Is irradiated food related to radiation? Can we eat it safely?

As the saying goes, "food is the first necessity of the people", which shows how much people value food. However, people are also afraid of "diseases coming from the mouth". Therefore, people's requirements for food quality are gradually increasing, and food safety issues have always been a hot topic for discussion.

Among the numerous food processing technologies, irradiation technology has gradually come into our sight. But for those of us who are afraid of "irradiation", can we eat irradiated food?

01

How does food irradiation work?

As the name implies, irradiated food is food that has been exposed to radioactive rays. This technology has been developed since the 20th century and has become a common technology for food sterilization and preservation . China's annual irradiated food production reaches hundreds of thousands of tons, ranking first in the world.

The principle is to use high-energy electron beams, X-rays or gamma rays and other radioactive rays to irradiate food. Due to their strong penetrating ability, the radiation can ionize the water, microorganisms, etc. in the food and destroy the DNA in the substance, thereby destroying the biofilm of the substance and causing cell damage, thereby effectively killing harmful substances such as insect eggs and bacteria on the surface of the food, inhibiting the germination and decay of the food , and thus extending the shelf life of the food.

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02

What is the difference between irradiated food and radioactive food?

Are irradiated foods and radioactive foods the same, given the same nuclear radiation source? Of course not! Radioactive foods usually refer to foods that have been contaminated by the accumulation of radioactive substances in large quantities after a nuclear accident. When humans eat foods contaminated by nuclear radiation, the radioactive contaminants cannot be metabolized out of the body in time and will accumulate in various organs of the body, greatly increasing the risk of disease.

It can be seen that radioactive food is not edible. Irradiated food is usually supervised by relevant national regulatory departments, and a strict food safety assessment mechanism is adopted. Irradiation is carried out in accordance with relevant standards to extend the shelf life of food and kill harmful substances on the surface of food. Irradiated food has no radioactive contamination residue. It can be seen that irradiated food and radioactive food are completely different.

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03

Is irradiated food safe?

Although food irradiation can extend the shelf life and help sterilize food, food safety is always the most important. The safety of irradiated food can be judged from the following points:

(1) Irradiation method and dose:

Excessive irradiation may cause food safety problems, but studies have shown that when the radiation dose absorbed by food does not exceed 10kGy (Gy: Gray, 1Gy=1J/kg, the standard unit of ionizing radiation energy absorption dose), there is no toxicological hazard and the food can be eaten safely.

Therefore, as early as 1980, the Joint Committee of the World Health Organization set the upper limit of food irradiation dose at 10kGy. After the standard was established, the commercialization process of food irradiation technology was further accelerated. About 20 years later, further research showed that even if the irradiation dose exceeded 10kGy, under strict operation, there would be no food safety problems. Since the beginning of the 20th century, my country has also been continuously formulating standards for food irradiation processes.

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According to the different purposes of irradiation, the common irradiation methods are divided into the following categories:

i. Irradiation sterilization

The use of irradiation doses exceeding 10 kGy can reduce the number of microorganisms in food to a limited number, thereby extending the shelf life of the food.

ii. Irradiation pasteurization

Using 5-10kGy irradiation dose to reduce non-spore pathogenic bacteria in food is an effective method to eliminate pathogenic microorganisms.

iii. Storage and irradiation resistance

The radiation dose of less than 5kGy is used to kill microorganisms, parasites, etc. in food, and is mainly used to preserve food and extend its storage life.

(2) Irradiation reaction mechanism:

From the mechanism of irradiation, we know that, in theory, when the irradiation energy acts on food, irradiation reaction products will inevitably be produced. However, the energy of the gamma rays used in irradiation does not exceed 1.33 MeV, and it is usually carried out at room temperature or low temperature. Therefore, during this process, the temperature of the food remains basically unchanged. Compared with the thermal processing process, the irradiation decomposition products produced are very small and can be ignored.

This shows that food that has been irradiated is safe.

04

Will irradiating food cause loss of nutrients in the food?

In today's society, people not only want to eat enough but also want to eat well. Will the nutritional value of irradiated food be reduced?

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Nutrients in food mainly include protein, essential amino acids, carbohydrates, fats, vitamins, trace elements, minerals, etc. Nutrients in food are closely related to storage conditions, radiation dose, etc.

For the currently used irradiation method, due to its strong penetrating power and low irradiation dose, it will not cause the temperature of the food itself to change. Therefore, research has shown that the relatively stable proteins, essential amino acids, carbohydrates, fats, minerals, and trace elements in food remain basically unchanged before and after irradiation. However, vitamins are relatively unstable and different types of vitamins have different sensitivities to irradiation.

Studies have shown that vitamins A, B1, C, and E are relatively sensitive to irradiation and therefore more easily decomposed, but these vitamins are less heat-resistant, so irradiated foods maintain their vitamins better than heat sterilization. Vitamin losses can be minimized by irradiating foods under frozen conditions .

In general, the mature food irradiation technology does not pose a threat to food safety and does not damage the taste and nutritional value of the food itself. In the future, the food irradiation process still needs to be continuously optimized, and more appropriate irradiation energy should be selected to achieve safer food sterilization, extend the shelf life of food, and achieve the best social and economic benefits. As food consumers, we must believe in the power of scientific and technological development and do not need to be afraid of "irradiation"!

References:
1. Pi X, Yang Y, Sun Y, et al. Food irradiation: a promising technology to produce hypoallergenic food with high quality. Critical Reviews in Food Science and Nutrition, 2021:1-16.

2. Hafiz, Muhammad, Shahbaz, et al. Worldwide Status of Fresh Fruits Irradiation and Concerns about Quality, Safety, and Consumer Acceptance. Critical Reviews in Food Science and Nutrition, 2016, 56(11):1790-1807.

3. Gao Meixu, Chen Hao, Liu Chunquan, et al. Research and commercial application of food irradiation technology in China. Journal of Nuclear Agricultural Sciences, 2007, 21(6):606-611.
4. Nian An. What is irradiated food?. China Food Industry, 2021, (10): 116-116.

Author | De novo

Review | Han Hongwei, Director and Researcher of Risk Communication Department, National Food Safety Risk Assessment Center

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