FOOD IRRADIATION: PROCESS, APPLICATIONS AND ADVANTAGES - NUTRITION - 2025

The food irradiation involves exposure to ionizing radiation under controlled conditions. Irradiation is intended to extend the shelf life of food and improve its hygienic quality. Direct contact between the radiation source and the food is not necessary.

Ionizing radiation has the energy necessary to break chemical bonds. The procedure destroys bacteria, insects, and parasites that can cause foodborne illness. It is also used to inhibit or slow down physiological processes in some vegetables, such as germination or ripening.

The treatment causes minimal changes in the appearance and allows a good retention of nutrients, since it does not increase the temperature of the product. It is a process considered safe by the competent bodies in the field worldwide, as long as it is used in the recommended doses.

However, consumer perception of foods treated with irradiation is rather negative.

Process

The food is placed on a conveyor that penetrates into a thick-walled chamber, containing the source of ionizing radiation. This process is similar to X-ray baggage screening at airports.

The radiation source bombards the food and destroys microorganisms, bacteria and insects. Many irradiators use gamma rays emitted from radioactive forms of the element cobalt (Cobalt 60) or cesium (Cesium 137) as a radioactive source.

The other two sources of ionizing radiation used are X-rays and electron beams. X-rays are generated when a high-energy electron beam is decelerated upon striking a metal target. The electron beam is similar to X-rays and is a stream of strongly energized electrons propelled by an accelerator.

Ionizing radiation is high-frequency radiation (X-rays, α, β, γ) with great penetrating power. These have enough energy so that, when interacting with matter, they cause the ionization of its atoms.

That is, it causes ions to originate. Ions are electrically charged particles, the product of the fragmentation of molecules into segments with different electrical charges.

The radiation source emits particles. As they pass through food, they collide with each other. As a product of these collisions, chemical bonds are broken and new very short-lived particles are created (for example, hydroxyl radicals, hydrogen atoms and free electrons).

These particles are called free radicals and are formed during irradiation. Most are oxidizing (that is, they accept electrons) and some react very strongly.

The free radicals formed continue to cause chemical changes by binding and / or separating nearby molecules. When collisions damage DNA or RNA, they have a lethal effect on microorganisms. If these occur in cells, cell division is often suppressed.

According to the reported effects on free radicals in aging, excess free radicals can lead to injury and cell death, leading to many diseases.

However, these are generally the free radicals generated in the body, not the free radicals consumed by the individual. Indeed, many of these are destroyed in the digestive process.

Applications

Low dose

When irradiation is carried out at low doses - up to 1kGy (kilogray) - it is applied to:

- Destroy microorganisms and parasites.

- Inhibit germination (potatoes, onions, garlic, ginger).

- Delay the physiological process of decomposition of fresh fruits and vegetables.

- Eliminate insects and parasites in cereals, legumes, fresh and dried fruits, fish and meat.

However, radiation does not prevent further infestation, so steps must be taken to avoid it.

Medium dose

When developed at medium doses (1 to 10 kGy) it is used to:

- Extend the shelf life of fresh fish or strawberries.

- Technically improve some aspects of food, such as: increasing the yield of grape juice and reducing the cooking time of dehydrated vegetables.

- Eliminate alteration agents and pathogenic microorganisms in shellfish, poultry and meat (fresh or frozen products).

High dose

At high doses (10 to 50 kGy), ionization provides:

- Commercial sterilization of meat, poultry and seafood.

- Sterilization of ready-to-eat food, such as hospital meals.

- Decontamination of certain food additives and ingredients, such as spices, gums and enzyme preparations.

After this treatment the products have no added artificial radioactivity.

Advantage

- Food preservation is prolonged, since those that are perishable can withstand greater distances and transport time. Seasonal products are also preserved for a longer time.

- Both pathogenic and banal microorganisms, including molds, are eliminated due to total sterilization.

- Replaces and / or reduces the need for chemical additives. For example, the functional requirements for nitrites in cured meat products are substantially reduced.

- It is an effective alternative to chemical fumigants and can replace this type of disinfection in grains and spices.

- The insects and their eggs are destroyed. It reduces the speed of the ripening process in vegetables and the germination capacity of tubers, seeds or bulbs is neutralized.

- Allows the treatment of products of a wide range of sizes and shapes, from small packages to bulk.

- Food can be irradiated after packaging and then be destined for storage or transport.

- The irradiation treatment is a "cold" process. Sterilization of food by irradiation can take place at room temperature or in a frozen state with a minimum loss of nutritional qualities. The temperature variation due to a 10 kGy treatment is only 2.4 ° C.

The absorbed radiation energy, even at the highest doses, hardly increases the temperature in food by a few degrees. Consequently, radiation treatment causes minimal changes in appearance and provides good nutrient retention.

- The sanitary quality of irradiated food makes its use desirable in conditions in which special safety is required. Such is the case of rations for astronauts and specific diets for hospital patients.

Disadvantages

- Some organoleptic changes occur as a result of irradiation. For example, long molecules such as cellulose, which is the structural component of the walls of vegetables, break down. Therefore, when fruits and vegetables are irradiated they soften and lose their characteristic texture.

- The free radicals formed contribute to the oxidation of foods containing lipids; this causes oxidative rancidity.

- Radiation can break down proteins and destroy part of the vitamins, particularly A, B, C and E. However, at low doses of radiation these changes are not much more marked than those induced by cooking.

- It is necessary to protect personnel and the work area in the radioactive zone. These aspects related to the safety of the process and the equipment lead to an increase in costs.

- The market niche for irradiated products is small, even though the legislation in many countries allows the commercialization of this type of products.

Irradiation as a complementary process

It is important to bear in mind that irradiation does not replace good food handling practices by producers, processors and consumers.

Irradiated food should be stored, handled and cooked in the same way as non-irradiated food. Post-irradiation contamination can occur if basic safety rules have not been followed.

References

1. Casp Vanaclocha, A. and Abril Requena, J. (2003). Food preservation processes. Madrid: A. Madrid Vicente.
2. Cheftel, J., Cheftel, H., Besançon, P., & Desnuelle, P. (1986). Introduction à la biochimie et à la technologie des alimentants. Paris: Technique et Documentation
3. Conservation d'aliments (nd). Retrieved on May 1, 2018 at laradioactivite.com
4. Gaman, P., & Sherrington, K. (1990). The science of food. Oxford, Eng.: Pergamon.
5. Food irradiation (2018). Retrieved on May 1, 2018 at wikipedia.org
6. Irradiation des aliments (nd). Retrieved on May 1, 2018 at cna.ca