Storing kegs
Q: I have a question about storing kegs after they’ve been cleaned and sanitized. I had a bad experience when I had purged a keg with CO2 and stored it that way for months before using it for kegging. On the day we were going to keg, I popped the lid and got a very strong, pungent odor from the keg. I would say it was even acidic, as if carbonic acid gas had formed over time. How could this have happened? Perhaps I left too much sanitizer in the keg, though I do my best not to do that. Or maybe some other contaminant was present because I didn’t clean well enough? Or perhaps this is a natural process that occurs over several months and the long-term storage of kegs needs to be done differently?
— Jeff Vandewinckel • Arlington, Tennessee
Mr. Wizard says…
Your example is an extreme case between sanitizing and use, but the broader question is one I’ve often heard craft brewers discuss when preparing equipment. My preferred method is to clean equipment immediately after use, then sanitize just before use. Fermentation vessels, for instance, are easiest to clean shortly after emptying. Often, a simple water rinse with gentle scrubbing, followed by another light rinse and then a cleaning cycle — either by hand or with a pump and spray ball — is quick and effective. Some brewers then sanitize the vessel and store it closed and under pressure until needed, as you describe.
The real issue with cleaning and sanitizing is that neither process is absolute — sanitized equipment is not sterile. And because no-rinse sanitizers used in brewing and food processing rarely provide residual activity, any surviving microorganisms can grow if nutrients are present. It’s impossible to know exactly what developed in your keg during extended storage, but the sour smell is a clear indicator that something did. Carbonic acid itself is odorless, but when you sniff carbonated beverages, it creates a tingling sensation in your nose. By contrast, organic acids such as acetic, propionic, and butyric have sharp aromas that are easy to detect.
Going forward, I recommend cleaning equipment immediately after use, allowing it to drain, and then storing it. Dust is difficult to control at home and can carry yeasts, molds, and bacteria. A quick rinse followed by sanitization right before use is the best practice.
