506 ◾ Fundamental Food Microbiology
Use of Irradiation in Food
The ability of X-rays, γ-rays (E-beam), and β-rays to kill microorganisms was recognized soon
after their discovery in the late 19th and early 20th centuries. Some were even tested to determine
their effectiveness in killing microorganisms in food in those early years. However, until the late
1940s and early 1950s, their use in food preservation was not actively studied. One reason was
the unavailability of a large economical supply of radioisotopes, the technology of which was
developed during World War II. Early studies showed that different foods can be irradiated to
extend shelf life without making them radioactive, but the process affected the flavor qualities of
the foods. Later, the problems were overcome by reducing exposure time and lowering product
temperature. At that time, it was thought that irradiation of food would give storage stability
for indefinite periods of time. The U.S. Army started a research program to determine whether
storage-stable, acceptable, safe army rations could be produced by irradiation. Although foods do
not become radioactive at low doses of irradiation, it was found that food accumulated radiolytic
products. Extensive studies showed that they are present in very low concentrations (~3 ppm).
Most of them are not unique to irradiated foods because they are present naturally in different
foods and are also produced in heated foods (thermolytic products). Well-designed feeding studies, with animals as well as humans and 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 because of 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. 4–6 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.
Globally, in 2005, 405,000 tons of food, such as spices, dry vegetables, grains, fruits, meat
and fish, sprouts, garlic, mushrooms, honey, potatoes, and other food items, were disinfected by
irradiation. While commercial food irradiation is increasing significantly in Asian countries, the
trend is opposite in the European Union. 2,5
objectives
A food is irradiated because of the destructive power of ionization on the 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,
Use of Irradiation in Food
The ability of X-rays, γ-rays (E-beam), and β-rays to kill microorganisms was recognized soon
after their discovery in the late 19th and early 20th centuries. Some were even tested to determine
their effectiveness in killing microorganisms in food in those early years. However, until the late
1940s and early 1950s, their use in food preservation was not actively studied. One reason was
the unavailability of a large economical supply of radioisotopes, the technology of which was
developed during World War II. Early studies showed that different foods can be irradiated to
extend shelf life without making them radioactive, but the process affected the flavor qualities of
the foods. Later, the problems were overcome by reducing exposure time and lowering product
temperature. At that time, it was thought that irradiation of food would give storage stability
for indefinite periods of time. The U.S. Army started a research program to determine whether
storage-stable, acceptable, safe army rations could be produced by irradiation. Although foods do
not become radioactive at low doses of irradiation, it was found that food accumulated radiolytic
products. Extensive studies showed that they are present in very low concentrations (~3 ppm).
Most of them are not unique to irradiated foods because they are present naturally in different
foods and are also produced in heated foods (thermolytic products). Well-designed feeding studies, with animals as well as humans and 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 because of 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. 4–6 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.
Globally, in 2005, 405,000 tons of food, such as spices, dry vegetables, grains, fruits, meat
and fish, sprouts, garlic, mushrooms, honey, potatoes, and other food items, were disinfected by
irradiation. While commercial food irradiation is increasing significantly in Asian countries, the
trend is opposite in the European Union. 2,5
objectives
A food is irradiated because of the destructive power of ionization on the 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,