Yeast harvesting is a crucial practice in the brewing world, and it involves collecting and culturing yeast from a previous batch, yeast pack, or bottle in order to build up the cell count and use it for future fermentations. This process allows brewers to save money on yeast purchases and maintain consistency in their beer production.
When it comes to harvesting yeast, there are a few different methods that brewers can employ. One common approach is to collect yeast from the primary fermenter after fermentation is complete. By carefully siphoning off the beer, leaving behind the sediment at the bottom, brewers can obtain a relatively pure yeast slurry. This slurry can then be transferred to a sanitized container and stored in the refrigerator until it's needed for the next batch.
Another method involves using the yeast cake that forms at the bottom of the fermenter. After racking the beer off the yeast, brewers can add a small amount of sterile water or wort to the cake, swirl it around to suspend the yeast, and then collect the resulting mixture for storage. This method is particularly useful for high-gravity beers or those with unique yeast strains, as it allows for the preservation of specific yeast characteristics.
It's worth noting that not all yeast strains are suitable for harvesting. Some strains may not flocculate well, meaning they remain suspended in the beer even after fermentation is complete. In these cases, harvesting yeast becomes more challenging, and brewers may need to rely on purchasing fresh yeast for each batch.
Once yeast has been harvested, it's important to store it properly to maintain its viability and health. Yeast can be stored in the refrigerator for a short period, typically a few weeks, but for longer-term storage, freezing is often recommended. Freezing yeast can extend its lifespan by several months or even years, allowing brewers to build up a yeast bank over time.
When it comes time to use harvested yeast, it's crucial to ensure that it's still viable and healthy. This can be done through a viability test, such as making a small yeast starter to observe signs of fermentation. If the yeast shows signs of life, it can be pitched into the new batch of beer. However, if the yeast appears weak or shows no signs of fermentation, it may be necessary to purchase fresh yeast to avoid potential fermentation issues.
In my personal experience as a brewer, yeast harvesting has been both a cost-saving and quality-enhancing practice. By reusing yeast from previous batches, I've been able to maintain consistency in my beers and save money on yeast purchases. There's also a certain satisfaction in knowing that I'm utilizing a living organism and nurturing it from batch to batch.
Yeast harvesting is a valuable technique for brewers, allowing them to recycle and reuse yeast while maintaining the desired characteristics in their beers. It requires careful attention to cleanliness and storage conditions, but the rewards in terms of cost savings and beer quality make it well worth the effort.