Can irradiated food be eaten safely?

In your daily life, you may come across foods like the following, with the words "irradiated food" written on the packaging. But when it comes to "irradiation", it is inevitable that people will think of radiation and nuclear pollution. Can irradiated food be eaten safely?

What is irradiated food?

Irradiated food refers to food that has been processed using radiation to help preserve it. Irradiation can kill insects, their eggs and larvae in food. It can eliminate foodborne diseases that endanger global human health, make food safer and extend the shelf life of food. Irradiation can kill bacteria, yeasts and yeasts, which can cause fresh food such as fruits and vegetables to rot and spoil. Irradiated food can maintain its original flavor for a long time and maintain its original taste.

Food irradiation technology is a sterilization and preservation technology that was patented in 1905 and developed in the 20th century. After years of research, irradiation sterilization technology has been widely recognized by the international community. More than 60 countries around the world have formulated regulations allowing the use of irradiation on one or more foods, and hundreds of irradiation plants are engaged in food and medical device sterilization business.

What is the principle of irradiation sterilization?

The effects of radiation on food can be divided into direct and indirect effects.

Direct effect refers to the process in which biological molecules in the organism are directly affected by ionizing radiation, absorb radiation energy and cause damage to the body.

Indirect effect means that ionizing radiation first reacts with water molecules in the body to produce active particles such as hydrogen atoms, hydroxyl free radicals, and hydrated electrons. These active particles then react with biological molecules such as proteins, nucleic acids, enzymes, etc., causing changes in the function, metabolism, and structure of the organism, resulting in damage.

Since 80% of living organisms are water, the total effects of radiation are usually dominated by indirect effects.

Types of irradiation sterilization

There are three types of radiation commonly used for irradiation sterilization:

Electron irradiation: Electron irradiation is produced by an electron emitter (accelerator). It has weak penetrating power and is generally used for sterilization of small packaged foods or frozen foods. It is particularly suitable for sterilization of food (items) surfaces.

γ-ray irradiation: γ-rays are generally produced by radioactive isotopes such as iodine and cobalt. They have strong penetrating power and are suitable for internal sterilization of whole foods and various packaged foods.

X-ray irradiation: X-rays are produced by an X-ray generator and have greater penetrating power and a shorter sterilization time, but are currently more expensive.

Irradiation sterilization is mainly used to sterilize the inside of packaged food that is not convenient for high temperature or chemical sterilization, such as:

Special food: sterile food for patients.

Dehydrated food: onion powder, star anise powder, shrimp powder, shallots, chili powder, garlic powder, shrimp and other dehydrated products.

Foods with extended shelf life: moon cakes, packaged meat products, preserved fruits and other products.

Frozen products: frozen squid, frozen shrimp, frozen crab meat, frozen frog legs and other products.

Health products: slimming tea, American ginseng, pollen, ganoderma products, tea bags, oral beauty and health foods.

Standards for irradiation sterilization process

The only national food safety standard related to irradiation currently issued by my country is "GB 18524-2016 National Food Safety Standard Food Irradiation Processing Hygienic Specification", which stipulates that the types of irradiated food should be within the scope of the GB 14891 series of standards, and other foods are not allowed to be irradiated. The radiation dose (Gy: Gray, 1Gy=1J/Kg, the standard unit of ionizing radiation energy absorption dose) used for food irradiation sterilization is different for different objects and purposes:

Standard name Standard number Overall average absorbed dose (kGy) Average absorbed dose distribution unevenness Hygienic standard for irradiated cooked meat GB14891.1 - 1997 ≤8.0 ≤1.5 Hygienic standard for irradiated pollen GB14891.2 - 1994 8.0 —— Hygienic standard for irradiated dried fruits and preserved fruits GB14891.3 - 1997 0.4 - 1.0 ≤2.0 Hygienic standard for irradiated spices GB14891.4 - 1997 ≤10.0 ≤2.0 Hygienic standard for irradiated fresh fruits and vegetables GB14891.5 - 1997 ≤1.5 ≤2.0 Hygienic standard for irradiated pork GB14891.6 - 1994 0.65 —— Hygienic standard for irradiated frozen packaged livestock and poultry meat GB 14891.7 - 1997 ≤2.5 ≤2.0 Hygienic standard for irradiated beans, cereals and their products GB14891.8 - 1997≤0.2 (beans) 0.4-0.6 (cereals)≤1.5

Important differences between irradiation sterilization and radioactive contamination

The radioactive contamination that food may come into contact with mainly comes from the mining, smelting, production, and application and discharge of radioactive materials in daily life. These pollution sources come into contact with or enter food, causing the food to carry radioactivity. After consuming such contaminated food, its radioactive contaminants may adhere to the human skin and cause external radiation damage, or enter the human body after being digested and cause internal radiation. If the radioactivity of these pollution sources is high, it is equivalent to having an "irradiation sterilization device" on the body at all times, and long-term exposure to radiation will cause damage to human tissues.

The biggest difference between food irradiation sterilization and radioactive contamination is that irradiated foods are tightly packaged and do not directly contact the radiation source, so they do not carry radioactivity. In addition, studies have shown that when the radiation dose absorbed by food does not exceed 10kGy, there is generally no toxicological hazard. In addition, therefore, food that is irradiated and sterilized according to standards can be eaten with confidence.

References:

[1] International Atomic Energy Agency. Food irradiation

GB 18524-2016 National Food Safety Standard Hygienic Specification for Food Irradiation Processing

[2] Duan Xin, Ou Jie, Li Bolin. Application of irradiation technology in sterilization and preservation of meat products[J]. Food Science, 2010, 31(1): 278-282.

[3] Qing Lifang, Wei Min, Yang Pinghua, Li Qing, Liu Ying. Mechanism and microbial detection of food sterilization by γ-irradiation. Food Research and Development, 2016, 37(5):218-220

Author: Su Haozhan popular science author

Reviewer: Ruan Guangfeng, Deputy Director of Kexin Food and Health Information Exchange Center

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