lowers surface tension, increases pH, decreases
viscosity, and creates other changes that may
help bactericidal action. An exception is the
iodophors that vaporize above 50°C. These
chemicals are more aggressive to surfaces,
especially elastomers and gasketing materi-
als, as the temperature rises. Thus, chemical
sanitizers should be applied at ambient tem-
peratures, ideally 21 to 38°C. Generally, the
degree of sanitation greatly exceeds the
growth rate of the bacteria, so that the final
effect of increasing temperature is to enhance
the rate of destruction of the microorgan-
isms.
Concentration:Increased sanitizer concen-
tration enhances the rate of destruction of
the microorganisms.
pH:The activity of antimicrobial agents
occurring as different species within a pH
range may be dramatically influenced by rel-
atively small changes in the pH of the
medium. Chlorine and iodine compounds
generally decrease in effectiveness with an
increase in pH.
Equipment cleanliness:Hypochlorites,other
chlorine compounds, iodine compounds,
and other sanitizers can react with the
organic materials of soil that have not been
removed from equipment and other surfaces.
Failure to clean surfaces properly can reduce
the effectiveness of a sanitizer. Oxidizing
chemicals react with organic materials, such
as soils, reducing their effectiveness against
target microorganisms.
Water hardness:A sanitizer is affected by
water composition, which can make the san-
itizer chemically inactive or buffer the pH
and diminish effectiveness. Quaternary
ammonium compounds are incompatible
with calcium and magnesium salts and
should not be used with over 200 parts per
million (ppm) of calcium in water or without
a sequestering or chelating agent. As water
hardness increases, the effectiveness of these
sanitizers decreases.
Microbial population: All sanitizers are
not equally effective against all microorgan-
isms. Cells in the spore state or in a biofilm
are more resistant than those in the vegeta-
tive and freely suspended state. Beverage
plants with yeasts and molds as their pri-
mary contaminants may need a different
sanitizer than fluid milk plants, which are
primarily concerned with psychrotrophic
spoilage bacteria. Since a sanitizer can only
reduce the number of bacteria, the higher
the initial number present, the higher the
amount of possible survivors. High numbers
can overwhelm the sanitizer.
Bacterial attachment:It has been demon-
strated by Le Chevallier et al. (1988) that
attachment of certain bacteria to a solid sur-
face provides an increased resistance to chlo-
rine. Other factors, such as nutrient limitation
(stringent response), also do so, and with
attachment, the resultant resistance to chlo-
rine is increased.
Most of these factors are interrelated and
one can normally compensate by adjusting
another. For example, if one can only pre-
pare the ideal sanitizer in cold water, it may
be possible to increase the contact time or
the concentration to obtain effectiveness
comparable to warm temperature in shorter
contact time or lower concentration.Desired Sanitizer Properties
The ideal sanitizer should have the follow-
ing properties:
●Microbial destruction properties of uni-
form, broad-spectrum activity against
vegetative bacteria, yeasts, and molds to
produce rapid kill
●Environmental resistance (effective in the
presence of organic matter [soil load],
detergent and soap residues, and water
hardness and pH variability)
●Good cleaning properties
●Nontoxic and nonirritating propertiesSanitizers 169