methods and sanitation techniques that will
reduce the probability that this pathogen will
occur in food.
Properly constructed and maintained
facilities and equipment are fundamental to
an effective cleaning and sanitation program
for the control of L. monocytogenes. Con-
struction characteristics that will be
described in this chapter and in Chapters 17,
18, and 19 should be considered when plan-
ning a program for the control of this
pathogen.
L. monocytogenesis sensitive to sanitizing
agents commonly employed in the food
industry. Chlorine-based, iodine-based, acid
anionic, and/or quaternary ammonium-
type sanitizers are effective against this
pathogen when used at concentrations of
100 ppm, 25 to 45 ppm, 200 ppm, and 200
ppm, respectively. Although these concentra-
tions may require adjustment to compensate
for in-plant use (as may oxidation-reduction
factors relating to water quality and hard-
ness), recommended concentrations should
not be markedly exceeded, as use of
extremely concentrated sanitizing solutions
heightens the danger to employees, increases
the risk of chemical contamination of food,
and in some instances, causes corrosion of
equipment.
Quaternary ammonium-based sanitizers
are not recommended for use on food-con-
tact surfaces and should not be used in
cheese factories, as lactic acid starter culture
bacteria are inactivated rapidly by small
residues of these sanitizers. In contrast, acid
anionic and iodine-type sanitizers are best
suited for equipment surfaces, with the for-
mer readily neutralizing excess alkalinity
from cleaning compounds and preventing
the formation of alkaline mineral deposits.
The use of steam should be discouraged (due
to energy costs) and, if used, should be con-
fined to closed systems because of potential
hazards associated with aerosol formation.
Sanitizing with hot water is not recom-
mended because of the energy costs of heat-
ing water and because high temperatures
cannot be maintained easily.
Effectiveness of a Listeriacontrol program
can be measured by conventional and rou-
tine, preoperative microbial monitoring, such
as aerobic plate count and coliform count
(see Chapters 3 and 8). However, industry
experience has suggested that the most accu-
rate measurement relies on specific testing for
Listeriaorganisms in the plant environment.
Environmental sampling should be organized
to guide preoperative sanitation practices
and direct management toward a Listeria-
controlled operation.Escherichia coliO157:H7
Outbreaks of this pathogen associated
with raw milk have challenged investigators
to further research this microorganism in
dairy products. This pathogen can grow in
cottage cheese and cheddar cheese but is
inactivated by the pasteurization of milk.
Buchanan and Doyle (1997) suggested
that alternative technologies to thermal pro-
cessing control E. coliO157:H7 while main-
taining the acceptability of dairy products.
A viable alternative technology for dairy,
meat, and poultry products is ionizing radia-
tion. This pathogen is relatively radiation-
sensitive, and radiation pasteurization doses
of 1.5 to 3.0 KGy appear to be destructive at
the levels that are most likely to occur in
ground beef (Clavero et al., 1994).Salmonella
Milk and milk products have been identi-
fied as a vehicle for transmission in approxi-
mately 5% of salmonellosis cases, although
the sources of infection in Maine identified in
most cases (Center For Disease Control and
Prevention, 2000). Salmonellosis is commonly
diagnosed in dairy animals (Wells et al., 2001)
and there is evidence that it is shed from theDairy Processing Plant Sanitation 285