For many years, chlorine has done a very good job sanitizing foods and implements used in the food processing area. However, a concern for discharge of chlorine into surface waters and for the byproducts of chlorine reactions has prompted the use of two different sanitizers in the food area. These are peracetic acid and chlorine dioxide.
Peracetic acid
is actually a combination of peracetic acid and hydrogen peroxide. It is usually sold in liquid form, under many different brand names. While it is mostly used in the food area, it is being researched for use in industrial water systems, particularly cooling towers. The environmentalists like its break-down products, acetic acid, oxygen, carbon dioxide and water. Because of its tolerance of temperature, pH, hardness and soil contamination, its main area of use today is with fruit and vegetable processing. It is used for surface cleaning in concentrations ranging from 85-300 ppm. Concentrations in the environmental and medical areas extend from 1,200 to 2,600 ppm The FDA has set a minimum of 85 ppm peracetic acid for food hard surface cleaning. For cleaning the surface of food 20-50 ppm is sufficient.
There are two options for testing peracetic acid. There is a titration method whereby both the peracetic and peroxide fractions are separately determined. There is also a test strip method.
Chlorine dioxide
has been around for many years, used primarily in the pulp and paper industry. Its main drawback has been that it had to be generated on-site by reacting sodium chlorite and acid or chlorine. This usually required installation of large generating units. Today, new technology has allowed it to be generated more easily. In some systems the reactants are packaged in pouches and reacted together. Because chlorine dioxide is a stronger oxidizer than chlorine, it can better penetrate slime layers and is more effective against spores. It has received a lot of attention as the chemical used to clean government offices that were subject to anthrax contamination. Although in drinking water, less than 1 ppm is allowed, higher concentrations are used in the medical, dental and food areas.
There are colorimeters and field kits that use the DPD method for analysis. Glycine is also used with this method to eliminate chlorine interference. While the DPD method is limited to low concentration testing, there are test strips that will test as high as 500 ppm.
