Harvesting yeast is a fascinating process that allows brewers to save money, maintain consistency, and experiment with different yeast strains. There are several methods to harvest yeast, but I will focus on two popular techniques: top cropping and bottom harvesting.
1. Top Cropping:
Top cropping involves collecting yeast directly from the top of the fermenter during the active fermentation phase. This method is commonly used for ales and requires a fermenter with a removable lid or a blow-off tube that allows access to the yeast layer.
A. Choose the right time: Wait until the fermentation is at its peak, usually after 24-48 hours of pitching the yeast. The krausen, the foamy layer on top of the beer, should be thick and creamy.
B. Sanitize everything: Make sure all your equipment, including a sanitized ladle or spoon, a sanitized container, and your hands, are properly sanitized to prevent contamination.
C. Remove the lid: Gently remove the lid or open the blow-off tube to expose the yeast layer. Be cautious not to disturb the layer too much, as it may lead to unwanted flavors or contamination.
D. Collect the yeast: Carefully scoop out the yeast from the top using a sanitized ladle or spoon, ensuring you avoid any trub (sediment) or hop debris. Transfer the yeast into a sanitized container, leaving behind any excess beer.
E. Store the yeast: Seal the container tightly and store it in a refrigerator at a temperature between 34-40°F (1-4°C). The yeast can be stored for several weeks, but the viability and vitality may decrease over time.
2. Bottom Harvesting:
Bottom harvesting involves collecting yeast from the bottom of the fermenter once the primary fermentation has subsided. This method is commonly used for both ales and lagers and requires a fermenter with a conical shape and a bottom outlet.
A. Wait for fermentation to complete: Allow the fermentation to finish entirely, usually after one to two weeks. The yeast will settle at the bottom, forming a thick layer known as the yeast cake.
B. Sanitize everything: As with top cropping, ensure all equipment, including a sanitized collection vessel, is properly sanitized to maintain a sterile environment.
C. Prepare the collection vessel: Attach a sanitized hose or racking cane to the bottom outlet of the fermenter, leading to the collection vessel. Make sure the vessel is sanitized, airtight, and large enough to contain the harvested yeast.
D. Draw off yeast: Open the bottom outlet slowly to let the yeast flow into the collection vessel. Start with a slow flow rate to minimize the transfer of trub or sediment. Increase the flow rate gradually, being cautious not to disturb the yeast cake too much.
E. Store the yeast: Once you have collected enough yeast, seal the collection vessel tightly and store it in a refrigerator at a temperature between 34-40°F (1-4°C). The yeast can be stored for several weeks, but remember that its viability and vitality may decrease over time.
It's worth mentioning that yeast harvested using either method should be used within a reasonable time frame and may require a yeast starter to ensure proper fermentation in the next batch. Additionally, always refer to the specific instructions for the yeast strain you are using, as different strains may have unique requirements for harvesting and storage.
Harvesting yeast can be a rewarding and cost-effective way to enhance your brewing experience. By experimenting with different yeast strains and maintaining a healthy yeast bank, you can explore a wide range of flavors and styles in your homemade beers.