Isotopes. Food irradiation. DNA. And why gamma rays mean it’s game over for bacteria.
1-Minute NomNom
Keeping food safe is very important. Food safety technologies include pasteurization (which uses heat), and cold-pressing and high-pressure pascalization (both of which use pressure — read all about it in the 1-Minute NomNom “Hard pressed to give more“).
Another technology is food irraditation. Food irradiation has been approved by the US Food and Drug Administration (FDA) for use on foods such as beef, pork, poultry, crustaceans, fresh fruits and vegetables, eggs, spices and seasonings.
Food irradiation uses high-energy waves and particles (i.e. radiation) on food. These break the bonds in the DNA of any food-borne bacteria that may be present such as E. coli O157:H7 and salmonella. With their DNA damaged, the bacteria are neither able to repair nor reproduce themselves, and thus are eventually killed.
The process of breaking chemical bonds is called radiolysis. There are several ways to generate the high-energy radiation needed for radiolysis. One of the most common, according to the US Environmental Protection Agency, is to use an isotope of the element cobalt called cobalt-60 to generate gamma radiation.
Isotopes of a chemical element have the same number of protons as the element but a different number of neutrons. So while cobalt-59 (the one we usually see in a periodic table) has 27 protons and 32 neutrons, the isotope cobalt-60 has 27 protons and 33 neutrons.
But cobalt-60 is not just an isotope, it is a radioisotope. Radioistopes have excess energy and are unstable. In their quest for stability, they will find ways to lose this energy, moving from a higher energy state to a lower energy state.
In food irradiation, this excess energy of cobalt-60 is emitted as gamma radiation, which has the shortest wavelength along the electromagnetic spectrum.
We can identify food that has been irradiated by the “Radura” symbol. The symbol and use of irradiation has, however, not been widely adopted yet because there remains significant negative public perception about them.
On the other hand, according to the University of Wisconsin, food irradiation has been studied for more than 40 years. The researchers conclude that:
- Disease-causing microorganisms are reduced or eliminated
- The nutritional value is essentially unchanged
- The food does not become radioactive
The US Food and Drug Administration (FDA) also points out that “National Aeronautics and Space Administration (NASA) astronauts eat meat that has been sterilized by irradiation to avoid getting foodborne illnesses when they fly in space”.
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