Preservation of Foods by Ionizing Energy Flashcards
What is food irradiation?
The exposure of food to ionizing energy
What is radiation?
Radiation refers to the emission and propagation of energy through matter or space by electromagnetic disturbances.
These forms of energy are found within the electromagnetic spectrum of radiation.
What is the electromagnetic spectrum?
This is an organized scale where we find energy ranging from radio waves, microwaves, visible light to ionizing radiation.
These forms of energy vary in frequency, wavelength, energy value, penetrating power, and their effects on biological systems.
What wavelength of electromagnetic energy are we familiar with?
What are they characterized by?
The longer wavelengths of electromagnetic energy that we are familiar with include visible light, infrared and ultraviolet rays.
These are characterized by having low penetrating power.
Microwaves and infrared radiation are two examples of the longer wavelengths in the electromagnetic spectrum.
How do microwaves work?
Microwaves are used in food for their heating properties. The microwaves travel in straight lines and pass through air, glass, paper and plastic, but reflected by metals.
They are readily absorbed by water (polar molecule), causing it to vibrate. Heat is generated by the intermolecular friction generated from the vibrating water (polar) molecules in food.
Microwaves are absorbed by food up to a depth of 5 to 7.5 cm.
Give examples of infrared energy in food production.
Infrared energy can generate heat.
They can reach temperatures above 100°C.
Typical examples of infrared energy can be seen in ovens, toasters, and even those “infrared” lamps used to keep food warm.
What forms of energy are referred to as ionizing energy, and why?
Examples of short wavelengths include X-rays, beta rays and gamma rays, which can be employed as energy sources in food irradiation, since they have good penetrating power.
What does food irradiation mean according to Health Canada?
Food Irradiation is the application of radiation, in the form of ionizing energy, to foods.
According to Health Canada, Food Irradiation means “the treatment of food with ionizing radiation” from the following sources:
- Gamma radiation from a Cobalt-60 or Cesium 137
- X-rays generated from a machine source operated at or below 5 MeV
- Electrons generated from a machine source operated at or below 10 MeV
Define: Gamma radiation
Electromagnetic radiation that has very short wavelengths, similar to “short” x-rays.
Isotopes such as Cobalt-60 and Cesium-137 emit gamma radiation as they disintegrate.
Define: x-rays
Electromagnetic radiations that are highly energetic and of short wavelength.
X-rays are produced by x-ray machines that emit a beam of fast electrons which hit a metal target in a vacuum.
X-ray machines emit radiation only when the machines are turned on.
Define: electron beam
Can be produced with high-energy (speed) electrons or may also be generated by an electron beam accelerator.
Electron Beam Accelerators need only electricity to operate and produce no waste materials
Define: the gray
A unit of energy absorbed by a food irradiated with ionizing radiation.
One thousand grays equals one kilogray (kGy).
Most of the ionizing radiation processes permitted around the world involve absorbed doses of <10 kGy.
Define: the rad
This is another unit used to express the radiation absorbed dose (rad), where 100 rads = 1 Gy.
However, the preferred unit is the kGy
Where are the food irradition plants in Canada?
Most of the irradiation facilities in Canada process medical and personal care supplies.
MDS Nordion (Laval, Quebec) and Iotron (Port Coquitlam, BC) process some dry food ingredients.
The former uses gamma rays, while the latter uses electron beam technology.
The Canadian Irradiation Centre (CIC) is a training centre operated as a joint venture by MDS Nordion and the Université du Québec, Institut Armand-Frappier (IAF).
What is the basis of food preservation by treatment with ionizing energy?
The ability of the absorbed quanta of energy to dislodge electrons from molecules with the concomitant creation of free radicals without inducing radioactivity in the food.
