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Controlling Growth with Chemical Agents

©2000 Kenneth Todar, University of Wisconsin-Madison

Antimicrobial agents are chemicals that kill or inhibit the growth microorganisms. Antimicrobial agents include chemical preservatives and antiseptics, as well as drugs used in the treatment of infectious diseases of plants and animals. Antimicrobial agents may be of natural or synthetic origin, and they may have a static or cidal effect on microorganisms.

Types of antimicrobial agents

Antiseptics: microbicidal agents harmless enough to be applied to the skin and mucous membrane; should not be taken internaslly. Examples: mercurials, silver nitrate, iodine solution, alcohols, detergents.

Disinfectants: Agents that kill microorganisms, but not necessarily their spores,not safe for application to living tissues; they are used on inanimate objects such as tables, floors, utensils, etc. Examples: chlorine, hypochlorites, chlorine compounds, lye, copper sulfate, quaternary ammonium compounds.

Note: disinfectants and antiseptics are distinguished on the basis of whether they are safe for application to mucous membranes. Often, safety depends on the concentration of the compound. For example, sodium hypochlorite (chlorine), as added to water is safe for drinking, but "chlorox" , an excellent disinfectant, is hardly safe to drink.

Common antiseptics and disinfectants and their uses are summarized in Table 2.

Table 2. Common antiseptics and disinfectants
Ethanol (50-70%)Denatures proteins and solubilizes lipidsAntiseptic used on skin
Isopropanol (50-70%)Denatures proteins and solubilizes lipidsAntiseptic used on skin
Formaldehyde (8%)Reacts with NH2, SH and COOH groupsDisinfectant, kills endospores
Tincture of Iodine (2% I2 in 70% alcohol)Inactivates proteinsAntiseptic used on skin
Chlorine (Cl2) gasForms hypochlorous acid (HClO), a strong oxidizing agentDisinfect drinking water; general disinfectant
Silver nitrate (AgNO3) Precipitates proteinsGeneral antiseptic and used in the eyes of newborns
Mercuric chlorideInactivates proteins by reacting with sulfide groupsDisinfectant, although occasionally used as an antiseptic on skin
Detergents (e.g. quaternary ammonium compounds)Disrupts cell membranesSkin antiseptics and disinfectants
Phenolic compounds(e.g. carboloic acid, lysol, hexylresorcinol, hexachlorophene)Denature proteins and disrupt cell membranesAntiseptics at low concentrations; disinfectants at high concentrations
Ethylene oxide gas Alkylating agentDisinfectant used to sterilize heat-sensitive objects such as rubber and plastics

Preservatives: static agents used to inhibit the growth of microorganisms, most often in foods. If eaten they should be nontoxic. Examples; calcium propionate, sodium benzoate, formaldehyde, nitrate, sulfur dioxide. Table 3 is a list of common preservative and their uses.

Table 3. Common food preservatives and their uses
PreservativeEffective ConcentrationUses
Propionic acid and propionates0.32%Antifungal agent in breads, cake, Swiss cheeses
Sorbic acid and sorbates0.2%Antifungal agent in cheeses, jellies, syrups, cakes
Benzoic acid and benzoates0.1%Antifungal agent in margarine, cider, relishes, soft drinks
Sodium diacetate0.32%Antifungal agent in breads
Lactic acid?Antimicrobial agent in cheeses, buttermilk, yogurt and pickled foods
Sulfur dioxide, sulfites 200-300 ppmAntimicrobial agent in dried fruits, grapes, molasses
Sodium nitrite200 ppmAntibacterial agent in cured meats, fish
Sodium chloride?Prevents microbial spoilage of meats, fish, etc.
Sugar?Prevents microbial spoilage of preserves, jams, syrups, jellies, etc.
Wood smokeNAPrevents microbial spoilage of meats, fish, etc.

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