Chemical Sanitizers

The chemical sanitizer, as the name suggests is a chemical substance used at specific conditions to achieve the desired sanitizing effect. An ideal chemical sanitizer should have following characteristics:

•  approved for food contact surface application,
•  inexpensive,
•  low in toxicity and corrosiveness,
•  readily solubilized and possess some detergency,
•  stable under all types of conditions,
•  tolerant of a broad range of environmental conditions,
•  destroy microorganisms rapidly, and
•  have a wide range or scope of activity.

As no available sanitizer meets all of the above criteria, it is important to evaluate the properties, advantages, and disadvantages of available sanitizer for each specific application.The chemical sanitizers used in a dairy are normally used as rinses, sprayed on to surfaces or circulated through equipment in CIP operations. Their major groups are discussed below.

 

i. Chlorine and its compounds

Chlorine, in its various forms, is the most commonly used sanitizer in any food processing plant. Chlorine compounds that are employed include liquid chlorine,hypochlorites, inorganic and organic chloramines. These are broad-spectrum germicides, which destroy microbes by the following means:

•  acting on microbial membranes
•  having a lethal effect on DNA
•  inhibiting cellular enzymes involved in glucose metabolism and
•  oxidizing cellular protein.

The maximum level of application is 200 ppm available chlorine, but recommended usage levels vary. For hypochlorites, an exposure time of 1 min at a minimum concentration of 50 ppm and a temperature of 24° C are recommended. For each 10° C drop in temperature, double the exposure time is suggested. For chloramines,200 ppm for 1 min is recommended.Chlorine has activity at a low temperature, is relatively cheap and leaves minimal residue or film on surfaces. The activity of chlorine is affected by pH, temperature and organic load. However, chlorine is less affected by water hardness when compared to other sanitizers (especially the quaternary ammonium compounds).

The major disadvantage to chlorine compound is corrosiveness to many metal surfaces (especially at higher temperature). Health and safety concerns can occur due to skin irritation and mucous membrane damage in confined areas. At low pH(below 4.0), deadly Cl2 (mustard gas) can form. In recent years, concerns have also been raised about the role of chlorine in the formation of potential carcinogens and therefore, its use as a disinfectant in drinking water.Chlorine dioxide (ClO2), being more environmental-friendly is currently being considered as a replacement for chlorine. ClO2 has 2.5 times the oxidizing power of chlorine and thus, less chemical (1 to 10 ppm typically) is required. It has the disadvantage of being toxic and hazardous. Its highly concentrated gases can be
explosive at risks higher than that for chlorine. As ClO2 decomposes readily in the presence of light or at temperatures greater than 50°C, making it on the factory premises rather than procuring it from outside is recommended.The methods of application of chlorine compounds include

•  circulation with 200 ppm for 5 min through pumps and pipelines,
•  immersion in a 200 ppm solution for 5 min,
•  spraying large open vats with 300 ppm solutions for 5min contact time,
•  fogging closed vats and tankers with 500 ppm solutions with atomizing devices, and
•  brushing cheese vat surfaces, agitators, weighing vats and similar open vessels with 400 ppm solution.

 

ii. Iodine and its derivatives

Iodine has been used as an antimicrobial agent since the 1800s. It is normally marketed in combination with a surfactant as a carrier. These mixtures are termed as iodophors. Generally recommended usage for iodophors is 12.5 to 25 ppm for 1 min. The antibacterial activity of iodine is dependent on

It is generally thought that the bactericidal activity of iodine is due to

•  cell wall damage,
•  destruction of microbial enzyme activity, and
•  direct halogenation of proteins.

Iodophors, like chlorine compounds have a very broad spectrum of activity, being active against bacteria, viruses, yeasts, molds, fungi and protozoa. As iodine is highly temperature-dependent (vaporizes at 49° C), it is suitable for lower temperature applications. The most active, but less stable form is the dissociated free iodine,prevalent at low pH. The amount of dissociation from the surfactant depends on the type of surfactant. The degree to which iodophors are effective depends on properties of the surfactant used in the formulation. Iodine has limited solubility in water. Organic matter and water hardness generally affect iodophors less than chlorine. Although iodine has been used since long in treating wounds, ingestion of iodine gas involves the risk of toxicity in closed environments. Iodine also leads to staining on some surfaces (especially plastics).

 

iii. Quaternary Ammonium Compounds (QACs)

Quaternary ammonium compounds (QACs) are a class of compounds, which are used widely in dairy and food sanitation operations. Since QACs are positively charged cations, their mode of action is related to their attraction to negatively charged materials such as bacterial proteins. It is generally accepted that the mode of action is at the membrane function.These are non-irritant to skin and possess antibacterial and surfactant properties.They should be used with soft water. They are active and stable over a broad temperature range. QACs generally have higher activity at alkaline pH. QACs form deposits that are hard to remove on rinsing glass surfaces. An advantage of QACs in some applications is that they leave a residual antimicrobial film. However,this would be a disadvantage in operations such as cultured dairy products and cheeses, where microbial starter cultures are used.Many QAC formulations can cause foaming problems in CIP applications. Under recommended usage and precautions, QACs pose little toxicity or safety risks.Thus, they are in common use as environmental fogs and as room deodorizers.However care should be exercised in handling concentrated solutions or use as environmental fogging agents.

 

iv. Acid Anionic Sanitizers

These formulations include an inorganic acid plus a surfactant, and are often used for the dual function of acid rinse and sanitization. Unlike QACs, they are negatively charged. Their activity is moderately affected by water hardness. Their low use pH, detergency, stability, low odor potential, and non-corrosiveness make them highly desirable in some applications. Disadvantages include relatively high cost, a closely defined pH range of activity (pH 2 to 3), low activity on molds and yeasts,excessive foaming in CIP systems and incompatibility with cationic surfactant detergents.

 

v. Fatty Acid Sanitizers

Fatty acid or carboxylic acid sanitizers have been in use since the 1980s. Typical formulations include fatty acids plus other acids such as phosphoric or organic acids. These agents also have the dual function of acid rinse and sanitization. The major advantage these offer over anionic-acid sanitizers is lower foaming potential.Fatty acid sanitizers have a broad range of activity, are highly stable in dilute form,are stable to organic matter and also to high temperature applications. They have low activity above pH 3.5-4.0, are not very effective against yeasts and molds and some formulations lose activity at temperatures below 10° C. They are corrosive to soft metals and can degrade certain plastics and rubber.