Control by Irradiation ◾ 509
energy of 1 joule (1 joule = 10 7 ergs), it has received a dose of 1 Gy. According to the international
health and safety authorities, foods irradiated up to 10,000 Gy (10 kGy) are considered safe.
The relative sensitivity of microorganisms to an irradiation dose is a function of their size and
water content. Approximate lethal dose levels for insects and different microorganisms have been
suggested as follows: insects, ≤1 kGy; molds, yeasts, bacterial cells, 0.5–10 kGy; bacterial spores,
10–50 kGy; and viruses, 10–200 kGy. Thus, at the recommended level of 10 kGy, Clo. botulinum
spores are not destroyed in foods (they need ca. 30–60 kGy) although cells of pathogenic (and spoilage) bacteria are destroyed. The products thus treated should have other barriers (low pH, low A W ,
temperature ≤ 4°C) to control germination and growth of spore formers. But some spore formers
(such as Clo. laramie) can germinate and multiply below 4°C. At present, a low dose level (<1 kGy)
is used to control insects in fruits and grains, parasites in meat and fish, and sprouting in vegetables.
Medium doses (1–10 kGy) are used to control foodborne pathogens and spoilage microorganisms to
extend the safety and stability of refrigerated foods. Higher doses (>10 kGy) to destroy spores are not
used in foods except in spices and vegetable seasonings that are used in very small quantities.
Irradiated foods, such as post-heat contamination in heated foods, can be contaminated later
with pathogenic and spoilage microorganisms from various sources unless proper precautions
(such as packaging) are used. Also, a food can be reradiated to inactivate microorganisms.
Specific Terms
Radurization
Radiation pasteurization is mainly intended to destroy spoilage bacteria in high-pH–high-A W
foods, especially Gram-negative psychrotrophs in meat and fish, and yeasts and molds in lowpH–low-A W foods. The treatment is generally milder (~1 kGy). The products should be packaged
and chilled to prevent growth of pathogens, which were previously thought to be mesophiles.
However, with the recognition of psychrotrophic pathogens and the importance of psychrotrophic
gram-positive spoilage bacteria, this treatment may not be effective.
Radicidation
This is the radiation of foods to destroy vegetative foodborne pathogens. The dose level used is approximately 2.5–5.0 kGy. Although it is effective against pathogenic vegetative bacterial cells and molds,
spores of the pathogens are not destroyed. Also, some radiation-resistant strains of pathogens can
survive, such as some Salmonella enterica serovar Typhimurium strains. Irradiated products thus need
to be stored at ≤4°C, especially to prevent germination and outgrowth of spores of Clo. botulinum.
Radappertization
This method involves radiation of food at a high dose (~30 kGy) to destroy Clo. botulinum spores
in order to get a safety similar to that by 12D heat treatment. However, this is not recommended
for use in food.
Current Recommendations
Irradiated fresh fruits, vegetables, spices and herbs, meat, and fish have been approved in 37 countries and are used in nations such as France, Belgium, and the Netherlands. In the United States,
energy of 1 joule (1 joule = 10 7 ergs), it has received a dose of 1 Gy. According to the international
health and safety authorities, foods irradiated up to 10,000 Gy (10 kGy) are considered safe.
The relative sensitivity of microorganisms to an irradiation dose is a function of their size and
water content. Approximate lethal dose levels for insects and different microorganisms have been
suggested as follows: insects, ≤1 kGy; molds, yeasts, bacterial cells, 0.5–10 kGy; bacterial spores,
10–50 kGy; and viruses, 10–200 kGy. Thus, at the recommended level of 10 kGy, Clo. botulinum
spores are not destroyed in foods (they need ca. 30–60 kGy) although cells of pathogenic (and spoilage) bacteria are destroyed. The products thus treated should have other barriers (low pH, low A W ,
temperature ≤ 4°C) to control germination and growth of spore formers. But some spore formers
(such as Clo. laramie) can germinate and multiply below 4°C. At present, a low dose level (<1 kGy)
is used to control insects in fruits and grains, parasites in meat and fish, and sprouting in vegetables.
Medium doses (1–10 kGy) are used to control foodborne pathogens and spoilage microorganisms to
extend the safety and stability of refrigerated foods. Higher doses (>10 kGy) to destroy spores are not
used in foods except in spices and vegetable seasonings that are used in very small quantities.
Irradiated foods, such as post-heat contamination in heated foods, can be contaminated later
with pathogenic and spoilage microorganisms from various sources unless proper precautions
(such as packaging) are used. Also, a food can be reradiated to inactivate microorganisms.
Specific Terms
Radurization
Radiation pasteurization is mainly intended to destroy spoilage bacteria in high-pH–high-A W
foods, especially Gram-negative psychrotrophs in meat and fish, and yeasts and molds in lowpH–low-A W foods. The treatment is generally milder (~1 kGy). The products should be packaged
and chilled to prevent growth of pathogens, which were previously thought to be mesophiles.
However, with the recognition of psychrotrophic pathogens and the importance of psychrotrophic
gram-positive spoilage bacteria, this treatment may not be effective.
Radicidation
This is the radiation of foods to destroy vegetative foodborne pathogens. The dose level used is approximately 2.5–5.0 kGy. Although it is effective against pathogenic vegetative bacterial cells and molds,
spores of the pathogens are not destroyed. Also, some radiation-resistant strains of pathogens can
survive, such as some Salmonella enterica serovar Typhimurium strains. Irradiated products thus need
to be stored at ≤4°C, especially to prevent germination and outgrowth of spores of Clo. botulinum.
Radappertization
This method involves radiation of food at a high dose (~30 kGy) to destroy Clo. botulinum spores
in order to get a safety similar to that by 12D heat treatment. However, this is not recommended
for use in food.
Current Recommendations
Irradiated fresh fruits, vegetables, spices and herbs, meat, and fish have been approved in 37 countries and are used in nations such as France, Belgium, and the Netherlands. In the United States,