October 8, 2018
Sanitation In The Food Industry With Peracetic Acid
By Michael D. Shaw
This column first discussed peracetic acid (aka peroxyacetic acid aka PAA) around five years ago. In that article, we described PAA’s antimicrobial properties, and its advantage of leaving no harmful residual. Peracetic acid quickly breaks down into carbon dioxide, oxygen, and water.
PAA is a strong oxidizer, and is thought to kill microbes in a variety of ways…
1. Sulfhydryl and sulfur bonds in proteins are attacked.
2. It reacts with many chemical double bonds, impeding cellular processes.
3. It disrupts the functioning of the cell membrane, and the transport mechanisms of the cell wall.
4. It can prevent DNA replication.
5. It will inhibit the enzyme catalase, which catalyzes the breakdown of hydrogen peroxide.
The latter quality is interesting since commercial PAA is supplied as a mixture of peracetic acid, hydrogen peroxide, and acetic acid. Research has suggested that a particular synergy is occurring via a staged process. The peracetic portion of the mix initiates the attack on the cell, damaging its protective systems, allowing the hydrogen peroxide to do its free radical style damage undeterred. This leads to lysis (the disintegration of a cell by rupture of the cell wall or membrane) and rapid cell death.
Within the food industry, PAA is primarily used as a sanitizer during the processing and handling of meats, poultry, seafood, fruits, and vegetables, as well as the bottling of beverages. In 2014, the good folks at All American Chemical published an informative presentation entitled “Premium PAA Sanitation with Peracetic Acid.” Here are some of the key points:
- Is less affected by organic load (soil) than either chlorine or quaternary ammonium compounds (quat) sanitizers
- Disperses/penetrates biofilms
- Kills bacteria, mold, fungus, and yeast
- Is very fast acting
- Is non-foaming
- Does not contribute taste, odor, or color
- Does not require rinsing
- Does not form disinfection byproducts
- Does not add conductivity (Total Dissolved Solids)
- Is non-corrosive to stainless steel and aluminum
- Does not fall under the EPA Risk Management Planning (RMP) rule requirement
- Is easily dispensed as a liquid
- Is easy to test for
We add the next four points, courtesy of the Aseptic and Antimicrobial Processing and Packaging Association (AAPPA).
- Does not promote microbial resistance
- Has efficacy over a wide range of temperature (0-40°C / 32-104°F) and pH (3-7.5)
- Allows for clean-in-place processes
- Is unaffected by protein residue
Sounds great. However, most excellent germicides also have toxic properties. In the case of PAA, the American Conference of Governmental Industrial Hygienists has set its Threshold Limit Value at 0.4 parts-per million (in air) for a 15 minute short term exposure limit. Other agencies, including Cal/OSHA and NIOSH have proposed similar regulatory levels.
While federal OSHA does not yet have a permissible exposure limit for peracetic acid, other standards do exist. Thus, it has issued Rapid Response letters and citations under the General Duty Clause, for what it deems to be high exposures.
PAA is corrosive/irritating to the eyes, mucous membranes of the respiratory tract, and skin. It causes lacrimation, extreme discomfort, and irritation to the upper respiratory tract in humans after exposure to concentrations as low as 5 ppm for only three minutes.
Last year, NIOSH requested information on health risks to workers associated with occupational exposures to peracetic acid. One of the responses came from The National Employment Law Project, and it raised compelling issues regarding exposures to PAA, in light of its increased use in the meat and poultry industries.
Certainly, changes in workplace procedures and enhanced protective equipment will go a long way in improving the situation, but it is also necessary to monitor the air for the presence of peracetic acid. PAA, though, is a difficult compound to measure. One reason is because the instrument must detect this chemical at extremely low levels–less than 1 ppm. Another issue is calibration.
No commercial calibration standard exists for peracetic acid, and it is unlikely that one ever will, owing to the instability of the pure substance. As such, Interscan developed an in-house calibration method, which involves generating a stream of PAA, and using wet chemistry analytics to standardize it on the fly. This stream can then be used to calibrate instruments in the lab. The company offers a full line of gas detection instruments, including models for PAA.
Used properly, peracetic acid can be a great boon to food safety and public health.