By Brian Bojko
Oxygen plays a dual role in beer brewing, it can be your best friend when you need to oxygenate your wort post-boil for healthy yeast growth, or it can be your worst enemy after fermentation, leading to cardboard tasting beers with low hop character. The key to keeping oxygen out of post-fermentation is the infamous “closed-loop” transfer, which is typically described by those using pressurized systems. But you don’t need fancy or even expensive equipment to complete the transfer from fermenter to keg oxygen-free, you just need a spigot on your fermenter, tubing, ball lock disconnects, and gravity.
Key equipment required, as referenced from the image, (1) a fermenter with a spigot. This can be a fermenter with one built in already, there are plenty of available options on the market, or if you’re brewing in plastic buckets, you can just add your own. Drill a hole in the bottom of your bucket and fit a spigot similarly to how bottling buckets are setup – leave at least an inch from the bottom for the trub. This may require extra cleaning and sanitizing on brew day, but it is well worth it. Next, (2) you need 1/4" tubing to connect a ball lock liquid side disconnect. In this case, you can either use the barbed version and fit the 3/16” tubing within the 1/4" tube and secure with hose clamp or get the ball lock disconnect with the 1/4" threaded fittings (still using a hose clamp – these are your friends). Similarly, (3) you need gas-side disconnect with 1/4" tubing to feed the CO2 from the keg into (4) the airlock hole within the fermenter lid. This completes your loop, as liquid pours into your keg outpost, the CO2 from the keg fills the headspace in the fermenter.
Here’s how you complete this entire process in a few easy steps. First, when you clean your keg, also clean your transfer line and anything else that has direct contact with your beer – choose your favorite cleaner (PBW, Oxi-clean, etc.). Then sanitize with a no-rinse sanitizer, my go-to is Star San, which can be mixed up in one gallon batches using 6.1g of Star San. This is enough to completely sanitize the inside of your keg with little waste, making sure to rotate the keg so it coats every surface. Empty the sanitizer from the keg by hooking up your CO2 tank, pushing the sanitizer from the out post of the keg through your transfer line thus sanitizing it in the process. Disconnect the transfer line so you can burp the keg, pressurize it to 5 psi, shut off the gas, and then vent it through the keg lid. The CO2 is heavier than air, so as you add it to the keg it will sink to the bottom, pushing air out through the top.
With the keg full of CO2, it’s now time to connect the hoses. Make sure to sanitize the spigot as normal and connect your liquid tubing, then connect the liquid disconnect to the “out” post on the keg. Pull the airlock or blow-off tube out and spray the end of the gas tubing with sanitizer before inserting into the lid, connecting the gas disconnect to the keg. With the fermenter higher than the keg, you can now open the valve and watch the beer flow into your keg, displacing the CO2 into the headspace and completely eliminating any oxygen from contaminating your fresh beer. The best part about this setup, is that it’s a cheap option for closed-loop transfers, especially considering gravity is free.
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