Radiation Protection of Foods, and Nature of Microbial Radiation Resistance
377
Electron Beams/Accelerated Electrons
The use of electron accelerators offers certain advantages over radioactive elements that make this
form of radiation somewhat more attractive to potential commercial users. Koch and Eisenhower
39
listed the following:
1. High efficiency for the direct deposition of energy of the primary electron beams means high
plant-product capacity.
2. The efficient convertibility of electron power to X-ray power means the capability of handling
very thick products that cannot be processed by electron or gamma-ray beams.
3. The easy variability of electron-beam current and energy means flexibility in the choice of
surface and depth treatments for a variety of food items, conditions, and seasons.
4. The mono directional characteristic of the primary and secondary electrons and X-rays at the
higher energies permits a great flexibility in the food package design.
5. The ability to program and to regulate automatically from one instant to the next with simple
electronic detectors and circuits and various beam parameters means the capability of efficiently
processing small, intricate, or nonuniform shapes.
6. The ease with which an electron accelerator can be turned off or on means the ability to shut
down during off-shifts or off-seasons without a maintenance problem, and the ability to transport
the radiation source without a massive radiation shield.
Two differences between gamma rays and accelerated electrons are worthy of note. First, with regard
to penetration capacity, gamma is higher than accelerated electrons, but the penetration capacity of the
latter increases with their energy. For example, electrons at 10 MeV are more penetrating than those
at 4 MeV. The second difference is dose rate. The gamma rate from
60 Co is 1–100 Gy/min, whereas
electron beams from an electron accelerator are 10
3 –10
6 Gy/sec.
RADAPPERTIZATION, RADICIDATION, AND RADURIZATION OF FOODS
Definitions
Initially, the destruction of microorganisms in foods by ionizing radiation was referred to by terminology carried over from heat and chemical destruction of microorganisms. Although microorganisms
can indeed be destroyed by chemicals, heat, and radiation, there is, nevertheless, a lack of precision in
the use of this terminology for radiation-treated foods. Consequently, in 1964 an international group
of microbiologists suggested the following terminology for radiation treatment of foods.
25
Radappertization is equivalent to radiation sterilization or “commercial sterility,” as it is -understood
in the canning industry. Typical levels of irradiation are 30–40 kGy. The term was coined to honor N.
Appert.
Radicidation is equivalent to pasteurization—of milk, for example. Specifically, it refers to the
reduction of the number of viable specific non-spore-forming pathogens, other than viruses, so that
none is detectable by any standard method. Typical levels to achieve this process are 2.5–10 kGy.
Radurization may be considered equivalent to pasteurization. It refers to the enhancement of the
keeping quality of a food by causing substantial reduction in the numbers of viable specific spoilage
microbes by radiation. Common dose levels are 0.75–2.5 kGy for fresh meats, poultry, seafood, fruits,
vegetables, and cereal grains.
377
Electron Beams/Accelerated Electrons
The use of electron accelerators offers certain advantages over radioactive elements that make this
form of radiation somewhat more attractive to potential commercial users. Koch and Eisenhower
39
listed the following:
1. High efficiency for the direct deposition of energy of the primary electron beams means high
plant-product capacity.
2. The efficient convertibility of electron power to X-ray power means the capability of handling
very thick products that cannot be processed by electron or gamma-ray beams.
3. The easy variability of electron-beam current and energy means flexibility in the choice of
surface and depth treatments for a variety of food items, conditions, and seasons.
4. The mono directional characteristic of the primary and secondary electrons and X-rays at the
higher energies permits a great flexibility in the food package design.
5. The ability to program and to regulate automatically from one instant to the next with simple
electronic detectors and circuits and various beam parameters means the capability of efficiently
processing small, intricate, or nonuniform shapes.
6. The ease with which an electron accelerator can be turned off or on means the ability to shut
down during off-shifts or off-seasons without a maintenance problem, and the ability to transport
the radiation source without a massive radiation shield.
Two differences between gamma rays and accelerated electrons are worthy of note. First, with regard
to penetration capacity, gamma is higher than accelerated electrons, but the penetration capacity of the
latter increases with their energy. For example, electrons at 10 MeV are more penetrating than those
at 4 MeV. The second difference is dose rate. The gamma rate from
60 Co is 1–100 Gy/min, whereas
electron beams from an electron accelerator are 10
3 –10
6 Gy/sec.
RADAPPERTIZATION, RADICIDATION, AND RADURIZATION OF FOODS
Definitions
Initially, the destruction of microorganisms in foods by ionizing radiation was referred to by terminology carried over from heat and chemical destruction of microorganisms. Although microorganisms
can indeed be destroyed by chemicals, heat, and radiation, there is, nevertheless, a lack of precision in
the use of this terminology for radiation-treated foods. Consequently, in 1964 an international group
of microbiologists suggested the following terminology for radiation treatment of foods.
25
Radappertization is equivalent to radiation sterilization or “commercial sterility,” as it is -understood
in the canning industry. Typical levels of irradiation are 30–40 kGy. The term was coined to honor N.
Appert.
Radicidation is equivalent to pasteurization—of milk, for example. Specifically, it refers to the
reduction of the number of viable specific non-spore-forming pathogens, other than viruses, so that
none is detectable by any standard method. Typical levels to achieve this process are 2.5–10 kGy.
Radurization may be considered equivalent to pasteurization. It refers to the enhancement of the
keeping quality of a food by causing substantial reduction in the numbers of viable specific spoilage
microbes by radiation. Common dose levels are 0.75–2.5 kGy for fresh meats, poultry, seafood, fruits,
vegetables, and cereal grains.