Principles of Food Sanitation

of approximately 7.5 cm, whereas gamma
and X-rays can penetrate one or more meters
(Zammer, 2004). Figure 10–1 illustrates how
palletized foods may be irradiated.
Bacterial resistance determines the lethal
exposure time. The light rays must actually
strike the microorganisms. Radiation does
not penetrate well and its use as an antimi-
crobial agent should be restricted to
microorganisms on sources, in the air, or in
clear liquids. Liquids that may be treated
with UV light include: beverage plant water,
brine solutions, vegetable product transfer
water, cleaning-in-place rinse water, heating
and cooling water, cheese curd ranch water,
and wastewater effluents. They may be
absorbed by dust, thin films of grease, and
opaque, or turbid solutions. Also, radiation
controls the infestation of insects; regardless
of the stage of their life cycle. The effective-
ness of UV lamps depends on the spectral
characteristics of the bulb, time of exposure,
distance from the light source, and any inter-
fering substances that interfere with the light
such as fouling of the interior sources of the

UV reaction chamber or the protective bulb

shield. Because the process uses glass bulbs

and quartz reaction chambers, there is a risk

of breakage that makes a protective shield

essential. Since UV intensity dissipates with

distance from the light source, there is need

to minimize the distance from the lamp of

the material or surface being treated (Anon.,

2003).

Safety is a major concern since UV radia-

tion can cause severe eye damage and skin

irritation of exposed individuals. Further-

more, bacterial regrowth may occur because

there is no residual antimicrobial activity.

When exposed to visible light, bacterial cells

that had been injured by UV light can repair

themselves.

High Hydrostatic Pressure (HHP)

This technique is applied to foods, which

can be liquid or solid, packaged or unpack-

aged, to high pressure (which varies depend-

ing upon application) usually for 5 minutes or

less. HHP can be used on many foods such as

raw and cooked meats, fish and shellfish, fruit

Sanitizers 167

Figure 10–1Irradiation equipment for palletized foods. (Courtesy of Ecolab Inc., St. Paul, Minnesota.)