Food irradiation refers to the use of radiation irradiation of food (including raw materials), delaying the development of certain physiological processes (germination and ripening) of fresh food, or insecticidal, disinfectant, bactericidal, anti-mold and other treatments of food to achieve the purpose of prolonging the preservation time, stabilization, and improvement of the quality of the food operation process.

Technical features

1. It can be carried out at room temperature or low temperature, and the temperature rise of food during treatment is very small, which is conducive to maintaining the quality of food;

2. The ray (e.g. γ-ray) has strong penetrating power, which can irradiate the food under the package and without thawing, and kill the pests, parasites and microorganisms that are deeply hidden inside the food;

3. Irradiated food will not leave any residue;

4. Irradiation preservation methods can save energy compared with methods such as food freezing and preservation;

5. It can improve the process and quality of certain foods;

6. requires large investment and specialized equipment to generate radiation lines (radiation source) and provide safety measures to ensure that the radiation lines do not leak;

7. for different products and different irradiation purposes to choose to control the appropriate dose of irradiation, in order to obtain the best economic effect and social benefits.

Influencing factors

1. Irradiation dose
According to the different purposes of food irradiation and its characteristics, FDA, IAEA, WHO food irradiation is divided into 3 categories:

A Resistance to storage irradiation (radurization): The main purpose is to reduce the number of microorganisms and other organisms in the food, to prolong the post-cooking period and shelf life of fresh food (e.g., inhibition of germination, delayed ripening, elimination of insects, inactivation of parasites). This process is the result of enzymatic changes in plant tissues. This shelf-life-extending treatment is sometimes called “irradiation preservation” and uses irradiation doses of 5 kGy or less.

B Radiation Pasteurization (radicidatron): Radiation pasteurization of solid foods such as meat, poultry, seafood, etc. is a practical method for eliminating pathogenic organisms and microorganisms other than viruses. It is achieved by reducing the number of non-spore forms of pathogenic microorganisms that are particularly viable and cannot be detected in irradiated products by any standard method. Typically, freezing is continued after the irradiation process. This treatment, which improves the hygienic quality of food by inactivating food with pathogenic bacteria and parasites, is sometimes called “radiation sterilization”. Medium-dose applications are very similar to heat pasteurization, hence the name radiation pasteurization, in that specific non-spore-forming pathogenic bacteria (e.g., salmonella) are not detected in the food. The range of irradiation doses used is 5-10 kGy.

C Irradiation Arrhenius sterilization (radappertizaton): the irradiation dose used reduces the microorganisms in the food to zero or a limited number (reducing the microbial population to the point of sterilization), and after this irradiation treatment, the food reaches a certain storage period under conditions of no recontamination. The dose range is 10 kGy or more.

2. The state of foodstuffs when irradiated
Contaminated microorganisms, pests and other types and number of food growth and development stage, maturity, respiration and metabolism of the fast and slow and other factors have a great influence on the irradiation effect.

3. Environmental conditions of the irradiation process
The presence of oxygen can increase the sensitivity of microorganisms to irradiation by 2-3 times, and also has an effect on the chemical effect of irradiation products, therefore, maintaining the stability of oxygen pressure in the irradiation process is one of the conditions for obtaining uniform irradiation effect.

Appropriately raise the temperature of irradiation, to achieve the same sterilization, insecticidal effect, often can reduce the irradiation dose; appropriate pressure heating, so that the bacterial spores germination, and then use a smaller dose, you can need a high dose of irradiation to kill the spores killed. Low-temperature irradiation below the freezing point can greatly reduce the odor and reduce the loss of vitamins produced by meat irradiation.

The addition or removal of moisture or salt can alter the sensitivity to pathogens when irradiating processed meat and poultry.

4. Synergies between irradiation and other preservation methods
In irradiation technology research, more attention has been paid to screening food products for irradiation damage protection and and physical methods to improve the effectiveness of intensive irradiation. Such as low-temperature irradiation, the addition of free radical scavengers, the use of sensitizers, and other preservation methods and choose the appropriate irradiation device.

Bacteria in spore form, such as Rhodobacter and Clostridia, are more sensitive to heat after irradiation, and even though the actual amount of irradiation received is only a barotropic dose, non-spore-forming pathogens that survive a small amount of irradiation are severely damaged and become more sensitive to heat. So they are quite different from the germs that survive cooking.

Advantages of Irradiation

1. Energy savings
According to the International Atomic Energy Agency (IAEA) statistics per ton of refrigerated food energy consumption of 3.2 * 108J, heat sterilization method energy consumption of 1.1 * 109J, while irradiation is only 2.2 * 107J. The latter than the conventional method of energy-saving dozens of times to dozens of times.

2. Freshness preservation ability
Conventional methods of preservation of food, has lost its original color and flavor, while the irradiation method belongs to the cold processing, can be carried out at room temperature or low temperature, in the process of food irradiation is generally a very small temperature rise. According to the definition of absorbed dose and the heat capacity of food can be calculated, for most vegetables, fruits, freshness required dose of 0.1-1kGy, in the irradiation of the usual temperature rise of up to no more than 1 degrees Celsius. Irradiation of this cold processing characteristics, can make the food to maintain its original color and flavor, and therefore has a strong competitive edge.

3. Strong penetrating power
Ionizing radiation has a strong penetrating power, cobalt-60 y ray for example, its half weakened layer in water for 11cm water layer, so can be in the packaging and not thawing the case of irradiation of food, and in-depth to the internal food, kill the hidden deep germs, pests, parasites and microorganisms, to achieve the purpose of long-term preservation. This feature of irradiation sterilization is also particularly suitable for those foods that cannot be heated, steamed or smoked.

4. Safe and hygienic
Food irradiation does not need chemical additives, there is no residual toxicity brought by chemical preservation method, and will not produce sense of raw radioactivity, does not pollute the environment. Irradiated food can be preserved almost indefinitely under sealed conditions. Due to good sterilization effect, irradiated food is especially suitable for astronauts, field workers, and intensive care patients, as sterile food consumption.

5. Improvement of food quality
For example: the irradiated wine can accelerate its mellowing process, increase the flavor; irradiated beef is tender and tasty; irradiated soybeans are easy to digest and absorb; dehydrated food after irradiation to shorten the cooking time; irradiated flour can improve the quality of its baking and so on.

6. Simple operation, easy to realize automation
A reasonably designed food irradiation facilities, as long as strict compliance with process specifications, the operation is quite simple. As long as the operator according to the irradiation requirements to determine the process parameters, the food by the transmission system into the irradiation area, after a certain period of time irradiation can be in line with the requirements of long-term preservation of food, the entire operation can be controlled by microcomputer, a high degree of automation.

Safety of irradiated food

1. Radioactive safety
As can be expected, sunlight and X-rays are radiation. Although excessive irradiation may bring harm, but the right amount of irradiation can sterilize and cure cancer. The same goes for irradiation of food. Radiation kills fast-growing pests, spoilage bacteria and pathogenic bacteria, while having little effect on the food itself because their cells do not multiply.

2. Toxicity safety
Theoretically, specific radiolytic products are produced in food irradiation because a small amount of energy is added to the food during irradiation to cause radiolytic products. In practice, the same type of molecule is produced in thermal processing, and the molecular weight is greater because it adds more energy. The USDA has concluded that there is no reason to consider the production of specific radiolysis products in irradiation.

3. Safety of microorganisms
Microorganisms in food are divided into 3 categories:
A Microorganisms: e.g. yeasts that produce fermentation and cause the required change in food.

B Spoilage organisms: cause food to change color, odor, and texture so that it loses the characteristic odor of the food, but it does not cause disease.

C Pathogens: Includes invasive and toxic bacteria, viruses, and parasites that can cause disease. Multiple irradiations may cause microorganisms to mutate and become resistant to radiation. Theoretically, there may be a risk of this, but several major international commentators have concluded that food irradiation does not create new pathogens.

Applications of Irradiation Technology

1. Vegetables and fruits
The purpose of food irradiation is mainly to prevent the spoilage effect of microorganisms, to control the infection and spread of pests, to inhibit germination and to delay ripening. After picking vegetables and fruits, most of their life activities are still not stopped, but there is a certain dormant period.
After the dormant period, life activities will be active again. Potatoes and onions, which are common in daily life, will sprout after a certain period of time. When potatoes germinate, they produce the highly toxic lobelia and cannot be eaten. Onions, once sprouted, produce leaves from the bulb that absorb nutrients and cause the onion to rot.

Ionizing radiation can reduce or inhibit the activity of enzymes, slowing down or even terminating life activities in food for the purpose of long-term preservation. In the case of potatoes, for example, after absorbing a dose of 0.1 kGy, they are stored at room temperature for 300 days and still do not germinate, whereas potatoes that have not been treated with radiation and are stored at room temperature for 40 days have a germination rate of 100% and are inedible.

Fruit growth and harvesting of the season is very strong, the origin and more concentrated, after harvesting is still living organisms, continue to carry out a series of physiological and biochemical processes, many nutrients are consumed.

At the same time they contain water, sugar, vitamins and other nutrients, so it is easy to breed corruption of microorganisms and insects. The microorganisms that cause spoilage in fruits are mainly molds, and the dosage for killing molds depends on the type of fruit and the storage period.

Fruits with short life activity period, such as strawberry, can stop its physiological action with a small dose. 0.1-4kGy irradiation can make many kinds of fruits and vegetables delay ripening and reduce rotting. In Central America, irradiation of unripe banana with 250-350Gy can delay the ripening period by 16 days. Mango irradiation with 250Gy can delay ripening for 16 days. In the United States, irradiating strawberries with 2kGy or higher doses prolonged the shelf life of strawberries by 5-8 days at 5 degrees Celsius.

2. Grain
One of the major causes of grain loss is insect damage and spoilage due to mold activity. The effect of killing insects is related to the irradiation dose, 0.1-0.2 kGy make insects sterile, 1 kGy make insects die within a few days, 3-5 kGy make insects die immediately, the irradiation dose to inhibit the spread of cereal mold development of 2-4 kGy, the amount of insecticides for wheat and flour is 0.2-0.75 kGy, and baked goods is 1 kGy.

3. Poultry, animal meat and products
Irradiation sterilization can be divided into three categories according to its purpose:

A Non-deep sterilization.
The main purpose is to inhibit the growth and reproduction of spoilage-causing microorganisms, which is suitable for preservation of fish, shellfish and other aquatic products during storage and transportation.

Low-dose irradiation of fish is usually combined with low-temperature (3 degrees Celsius) storage.

Different fish have different dosage requirements, e.g., freshwater perch, at a dose of 1-2 kGy, extends the storage period by 5-25 days, ocean perch at a dose of 2.5 kGy extends the storage period by 18-20 days, and oysters at a dose of 20 kGy extends the storage period by several months.

B Targeted sterilization.
The main objective is to kill Salmonella in livestock, fresh meat, eggs and aquatic products. Salmonella is an important cause of food poisoning, it is not sensitive to heat, so that heating methods can not kill it all.

However, the radiation sensitivity of Salmonella is high, thus irradiation sterilization is effective. A radiation dose of 1.5-10kGy can eliminate or significantly reduce Listeria monocytogenes, Salmonella, Staphylococcus and other bacteria and pathogens.

If most products receive 2.5kGy, then 99.9999+% of E. coli, 99.9% of Salmonella, and 99.999+% of Staphylococcus cells will be killed.

C Sterilization.
There are 2 types of foods that require sterilization rather than pasteurization. One is commercially sterilized food, which requires irradiation under refrigeration and should be consumed on patients with severe immunodeficiencies.

The second is shelf-stable foods, which means they can be stored at room temperature for long periods of time without spoilage. The purpose of sterilization is to kill all microorganisms in meat and its products, reducing their numbers by a factor of 1012, with a required dose range of 10-60 kGy.

This sterile food can be used for special purposes, e.g., patients with immunodeficiencies, campers, astronauts, military personnel, and so on.

The Apollo astronauts ate irradiated ham on the moon. Irradiated steaks are being consumed by astronauts, and radiation-sterilized meat and meat products are available in South Africa and are used by the South African military.

4. Spices and seasonings
Natural spices are susceptible to insect and mold growth, and the amount of mold contamination in untreated spices averages 104/g or more. Traditional heating or fumigation method not only has drug residues, and easy to cause flavor volatilization, and even produce harmful substances.

Irradiation treatment can avoid causing the above undesirable effects, not only can control the insect infestation, but also reduce the number of microorganisms to ensure the quality of raw materials. The irradiation dose is related to the initial microbial population of the raw material.

10-15kGy dose, irradiation of nylon / polyethylene packaging of pepper, five spice powder, product storage for 6-10 months, no insects, mold, no significant changes in the color, aroma and nutrient composition of the spices.

5. Quarantine treatment of fruits and vegetables
International trade law and national safety regulations often require imported fruits and vegetables for safety treatment (especially tropical and subtropical fruits and vegetables), in order to kill fruit flies and other infectious diseases.

Conventional fumigation with dibromoethane, bromomethane, ethylene oxide and other gases, due to the carcinogenic effect of such gases, the patient and the user are a threat to the environment caused by pollution, belonging to the international is being phased out, can not be used for export products; radiation sterilization will become the mainstream.

The dose required to kill fruit flies (0.15kGy) will not change the physicochemical properties of most fruits and vegetables, and the low dose of 0.1kGy can prevent the eggs of most species of fruit flies from developing into adult insects. A guaranteed dose of 0.3kGy has been established internationally for quarantine reliability against all insect pests.

6. Other
China has made remarkable achievements in irradiation aging of liquor. Irradiation treatment of dried potato wine, so that the wine in the esters, acids, aldehydes and so on increased, ketones reduced, methanol, heterohydric alcohol content is reduced, the taste of the wine mellow, astringent pungent taste is reduced, and the quality of the wine is improved.
Experiments with 0.888kGy and 1.331kGy dose irradiation of the two brandy wine, stored for 3 months after tasting identification, the quality of its wine is equivalent to 3 years old wine.
In addition, the degradation of antibiotics by irradiation is also obvious.

Irradiation related standards

1. National mandatory standards.
GB 14891.1-1997 Hygienic Standard for Radiation Cooked Livestock and Poultry Meat
GB 14891.2-1994 Radiation pollen hygiene standards
GB 14891.3-1997 Hygienic Standard for Radiation Dried Fruits and Dried Fruits
GB 14891.4-1997 Hygienic Standard for Radiation Spices
GB 14891.5-1997 Hygienic Standard for Radiation Fresh Fruits and Vegetables
GB 14891.6-1994 Radiation pork hygiene standards
GB 14891.7-1997 Hygienic Standard for Radiation Frozen Packaged Livestock and Poultry Meat
GB 14891.8-1997 Hygienic Standard for Radiation Beans, Cereals and Their Products
GB 18524-2016 National Standard for Food Safety Hygienic Standard for Food Irradiation Processing

2. National Recommended Standards.
National Recommended Standard for Irradiated Food Processing
GB/T 18525.1-2001 Radiation Insecticidal Process for Legumes
GB/T 18525.2-2001 Radiation Insecticidal Process for Cereal Products
GB/T 18525.3-2001 Radiation insecticidal process for red dates
GB/T 18525.4-2001 Radiation insecticidal process for dried goji berries and raisins
GB/T 18525.5-2001 Radiation pesticide and mold prevention process for dried shiitake mushrooms
GB/T 18525.6-2001 Radiation pesticide and mold prevention process of dried cinnamon
GB/T 18525.7-2001 Radiation insecticidal process of hollow lotus
GB/T 18526.1-2001 Radiation sterilization process of instant tea
GB/T 18526.2-2001 Radiation sterilization process of pollen
GB/T 18526.3-2001 Radiation sterilization of dehydrated vegetables
GB/T 18526.4-2001 Radiation sterilization of spices and condiments
GB/T 18526.5-2001 Radiation sterilization of cooked animal and poultry meat
GB/T 18526.6-2001 Radiation sterilization of bad meat products
GB/T 18526.7-2001 Radiation sterilization of cooled and packaged split pork
GB/T 18527.1-2001 Radiation sterilization process for apples
GB/T 18527.2-2001 Garlic radiation germination inhibition process
GB/T 22545-2008 Technical specification for irradiation sterilization of pet dry foodstuffs
GB/T 21659-2008 Guidelines for phytosanitary measures Radiation treatment

Standards for the detection and identification of irradiated foodstuffs
GB/T 21926-2008 Determination of 2-dodecylcyclobutanone in food containing fat by gas chromatography/mass spectrometry
GB/T 23748-2009 Identification of irradiated foodstuffs DNA comet assay screening method

3. Laws and regulations
2007 AQSIQ Decree No. 47 “Food Labeling Regulations”.
GB 7718-2011 National Standard for Food Safety General Principles for Labeling of Prepackaged Foods

4. Industry Standards
NY/T 1206-2006 Tea irradiation sterilization process
NY/T 1207-2006 Thermoluminescent identification methods for irradiated spices and dehydrated vegetables
NY/T 1390-2007 Thermoluminescent Identification of Fresh Fruits and Vegetables by Irradiation
NY/T 1448-2007 Technical specification for irradiation sterilization of feeds
NY/T 1573-2007 Identification of Foods of Animal Origin Containing Bones by Radiation – ESR Method
SN/T 1887-2007 Good Irradiation Practice for Import and Export of Irradiated Foodstuffs
SN/T 1890-2007 Code of Practice for the Irradiation of Frozen Meat for Import and Export
NY/T 1895-2010 Technical Specification for Electron Beam Irradiation of Legumes and Cereals
NY/T 2209-2012 General Practice for Electron Beam Irradiation of Foodstuffs
NY/T 2210-2012 Technical Specification for the Inhibition of Sprouting of Potatoes by Irradiation
NY/T 2317-2013 Technical Specification for Irradiation Sterilization of Soy Protein Powder and Products
NY/T 2318-2013 Technical Specification for the Irradiation Sterilization of Edible Algae
NY/T 2319-2013 Technical Specification for Electron Beam Irradiation Processing of Tropical Fruits
SN/T 3707-2013 Technical Requirements for Quarantine Irradiation of New Pineapple Gray Mealybugs in Bananas

Irradiated Food Labeling

According to GB 18524-2016 “National Standard for Food Safety Hygienic Code of Practice for Food Irradiation Processing”, the labeling of irradiated food shall comply with the provisions of 4.1.11.1 in GB 7718 and GB 14891. Food Labeling Regulations: Those treated with ionizing radiation or ionizing energy shall be marked with Chinese instructions on their labels.

GB 14891 Requirements for package marking: It should comply with the relevant provisions of GB 7718 and Ministerial Decree No. 47 of the Ministry of Health “Measures for the Hygienic Management of Irradiated Food”. 4.1.11.1 of GB 7718-2011 “General Rules for Labeling of Prepackaged Foods of the National Standard for Food Safety” stipulates that: Foods treated with ionizing radiation or ionizing energy should be marked with “irradiated food” near the name of the food. “irradiated food”; any ingredient treated with ionizing radiation or ionizing energy should be marked in the list of ingredients. According to the Measures for the Hygienic Management of Irradiated Foods published by the Ministry of Health in 1996, irradiated foods must bear the irradiated food label uniformly formulated by the Ministry of Health on their packaging.

The Measures for the Hygienic Administration of Irradiated Foods were repealed on December 28, 2010 (Notice on the Repeal and Declaration of Invalidity of 48 Departmental Regulations, including the Procedures for Food Hygiene Supervision (MOH Decree No. 78)).

Irradiated Food Supervision

In order to strengthen the supervision and management of irradiated food and ensure food safety, the State Council and the Central Editorial Committee have made a clear division of responsibilities of the relevant supervisory departments in respect of the application of irradiation process and the use of irradiated food raw materials in the food production chain: the Ministry of Health is responsible for organizing the assessment of the safety of irradiated food and organizing the formulation of relevant standards, catalogs and test methods for irradiated food.

The Ministry of Environmental Protection is responsible for radiation safety licensing and supervision and management of irradiation units, irradiation personnel qualifications and training management. AQSIQ is responsible for regulating the labeling management of irradiated food, in accordance with the relevant standards, directories and test methods for irradiation device units processed food, food production units using irradiated food raw materials for supervision and management.

The Ministry of Health, the Ministry of Environmental Protection and the General Administration of Quality Supervision, Inspection and Quarantine each perform their own duties, strengthen cooperation, and attach importance to the active role of the relevant industry associations, and jointly do a good job in the supervision of irradiated food.

In addition to the import and export inspection and quarantine departments, the domestic regulatory authorities are not now carrying out inspections on the use of irradiated food doses in the market. Irradiated products are very common, only because of consumer acceptance reasons, many manufacturers of irradiated food is not clearly marked on the packaging of “irradiated food” words, most of the products marked “irradiated food”, the font is generally smaller, some brands in the packaging Some brands are marked in small letters on the outer packaging “this product dehydrated vegetables, spices using the international customary irradiation sterilization technology processing”, if not carefully observed, it is difficult to find.

Most companies do not have their own irradiated food tester, there is no way to know what has been irradiated, most of the instant noodle companies are from outside to buy back dehydrated vegetables, pepper, chili powder, ginger and other seasonings single product back to the factory mixed and processed into seasoning packets, however, these seasonings are often in the factory before they have been irradiated.

Irradiation may also be used by unscrupulous elements to deal with spoilage or do not meet the quality and safety standards of food, the state strictly prohibit the use of irradiation processing means to deal with poor-quality unqualified food. In general, food products should not be irradiated repeatedly.