The main difference between top fermentation and bottom fermentation is that top fermentation uses ale yeast at warmer temperatures and produces ales, while bottom fermentation uses lager yeast at colder temperatures and produces lagers.
Top fermentation and bottom fermentation are two distinct methods of yeast-driven fermentation used in the production of alcoholic beverages, particularly beer. Top fermentation, also known as ale fermentation, involves the use of yeast strains that float on the surface of the fermentation vessel. On the other hand, bottom fermentation, or lager fermentation, employs yeast strains that settle at the bottom of the fermentation vessel.
Key Areas Covered
1. What is Top Fermentation
– Definition, Features, Ale
2. What is Bottom Fermentation
– Definition, Features, Lager
3. Similarities – Top Fermentation and Bottom Fermentation
– Outline of Common Features
4. Difference Between Top Fermentation and Bottom Fermentation
– Comparison of Key Differences
Key Terms
Top Fermentation, Bottom Fermentation, Ale, Lager
What is Top Fermentation
Top fermentation is a traditional brewing method that involves the use of ale yeast strains fermenting at warmer temperatures, typically between 60 degrees Fahrenheit. This process results in a variety of beer styles with diverse flavors and aromas. During top fermentation, yeast cells are introduced to a mixture of malted grains, water, and hops, collectively known as wort. The yeast used in top fermentation, often referred to as ale yeast or top-fermenting yeast, is a strain of Saccharomyces cerevisiae. Unlike bottom-fermenting yeast, which settles at the bottom of the fermentation vessel, top-fermenting yeast rises to the top, giving this process its name.
The fermentation process begins at a relatively higher temperature compared to bottom fermentation, typically between 60 to 72 degrees Fahrenheit (15 to 22 degrees Celsius). This elevated temperature range promotes the rapid and active metabolism of yeast, resulting in a more vigorous fermentation process. As the yeast consumes the sugars present in the wort, it produces alcohol and carbon dioxide as byproducts. The carbon dioxide is released into the atmosphere, creating bubbles and froth on the surface of the wort.
Figure 1: Beer Fermentation
Top fermentation is associated with a shorter fermentation period, typically lasting from a few days to a week, depending on the specific style of beer being produced. This shorter fermentation time often contributes to the distinct fruity flavors that are characteristic of many top-fermented beers.
After the initial fermentation is complete, the beer may undergo additional conditioning to develop its flavors and clarity. This could involve transferring the beer to secondary vessels, adding additional hops for flavor and aroma, or even introducing other flavoring agents, such as fruits or spices. Once the beer has reached the desired level of maturity, it can be packaged and enjoyed.
What is Bottom Fermentation
Bottom fermentation, also known as lager fermentation, is a traditional brewing method that involves fermenting beer at colder temperatures using specific yeast strains. Unlike top fermentation, where ale yeast strains rise to the surface during fermentation, bottom fermentation uses lager yeast strains that settle at the bottom of the fermentation vessel. The primary yeast used in bottom fermentation is known as Saccharomyces pastorianus, a species of yeast that ferments at lower temperatures and is well-suited for lager production. Bottom fermentation takes place at colder temperatures, typically between 44°F to 55°F (7°C to 13°C), which is considerably cooler than the temperatures used in top fermentation (ale fermentation).
Figure 2: Ale
Compared to top fermentation, bottom fermentation generally takes longer to complete. It can range from several weeks to several months, depending on the specific lager style and fermentation conditions.
After the initial fermentation, lagers typically undergo an extended maturation or conditioning phase at cool temperatures, often near freezing. This process, known as lagering, allows the flavors to mature and results in a smoother, cleaner profile.
Bottom-fermented lagers are known for their crisp, clean, and smooth taste, with a restrained yeast character and fewer fruity or spicy esters compared to ales. The flavor profile primarily depends on the choice of ingredients, especially the malt and hops used during the brewing process.
Similarities Between Top Fermentation and Bottom Fermentation
- Both top fermentation and bottom fermentation are essential steps in the beer production process.
- The basic ingredients used in brewing, such as malted barley, hops, water, and yeast, are common to both top fermentation and bottom fermentation.
- The initial steps of brewing, such as mashing and boiling, are consistent regardless of the fermentation method.
- Both top-fermented and bottom-fermented beers can be carbonated naturally during fermentation or artificially through forced carbonation methods.
Difference Between Top Fermentation and Bottom Fermentation
Definition
Top fermentation is a traditional brewing method that involves the use of ale yeast strains fermenting at warmer temperatures, while bottom fermentation is a traditional brewing method that involves fermenting beer at colder temperatures using specific yeast strains.
Temperature
Top fermentation occurs at warmer temperatures, typically between 60°F to 72°F, while bottom fermentation occurs at colder temperatures, typically between 44°F to 55°F.
Type of Yeast
The primary yeast used in top fermentation is a strain of Saccharomyces cerevisiae, but the primary yeast used in bottom fermentation is known as Saccharomyces pastorianus.
Behavior of Yeast
Ale yeast, which is used in the production of top-fermented beer, has a tendency to rise to the upper part of the fermentation vessel, whereas lager yeast settles in the lower portion of the fermentation vessel.
Fermentation Duration
Top fermentation is generally faster compared to bottom fermentation, taking a few days to a week to complete. Bottom fermentation often takes several weeks or even months to complete.
Flavor Profile
Ales produced through top fermentation offer a wide range of flavors and aromas, often with fruity and spicy notes. The flavor profile is influenced by the choice of ingredients, especially the malt and hops used. However, lagers produced through bottom fermentation are known for their clean, crisp, and smooth taste. Lager yeast produces fewer fruity or spicy esters compared to ale yeast, allowing the malt and hops to shine through more prominently.
Foam in Beer
Beers that undergo top fermentation display a creamier foam, whereas those undergoing bottom fermentation typically exhibit a crisper and effervescent foam.
Beer Styles
Top fermentation gives rise to a variety of beer styles, such as pale ales, India pale ales (IPAs), stouts, porters, and wheat beers, whereas bottom fermentation gives rise to popular lager beer styles, including pilsners, Märzen, bocks, doppelbocks, Helles, and Vienna lagers.
Conclusion
Top fermentation and bottom fermentation are two distinct methods of yeast-driven fermentation to produce beer. The main difference between top fermentation and bottom fermentation is that top fermentation uses ale yeast at warmer temperatures and produces ales, while bottom fermentation uses lager yeast at colder temperatures and produces lagers.
Reference:
1. “Top Fermentation.” Encyclopedia Britannica.
2. “Bottom Fermentation.” Encyclopedia Britannica.
Image Courtesy:
1. “Beer fermentation at the brewery” (CC0) via Public Domain Pictures.net
2. “Beer Filled Mug on Table, alcohol, alcoholic beverage, ale, bar” (CC0) via Wallpaper Flare
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