and bottom, so stupid name. Then we moved to to top and bottom cropping yeasts, as that was were the yeast was collected from to use again. But since modern brewing almost always collects at the bottom, it's kind of a silly name too[6]. So what to do?
What was finally discovered is that the former "top-fermenting" yeasts, simply prefer to work at warmer temperatures (15-25°C), and the now defunct "bottom-fermenting" yeasts like it a bit cooler (7-15°C). Finally, to confuse the topic and make this explanation a little more hazy[7], there are now genetically hybridised strains of yeasts that are mix of what were called top and bottom-fermenting yeasts[8] being used by some breweries[9], and some breweries use a mix of both types of yeast. Ugh.
Warm Fermentation
Warm fermentation is performed by the yeast species Saccharomyces cervisiae, and due to the warmer temperatures, the conversion of sugar to alcohol and carbon dioxide occurs faster. Ale yeasts (as they're sometimes called) come from the same family of yeasts as baking yeasts, and it may be that this is the origin of the yeasts we began to cultivate.
Warm fermentation is the method of fermentation that was almost certainly first used in organised brewing, and the brew cycle takes as little as seven days. Due to the faster brew cycle, beers produced in this way yield more esters[10], and potentially, more impurities[11].
Warm fermentation is typically used to produce ales, porters, stouts, Kölsch and wheat beers (to name a few). The beers produced this way are often served at a "warmer" temperature[12], approximately10-14°C, which is called cellar temperature, and this is done for two reasons. First, it's the rough temperature of cellars before refrigeration technology, and second, serving the beer too cold chemically locks up some of the esters, causing the beer to lose some flavour[14].
Cool Fermentation
Since cool fermentation by the yeast species Saccharomyces pastorianus occurs at lower temperatures, and more slowly, the conversion of sugars to alcohol and carbon dioxide produces far fewer impurities. The brewed beer is then stored[15], typically for months, at near freezing temperatures, and it is then called a lager.
Historically these near freezing lagering conditions were found in the cold alpine caves of Bavaria, as refrigeration technology was still centuries away, and something was needed to stop beer from spoiling. These conditions selected for yeasts that could survive at lower temperatures, and the modern cool fermenting yeasts were slowly born[16].
However, there are no indigenous strains of Saccharomyces pastorianus to Europe, so where did it come from? Well, without going into too much detail, modern research indicates that there exists two cold-tolerant strains of yeast, both from the Patagonian forests, and both from the yeast family Saccharomyces eubayanus. After comparing the genomes of Saccharomyces pastorianus (lager yeast), Saccharomyces cervisiae (ale yeast) and Saccharomyces eubayanus (the Patagonian cold-tolerant yeast), it was discovered that lager yeast is a hybrid offspring of ale yeast and Patagonian yeast[17]!
During the lagering phase, many of the compounds leading to certain flavours in the beer dissipate, and this leaves the beer with a "cleaner, cripser" taste. These beers will be served colder, at approximately 4-7°C, and without the comparable flavour profile, little is lost in the lower serving temperature, and the beer is more "refreshing". That isn't to say that lagers can't have interesting flavour profiles, but it is often the aim of a lager to be as clean and refreshing as possible.
Spontaneous Fermentation
Some breweries still encourage the use of wild yeasts in their beers. Spontaneous fermentation occurs when yeast that is not brewing yeast is part of the fermenting process. The yeast may come from an open topped fermentation vessel near an open window, or perhaps it was in the barrels that a beer is further aged in.These yeasts are regularly members of the Brettanomyces family (a beer made with a Brettanomyces yeast is called a "Brett beer"), and will produce sour flavours in the beer. While this may not be a flavour characteristic that many beers will want, it is certainly in vogue at the moment in craft beer! A classic example that has been continuously brewed for centuries are the lambic beers of Belgium. These wort of these beer are cooled in open vats, and never have yeast introduced by the brewers. Instead, they are fully naturally inoculated by wild yeasts, and then left to condition and age in wooden barrels for up to three years.
The presence, abundance and diversity of wild yeasts will vary from location to location. For this reason spontaneously fermented beers will have a sort of terroir[18], making for an even greater range of beers in this style!
Conclusions
So, the story of fermentation is one of opportunity, development, and a little Frankenstein's Monster. We first produced beer accidentally when wild yeasts made their way into watery grain. Shortly after this, humanity decided to do this on purpose, and the yeasts that helped us do this likely came from baking yeast, and were fermented at "warm temperatures". Later on, some Patagonian yeast decided to get to Europe, and with a little forced cold fermentation, and a romantic few years hanging around ale yeasts, lager yeast was born. This allowed "cold fermented" beers to be produced, and these quickly became very popular. Then, many years later, craft beer production has seen the return (although it never fully died off thanks to Belgium) of wild yeasts, and their tasty sour beers.
It's amazing that an accidentally made beer, and humanities love of social lubrication, has led to such an in-depth and complicated process as beer production. We can never really know, but I don't think beer would have become quite as popular as it has without it being an alcoholic beverage, and so yeast is the key part of the world's most popular drink[19].
So this ends the series on how beer is made. Naturally, I didn't cover everything, nor could I hope to. I may over-simplified some topics, or completely missed them out altogether (such as bottle conditioning say). I hope you've enjoyed these posts, and if you've made it this far, thanks so much for reading!
So this ends the series on how beer is made. Naturally, I didn't cover everything, nor could I hope to. I may over-simplified some topics, or completely missed them out altogether (such as bottle conditioning say). I hope you've enjoyed these posts, and if you've made it this far, thanks so much for reading!
Sources
a) https://www.beeradvocate.com/beer/101/yeast/
b) https://justbeerapp.com/article/beer-types-ales-lagers-hybrids-and-others
c) https://www.craftbeer.com/craft-beer-muses/immaculate-fermentation-science-not-sorcery
b) https://justbeerapp.com/article/beer-types-ales-lagers-hybrids-and-others
c) https://www.craftbeer.com/craft-beer-muses/immaculate-fermentation-science-not-sorcery
Figures
1) https://cdn2.justwineapp.com/assets/article/2016/04/lagervsalediag.jpg
Footnotes
[1] A particularly brave decision, as it was probably bubbling away, and would've smelled terrible. What a hero.[2] They probably also experienced the first ever hangover, and still decided to try and recreate the process of making beer. What a hero.
[3] In some places the "cool" method is known as the "3wordsBen" method. These places are my living room and in my dreams due to the fact that I am in fact not cool, and do maths for a living.
[4] Clumps together during the fermentation process. Think about it as the yeast having a meal, creating byproducts (alcohol and carbon dioxide) and then getting together in groups afterwards.
[5] There are of course some exceptions to these rules. Some breweries go outside of these temperature ranges, and the ones I've found tend to be Belgian. You keep doing you Belgium.
[6] But for some reason we're okay with other stupid words, like eggplant, which must have been named by a very confident liar that had never seen the colour or the shape of an egg, or the relative size of a chicken.
[7] A hazy New England Explanation if you will. Ha ha..........I'm so sorry.
[8] While trying to find the temperatures that these hybrid yeasts are fermented at, I discovered an interesting paper on yeast hybridisation in brewing. At this stage the effect on the phenotype "temperature tolerance" is "not yet clear". I think I may have found a new topic of research I'm interested in!
[9] Each example I could find was from a Belgian brewery, though this was not an exhaustive search. Again, Belgium marches to the beat of its own drum.
[10] Tasty little chemicals that produce the aromas in fruits.
[11] I brewed a pale ale with my friend once. Even after three weeks it was not fit for human consumption, but we drank it anyway. It tasted distinctly of sulphur and washing detergent. Still better than a Bud Light.
[12] It's a myth that English ales are served warm at room temperature. It's served at 10-14°C, which if that's room temperature for you, I'd encourage to google the word "heater"[13].
[13] Fun fact, Tasmanians call a "heater" a "heat pump". Aren't they adorable?
[14] It's the same reason you shouldn't add ice to a good whisky, as it robs the drink of some of the character the brewer/distiller intended you to experience. If you try a whisky neat, and it's terrible, by all means add some ice!
[15] "Lager" is the German word for "to store".
[16] In 1845 the Spaten brewery in Bavaria sent some of their yeasts to Carlsberg in Denmark. This pure lager yeast strain entered industrial production in 1884. Another little known brewery, Heineken, also started production of their own pure lager yeast strain, and between them supplied all cold fermenting lager yeasts to breweries in Europe.
[17] How the Patagonian yeast got to Europe I don't know, but I like to imagine a yeast version of Fievel Goes West.
[18] That is, the actual location of the brewery/maturation cellar plays a role in the flavours of the finished product. That is, if you brew and ferment a lambic beer in the exact same way in two distant places, they will likely taste quite different. For this reason, lambic beer producers rarely wish to move their facilities if possible.
[19] I'm not including water as a "drink" here, because it's really just the most boring possible beer. I'm worried about what that opinion says about me.
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