Encyclopedia of Diets - A Guide to Health and Nutrition

Purpose

There are many reasons that foods are irradiated.
The most common reason is for increasedfood safety.
The United States Centers for Disease Control (CDC)
estimates that there are about 76 million cases of food-
borne illness each year in the United States, resulting
in about 5,000 deaths annually. Irradiating foods can
reduce the risk of many foodborne illnesses by killing
the bacteria or pathogens responsible, or harming
them to such an extent that they are not able to repro-
duce or cause disease. The National Aeronautics and
Space Administration (NASA) exposes the food that
astronauts eat while in space to a level of irradiation
far higher than that approved for commercial use in
order to reduce the risk that astronauts will develop
illness while in space. Patients who have diseases that
severely impair the functioning of the immune system
are often fed irradiated foods to decrease the risk that
they will develop a serious disease.

Irradiation can also be used to destroy insects and
other pests that may be present on produce. When
produce is shipped from Hawaii to the mainland
United States, it must be fumigated to kill any insects
or insect eggs that might be present so that they do not
spread to the mainland. Irradiating this produce is
sometimes used as an alternative to fumigation, and
does not leave residue of chemicals on the produce in
the way that fumigation can.

Some fruits and vegetables can be kept fresh lon-
ger by the use of low to moderate levels of irradiation.

When exposed to low levels of radiation, potatoes,

onions, and other vegetables do not sprout as quickly.

Strawberries and other berries can benefit from irra-

diation as well, as irradiation can significantly delay

the growth of mold. Strawberries stay fresh from 3–5

days when they are not irradiated or treated in any

way, but can stay fresh and unspoiled for up to three

weeks after being irradiated.

Description

Irradiated foods are foods that have been exposed

to ionizing radiation. Ions are electrically charged

particles, and ionizing radiation is radiation that pro-

duces these charged particles. Nonionizing radiation is

produced by microwaves, television and radio waves,

and visible light. Ionizing radiation is higher in power

than these types of radiation, although it is in the same

spectrum. The kinds of ionizing radiation used for

food irradiation include gamma rays, beams of high-

energy electrons, and x rays.

When foods are irradiated, they are exposed to the

source of the ionizing radiation for a short time. This

radiation produces short-lived compounds that dam-

age the deoxyribonucleic acid (DNA) of living organ-

isms, such as bacteria that are in the food. Because

DNA makes up the genes that contain the instructions

that tell an organism how to grow and reproduce, once

the DNA is damaged the organism cannot do this

correctly and will die.

The amount of radiation required to irradiate

foods depends on the type and thickness of the food

product and the type of organism that are present. The

larger the DNA of the organism, generally the less

radiation is required to irradiate it. Insects and para-

site have the larger DNA and require the lowest levels

of radiation, while bacteria generally require slightly

more, and viruses have very small amounts of DNA

and require very high levels of radiation. Most para-

sites, insects, and bacteria can be eliminated at levels of

Approved uses of irradiation

Food Approved use Dose

KGy  kiloGray

SOURCE: Food and Drug Administration, U.S. Department of

Health and Human Services

Spices and dry

vegetable seasoning

Dry or dehydrated

enzyme preparations

All foods

Fresh foods

Poultry

Red meat (such as

beef, lamb and pork)

Decontaminates and controls

insects and microorganisms

Controls insects and

microorganisms

Controls insects

Delays maturation

Controls disease-causing

microorganisms

Controls spoilage and disease-

causing microorganisms

30 kGy

10 kGy

1 kGy

1 kGy

3 kGy

4.5 kGy (fresh)

7 kGy (frozen)

The U.S. Food and Drug Administration approved the first
use of irradiation in 1963 on wheat and wheat flour. The FDA
sets the maximum radiation dose the product can be exposed
to, measured in a unit called kiloGray (kGy).(Illustration by
GGS Information Services/Thomson Gale.)

KEY TERMS

Ion—an electrically charged particle.

Ionizing radiation—radiation that produces ions.

Vitamin—A nutrient that the body needs in small

amounts to remain healthy but that the body cannot

manufacture for itself and must acquire through

diet.

Pathogen—an organism that causes a disease

Irradiated food