What is Food Irradiation? Why is it Done?

Hi, Dr. Zoomie –

I got some ground beef at the store the other day that says it was irradiated. Can you tell me what that means and why it’s done? My brother tells me irradiation makes the food dangerous – is there any truth to that?

It’s not only the ground beef that’s irradiated – a lot of spices are irradiated, along with some fruits, meats, and more. What’s happening is that the food is exposed to very high levels of radiation; that radiation is enough to kill off any bacteria that might be inside (or on the outside)of the food. We all know that radiation can harm people – what many don’t realize that a high enough dose of radiation can kill microbes to boot. So if we slam enough radiation into food, it ought to kill all of the microbes; since those microbes are what makes the food go bad, food irradiation keeps it fresher longer.

Incidentally, it’s not only food that’s irradiated to sterilize it – there are a number of facilities in the US that use radiation to sterilize surgical supplies, some mail, and much of the blood supply.

Some types of food don’t do well under irradiation – it can cause strawberries to become mushy, for example. But in addition, some people are concerned about food irradiation because exposure to high levels of radiation can cause chemical changes in the food. And it’s true – exposing food to radiation can cause new chemicals to form, but these chemicals don’t seem to be harmful to people. And I should point out that any sort of cooking causes chemical changes to the food – that’s what cooking is. When you brown meet or caramelize onions, for example, the sugars in the food are undergoing a chemical reaction called the Maillard reaction. But what really causes chemical changes is grilling food over charcoal, wood, or even a gas flame, and some of these changes (especially the ones that include the soot or combustion products from the flame) can create chemicals that are potentially much more dangerous than anything caused by radiation. This isn’t to say that grilling out is dangerous – more to put the changes caused by irradiation in perspective. The bottom line is that cooking, grilling, and food irradiation can all cause chemical changes in your food – and irradiation causes fewer changes than the other techniques.

Something else that people worry about is that irradiation might cause food to become radioactive. Luckily there’s nothing to this at all – the gamma radiation from cobalt-60 or cesium-137 is simply unable to cause food to become radioactive (neither can the x-rays or electron beams that are sometimes used). And the food doesn’t somehow store up the radiation – no more than, say, your furniture stores up light and glows when you turn the lights off. For that matter, the only type of radiation that is effective at causing things to become radioactive is neutron radiation, and neutron radiation isn’t used for irradiating food.

Something else to keep in mind is that the whole purpose of food irradiation is to kill microbes. Think of all the food recalls and food poisoning outbreaks that have been in the news – millions of pounds of ground beef have been recalled, contaminated spinach caused illness and death, and much more. The bottom line is that food irradiation makes food safer – another of the GAO’s findings.

When you put it all together, you can reassure your brother that we get a lot more benefit than risk from food irradiation. In fact, the greatest risk is to the people working at the food irradiation facility – there have been injuries and fatalities from people who just didn’t work safely with the high levels of radioactivity that’s present. But as long as the workers are careful to follow the proper safety precautions they’ll stay safe also.

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