By: John Jones
Throughout history, there’s a clear linkage to humans and their love for fermented beverages, one which dates all the way back to ancient Egypt and China, where the processes of brewing and baking seem to have paralleled with the beginning of agriculture. One that reigns increasingly evident to date is beer. This may be due the resilient nature of brewer’s yeast, the simplicity of creating a mind-altering fermented beverage from sugars produced by grain, water, and yeast, or the fact that we share 23% homologous genes as our eukaryotic fungal ancestor.
What is Beer Brewing Yeast?
The main two types are Saccharomyces cervisiae, known as ale yeast (or top-fermenting yeast), and Saccharomyces pastorianus, known as lager yeast (or bottom-fermenting yeast). Both species belong to the same family of yeasts, which also includes the notable Candida genus, a known human pathogen as well as endosymbiont. Yeast can be found anywhere; on plant leaves, flowers, fruits, in the soil, on your skin, and even in the air.
For homebrewers, the main two forms of yeast available are liquid yeast and dry yeast. Two of the general differences between the two forms are the variety available and durability in storage and shipping. Liquid yeast is affected more by drastic temperature shifts and on the market, has a higher variability of diverse offerings to the average homebrewer. However, over the past few years, the dry yeast diversity of offerings on the market has been increasing to compete with liquid yeast variability. It is important to note, both forms of yeast will still make excellent beer!
As mentioned before, ale yeast or Saccharomyces cervisiae are considered top-fermenting yeasts due to their hydrophobic (water repelling) surfaces which causes them to adhere to CO2 molecules and rise to the top of the fermenter. There are three important components of yeast characteristics you may notice when shopping for your next yeast strain. These components are: Flocculation, Attenuation, and Temperature Range.
What is Flocculation in Beer Brewers Yeast?
Flocculation in brewing is a very important aspect of the yeast you’re interested in choosing for your next batch of beer. Depending on the level of flocculation, the yeast will have varying affinities of aggregating together and forming ‘flocs’ at the end of fermentation and ultimately dropping to the bottom of the fermenter. Since the average homebrewer usually does not filter or centrifugate their beer like commercial breweries, flocculation levels can allow the brewer to determine a final clarity and taste of their beer. Flocculation levels are classified as High, Medium, and Low. It is very common to find ale yeasts in every single level of flocculation ability, while lager yeasts are usually medium flocculators, and low flocculating strains are ideal of wheat beers.
What is Attenuation Brewing Yeast?
The second important characteristic of brewer’s yeast is attenuation. Attenuation is found as a percentage when choosing yeast, and usually falls between 65-85%. The attenuation of a specific yeast is how a brewer can tell if the yeast has finished consuming all or most of the available sugars. Most recipe calculators nowadays will have the expected attenuation of the yeast being used and will be able to determine your expected Final Gravity of the beer you’re brewing, which is highly dependent on yeast strain, fermentation conditions, and specific gravity. Attenuation is directly correlated to selecting the right yeast strain for the right style of beer you’re making. If you want a drier finish, select a high attenuator; for a sweeter finish, choose a lower attenuator. The more leftover sugars the yeast is unable to consume will impart a sweeter finish.
What is the best temperature for Home Brewing Yeast?
Saving the best for last, yeast strain temperature ranges for optimal fermentation. Considered to be the most important aspect of making your yeast happy and producing great tasting beer, maintaining fermentation temperature according to your yeast’s optimal temperature will allow you to make award-winning beer. Off flavors, poor attenuation, and stuck fermentations are common indicators that your yeasts were non-intentionally stressed, with a common culprit being inadequate control on fermentation temperature.
Ale yeasts optimal temperature range is usually 66F-72F, however this range is highly dependent on the strain and style. For lager yeasts, the optimal temperature range is typically in thee 45F-58F range, but again, heavily dependent upon the strain isolated. Fermentation temperature has a direct correlation to the production of flavor and aroma imparting molecules in the final product of your beer, good or bad. Due to the variability of yeast strains and their optimal fermentation temperature ranges, many different styles tend to select for certain levels off flavors from flavor imparting molecules on your finished beer, typically identified as esters and fusel alcohols.
My suggestions on Beer Yeast!
If you’re interested in making a well-balanced pale ale, give GigaYeast's Double Pitch - NorCal Ale #1 Yeast a try on your next batch. A strong attenuator (76%-80%) and a medium flocculator, this yeast strain will impart a clean and neutral flavor profile, which will allow any hop varietal you choose to be center stage and impress all your family and friends. How about taking a ride on the hazy train? Check out one of my favorite strains, Imperial Organic Yeast - Juice. This yeast is a medium flocculator and a slightly lower attenuator than NorCal Ale (72%-76%), which will impart more of a juicy and fruity ester profile to partner perfectly with your next tropical hop experiment. Be prepared to use a blow-off tube, this yeast strain will try and climb out of your fermenter. For your next lager, take a look at: Imperial Organic Yeast - Urkel and GigaYeast's Double Pitch - Czech Pilsner Yeast. Both strains are medium flocculators, strong attenuators, and will produce a crisp, clean lager which is perfect for the summer months. All of these strains mentioned above are double pitches (200 billion cells per yeast pack), so for your next 5-gallon batch, a yeast starter may not be necessary. However, it is crucial to check the manufacture date of your yeast pack, as 3 months past the manufacture date and your yeast viability will decrease and a starter may be required.
Although ale and lager yeasts dominate the market, there are a few important alternative yeasts to note that are wielded to make amazingly intricate and unique beers. Mixed fermentation beers utilize a mixed bag approach, pitching normal Saccharomyces yeast strains, Lactobacillus bacterial strains, and Brettanomyces yeast strains to produce incredibly complex, funky, sour and tart beers, see GigaYeast's Double Pitch - Sour Cherry Funk Blend. For more clean lactic acid sour beers, check out Lallemand Dry Yeast Wildbrew Sour Pitch. Remember how yeast is everywhere? Many breweries take a spontaneous fermentation approach. Typically, they will employ a cooling tank, known as a ‘coolship’ which is large, shallow open-top vessel that allows beer to naturally cool while pulling outside air into the space allowing anything floating around in the air and within the brewery to spontaneously inoculate the beer. Similarly, many homebrewers are taking the great outdoors to catch wild yeast and propagate wild yeast for themselves, see Wild Yeast Detection & Remediation. Many of these yeast and bacterial strains benefit from long-term aging and maturation, which is completely contradicted by another ‘hot’ yeast on the market, known as Kveik (“kuh-vike”). This ancient Norwegian yeast likes to be fermented hot (70F-95F), is a high flocculator, and is a robust attenuator (75-82%). Luckily for the homebrewer of today, these strains are recently widely available on the market. They have a great advantage in that they can be used to produce ales with intense tropical flavors (see Omega Yeast - Hornindal Kveik), all the way to clean lagers (see Omega Yeast - Lutra Kveik) without the longer wait times for normal ale and lager yeast strains. Kveik is an incredibly fast fermenter, with some batches completely attenuated within 24-72 hours. If time is not on your side and you need to get a beer done quickly for an upcoming event or simply want to try a new experimental yeast, be sure to try out Kveik yeast. If you’d like to learn more about bacteria, alternative yeast cultures and brewing methods, please be sure to check out Milk The Funk Wiki.
There’s still so much more learn in these categories, and the members of Milk the Funk, commercial brewers and homebrewers alike, share their experiences and techniques in an open forum. Brewing spontaneous beers, using wild yeast, Brettanomyces, and Lactobacillus are techniques and brewing styles that have been used frequently throughout history, but are making a huge resurgence to the craft brewing industry due to the complexities of the beer as well feeding into the natural artistic and creative aspect of homebrewers and craft brewers alike. Brewing is a science. Be creative and don’t be afraid to experiment.