Steam sanitation
I use a half barrel, with the center tube removed, for a fermenter. I like to fill the keg completely with water and then boil it for twenty minutes to sanitize it. Do I need to fill the keg completely with water, or can I boil a partially filled keg, letting the steam sanitize the rest of the surfaces? Which way would be more efficient
or effective?
Jeremy Ruetz
Rhinelander, Wisconsin

Heat, especially moist heat, is an excellent way to sanitize and even sterilize brewing equipment. If you partially fill your keg with water, bring it to a boil and restrict the flow of steam out of the kettle you will indeed be steam sterilizing the surfaces above the water level. An easy way to create a little back pressure in your keg would be to insert a rubber stopper with a very small hole drilled through the middle into the hole in the top of your keg. This restriction will build a small pressure in the keg and help to vent air from the keg and create
a head space full of steam. Twenty minutes is a common set point in heat sanitation techniques.   

Heat sanitation works very well, but it’s not commonly used in breweries. Most of these methods are expensive because of the energy required, present certain safety challenges and can damage equipment if conducted improperly. Some of the more dramatic failures caused by heat sanitation are a result of a vacuum that forms when hot vessels are cooled. If the vessel, for example a big and expensive fermenter, is not properly vented during cooling the result is vessel collapse. This whole cooling issue is another reason that heat sanitation is not commonly used because cooling requires time and energy and most brewers want to put their wort or beer into a cool vessel.   

With this being said, we use hot water at Springfield Brewing Company to heat sanitize our wort cooler, wort lines to the fermentation cellar and our filter. The reason we use heat for these areas is that it works very well. I had a very active role in designing this brewery and I decided to use hot water in these areas of the brewery and designed the process piping to permit this method to easily and safely be used. Other brewers use heat in these same areas. It’s also common to heat sterilize yeast propagation equipment. I use the term sterilize here because yeast equipment is truly designed to be sterilized with steam, similar to pharmaceutical equipment. The funny thing with this comparison is that brewers were the ones who led the way in pure culture growth on large scales and much of what is done today in the biopharmaceutical industry came from brewing technology.   

If you like using this method and find it effective, then use it. I do offer three suggestions: 1) use a thermometer to verify that your temperature goal is met (we use 180 °F/83 °C minimum for our filter and measure this at the discharge), 2) use a timer to make sure you have held it for the proper duration, and 3) exercise caution since hot water and steam can be dangerous when not respected.