Food irradiation

Irradiation sterilization is a kind of nuclear technology that uses the physical, chemical and biological effects produced by the interaction between ionizing radiation and substances to sterilize materials and materials.

 

There are three kinds of irradiation devices used in food processing, such as gamma irradiation device, electron beam irradiation device and X-ray irradiation device.

In order to ensure the safety of food irradiation, the radiation energy used for food irradiation is limited: the energy of electron beam of accelerator is not more than 10 MeV; the energy of X-ray is not more than 5 MeV; the gamma radiation source is cobalt-60 and cesium-137.

 

In order to ensure that the food is not contaminated and residual by radioactive sources, but also can not produce induced radioactivity after being processed by irradiation

There are 21 irradiation devices from 10 countries in the EU, which have been approved by EU for food irradiation;

Seven irradiation devices from 4 countries outside the EU have been approved by EU for food irradiation;

Several Chinese units have applied to the EU, but they have not yet been approved.

 

EU Member States

France: 7 food irradiation units

Germany: 4 food irradiation units

Spain, Netherlands: 2 food irradiation devices

Belgium, Czech Republic, Hungary, Netherlands, Italy, Poland, UK: 1 food irradiation device

 

Number of food irradiation devices in non EU Member States

South Africa: 3 food irradiation units

Thailand: 2 food irradiation units

Switzerland and Turkey: 1 food irradiation device.

 

South Africa: approved the irradiation treatment of most food; main irradiation products: condiments, honey, etc. The total amount of irradiated food is very large;

Israel: the development of irradiated food is fast.

 

In Thailand, there are two U.S. Department of Agriculture approved irradiation facilities: one is a government-owned Thai Irradiation Center, the other is isotron's gamma irradiation facility, both of which are close to Bangkok, Thailand

Vietnam: vinagamma's cobalt source irradiation device and sonson's electron accelerator device are used for fruit irradiation.

 

As the main technical equipment of food and agricultural and sideline products irradiation processing, gamma irradiation device has been more and more widely used. Industrial gamma irradiation device is developing towards large-scale, specialization and standardization. The single seat source loading capacity of a certain country has exceeded 4.44 × 1017bq (12 million Curie). However, most of the industrial gamma irradiation devices designed by China are small and medium-sized comprehensive multi-purpose devices Most of the newly-built irradiation facilities are large-scale industrial ones.

Quality control of food irradiation equipment

The effects of irradiation on food pigments were different. Plant pigment is stable to irradiation, while animal pigment is sensitive to irradiation. The irradiated hydrolysate can cause the oxidation of myoglobin and fat, and cause discoloration. Irradiation can deepen the stable red or pink color of frozen poultry breast meat. The deepening of red color depends on the type of meat, intramuscular type, radiation dose and packaging materials. According to the report of NHM et al., the reducibility of irradiated meat is increased and CO is produced. CO is strongly compatible with red pigment of blood and the intensity of red or pink is enhanced. According to relevant research reports, the strawberry red color of meat can be kept stable by using less than 1% CO and modified atmosphere packaging, and the red color can be kept for 8 weeks, and the shelf life of meat can be prolonged. Kusmider further studies showed that the color and flavor of fresh beef powder could be greatly improved by adding less than 1% CO during packaging. At the dose of 4.5 kGy, CO could reduce fat oxidation and provide a stable strawberry red color. In other words, packaging with CO and low or medium dose irradiation can bring pleasant and safe color to fresh beef inner powder, and the quality damage is the least.

 

Irradiation usually causes the loss of the unique aroma of food, but also produces unpleasant "radiation odor", especially meat food. Pratl reported that the odor of raw ham was produced by irradiation with 24kgy. Nam et al. Compared the irradiation effects of aerobic packaging and vacuum packaging on turkey breast meat. The experiment showed that the volatile odor would be produced during irradiation. With the oxidation of fat and the formation of volatile sulfur, the formation of volatile substances in aerobic packaging increased with the increase of radiation dose and storage time. Ahn et al. Pointed out that sulfur compounds were the source of odor in irradiated frozen pork. Irradiation hydrolysate of protein plays an important role in the odor of irradiated meat.

 

On the contrary, it can inhibit softening, destroy the activities of some enzymes that cause fruit ripening and delay the subsequent ripening of some fruits. When the food is treated with high dose irradiation, the softening effect will be different degrees, which is caused by the depolymerization of food macromolecules. The experiments of Setsuko et al. Show that the surface of dry materials can be removed by irradiating the surface of dry materials with 300kV or lower electrons, such as beans, spices, dehydrated vegetables and tea leaves, without harmful effects. When soybean was treated with 170 kV voltage, the number of microorganisms could be reduced to an undetectable level. The gelling properties of soybean milk treated with soft electron are better than that of soybean milk sterilized by high pressure. The quality of soybean milk processed by soft electron sterilization can be improved. McKenna et al. Pointed out that irradiation can increase the sensory tenderness and juice score of salmon, and increase the flavor intensity of catfish fillets.

 

Aquatic products, meat products, eggs, bee pollen can be preserved for a long time after irradiation. After pretreatment, vacuum sealed packaging and freezing, irradiation at - 40 ℃ had no adverse effect on meat products. Beef, chicken, ham, sausage, fish and shrimp that have been completely sterilized by radiation can be stored for a long time at room temperature, but the storage time will be longer if it is treated under hypoxia or anaerobic conditions. Generally, about 10 kGy dose of irradiation can kill Salmonella. If fresh eggs are irradiated with 80 kGy electron rays, coated with polyvinyl alcohol plastic thin layer, and stored at 28 ℃ ~ 30 ℃ for more than one month, the rate of good eggs is 91.0% ~ 91.3%. The egg liquid and frozen egg liquid can be irradiated by β - and γ - rays, and the sterilization effect is good. Irradiation with 1.0 kGy dose of bee pollen can effectively kill the microorganisms in the pollen, and the temperature rise of the pollen is not obvious, which is very good for the preservation of the nutritional components of the pollen. In addition, radiation is also widely used for surface sterilization of packaging materials and packaging containers, and the general dose of 20 ~ 30kgy can meet the sterilization requirements. High voltage electron beam is suitable for sterilization of single-layer films.