food irradiation (edit 1)

8/2/2019 Food Irradiation (Edit 1)

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Introduction

Food is necessary for every single living thing in the world, including people. It is important that

such a vital aspect to life is safe and clean to consume. Spoiled food contains bacteria and parasites that

cause sickness and sometimes even death. Before, the most common methods of sterilizing and

preserving food involved canning, pickling and pasteurizing. Those processes are still used, but newnuclear processes have recently come into the industry and are continually expanding.

The Process

Food irradiation is the process in which food items are exposed to ionizing radiation from a

radioisotope for a specific amount of time in order to eradicate bacteria and therefore, sterilize them.

The process takes place in a special facility where the necessary equipment is. All facilities vary

in size but generally have three areas:

Fig. 1: A general layout of an irradiation facility

1) The outer area is where food is received and stored. This place functions as a warehouse

and must have appropriate equipment for whatever type of food received. For instance, if

frozen or perishable foods are received, this area must have refrigerators.

2) The second area is a transport system that brings the food to the source of radiation. It is

usually a simple conveyor belt that allows the food to be irradiated evenly on all sides.


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3) The final area is where the source of radiation is located. The food is positioned and a

computer calculates and delivers a measured dose of ionizing radiation. Thick concrete

walls surround the machine holding the source in order to prevent radiation from

escaping.

The sources used for this process are limited due to safety. Any food irradiation facility uses one

of three sources.

1) Gamma rays: high energy radiation with the shortest wavelengths that penetrate easily

through most materials. Only certain materials are usable as the source, the most common

being cobalt-60 and cesium-137. The source is always placed in water when not in use so

that no rays escape.

2) Accelerated electrons: a beam of high-energy electrons are shot out of an electron gun.

The electron gun resembles an enlarged television tube and can simply be switched on or

off. There is no radioactive materials in this process so switching it off stops all activity.

Since electrons can only penetrate about three centimetres, the food it treats must be

thinner to make sure all particles pass through it.

Fig. 2: Diagram of facility using electron guns

3) X-ray machines: a beam of electrons are fired at a piece of gold or any other metal to

create x-ray beams. They penetrate just as much as gamma rays do, but like accelerated

electrons, the machine can be switched off and no radioactive material is involved.

A certain dose of radiation energy is delivered through a computer. Doses are measured in a unit


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called the Gray (G). One Gray is equal to 0.001 kiloGrays (kGy) which also equals one joule per

kilogram of food irradiated. The magnitude of a dose depends on the food product as well as what type of

effect is desired.

A low dose (about 1 kGy) is used as an alternative method to chemical processes. It is used to

inhibit sprouting (on potatoes for example), eradicate insect infestations, and delays ripening. However,this irradiation does not protect against re-infestation since the insides of the food are unchanged. Food

treated with a low dosage are not fully sterilized and must be handled as non-radiated food.

Medium dosage is anywhere between 1-10 kGy. It is used to control food borne bacteria that can

cause illnesses, such as salmonella. Since the higher dosage means that bacteria can be destroyed, this

means that food can be preserved to have a longer shelf life. It is more efficient than canning since it does

not add any liquid to the food and preserves most of the original flavour.

The largest dose is between 10-50 kGy and is usually used for more specialized food. Food

treated with this amount of radiation energy can last for many years without spoiling. This makes food

completely sterile.

Safety and Handling

To ensure that the food irradiation process is safe, certain precautions are taken to prevent any

harmful rays from escaping.

Firstly, only approved sources are used in irradiation facilities. Cobalt-60 is a man-made

radioisotope and it is the one most commonly used. It is produced in CANDU reactors located in Ontario

and Quebec. Cobalt makes an excellent choice as the source due to its short half-life of about 5 years and

its re-usability. When the energy in cobalt becomes close to being used up, it is shipped back to the

original nuclear reactor to be reactivated. It is a relatively solid metal that rarely breaks and does not

spread its waste in the environment.

Fig. 3: The Darlington Nuclear Generating Station in Clarington, Ontario contains four CANDU reactors


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Then, irradiation facilities are built with safety features such as thick concrete walls that prevent

gamma rays from escaping the building. When not in use, the sources are kept in a pool of water which

completely absorbs any emitting energy. Eventually over many years, the radioactive sources will decay

into safer, more stable substances like nickel.

For places that do not use gamma rays and instead use electrons, they must make sure that anyfood they treat is less than 3 centimetres in thickness. Electrons can only penetrate a maximum of 3

centimetres as opposed to gamma rays which can travel through most materials easily for up to 2

kilometres. Food that is too thick risk having particles stuck inside that may cause problems. Sometimes,

a second opposing beam is used to treat food that is thicker. Two beams can safely penetrate twice as far

as one.

The Advantages

The benefits of food irradiation are numerous.

Its main job is to destroy bacteria, parasites and insects that can cause illness. It can reduce the

amount of common food-borne bacteria like salmonella, listeria and E.coli. This prolongs the shelf life of

a food product, which means it can be stocked up or sent long distances without spoiling. This is

particularly beneficial for hospital patients with weak immune systems, such as those recovering from

cancer or AIDS, who cannot risk any infections. It can be used in the military and for space travel as well,

where they need food that lasts for months or even years. Also, it makes it easier for food to be exported

to other countries without worrying about them losing their freshness. It is because of this process that we

are able to enjoy delicious produce that is not grown in Canada such as pineapples, kiwis and bananas.

An advantage of this process over chemical processes is that the original flavour and freshness of

the food is better preserved. Not only does it taste good, the nutritional values are virtually unchanged.

Proteins, carbohydrates and fats are stable up to a medium dose of 10 kGy. Micro-nutrients, such as

vitamins, are much more difficult to preserve as they are extremely sensitive to all food processing

methods. Vitamin C can diminish up to 10% while vitamin E can be reduced by up to 25% when

irradiated. However, with a dose of 1 kGy, the amount lost is considered negligible. Temperature can also

be a factor in preservation. Under careful handling, irradiation is still the best method overall.

Despite popular superstitions, food processed with irradiation does not become radioactive

themselves. The same goes for how an x-ray at the doctor's or at the airport does not make a person or

their luggage radioactive. This is because food never comes in physical contact with the radioactive

source. Even when food is exposed to a high dose, the radiation it gains is insignificant, 200,000 times

less than the amount of radiation found naturally in food.


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Negative Aspects

There are a few negative sides to food irradiation.

The cost of constructing an irradiation facility can cost anywhere between $4-10 million. Each

low dose on one ton of food can cost about $10 while a high dose can be up to $250. This makes itdifficult to compete with canning, freezing or pasteurization, which cost significantly less.

In every country using irradiation, there exists guidelines on what food products are approved to

undergo the process. Canada only allows onions, potatoes, wheat, flour, whole wheat flour, and whole or

ground spices and dehydrated seasonings. Therefore, no meat, poultry or salad food can be treated in this

fashion in Canada.

The reason limitations exist is not because the process causes certain foods to be harmful. In fact,

sufficient research has been completed in order to conclude that irradiation does not make food dangerous

for human consumption. The real problem is that there is lack of public understanding on the subject of

nuclear science. Many people are still skeptical about using nuclear power for anything. Sometimes, this

fear may date back to the days of World War II and the Cold War when nuclear science was used for

destruction. Since processors tend to be more interested in making a profit, they generally refuse to

irradiate foods out of fear that no one will buy them. This can be an issue, as food related disease

outbreaks are becoming frequent, and irradiation could have been used as prevention. But as long as

nuclear topics are greeted with controversy, extending the list of approved food products will be nearly

impossible.

Conclusion

Although food irradiation is an effective method of sterilization, it is still too costly to be widely

used. The general public's misunderstanding is also a factor that is slowing down the expansion of

nuclear inventions. It would be beneficial if people were educated better about how nuclear technology

really works. This way, lives can be improved and be made healthier by taking advantage of these

sterilization processes, without worries or fear.

Works Consulted


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American Nuclear Society, Food, http://www.aboutnuclear.org/home.cgi, [April 28, 2012].

Canadian Nuclear Association, Why Food Irradiation?,http://www.cna.ca/english/nuclear_facts/applications/food_irradiation.html, 2010 [April 28, 2012].

Canadian Nuclear Worker's Council. Darlington Nuclear Generating Station, http://www.cnwc-cctn.ca/ontario-power-generation-opg-darlington/ , [April 29, 2012].

Carol Ness. Zapped Meats Headed Our Way: Food scares renew efforts to irradiate beef, chicken,http://www.mindfully.org/Food/Irradiated-Meat-Scares10nov02.htm, Nov. 2, 2010 [April 29, 2012].

Duke University. Food Irradiation, http://www.chem.duke.edu/~jds/cruise_chem/nuclear/food.html,[Apr. 27, 2012].

Pat Hewitt. Canada urged to rethink irradiated food after E. coli outbreak,http://www.citytv.com/toronto/citynews/life/health/article/135702canada-urged-to-rethink-irradiated-food-after-e-coli-outbreak, June 8, 2011 [April 29, 2012].

"The Process, http://uw-food-irradiation.engr.wisc.edu/Process.html, [April 27, 2012].
http://www.aboutnuclear.org/home.cgihttp://www.cna.ca/english/nuclear_facts/applications/food_irradiation.htmlhttp://www.cnwc-cctn.ca/ontario-power-generation-opg-darlington/http://www.cnwc-cctn.ca/ontario-power-generation-opg-darlington/http://www.mindfully.org/Food/Irradiated-Meat-Scares10nov02.htmhttp://www.chem.duke.edu/~jds/cruise_chem/nuclear/food.htmlhttp://www.chem.duke.edu/~jds/cruise_chem/nuclear/food.htmlhttp://www.citytv.com/toronto/citynews/life/health/article/135702http://www.citytv.com/toronto/citynews/life/health/article/135702--canada-urged-to-rethink-irradiated-food-after-e-coli-outbreakhttp://www.citytv.com/toronto/citynews/life/health/article/135702--canada-urged-to-rethink-irradiated-food-after-e-coli-outbreakhttp://www.citytv.com/toronto/citynews/life/health/article/135702--canada-urged-to-rethink-irradiated-food-after-e-coli-outbreakhttp://uw-food-irradiation.engr.wisc.edu/Process.htmlhttp://www.cna.ca/english/nuclear_facts/applications/food_irradiation.htmlhttp://www.cnwc-cctn.ca/ontario-power-generation-opg-darlington/http://www.cnwc-cctn.ca/ontario-power-generation-opg-darlington/http://www.mindfully.org/Food/Irradiated-Meat-Scares10nov02.htmhttp://www.chem.duke.edu/~jds/cruise_chem/nuclear/food.htmlhttp://www.citytv.com/toronto/citynews/life/health/article/135702http://www.citytv.com/toronto/citynews/life/health/article/135702--canada-urged-to-rethink-irradiated-food-after-e-coli-outbreakhttp://www.citytv.com/toronto/citynews/life/health/article/135702--canada-urged-to-rethink-irradiated-food-after-e-coli-outbreakhttp://uw-food-irradiation.engr.wisc.edu/Process.htmlhttp://www.aboutnuclear.org/home.cgi

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