Hygiene and management of irradiated food
作者：admin 点击次数：195 发布时间：2025-07-09
1. Overview
In 1916, strawberries were irradiated for the first time in Sweden, creating a precedent for irradiation preservation of food. In 1921, the United States applied for the first patent on food irradiation preservation technology. Now, with the rapid development of science and technology and the needs of the food industry, irradiation technology has been widely used in the processing and storage of food. On June 7, 2009, the irradiation unit of the Limin Irradiation Center in Qi County, Kaifeng City, Henan Province, accidentally collapsed while the irradiation unit was running, causing the protective cover of the radioactive source to tilt, and "the Co radioactive source was stuck and could not return to the well." Due to prolonged exposure to radioactive sources, the irradiated paprika spontaneously combusted. Since then, irradiated food has gradually become known to the public, and its safety has further become the focus of attention. This section focuses on the basics of irradiated foods.
(1) Definitions
There are some naturally unstable isotopes in nature, but some isotopes can be artificially created using atomic reactors and particle accelerators. Due to the difference in the binding energy of atomic nuclei, some are stable and some are unstable, resulting in nuclear decay or radioactive decay. In this way, the nucleus of an atom decays over time according to a certain law (exponential law) to produce measurable changes, spontaneously changes its structure, and is transformed into another nucleus or transitions to another state with the release of charged or uncharged particles, and this unstable nucleus is called a radioactive nucleus. The corresponding unstable isotopes are called radioisotopes or radionuclides, and this phenomenon is known as radioactive decay or atomic nuclear decay. Nuclear decay produces radiation in five main ways: α, B, B', y decay and electron capture (EC) rays. Along with decay isotopes, α, B, B, B, and y rays are emitted.
The irradiation energy of these atomic energy rays is used to sterilize, insecticide, inhibit germination, delay ripening, etc., so that the loss of food can be minimized, so that it does not germinate, spoil and deteriorate within a certain period of time, and does not change in quality and flavor, so that the supply of food can be increased and the shelf life of food can be extended. This technique of preserving food is called irradiation preservation technology, and the food that has been treated with this technique is irradiated food. According to the "Measures for the Hygiene Management of Irradiated Food", irradiated food refers to the food processed and preserved by irradiation of y-rays generated by "Co," Cs or electron beams below 10MeV generated by electron accelerators.
(2) Radiation dose
The physical and chemical changes caused by radiation in a substance are related to the energy absorbed by the irradiated object from the radiation field. In the process of food irradiation, if the absorption energy is too low, the purpose of irradiation processing and preservation cannot be achieved: if the absorption energy is too high, it will damage the normal tissue of food and reduce food nutrition. Therefore, in a sense, controlling the energy absorbed by a substance also controls the effect of irradiation. The absorbed dose refers to the energy absorbed by the irradiated substance, which is measured in rad and megarad (MRad) or Gy and kilograys (kGy). Among them, Rad does not belong to the International System of Units, but because people have been accustomed to using this unit for a long time, Rad is still used in various literature at home and abroad.
If 1kg of any substance absorbs 1J of radiation, then its absorbed dose is 1Gy, i.e., 1Gy = 1J/kg, 1Gy = 100Rad.
The absorbed dose is the energy absorbed by the radiation-initiated reaction of the irradiated substance, which is a very strict definition, which is generally obtained by converting the irradiation dose measured when the dosimeter and the irradiated substance are irradiated at the same time. Irradiation dose refers to the absorption measurement of the dosimeter when irradiated at the same time as the irradiated substance. Strictly speaking, if the chemical composition of the dosimeter and the irradiated substance is different, the absorbed dose and the irradiation dose are also different, but for irradiation processing, because the irradiation dose and the absorbed dose are not much different, and there is a systematic error for the same substance and the same dosimeter, the irradiation dose is often used instead of the absorbed dose.
(3) Characteristics
Compared with other processing preservation methods, such as thermal sterilization, freezing and chemical preservation, irradiation processing preservation has the following characteristics. 1. Favorable aspects
(1) The sterilization effect is good, and the dose can be adjusted according to the purpose, and the food can be irradiated for sterilization, irradiation pasteurization and irradiation storage-resistant sterilization to achieve a variety of processing purposes. For example, potatoes, onions, garlic and other tubers need a dose of 0.08~0.1kGy to inhibit germination, fruits and vegetables need 0.2~1kGy to keep fresh, and cooked meat products or other foods are irradiated to kill
Insect sterilization requires 1~10kGy. (2) There was no sensory change in food irradiated at low doses (5kGy). Even at high doses (10 kGy) of irradiation, the chemical changes in food are minimal. Because it is cold processing, the internal temperature of the food will not rise, will not cause major changes in the color, aroma and taste of the food, the appearance is good, the nutritional value is not reduced, and the preservation effect is better than other methods.
(3) It will not leave residues and pollution, irradiation processing is a physical process, without adding any additives, nor does it need to add any chemicals, so there is no drug residue, no radiation residue, and it will not cause any pollution to food and the environment. (4) Compared with heating sterilization, the radiation has strong penetration, and can reach the interior instantly and uniformly to kill germs and pests. (5) Energy saving, high processing efficiency.
(6) The treatment method is simple and the scope of adaptation is wide. Regardless of whether the food is solid, liquid, frozen, dry or fresh, large, small or loose, it can be packaged or bundled for sterilization. 2. Downsides
(1) Enzymes in food may not be completely inactivated due to different sterilization doses.
(2) Due to the action of free radicals, food may produce undesirable sensory changes.
(3) The lethal dose of microbial irradiation is quite large for people, therefore, the protection of operators must be done, and the operation area and operators must be continuously monitored frequently.
(4) Types of irradiated foods in various countries
In the 80s of the 20th century, the international food irradiation sterilization treatment was restricted like the control of additives, but now the research has made it clear that it is a safe and convenient means of processing, especially in developing countries, which can effectively solve the problems of corruption and rot of agricultural products such as grain, fruits, vegetables and other agricultural products caused by the low level of processing technology. At present, more than 240 kinds of irradiated agricultural products and foods have been approved by 42 countries and regions in the world, and the total amount of irradiated food sold in the market has reached more than 200,000 tons per year. The types of irradiated foods are also increasing year by year, and as of 2005, the types of irradiated foods have reached 56 varieties in 7 categories. The 7 categories of products are irradiated beans, cereals and their products, dried fruits and preserved fruits, cooked livestock and poultry meat, irradiated frozen packaged livestock and poultry meat, irradiated spices, irradiated fruits and vegetables, irradiated aquatic products, etc.