54 PRINCIPLES OFFOODSANITATION
tional discussion related to this subject is
presented in Chapter 10.) Chlorine, acids,
and phosphates are potential decontami-
nants for microbial load on red meat and
poultry carcasses.
Radiation
When microorganisms in foods are irradi-
ated with high-speed electrons (beta rays) or
with X-rays (or gamma rays), the log of the
number of survivors is directly proportional to
the radiation dose. The relative sensitivity of a
specific strain of microorganisms subjected to
specific conditions is normally expressed as the
slope of the survivor curve. The log 10 of sur-
vivors from radiation is plotted against the
radiation dosage, and the radiation D or D 10
value, which is comparable with the thermal D
value, is obtained. The D 10 value is defined as
the amount of radiation in rads (ergs of energy
per 100 g of material) to reduce the microbial
population by 1 log (90%).
The destructive mechanism of radiation is
not fully understood. It appears that death is
caused by inactivation of cellular compo-
nents through energy absorbed within the
cell. A cell inactivated by radiation cannot
divide and produce visible outgrowth. (Addi-
tional information related to radiation as a
sanitizer is presented in Chapter 10.)
Electronic Pasteurization
Pasteurization is an act or process, usually
involving heat, which reduces the number of
bacteria in a food product without changing
the chemistry or property of the food. Elec-
tron-beam accelerators can be used for elec-
tron pasteurization of food products by
impacting the products directly with elec-
trons or optimizing the conversion of elec-
tron energy to X-rays and treating the
product with these X-rays. For electron treat-
ment, 10 million electron volts (meV) kinetic
energy is the maximum allowed by interna-
tional agreement.
Accelerators provide X-rays or electrons
for treatment of food. An accelerator pro-
vides energy to electrons by providing an
electric field (potential energy) to accelerate
the electrons. Electrons are atomic particles,
rather than electromagnetic waves, and their
depth of penetration in the product is
smaller. Therefore, the direct use of electrons
is limited to packages less than 10 cm thick
(Prestwich et al., 1994).Pulsed Light
A potential method of microbial reduc-
tion on both packaging and food surfaces is
the utilization of intense pulses of light.
Pulsed light is energy released as short, high-
intensity pulses of broad-spectrum “white”
light that can sterilize packaging materials
and decrease microbial populations on food
surfaces. Microorganisms exposed to pulse
light are destroyed. Reductions of more than
8 logs of vegetative cells and 6 logs of spores
on packaging materials, and in beverages,
and 1 to 3 logs on complex or rough surfaces,
such as meat, may be achieved.
Pulsed-light flashes are created by com-
pressing electrical energy into short pulses
and using these pulses to energize an inert
gas lamp. The lamp emits an intense flash
of light for a few hundred microseconds.
Because this lamp can be flashed many times
per second, only a few flashes are required to
produce a high level of microbial kill. Thus,
an on-line procedure for food processing can
be very rapid.
Pruett and Dunn (1994) reported that the
incorporation of an acetic acid spray before
pulsed-light treatment led to higher levels of
pathogen kill. Further analysis of the multi-
hurdle concept is planned using a hot-water
spray in combination with pulsed light, but
the results are unavailable at the time of this
writing. Past investigations have revealed no
nutritional or sensory changes attributable
to pulsed light.