Peracetic Acid (PAA), the antimicrobial properties of peroxyacetic acid, was first described in 1902. However, it was more than 50 years before PAA was “rediscovered” and commercially introduced. The long lag time was likely caused by a lack of understanding of how to stabilize PAA solutions and by reports of spontaneous decomposition of highly concentrated solutions. Today, PAA has become a common choice of sanitizer/disinfectant for breweries because of its broad antimicrobial activity and its “compatibility” with beer.

PAA is a clear liquid shipped in specially vented containers similar to those used for bleach and hydrogen peroxide. In concentrate and strong-use solutions, it exhibits a strong, characteristic odor reminiscent of acetic acid or vinegar, especially when handled or agitated. PAA solutions are produced by mixing acetic acid and hydrogen peroxide in an aqueous solution, often assisted through a sulfuric acid catalyst. PAA has a very high oxidation potential and is therefore an ideal antimicrobial agent. PAA has an extremely broad killing spectrum and is effective against bacteriophages and spores. PAA is a very effective cold sanitizer and can be used over a wide range of temperatures (0°C–40°C) as well as a wide range of pH (1–7.5). It is non-foaming and therefore an excellent choice for use in cleaning in place applications.

PAA is relatively unstable and breaks down readily into acetic acid (acetate), water, and atomic oxygen. This form of oxygen poses no risk of oxidation to beers that come into contact with it. These breakdown products are environmentally friendly and PAA is certified for use in the production of organic beers. Brewers appreciate the effectiveness of PAA; however, it must be handled carefully because it is highly concentrated and can cause burns.