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Master Brewers Association of the Americas > BREWING RESOURCES > Ask the Brewmaster > Posts > Off-flavors from Peracetic Acid (PAA) Residual?
April 08
Off-flavors from Peracetic Acid (PAA) Residual?

​Q: I have a question about sensory change of beer. One of the sanitizers is POAA(Peroxyactate) which is known as no-rinsing sanitizer. Even though CIP is done including final rinsing after POAA step, is there any possible that residual POAA can change beer flavor? I checked beer sensory which described as burned rubber. It is not sure but certainly it is off-flavor. I guess, one of direct causes is that residual POAA is mixed with beer after CIP step and stored for 5days. That may change beer chemistry. Please let me know any possibility making sensory change using POAA for sanitizer. Or help me to find any resources related with no rinsing sanitizer. Thank you.​

A: Peracetic Acid (AKA Peroxyacetic Acid or PAA)​. PAA is the preferred no-rinse sanitizer in many breweries. One of the main reasons for this is the absence of off-flavors when used properly. I've used PAA extensively in small and medium size breweries, but I reached out to MBAA members Steve Gerloff (Madison Chemical) and Dana Johnson​ (Birko Corporation) for some background on how PAA works and its potential for off-flavors. As you might expect, they both had plenty of interesting information about PAA. I've included a few highlights from Steve here:

PAA is an equilibrium of peroxyacetic acid, acetic acid, and hydrogen peroxide. The method of sanitation is accomplished by way of its oxidative potential; free oxygen attacks and kill microorganisms, fungi, yeast, and bacteria. Directions for proper use call for no rinse and time to allow the surface to air dry. 

One of the main features of PAA is that it completely breaks down to water and carbon dioxide. The rate of this disassociation depends on the concentration of the solution. Normal dosage rates range from 100-200 ppm (although some companies recommend stronger concentration levels). In a 100-200 ppm range the disassociation should be complete within a couple of hours, but can be sooner given ambient temperatures.

That said, introduction of product immediately upon application could unintentionally oxidize product. In terms of sensory evaluation the typical oxidation profiles aromas etc. could be picked up on a panel.

This could be encountered on improper purge on a keg washer where a small residual would come in contact with product when the keg is filled immediately after cleaning.

Personally, I’ve only had one experience where an off-flavor was clearly attributed to PAA. In that particular case a filler operator failed to dump all PAA from the bowl following startup SIP. The beer had a strong acetic acid (vinegar) flavor, which was noticed by all tasters at startup. The filler bowl was then dumped and refilled with new beer from the BBT. This resulted in a true to brand flavor profile with no perceived acetic acid notes.

Here is some information on degradation via Dana:

What is the impact of Peracetic acid products on the environment?
Peracetic acid products are environmentally responsible. The short half-life means that PAA is not persistent and rarely needs to be neutralized prior to discharge. No additional conductivity is introduced to the receiving waters. The results of a large aquatic toxic toxicity study (available on this web site) demonstrate PAA is far less toxic to marine and fresh water organisms than alternative disinfection chemistries. If spilled or applied to soil, PAA decays in a few minutes with no lasting impact on the soil quality. The ultimate end result is carbon, oxygen, and water.

Here are some great MBAA resources relevant to your question:

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