The old brewing process, known as top-fermentation, was widely used by brewers before the 15th century. This process involved allowing the yeast to rise to the top of the vat during fermentation. It was a simpler and more primitive method compared to the later development of bottom-fermentation.
During top-fermentation, the yeast would be added to the vat along with the other ingredients, such as malt and water. The yeast would then float to the top and begin to ferment the sugars present in the mixture. This process typically took place at warmer temperatures, around 15-20 degrees Celsius.
One of the main drawbacks of top-fermentation was the inconsistency in the fermentation process. The yeast would often form a thick layer at the top of the vat, making it difficult to control the fermentation temperature and resulting in uneven fermentation. This could lead to variations in flavor, aroma, and alcohol content in the final beer.
In the 15th century, German brewers introduced a revolutionary brewing process known as bottom-fermentation. This method involved fermenting the beer at the bottom of the vat, where the yeast would settle. The yeast used in this process was a different strain, known as lager yeast, which had the ability to ferment at lower temperatures.
Bottom-fermentation allowed for a more controlled fermentation process. The beer could be aged for longer periods, typically several weeks or even months, at colder temperatures, usually around 7-13 degrees Celsius. This extended aging period resulted in a milder and smoother taste, as well as a clearer appearance.
To achieve bottom-fermentation, brewers needed specialized equipment, such as large vats with a conical shape and a cooling system. The conical shape of the vat facilitated the settling of yeast at the bottom, while the cooling system helped maintain the lower fermentation temperatures.
The development of bottom-fermentation brought significant improvements to the brewing process. It allowed for more consistent and predictable results, as well as a wider range of beer styles. Lager beers, which are known for their clean and crisp flavors, became increasingly popular.
In my personal experience as a brewer, I have witnessed the impact of bottom-fermentation on the brewing industry. The ability to control fermentation temperature and the extended aging period have allowed for the creation of a wide variety of beer styles, each with its own unique characteristics.
The old brewing process of top-fermentation was gradually replaced by the more advanced and refined bottom-fermentation method. The development of bottom-fermentation not only improved the quality and consistency of beer but also paved the way for the wide range of beer styles we enjoy today.