Choosing beer yeast seems to be a simple matter at first glance. It is logical to always use the appropriate strain for a particular beer. But the question is whether that is enough to make the right choice. As you can guess, the matter is not so simple.
The first step is to select the right yeast for a particular beer you want to produce. For example, you need Scottish ale for wee heavy, American ale for a pale ale, and Czech lager for Pilsner. The next thing to do is to pick out performance indicators and become familiar with these organisms and how they work. Let’s see.
What Is Beer Yeast?
People have not always used brewer’s yeast to make beer. The Vikings used the family brewing sticks to stir the wort. In Germany, the Reinheitsgebot, a Beer Purity Law of 1516, listed the hops, malt, and water as allowable ingredients for brewing. It was changed after a century when Louis Pasteur discovered yeast in the late 1860s.
Beer yeast is a fungus that grows with or without oxygen and reproduces by budding (asexual splitting). The brewing process base includes yeast that uses glucose and maltose and converts them into ethyl alcohol and carbon dioxide during fermentation. Apart from them, you will get by-products, such as:
- Esters – These molecular compounds add recognizable fruity notes to the beer.
- Phenols – They are responsible for spicy and medicinal notes when combined with chlorine.
- Diacetyl – This ketone compound gives a beer a butter note, desired in Stouts, Pale Ales, and Scotch Ales. Be careful since it is quite unstable and takes on raunchy tones over time.
- Fatty acids – They produce off-flavors in old beers as a result of the oxidation process.
- Fusel alcohols – These alcohols with heavy molecular weight are responsible for sharp beer notes. They also cause unpleasant hangovers after drinking too much beer.
Contemporary brewing recognizes two primary beer yeast types that differ in characteristics, the temperature of growing and the way of working.
Which yeast strain you need will depend on the beer type you choose to produce. For example, you will get an entirely different beer when picking out ale or lager yeast regardless of what all the other ingredients are the same.
Top-fermenting yeast is necessary during the fermentation that takes place at the fermenter top. On the other hand, bottom-fermenting lager yeast will descend to the bottom during fermentation.
The crucial difference in using these two yeast strains is the brewing temperature. While ale yeast works at warmer temperatures above 55 F (13 C), the lager yeast type prefers working in a 50 to 55 F (10 – 13 C) range. An exception is the lager yeast that requires ale temperatures of 60 to 70 F (15.5 – 21 C) and helps to get California Common Beer.
If you enjoy home-brewing, you should experiment with various yeasts available until getting the perfect combination that fits you the best.
1. Ale Yeast
Top-fermenting ale yeast (Saccharomyces cerevisiae) is crucial for ales, stouts, porters, Kölsch, Altbier, and wheat beers. It rises to the container surface during the fermentation process.
Ale yeast history
Ale brewing is the oldest method of beer production dated back to ancient Egyptian times. You can use any of numerous ale yeast strains that ferment quickly, even in anaerobic fermentation conditions.
Their advantages include the ability to use the desired sugar profile and tolerate moderate alcohol levels. As a result, the ale yeast type provides a unique beer taste because its natural mutation prevents phenolic off-flavor production.
You can pick out any of many ale yeast strain varieties depending on the way of their performance. Each one will flocculate and attenuate differently and produce unique flavor profiles, so you can experiment and finally choose the one you like the most.
Regardless of the differences between the strains, these yeasts have something in common. The ideal fermentation temperature for all strains is 68 F (20 C), but they can tolerate the one up to 95 F (35 C). Keep in mind that the beer will taste best at the ideal temperature, and its change will significantly affect the final flavor.
As mentioned, all ale yeasts will rise to the fermenter top during the fermentation process and create a thick yeast head. Most strains will reach the surface after 12 hours of fermentation and keep fermenting there for additional 3 to 4 days.
You can collect them from the top during the cropping phase and use this healthy crop with a low protein level later for new production. A pitching rate for ale yeast is 5 to 10 million cells per milliliter.
Ale yeast that produces fruity beer is usually less versatile but attractive for most brewers. This strain ferments at the same temperature but flocculates quickly and creates different flavor compounds, well-known as ‘clean fermenters.’ For instance, yeasts that produce more fusel alcohols and esters are considered fruitier.
2. Lager Yeast
Bottom-fermenting lager yeast (Saccharomyces uvarum) is necessary for Märzen, Pilsners, Bocks, Dortmunders, and American malt liquors production. It settles to the container bottom at the end of the fermentation.
In some cases, brewers who prefer the bottom-fermentation use a hybrid of Saccharomyces cerevisiae and wild strain Saccharomyces eubayanus yeast from Patagonia to get alternative lager beers.
The advantage of Saccharomyces eubayanus and its baby-yeast Saccharomyces pastorianus is the possibility to thrive at low temperatures. As a result, the fermentation process takes longer, and the beer is crisper and almost without pronounced ale flavors.
The third option is the use of wild Brettanomyces strain that provides a decidedly funky flavor beer profile. Many American craft brewers experiment with wild fermentation but in a controlled setting.
Lager yeast history
Most brewers use Saccharomyces uvarum isolated in the Carlsberg Laboratories in 1881. Emil Christian Hansen developed the first techniques of the pure lager yeast culture growing.
That pure form created a semi-hard surface when combined with wort and agar and could stay alive for long. The long-term storage allowed this product transportation worldwide, making a new beer type with long shelf life trendy.
As I have already mentioned, lager yeast type ferments best at 50 to 55 F (10 – 13 C). The cold fermentation will result in producing fewer fusel alcohols and esters. On the other hand, the sulfur residue level in the solution is higher, making it much complicated for the yeast to absorb diacetyl.
You can solve that at the end of fermentation. Once the beer reaches a 1.022 to 1.020 specific gravity, you should let the fermentation temperature increases to 68 F (20 C).
When the specific gravity range drops at approximately 1.010 to 1.014, it is time to let the product sit for 3 to 5 days at the same temperature. It is then time to cool it to 50 F (10 C) for one day before lowering the temperature to desired 41 to 45 F (5 – 7 C).
Remember that the optimal lager pitching rate is almost twice the ale rate, so you need approximately 15 to 20 million yeast cells per milliliter for the beer of excellent taste.
3. Belgian Yeast Strains
Most Belgian brewers make their famous beers with unique yeast strains. Since they use numerous strains, it is almost impossible to determine the particular one for each beer type.
In general, you can make Belgian wit beer with traditional lager yeast. Still, it won’t have the unique taste of a Belgian beer fermented with an authentic yeast strain that provides clove, phenol, esters, earthy, and fusel alcohol flavors.
You need to be creative, reach the desired balance of compounds, and have the right recipe when trying to produce Belgian style beers. Unfortunately, all your preparations and high-quality ingredients mean nothing without the particular yeast determining the flavor beer profile.
4. Wheat Beer Yeast
As you probably know, you will need particular wild yeast strains to get a traditional European wheat beer rich in recognizable flavor. They are necessary when you want to brew a beer with a pleasing taste.
Nowadays, you can find only half a dozen wheat beer yeast that slightly differs in flavor. Keep in mind that most wheat beers have the traditional cloudiness because of the used strains that don’t flocculate well. This characteristic is their primary advantage.
This reaction is a considerable problem when you brew beer. Once your product is exposed to the open air, there is a possibility of natural (wild) yeast and bacteria infecting the beverage.
On the other hand, some brewers use spontaneous fermentation as a way to get a unique beer. The best example is the Belgium West Flanders region, where breweries traditionally use the Brettanomyces Lambicus yeast strain. The produced beer is non-filtered and a bit sour.
Nowadays, many people enjoy making homemade beer. Most of them experiment with different yeast strains to get unique flavors and desired alcohol content.
If you are one of them, you need to understand brewing yeast biology before starting with production. Only that way you can fully enjoy your favorite beverage. Cheers!