As an expert sommelier and brewer, I can provide you with some guidance on whether the FermZilla valve should be open or closed during fermentation. It's important to note that the FermZilla is a conical fermenter that utilizes a butterfly valve for controlling the flow of liquid.
During the active fermentation phase, it is generally recommended to keep the butterfly valve open. This allows the release of carbon dioxide produced during fermentation, preventing excessive pressure buildup inside the fermenter. Keeping the valve open also allows any excess yeast or trub to be discharged, which can help maintain a cleaner fermentation environment.
Closing the butterfly valve during fermentation can lead to increased pressure inside the fermenter, potentially causing issues such as leaks or even an explosion. It's crucial to ensure proper pressure relief during this active phase.
However, once fermentation has ceased, and hydrometer readings have stabilized for three consecutive days, it is then safe to close the butterfly valve. This step is important to prevent any potential oxidation or contamination that can occur if the valve remains open for an extended period.
Closing the valve after fermentation has completed helps to create a sealed environment, which can aid in the clarity and stability of the beer. It also prevents any potential ingress of oxygen or unwanted microorganisms that could negatively affect the final product.
In my personal experience, I have found that leaving the butterfly valve open during active fermentation and closing it once fermentation is complete has resulted in better overall beer quality. By allowing the carbon dioxide to escape during the vigorous fermentation phase, I have been able to prevent any excessive pressure buildup and maintain a healthy fermentation.
To summarize, it is important to keep the butterfly valve open during active fermentation to allow for the release of carbon dioxide and prevent pressure buildup. Once fermentation has ceased and hydrometer readings have stabilized, it is then safe to close the valve to create a sealed environment and protect the beer from oxidation and contamination. Remember to always prioritize safety and monitor the fermentation process closely to ensure the best possible outcome.