Principles of Food Sanitation

and diatomic iodine. Both the hypoiodous
acid and diatonic iodine are the active antimi-
crobial forms of an iodophor sanitizer.
Ionic surface-active agents (surfactants)
are compounds composed of two principal
functional groups-a lipophilic portion and a
hydrophilic portion. When placed in water,
these molecules ionize, and the two groups
induce a net charge to the molecule, which
results in either a positive or a negative
charge for the surfactant molecule. Cationic
and anionic sanitizers have similar modes of
action.
When elemental iodine is complexed with
nonionic surface-active agents such as nonyl
phenolethylene oxide condensates or a carrier
such as polyvinylpyrrolidone, the water-
soluble complexes known as iodophorsare
formed. Iodophors, the most popular forms
of iodine compounds used today, have greater
bactericidal activity under acidic conditions.
Thus, these compounds are frequently modi-
fied with phosphoric acid. Complexing
iodophors with surface-active agents and
acids gives them detergent properties and
qualifies them as detergent sanitizers. These
compounds are bactericidal and, when com-
pared to aqueous and alcoholic suspensions
of iodine, have greater solubility in water, and
are nonodorous and nonirritating to the skin.
To prepare the surfactant-iodine complex,
iodine is added to the nonionic surfactant and
heated to 55 to 65°C to enhance solution of
the iodine and to stabilize the end product.
The exothermic reaction between the iodine
and surfactant produces a rise in temperature,
dependent on the type of surfactant and the
ratio of surfactant to iodine. If the iodine
level does not exceed the solubilizing limit of
the surfactant, the end product will be com-
pletely and infinitely soluble in water.
The behavior of surfactant-iodine com-
plexes has been previously explained on the
basis of equilibrium R+I 2 ?RI+ HI,
where R represents the surfactant. Removal

of the iodides formed by oxidation to iodine

is responsible for further disposition of

available iodine, presumably due to increased

iodination of the surfactant.

The amount of free available iodine deter-

mines the activity of iodophors. The surfac-

tant present does not determine the activity of

iodophors but can affect the bactericidal

properties of iodine. Spores are more resistant

to iodine than are vegetative cells, and the

lethal exposure times noted in Table 10–1 are

approximately 10 to 1,000 times as long as for

vegetative cells. Iodine is not as effective as

chlorine in spore inactivation. Iodine-type

sanitizers are somewhat more stable in the

presence of organic matter than are the chlo-

rine compounds. Because iodine complexes

offer low toxicity and are stable at a very low

pH, they may be incorporated at a very low

concentration of 6.25 ppm and are frequently

used at 12.5 to 25 ppm. Iodine sanitizers are

more effective than other chemicals on

viruses. Only 6.25 ppm is required to pass the

Chambers test in 30 seconds. Nonselective

iodine compounds kill vegetative cells, over a

broader pH range than chlorine, and many

spores and viruses.

Sanitizers 175

Table 10–1Inactivation of Bacterial Spores by

Iodophors

Concentration

Time for a

Organism pH (ppm) 90%

Reduction

(min)

Bacillus cereus 6.5 50 10

6.5 25 30

2.3 25 30

Bacillus subtilis –25 5

Clostridium

botulinum

type A 2.8 100 6

Note:All tests were conducted in distilled water at 15°C to

25 °C.

Source:Odlaug (1981).