Ask Mr. Wizard

Accidentally Frozen Beer


Bob Burkhardt — Cameron Park, California asks,

My probe accidentally came out of my lagering freezer and I ended up freezing two full kegs of beer. Can they be saved?


The good news is that frozen kegs can be saved! I hope you decided to keep your beers, let them thaw, and enjoyed them post arctic chill. Accidentally freezing beers is a common occurrence, even in large and small commercial breweries with, what may seem like, ideal equipment.

Beer freezing can occur from a range of issues. In your case, your temperature probe was somehow pulled from your freezer and your controller did what it is designed to do by telling your freezer’s compressor to keep on chugging. Unfortunately, the controller was operating off of faulty data and continued running until you discovered the issue. Given enough time, the beer in your kegs would freeze to the point where the freeze-concentrated beers’ freezing points equaled the freezer temperature. You’re questioning the effect of freezing on your beers. Well, it depends on what you did after spotting the condition.

Some brewers intentionally freeze-concentrate beer by chilling beer to some temperature where water freezes to ice until the freezing point of the beer equals the environmental temperature (if the vessel is located in a cold environment) or when the beer temperature matches the cooling setpoint and glycol cooling valves shut. So-called freeze point depression and boiling point elevation are examples of colligative properties of water and explain why the freezing point of beer changes as beer becomes more concentrated when water is removed from the liquid system in the form of ice. Your goal was clearly not freezing your beer, but depending on how much ice was removed, you may have decided to convert your beers into unintentional ice beers, whatever that really means!

The traditional ice beer that most brewers know about is eisbock; this style is freeze-concentrated. In the mid-90s, golden-colored ice lagers were all the rage in North America. Labatt developed the Ice Brewing™ process and introduced their Labatt Ice to the world in 1993. This beer contains 5.6% ABV compared to Labatt’s Blue at 5% ABV. U.S. brewers began brewing ice beers shortly after the release of Labatt Ice, but were not permitted to freeze-concentrate beer because of
U.S. law. 

One thing that may have been interpreted as hype with these beers was the smoothness marketed with just about all ice beers. Unlike some marketing, smoothness is actually a thing with ice beer because the cold temperatures and ice crystallization removes polyphenols from beer and reduces astringency. In other words, ice beers have a smoother mouthfeel and finish. The takeaway here is that if you allow your beer to slowly thaw, it very well may end up being improved by the error.

Beer can also freeze because of poorly placed temperature probes or not covering all probes when filling tanks. This is not common for homebrewers, but is a frequently observed occurrence by commercial brewers. How do commercial brewers observe freezing when their tanks are all stainless steel? They see ice chunks in tank bottoms when preparing the tank for cleaning, or hear these ice chunks fall from the tank when racking a tank and hearing large chunks of ice fall from the upper surface of the tank and crash into the bottom of the vessel. In tall tanks, these falling chunks of ice can do real damage to thermal probes and even the bottom of tanks. And many brewers these days have in-line instrumentation or sampling procedures that may reveal freezing. For example, beer color, density, and alcohol readings change when beer is removed from a frozen tank because the top of the tank contains water from melted ice and the bottom of the tank contains beer that is darker in color, more dense, and higher in alcohol than the beer samples at the end of fermentation.

Long story short, frozen beer is not uncommon and allowing a tank to thaw and moving on with your normal brewing process is not the end of the world for affected batches. One freezing scenario that can cause real quality problems is when packaged beer freezes and thaws, especially if there are numerous freeze-thaw cycles. Chill haze, permanent hazes, beta glucan gels, and particulates in the bottom of a bottle or can are some of the things that form in freeze-damaged packages.

Always check on your temperature probe to help prevent similar issues from recurring. Happy brewing and stay chill!

Response by Ashton Lewis.