Control of Access of Microorganisms: Cleaning, Sanitation, and Disinfection ◾ 439
Chlorine-Based Sanitizers
Some of the chlorine compounds used as sanitizers are liquid chlorine, hypochlorites, inorganic
or organic chloramines, and chlorine dioxide. Chlorine compounds are effective against vegetative cells of bacteria, yeasts and molds, spores, and viruses. Clostridial spores are more sensitive
to chlorine compounds than the bacilli spores. The antimicrobial (germicidal) action of chlorine
compounds is a result of the oxidizing effect of chlorine on the –SH group in many enzymes and
structural proteins. In addition, damage to membrane, disruption of protein synthesis, reactions
with nucleic acids, and interference with metabolisms have been suggested.
The germicidal action of liquid chlorine and hypochlorites is produced by hypochlorous acid
(HOCl). It probably enters the cell and reacts with the –SH group of proteins. HOCl is stable at
acid pH and is thus more effective; at alkaline pH, it dissociates to H + and OCl – (hypochlorite ions),
which reduces its germicidal effectiveness. They are also less effective in the presence of organic matter.
Chloramines (inorganic or organic), such as Chloramine T, release chlorine slowly, but they are less
active against bacterial spores and viruses. They are effective, to some extent, against vegetative cells at
alkaline pH. Chlorine dioxide is more effective at alkaline pH and in the presence of organic matter.
Chlorine compounds are fast acting against all types of microorganisms, less costly, and easy
to use. However, they are unstable (especially at higher temperatures and with organic matter),
corrosive to metals, can oxidize food (color, lipid), and are less active in hard water.
Iodophores
Iodophores are prepared by combining iodine with surface-active compounds, such as alkylphenoxypolyglycol. Because of the surface-active compounds, they are relatively soluble in water.
Iodophores are effective against gram-positive and gram-negative bacteria, bacterial spores, viruses,
and fungi. Their germicidal property is attributed to elemental iodine (I 2 ) and hypoiodous acid,
which oxidize the –SH group of proteins, including key enzymes. They are more effective at acidic
pH and higher temperatures. In the presence of organic matters, they do not lose germicidal property as rapidly as chlorine does. However, their effectiveness is reduced in hard water.
They are fast acting, noncorrosive, easy to use, nonirritating, and stable. However, they are
expensive, less effective than hypochlorites against spores and viruses, can cause flavor problems
in products, and react with starch.
Quaternary Ammonium Compounds
Quaternary ammonium compounds (QACs) can be used as detergent sanitizers because they
have cleaning properties along with germicidal abilities. However, they are principally used as
sanitizers. They are synthesized by reacting tertiary amines with alkyl halides or benzyl chloride (Figure 31.1). The general structure is where R1, R2, R3, and R4 represent alkyl and other
groups. The cationic group is hydrophobic, and the anionic group is hydrophilic. QACs can act
as bactericides in high concentrations and when used in solution. However, they form a film on
the equipment surface, in which state (low concentrations) they are bacteriostatic. They are more
effective against gram-positive bacteria than many gram-negative bacteria, bacterial spores, fungi,
and viruses. The antimicrobial action is produced by the denaturation of microbial proteins and
destabilization of membrane functions. They are more effective against microorganisms at acidic
pH and higher temperature. Their effectiveness is not greatly reduced in the presence of organic
matters. However, they are less effective in hard water.
Chlorine-Based Sanitizers
Some of the chlorine compounds used as sanitizers are liquid chlorine, hypochlorites, inorganic
or organic chloramines, and chlorine dioxide. Chlorine compounds are effective against vegetative cells of bacteria, yeasts and molds, spores, and viruses. Clostridial spores are more sensitive
to chlorine compounds than the bacilli spores. The antimicrobial (germicidal) action of chlorine
compounds is a result of the oxidizing effect of chlorine on the –SH group in many enzymes and
structural proteins. In addition, damage to membrane, disruption of protein synthesis, reactions
with nucleic acids, and interference with metabolisms have been suggested.
The germicidal action of liquid chlorine and hypochlorites is produced by hypochlorous acid
(HOCl). It probably enters the cell and reacts with the –SH group of proteins. HOCl is stable at
acid pH and is thus more effective; at alkaline pH, it dissociates to H + and OCl – (hypochlorite ions),
which reduces its germicidal effectiveness. They are also less effective in the presence of organic matter.
Chloramines (inorganic or organic), such as Chloramine T, release chlorine slowly, but they are less
active against bacterial spores and viruses. They are effective, to some extent, against vegetative cells at
alkaline pH. Chlorine dioxide is more effective at alkaline pH and in the presence of organic matter.
Chlorine compounds are fast acting against all types of microorganisms, less costly, and easy
to use. However, they are unstable (especially at higher temperatures and with organic matter),
corrosive to metals, can oxidize food (color, lipid), and are less active in hard water.
Iodophores
Iodophores are prepared by combining iodine with surface-active compounds, such as alkylphenoxypolyglycol. Because of the surface-active compounds, they are relatively soluble in water.
Iodophores are effective against gram-positive and gram-negative bacteria, bacterial spores, viruses,
and fungi. Their germicidal property is attributed to elemental iodine (I 2 ) and hypoiodous acid,
which oxidize the –SH group of proteins, including key enzymes. They are more effective at acidic
pH and higher temperatures. In the presence of organic matters, they do not lose germicidal property as rapidly as chlorine does. However, their effectiveness is reduced in hard water.
They are fast acting, noncorrosive, easy to use, nonirritating, and stable. However, they are
expensive, less effective than hypochlorites against spores and viruses, can cause flavor problems
in products, and react with starch.
Quaternary Ammonium Compounds
Quaternary ammonium compounds (QACs) can be used as detergent sanitizers because they
have cleaning properties along with germicidal abilities. However, they are principally used as
sanitizers. They are synthesized by reacting tertiary amines with alkyl halides or benzyl chloride (Figure 31.1). The general structure is where R1, R2, R3, and R4 represent alkyl and other
groups. The cationic group is hydrophobic, and the anionic group is hydrophilic. QACs can act
as bactericides in high concentrations and when used in solution. However, they form a film on
the equipment surface, in which state (low concentrations) they are bacteriostatic. They are more
effective against gram-positive bacteria than many gram-negative bacteria, bacterial spores, fungi,
and viruses. The antimicrobial action is produced by the denaturation of microbial proteins and
destabilization of membrane functions. They are more effective against microorganisms at acidic
pH and higher temperature. Their effectiveness is not greatly reduced in the presence of organic
matters. However, they are less effective in hard water.