Radiation processing, which means that the electron accelerator (0.2MeV~10MeV)Electronic wire（βradial）Orradio isotope（Cs-137 or Co-60)γradialOfenergy transfer To the irradiated substance,ionizing radiationIt acts on the irradiated material, generates ionization and excitation, releases orbital electrons, and formsFree radical, by controlling radiation conditionsphysical property And chemical composition changes and can make it become a new material needed by people, or make organisms (microorganisms, etc.) suffer irrecoverable loss and destruction, so as to achieve the goals needed by people.This new processing technology is calledRadiation processing technology。For example, macromolecular materials can be grafted, polymerized, fission or cross-linked respectively to inhibit or stimulate biological growth and effectively killpest, worm eggsgermsEtc.
This is a radiation sterilization technology using radioactive elements, which was once popular in the food industry.Although the sterilization effect of this technology is very goodRadiation exposureIf you don't grasp it well, it may change the taste of food.To this end,National developmentHasRelevant standardsIrradiation shall be carried out in strict accordance with this dose, and irradiation words shall be marked on the package of irradiated food.
Irradiation processing
Announce
edit
concept
This technology is different from the traditional mechanical processing and thermal processing technology, so it is known as the third revolution of human processing technology. Its characteristics areRadioactive SourceThe emitted rays have strong penetration ability.It can go deep into the material for "processing", which is carried out at room temperature.Because the processor is a high-energy ray and a highly active intermediate triggered by it, rather thanMolecular thermal motionTherefore, low energy consumption and noresidueThere is no environmental protection problem.So it is a clean processing technology.Moreover, the reaction is easy to control, the processing flow is simple, and it is suitable for industrialization and large-scale production.
3. No environmental pollution;No chemistryDrug residues；Do not damage the appearance quality and internal characteristics of the processed products.
4. No impurities will be brought in during processing;It can be packaged and processed, improving efficiency withoutSecondary pollution。
5. Do not change the temperature of processing materials, also known as cold processing.
so to speakRadiation processing technologyIt is a kind of technology. Compared with other processing technologies, this new technology has obvious characteristics:
(1) The technology used covers a wide range of areas, is highly knowledge intensive, and has a strong professional nature.
Radiation processingIndustrial developmentFast,North AmericaIrradiation processing products have been widely used in Europe,Asia、South AmericaEven relatively backwardAfricaMany devices have been put into use, with an annual output value of hundreds of billions of dollars.For example, in the mid-1990s, the output value of the United States exceeded 200 billion US dollars, 3.5 times that of nuclear power (73 billion US dollars), accounting forgross domestic product3.9%, and created about 3.7 million jobs, 9.3 times that of nuclear power.Radiation processing technology is used in formulaAntioxidant, cross-linking mechanism, performance testing and other aspects of research are developing in a deeper and broader directionmaterial science 、life sciences、bioengineering, environmental protectionNutrition、Medical science, electronic engineeringAerospace, geologypetrochemical industryAnd other aspects have achieved important results.Therefore, radiation processing technology is breaking through the traditional application pattern, penetrating into the forefront of science and technology and production breadth, and forming many newapplication area 。
China's radiation processing industry
China's radiation processing industry has a good technical foundation.In the past decade, in the reform and opening upenvironmental effectThe industrialization process has developed rapidly, with an average annual growth rate of 20%.However, withdeveloped countryIn comparison, there is an obvious gap in China's radiation processing industry, mainly due to the lack of product varieties,Industrial scaleSmall, many important industrial fields are still blank,not suited tomarket demand。
According to the data from September 7 to 12, 2003Chicago, USAAccording to the information provided by the 14th International Annual Conference on Radiation Processing, the development opportunities of international radiation processing industries in the next five years are shown in Table 1-1:
Table 1-1: Development Opportunities of Radiation Processing Industries
With the development of technology and economymaterial civilizationWith the improvement of people's understanding of the advantages of radiation disinfection and sterilization, it is a global trend that radiation processing replaces chemical processing, and the prospect is very bright.withFood irradiationFor example, the development of food irradiation technology began in the 1940s. Many experts and scholars from all over the world have studied radiation technologyRadiation chemistry, radiation biologymicrobiology、NutritionandtoxicologyAnd other aspects have carried out a lot of research and experimental workIrradiated foodThere are thousands of safety research reports.Food irradiation is a physical process, which belongs to cold processing,Low energy consumption, no need to addChemicalsThere is no drug residue problem, and it can maintain the original color, fragrance and taste of foodFlavor foodIt is particularly important for foods that are not suitable for high-temperature sterilization.the United NationsFAOInternational Atomic Energy Agency andworld health organizationCo funded, the "Joint Expert Committee on the Safety of Irradiated Food" was established in 1963. The committee held several meetings from 1963 to 1980. Based on the research results and experimental accumulation over the years, it formally proposed to the world in 1980 that "any food is subject to less than 10KGyExposureNone of them will cause toxic hazard due to irradiation.Therefore, food processed by irradiation is hygienic and safe and no longer requiredtoxicologyInspection in theNutritionAnd microbiological safety.In 1997, the high dose research group of the committee declared that the high dose radiation of more than 10KGy was also safe.These conclusions have greatly promoted the development of irradiation industry around the world and have now been accepted internationally.
test
China also irradiated potatoes as early as 1958Human experiment, later in the National Science and Technology Commission andMinistry of HealthUnder the leadership ofAnimal experiment, including lifelong and generational experiments;During the "Sixth Five Year Plan" period, more than 400 human food trials were conducted, and seven irradiated foods were formulatedhygienic standard ；During the "Eighth Five Year Plan" period, based on the work of the former, the following work was carried out: (1) Formulation of standards for irradiated food categories (grain, fruits and vegetables, cooked meat, frozenlivestock ClassDry FruitsPreserved fruitFlavor taste);(2) Study on the identification method of irradiated food.In June 1997, six categories and seven items of irradiated foodnational standard。That is:
The establishment of health standards for irradiation willFood irradiationGoing on the road of healthy development is of great significance to protect people's health and the environment from pollution, and to improve product quality and market competitiveness.
Since the 1990s, especially in western developed countries, such as the United Statesfoodborne diseases The puzzlement of food irradiation has made consumers more and more aware of the role of food irradiation.Food safety andplant quarantineOur country has joined theWorld Trade OrganizationFood irradiation is a technology approved by WTO.Therefore, the development of radiation processing will promoteEuropean CommunityNationalexport trade It is of great practical significance to reduce trade risks.
GB 14891.5-1997 Hygienic standard for irradiated fresh fruits and vegetables
GB/T5137.3-2002 Test methods for automotive safety glazing Part 3: Irradiation resistance, high temperature, humid combustion and simulated climate resistance test
GB/T 15972.54-2008 Specification for Optical Fiber Test Methods Part 54: Environmental Performancemeasuring methodAnd test procedures Gamma irradiation
High temperature and high pressure method is the earliest sterilization method. Its main disadvantages are: incomplete sterilization;Not applicable to those heat sensitive materials (such as plastic products, someRubber productsEtc.);This method also consumes a lot of energy;It cannot work continuouslyMass production。This is a primitive and backward method.
The method of gas fumigation is chemicalmaterialThe main chemical substances used for fumigation of sterilized articles are ethylene oxideMethyl bromideEtc.Compared with the previous method, it has made great progress: it can be produced in large quantities and sterilized more thoroughly.However, this method has many disadvantages:process parameters More, difficult to control;Nocontinuous production ；Packaging materials must be breathable (and not permeable to bacteria);There will be microbial residues in the place where the sterilized product is compressed and cannot penetrate the gas;There are chemical residues in the product.In particular, these chemicals are strongCarcinogen, although rightResidueThere are definiteLimitsHowever, there are still residues, which pose a threat to human health.
Following the first two methods, people have adopted advanced radiationsterilizationMethod usedradiation sourceMainlyradio isotopeCobalt-60 producedγX-ray and high-energy electron beam generated by accelerator orX-ray。This method is an environment-friendly sterilization method: its sterilization process is easy to control (only need to controlIrradiation dose）；Completely sterilized and nonexistentThermal convectionAnd gas diffusion;Because it is carried out at room temperature, the method is applicable to various heat sensitive materials and products;Continuablemass production ；The product will not produceInduced radioactivityThere is no pollution.
It is easy to see from the above comparison that the irradiation sterilization method is the most advanced sterilization method, and most of the advanced countriesmedical and health workAll products are sterilized in this way.It is a consensus to replace other sterilization methods with irradiation sterilization methods, and the elimination of ethylene oxide fumigation sterilization method has become an irreversible trend.
In fact, irradiated food is gradually entering ordinary people's homes, such asDehydrated vegetables[2]、instant noodlesSeasoning andvacuum packingCooked meat productsHealth drinks, native products, etc.Since June 1, 1998, all irradiated food sold on the Chinese market must be labeledLabeling of irradiated foodLater, it was gradually recognized and accepted by consumers.
Irradiated food is produced byradioactivity60CoγX-rays, X-rays or high-energy electron beams pass through the food body to makeNutrientshappenIonizationAfter destroying the intracellularDNA molecule（cytoplasmDamage andBiomembraneThe destruction is also an important process), so as to inhibit the germination and rooting of vegetables.The irradiated grain will not produce insects within 3 yearsMildew；Garlic, potato and onion can be prolonged after irradiationRetention period6-12 months.
Meat and poultry food processIrradiation treatment, can be completely eliminatedmould、Escherichia coliSuch as corruption andPathogenicityMicroorganisms, thus greatly extending theirquality guarantee period。The development of irradiated meat products is conducive to enhancing the market share of meat products in Chinainternational marketThe competitive strength of.In recent years, China's meat output has continued to grow. For example, in 1995, China's livestock meat output reached 49.66 million tons, accounting for the world'stotal output20%, ranking first in the world;However, the export did not increase at the same time, and the export volume of major varieties even declined. One of the important reasons is that the health standards of related meat products could not meetEurope and AmericaImport requirements of developed countries and regions.Montreal ConventionIt stipulates that developed countries will, before 2005developing countryThe use of tradition will be completely prohibited before 2015cryogenMethyl bromide.This poses a challenge to the traditional method of preserving meat by freezing and cold storage in China, but it provides an opportunity for the development of irradiated meat market.For example, fresh meat products in small quantitative packages circulated in supermarkets,General packagingThe shelf life of fresh meat at 2~4 ℃ is 2 days, even ifvacuum packingOr vacuum -Inflatable packagingIts shelf life is only 5-7 days. If vacuum packaging or vacuum inflatable packaging is usedLow doseIrradiation treatmentThe shelf life is 30 days at 2~4 ℃, and the irradiated fresh meat has effectively killed all kinds ofparasiteandpathogenic bacteriaIt is greatly conducive to the prevention of various foodborne diseases.
Sterilization
Application of irradiation disinfection of medical products: irradiation disinfection has the advantages of complete sterilization, no pollution, no residue, cheap price, energy saving, easy operation, sterilization and disinfection at room temperature, etc. It has developed into an irreplaceable new technology, forming a certain industrial scale, especially after the international almost completely abolishment of chemical disinfection and sterilization methods.Its application has irreplaceable significance.China has a population of 1.3 billion, 310000Medical and health institutionsThere are about 15000 medical institutions above the county level, making it one of the top ten medical devices in the worldemerging marketOne, has become Asia except JapanLargest market。In 2000, China's medical equipmentMarket capacity22.7 billion yuan, average annualgrowth rate15%, accounting for 3% of the world share. A considerable part of the products are exported, and there is a large demand for irradiation sterilization.In China, medical equipment is mainly sterilized by ETO methodInternational Environmental Protection ConventionThe ETO method has been phased out and replaced byRadiation sterilizationTherefore, the radiation sterilization of disposable medical equipment is very importantpotential market。
Industrial field - radiation chemical industry
Radiation chemical products are radiation processingtechnological development The fastest area.Radiation chemical engineering is a new processing method to realize material modification by chemical changes (combination, decomposition, cross-linking, polymerization, grafting, curing, degradation, etc.) caused by ionizing radiation on substances.Compared with conventional processing technology (hot processing, smooth processing, chemical processing, etc.), it has the following main characteristics: no need to addInitiatorOr catalyst, which can react at room temperature to low temperature, and can synthesize or prepare high-performance special materials that are difficult to obtain by normal methods.
Radiation chemical products have high added value and wide applications, involving many important fields of national economy such as communication and electronics, electric power transportation, petrochemical industry, aerospace, etcSame radiation technologyIt occupies a very important position in the industry.In recent decades, with the worldwideindustrial structureUpgrade andenvironmental awarenessAs an efficient, energy-saving, pollution-free and easy to controlGreen chemical industryThe industry has received universal attention from the world, showing strong vitality.Because of itProcessSimple, easy to operate, good product quality, good efficiency, so it is rapidly industrialized at a high speed.Radiation chemical industry is mainly to make multiphase polymerγChemical products are produced by polymerization initiated by X-ray irradiation.Table 4 lists its application in detail.In this field, many products have been produced on a large scale, such asThermal shrinkageIn terms of materials, it has been applied to power and various departments.
Application in other aspects
① In agriculture: inducing man-made mutation by radiation is calledMutation breeding, that is, using mutationImproved variety。That is to say, useful forms can be selected from them, which can be used directly as varieties or as matingfemale parentMaterial Science.Its purpose is to increase yield and use varieties to ripen early.Gratifying results have been achieved in these areas.
② Animal useCompound feedSterilization of: Long ago in external feedAdditionsMore than 30 varieties are designated asRadiation treatmentObject of.Treatment with radiation processing technologysterileFeed has been developed considerably, and its application prospect is very considerable.Experiments prove that high dose irradiationproteinandamino acidAlmost no change in nutritionvitaminClassRadiolysis, exceptvitamin AOther than E, there is no problem.Decomposition degree of vitamin A and E andHeat treatmentThere is not much difference, especially the vast majority of experimental feedstuffs are processed by radiation.
③ Radiation processing starch: radiation processing starch has received extensive attention and is used as a by-product of aquatic refining products, infant food, patient food, dryGravyOfFiller。In a word, the purpose of radiation treatment of starch is to improve the quality of industrial raw materials, as well as the sterilization and processing adaptability of food materials.
④、Immobilized enzymeRadiation processing: enzyme hasCatalysisBecause the protein is soluble in water, it can only be used once. There is residual enzyme activity after reaction, but it is not recyclable for the enzyme. After heating, coagulation and precipitation, it can only be taken out and thrown away.The use of enzymes like this is uneconomical from the perspective of saving resources.If the enzyme can solidify and participate in the comprehensive reaction, it can be carried outEnzyme reactionAutomation and continuity ofcomplexationAt 60CoγIt is generated by radiation.For example, Kawayama Island in Japan willAcrylamideMonomeric and enzymaticMixed liquidPut togetherdry iceacetoneFreeze with 60Co on the premise of not replacing nitrogenγX-rays are irradiated at a dose of 1-9Gy per hour for 5-10 minutes to combine them. After thawing, sponges can be mademembrane structureorMoniliformImmobilized enzyme.
⑤ Disinfection, sterilization and antisepsis of leather: it has a special effect on fresh and freshly peeled leather.For example, the cowhide just peeled off.Sheepskin can be processed by radiation, so that it will not deteriorate and taste unchanged, and it will not rot for a long time.
⑥、forage grass: There are many microorganisms and pathogens in the forage eaten by cattle and sheepflock of sheepThe healthy reproduction of has been fed by eating the grass after radiation processing.In particular, these forages must undergo radiation processing when they are exported.
⑦ . There are many other applications, such asCommodity maintenance, flower preservation, etc.
It can be seen from the above that irradiationTechnology applicationThe field of is very wide.Facts have proved that radiation processing technology is a technology that is advancing towards industrialization and commercialization, which also shows that radiation processing technology is a cause full of vitality.
