The Gunk Left in the Bottom of a Homebrew Kit Jug: Utilizing Yeast Cake for Second Batch Brewing
After brewing, brewers often find a substance left in the bottom of their fermenter jug that looks like a yeast cake. This gunk, containing mostly dead yeast cells and some dormant cells, is accompanied by brewing byproducts such as hops that remained in suspension when the wort was transferred to the fermenter. In this article, we will explore the viability and benefits of using the yeast cake for subsequent batches of beer.
Understanding the Yeast Cake
The yeast cake is a collection of various components, including:
Dead and Dormant Yeast Cells: These play a crucial role in initiating the fermentation process in the second batch. Brewing Byproducts: Such as hops and other byproducts that can add unique flavors to the beer.Previous Experiences
Earlier, I used the yeast cake from my homebrew batches for making a second batch of beer. After transferring the fermented beer to the keg, I placed the next batch’s wort directly on top of the yeast cake. I would vigorously shake the fermenter to aerate the yeast and seal it back up. Interestingly, both times I used Wyeast WLP1056, a neutral American Ale strain. Fermentation was not only fast but also highly vigorous, leading to significant pressure within the fermenter:
Fermentation Lock Clogging: The heat generated from fermentation caused clogging, nearly resulting in the fermentation lock blowing off the top of the fermenter. Near Blow-off: To avoid the risk of blowing the top off, I installed a blow-off tube and closely monitored the fermentation process for 12 hours.Outcome and Observations
The resulting beers from these batches crossed a personal best, delivered no off-flavors, and achieved a balanced, slightly malty taste. The rapid fermentation process was significant:
Fast Fermentation: Both batches required about 10 days from brewing to packaging. Temperature Control: The heat generated from rapid fermentation necessitated vigilance in maintaining the temperature within acceptable ranges.As of now, I’m preparing to follow a similar process. My next batch will be an IPA, followed by a pumpkin ale recipe. The ingredients are prepared, and I'm just awaiting a 4-hour brewing slot to begin the next brew session.
New Method: Yeast Slurry Harvest
During the latest harvester, I discovered 5.5 gallons of wort. Worried about the capacity of the fermenter, I opted to harvest a quart of yeast slurry instead of using the entire yeast cake. I sanitized a canning jar for the slurry and sanitized the fermenter bucket. Added the yeast slurry to the new batch, shook to aerate, and sealed it. Airlock activity was observed within 6 hours and became clogged by the 18th hour, forcing the use of a blow-off tube. The activity has been steady, with some remaining calm by the 72-hour mark. I will check the progress in a couple of days to monitor further development.
Conclusion
From my experience, using the yeast cake from one batch for a new one can yield a robust and flavorful beer. However, it requires careful management to prevent bottlenecks and maintain control. Shaking the fermenter, temperature control, and monitoring for signs of excessive activity are all essential steps to ensure a successful second batch of beer.