Contaminated Beer painting by Drew Vics, January 2014

Does Alcohol in Beer Kill Bacteria?

In an older article — written very early on in the life of Cryptobrewology, when I knew very little about beer or home brewing and even less about microorganisms — I think I said something about the alcohol level in beer probably being substantial enough to kill off bacterial contamination if the method of sanitization was not optimum. [Kicks self in the ass.]

My naive logic at the time figured that, during fermentation, bacteria would be killed off as alcohol was produced by yeast and increased in the solution.

While the rising alcohol level will minimize it to some extent, it’s not guaranteed.

In cases of very mild contamination, yeast, during its growth, will tend to minimize other microorganisms though that is not guaranteed, and it won’t completely eradicate them. Any microorganism that remains will begin to reestablish itself.

If the yeast does stifle the growth of bacteria during fermentation the resulting alcohol level may be enough to slow regrowth for a period of time after the yeast becomes inactive, but contamination will remain. The bacteria will grow and greatly reduce the shelf life of the beer. Microorganisms are a pretty hearty bunch.

It takes a lot of alcohol to kill germs, and there is just not enough alcohol in beer or wine to do the trick. Believe it or not, wine actually is conducive to the growth of bacteria!

Cecil Adams, author of The Straight Dope, found that “[Wine] resulted in the biggest and most abundant colonies, even more than in the raw sample.”

Hops is the boon to beer. Antibacterial qualities of hops reduce the growth of most microorganisms except, luckily enough, yeast. Still, this is not a sure thing, bacteria will always find a way.

CryptoBeerGlassThere is no substitute for cleanliness and good sanitizing techniques, but if you’re not handy with Spray Nine or a mop bucket, brew a Double IPA and you should be okay. For a little while anyway. There is no way to completely eliminate bacteria. The idea is to work clean and sanitize to minimize contamination so that alcohol and hops can be more effective in lengthening the shelf life of your brew.

Here’s to clear, refreshing beer!

Want more in depth information on yeast and brewing? Read this… The Microbiology of Malting and Brewing