Fruit and vegetable processors use disinfectant products to treat fruit and vegetables to reduce their microbial load and extend shelf-life. This also suppresses the growth of pathogenic microorganisms, such as Salmonella, E. coli and Listeria and reduce their numbers on treated produce.
Globally, disinfectants are regulated by different bodies for different applications. Disinfectant products, including disinfectants that are used in the food industry in South Africa, are regulated by the National Regulator for Compulsory Specifications (NRCS). There are various types of disinfectant products approved for use on fruit and vegetables all over the world, including Bleach (sodium hypochlorite), chlorine dioxide (CIOS), peracetic acid (PAA), organic acids, etc.
One of the most widely used disinfectants is a blend of peracetic acid/hydrogen peroxide (PAA/HP). This chemical combination is referred to as a PAA product. In addition to its use as a disinfectant agent for treating fruit and vegetables, PAA has also been used for direct applications on other types of food, including poultry, red meat, seafood, nuts etc.
This article will focus on the benefits of using PAA as a disinfectant for treating/washing fruit and vegetables. Comparisons between PAA and sodium hypochlorite will be made as it is common for scientists, regulatory agencies and chemical suppliers to use Bleach as a standard to compare these types of chemicals and their applications.
Benefits of Using PAA for Fruit and Vegetables Wash:
Peracetic acid is one of the strongest, most effective oxidizing disinfectant products in the market. Its oxidation potential surpasses that of chlorine and chlorine dioxide. This oxidizing power is very effective against a wide variety of pathogenic microorganisms, such as Listeria, Salmonella and E. coli, etc. NutroChem’s PAA based products, Oxisan and Aerosan Plus, have been tested explicitly against these microorganisms. It is also effective against problem pathogens like Alicyclobacillus - NutroChem’s disinfectants have also passed the EN1276 testing method.
Act 119 of 1990, which regulates South African ORGANIC produce, lists PAA as an approved disinfectant. The active ingredients in these types of products break down entirely to non-harmful components. When dissolved in water, peracetic acid disintegrates into hydrogen peroxide and acetic acid, which will break down into water, oxygen and carbon dioxide. PAA degradation products are non-toxic and can easily dissolve in water. This means that PAA products leave no chemical residues on treated food nor on treated surfaces. After killing the microorganisms, PAA and HP degrade and disappear. (it is reported that the half-life of PAA is 8-30 hours).
Although it can be used in organic production facilities, including vegetable wash, Bleach will leave chemical residues on food. It can also react with food tissues (organic matter) and form carcinogenic substances. This is the reason some countries banned Bleach for use on food, including Russia. This could also be the reason the EPA asks that if Bleach is used to wash fruit and vegetables, treated fruit and vegetables should be rinsed with fresh water before packaging. On the other hand, when PAA is used, treated fruit and vegetables DO NOT need to be rinsed again with fresh water after treatment and before packaging. This brings us to another benefit of using PAA vs Bleach, which is “savings”. PAA-washed produce does not require a subsequent water rinse, and produce processors can thus save a lot of water and time. They also do not need to spend extra money on installing equipment for the potable water rinsing step.
Another benefit of using PAA over Bleach is that PAA has a much higher tolerance to organic load (produce in the wash water) than Bleach. Organic compounds hardly influence PAA activity in the water. So, you do not need to inject PAA into the produce wash water as frequently as you would with Bleach. Bleach degrades quickly in the presence of high organic load. To keep an effective Bleach concentration in the wash water, you need to inject Bleach into the wash water continuously. Therefore, even though Bleach is less expensive than PAA, you will need large amounts to do the job. This can result in almost the same bottom-line cost as if you use PAA.
Additionally, suppose Bleach is used as a disinfectant in the produce wash water. In that case, you also need to inject acid to maintain the pH of the bleach solution at 6,5 for maximum microbial inactivation. With PAA, you do not need to worry about adding another chemical; only dilute the PAA product with water, and you are good to go.
As mentioned above, unlike Bleach, PAA is environmentally friendly because it does not interact with organic matter to form carcinogenic material. On the other hand, Bleach can interact with organic matter (e.g. produce tissues in the wash water) and form carcinogenic substances that are dangerous to humans. Also, when bleach solutions are dumped into drains, Bleach will interact with organic matter in the drain and form carcinogenic substances, such as chloroform, which can emit from the drains as gas and can be hazardous to plant workers.
Additionally, when chlorine is used throughout the day to wash fresh produce, the wash water continuously emits chlorine gas into the plant environment. This chlorine gas can oxidize and damage the processing equipment. The first sign of that is the appearance of flash rust on the metal surfaces in the processing areas, including processing equipment (even on stainless steel) and overhead structure surfaces. Remember, rust is a chemical reaction called “oxidation”. The oxidation reaction of the metals is like a chain reaction - once it starts, it will never stop. Therefore, in the long run, all your processing equipment will be covered with rust. This oxidizing/rust effect also applies to ozone when used as a disinfectant product to wash produce: Ozone is a very reactive oxidant. Therefore, it can oxidize and ruin your processing equipment and other oxidative surfaces in your processing plant.
Last but not least, one of the significant advantages of using PAA is that it functions extremely well under cold conditions (4 °C) and does not experience cold temperature failure, unlike other disinfectants. For this reason, sanitization can be carried out on leafy vegetables that have been pre-cooled or in systems that use water to cool the vegetables, such as hydro coolers.
For recommendations and help with your disinfectant produce wash systems, please contact your NutroChem representative. NutroChem carries PAA-based disinfectant products and their dispensing and dilution systems.
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