Fundamental Food Microbiology, Third Edition - Fuad Fathir

CONTROL BY IRRADIATION 509
feeding studies, with animals as well as humans for a fairly long period, showed
that irradiated foods did not cause any toxic effect or genetic defects. A WHO expert
committee on the wholesomeness of irradiated food, after extensive review of more
than 200 well-designed studies conducted worldwide, has recommended irradiation
of food up to a certain dose level (10 kGy). This level is currently approved in more
than 30 countries for use in meat, fish, vegetables, fruits, and grains. Many countries
are regularly selling irradiated foods, especially some vegetables, fruits, and grains.
However, consumer resistance has been quite high. This is mainly due to their lack
of information and understanding that irradiated foods are not radioactive and radiolytic
products are not unique to only irradiated foods. This is probably the only
food preservation method that has been studied for safety for a long time (more than
40 years) before its recommendation, and whose use in many countries has been
found to be safe by the world body of expert scientists. The other reason is political.
A small but vocal group of lobbyists are waging a very successful campaign against
the acceptance of irradiated food by large numbers of consumers. As a result, food
industries are in a wait-and-watch situation.
There is no controversy among experts that food irradiation is an economical
and effective food preservation method. As the world population increases and food
production decreases, effective preservation methods must be used to feed the hungry
mouths, otherwise social unrest may start. Politics and lobbying will not stop hunger,
but food preservation methods (such as irradiation) will.
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II. OBJECTIVES
A food is irradiated because of the destructive power of ionization on microorganisms
a food harbors. Depending on the method used, it can either completely or partially
destroy molds, yeasts, bacterial cells and spores, and viruses. In addition, irradiation
can destroy worms, insects, and larvae in food. It also prevents sprouting of some
foods, such as potatoes and onions. However, irradiation cannot destroy toxins or
undesirable enzymes in a food, in which respect it differs from heat treatment (heat
also does not destroy heat-stable toxins and enzymes). Irradiation is a cold sterilization
process inasmuch as the temperature of a food does not increase during
treatment, and thus irradiated foods do not show some of the damaging effects of
heat on food quality. However, irradiation can cause oxidation of lipids and denaturation
of food proteins, especially when used at higher doses. 1–3
III. MECHANISMS OF ANTIMICROBIAL ACTION
When an object (food or microorganism) is exposed to high-energy g-rays (10 -1 to
10 -2 nm), the energy is absorbed by thousands of atoms and molecules in a fraction
of a second, which strips electrons from them. This produces negative and positive
ion pairs. The released electrons can be highly energized and thus can remove
electrons from other atoms and convert them into ions. This energization and ionization
can adversely affect the normal characteristics of biological systems.