Yeast harvesting is an essential process in brewing, as it allows brewers to capture and reuse the yeast for future batches of beer. The process of yeast harvesting involves separating the desirable yeast cells from other unwanted particles and substances that may have settled at the bottom of the fermentation vessel.
One common method of yeast harvesting is to use a conical tank. This type of tank is designed in a way that allows the yeast cells to settle into different layers based on their characteristics. The best yeast cells, which are the most desirable for harvesting, typically settle into a middle layer at the bottom of the tank.
To begin the yeast harvesting process, the first step is to discard the initial layer at the bottom of the tank. This layer, known as trub, consists of various substances such as hop particles, proteins, and dead yeast cells that tend to flocculate early during fermentation. Removing this layer is important as it helps to eliminate unwanted flavors and aromas that may have been absorbed by the trub.
After discarding the trub layer, the next step is to skim off the second layer that rises to the top of the tank. This layer contains the yeast cells that have settled above the trub but are still considered desirable for harvesting. Skimming off this layer ensures that the highest quality yeast cells are collected for future use.
It is important to note that subsequent layers that rise to the top of the tank should be discarded. These subsequent layers often contain a higher concentration of unwanted particles and substances, which can negatively impact the quality of the harvested yeast. By discarding these layers, brewers can maintain the purity and integrity of the yeast cells they collect.
In an open fermentation vessel, such as a traditional wooden barrel, the yeast harvesting process may vary slightly. In this case, the initial step would still involve discarding the trub layer at the bottom. However, instead of skimming off a second layer, brewers may choose to siphon off the liquid above the trub, leaving the yeast cells undisturbed at the bottom. This liquid can then be used as a starter for future fermentations or stored for later use.
Yeast harvesting is a crucial step in the brewing process that allows brewers to capture and reuse the best yeast cells for consistent and high-quality beer production. By carefully separating the desirable yeast cells from other unwanted particles and substances, brewers can ensure that their harvested yeast is of the highest standard.