In 1774 Swedish pharmacist Carl Wilhelm Scheele unwittingly discovered chlorine, but it wasn’t used as a sanitizer until 73 years later, in 1847, to prevent the spread of “child bed fever” in the maternity ward at Vienna General Hospital.
Today, it remains as the most widely used, yet most commonly misunderstood sanitizer in the food services industry. Even though chemistry has progressed, and many new and effective sanitizers have emerged, it seems that the food services industry has maintained the same paradigm. That is, if you want to sanitize, use a chemical.
The ideal disinfectant would offer maximum antimicrobial efficacy without harming other forms of life. Unfortunately, chemical disinfectants cannot satisfy this ideal. Virtually all chemical disinfectants, by their very nature, are potentially harmful, and in most cases, toxic. Political correctness has eliminated the skull and cross bones, but if you go back just a few years, that symbol appeared on virtually every sanitizer used in the food industry.
Let’s take a look at some of the sanitizers that are most common to our industry, and let’s take another look at one or more advanced alternatives that could signal a paradigm shift to a green, more effective and safer sanitizing solution.
Exactly how chlorine in the form of sodium hypochlorite kills microorganisms is still something of a mystery. What we do know is that its effectiveness varies widely based on a number of human factors. These factors are concentration, length of contact time, temperature, type and concentration of organism and perhaps most important, pH. For example, bleach concentrate out of the bottle has a pH of about 12.4. When diluted in water at a pH of around 7.0 its pH can remain as high as 10.4.
“At alkaline pH values of about 8.5 or higher, 90 percent of the bleach is in the form of the hypochlorite ion (OCL-), which is relatively ineffective antimicrobally,” says Dr. Norman Miner at MicroChem Labs (Newton Mass.). “At acidic pH values of about 6.8 or lower, more than 80 percent of the bleach is in the form of hypochlorous acid (HOCL). HOCL is about 80 to 200 times more antimicrobial than OCL-.
Both Dr. Miner and the EPA have recommended adding vinegar to bleach to drop the pH and raise its antimicrobial efficacy.
There are a variety of quat compounds that vary in effectiveness against a variety of pathogens. Quat compounds generally leave residues that can be a mixed blessing.
The good news about quat residue is that generally the residue continues to provide an antimicrobial effect. The bad news is that the residue needs to be removed from food preparation surfaces and food storage surfaces as contact with food could contaminate foods. In Florida, for example, grapefruit stored in bins with residue from quat compounds have been damaged and discolored by the residue.
Although fairly effective, quat compounds can be toxic if inhaled, ingested or if it comes into contact with skin. Concentrated solutions can be corrosive and can cause burns to dermal tissue. Other effects depend on length of exposure and concentrations include nausea, vomiting and convulsion. Death may occur within one to three hours after ingestion.
Peracetic acid, in a diluted form, is safe enough to apply directly to food without rinsing. It is an extremely effective sanitizer composed of varying quantities of acetic acid and hydrogen peroxide in an aqueous reaction medium containing a sulfuric acid catalyst.
The fact that a highly diluted concentration can be applied to food to effectively sanitize is where the good news ends.
At 110° F, a temperature of a truck cargo area on a hot summer day, it can explode. This is why many trucking companies and overnight delivery services will not ship it. In concentrated form it may react violently with organic materials. It is known to be toxic to inhale ingest or absorb through the skin. Most food service operators who choose to use this substance require a precise mixing device to mix exactly the correct dilution. However, if the mixing device ever malfunctions the consequences could be unthinkable.
Chlorine dioxide is also a very effective sanitizer. However, according to the New Jersey Department of Health, it is explosive at concentrations greater than 10 percent and can be ignited by sunlight, heat or sparks. This chemical can cause nose and throat irritation, and can irritate lung tissue. U.S. DOT regulations forbid its transport in non-hydrated form.