Uses Edit

Irradiation is used to reduce or eliminate the risk of food-borne illnesses, prevent or slow down spoilage, arrest maturation or sprouting and as a treatment against pests. Depending on the dose, some or all of the pathogenic organisms, microorganisms, bacteria, and viruses present are destroyed, slowed down, or rendered incapable of reproduction. Irradiation cannot return spoiled or over-ripe food to a fresh state. If this food was processed by irradiation, further spoilage would cease and ripening would slow down, yet the irradiation would not destroy the toxins or repair the texture, color, or taste of the food.[16] When targeting bacteria, most foods are irradiated to significantly reduce the number of active microbes, not to sterilize all microbes in the product. In this respect it is similar to pasteurization. Irradiation is used to create safe foods for people at high risk of infection, or for conditions where food must be stored for long periods of time and proper storage conditions are not available. Foods that can tolerate irradiation at sufficient doses are treated to ensure that the product is completely sterilized. This is most commonly done with rations for astronauts, and special diets for hospital patients. Irradiation is used to create shelf-stable products. Since irradiation reduces the populations of spoilage microorganisms, and because pre-packed food can be irradiated, the packaging prevents recontamination of the final product.[1] Irradiation is used to reduce post-harvest losses. It reduces populations of spoilage micro-organisms in the food and can slow down the speed at which enzymes change the food, and therefore slows spoilage and ripening, and inhibits sprouting (e.g., of potato, onion, and garlic).[17] Food is also irradiated to prevent the spread of invasive pest species through trade in fresh vegetables and fruits, either within countries, or trade across international boundaries. Pests such as insects could be transported to new habitats through trade in fresh produce which could significantly affect agricultural production and the environment were they to establish themselves. This "phytosanitary irradiation"[18] aims to render any hitch-hiking pest incapable of breeding. The pests are sterilized when the food is treated by low doses of irradiation. In general, the higher doses required to destroy pests such as insects, mealybugs, mites, moths, and butterflies either affect the look or taste, or cannot be tolerated by fresh produce.[19] Low dosage treatments (less than 1000 gray) enables trade across quarantine boundaries[20] and may also help reduce spoilage.

Impact Edit

Treatment Edit

Up to the point where the food is processed by irradiation, the food is processed in the same way as all other food. To treat the food, they are exposed to a radioactive source, for a set period of time to achieve a desired dose. Radiation may be emitted by a radioactive substance, or by X-ray and electron beam accelerators. Special precautions are taken to ensure the food stuffs never come in contact with the radioactive substances and that the personnel and the environment are protected from exposure radiation.[47] Irradiation treatments are typically classified by dose (high, medium, and low), but are sometimes classified by the effects of the treatment[48] (radappertization, radicidation and radurization). Food irradiation is sometimes referred to as "cold pasteurization"[49] or "electronic pasteurization"[50] because ionizing the food does not heat the food to high temperatures during the process, and the effect is similar to heat pasteurization. The term "cold pasteurization" is controversial because the term may be used to disguise the fact the food has been irradiated and pasteurization and irradiation are fundamentally different processes. Treatment costs vary as a function of dose and facility usage. A pallet or tote is typically exposed for several minutes to hours depending on dose. Low-dose applications such as disinfestation of fruit range between US$0.01/lbs and US$0.08/lbs while higher-dose applications can cost as much as US$0.20/lbs.[51] Packaging Edit Food processors and manufacturers today struggle with using affordable, efficient packaging materials for irradiation based processing. The implementation of irradiation on prepackaged foods has been found to impact foods by inducing specific chemical alterations to the food packaging material that migrates into the food. Cross-linking in various plastics can lead to physical and chemical modifications that can increase the overall molecular weight. On the other hand, chain scission is fragmentation of polymer chains that leads to a molecular weight reduction.[3] Dosimetry Edit The radiation absorbed dose is the amount energy absorbed per unit weight of the target material. Dose is used because, when the same substance is given the same dose, similar changes are observed in the target material. The SI unit for dose is grays (Gy or J/kg). Dosimeters are used to measure dose, and are small components that, when exposed to ionizing radiation, change measurable physical attributes to a degree that can be correlated to the dose received. Measuring dose (dosimetry) involves exposing one or more dosimeters along with the target material.[52][53] For purposes of legislation doses are divided into low (up to 1 kGy), medium (1 kGy to 10 kGy), and high-dose applications (above 10 kGy).[54] High-dose applications are above those currently permitted in the US for commercial food items by the FDA and other regulators around the world.[55] Though these doses are approved for non commercial applications, such as sterilizing frozen meat for NASA astronauts (doses of 44 kGy)[56] and food for hospital patients. Applications of food irradiation[54][57] Application Dose (kGy) Low dose (up to 1 kGy) Inhibit sprouting (potatoes, onions, yams, garlic) 0.06 - 0.2 Delay in ripening (strawberries, potatoes) 0.5 - 1.0 Prevent insect infestation (grains, cereals, coffee beans, spices, dried nuts, dried fruits, dried fish, mangoes, papayas) 0.15 - 1.0 Parasite control and inactivation (tape worm, trichina) 0.3 - 1.0 Medium dose (1 kGy to 10 kGy) Extend shelf-life (raw and fresh fish, seafood, fresh produce, refrigerated and frozen meat products) 1.0 - 7.0 Reduce risk of pathogenic and spoilage microbes (meat, seafood, spices, and poultry) 1.0 - 7.0 Increased juice yield, reduction in cooking time of dried vegetables 3.0 - 7.0 High dose (above 10 kGy) Enzymes (dehydrated) 10.0 Sterilization of spices, dry vegetable seasonings 30.0 max Sterilization of packaging material 10.0 - 25.0 Sterilization of foods (NASA and hospitals) 44.0 Processes Edit Gamma irradiation Edit Gamma irradiation is produced from the radioisotopes cobalt-60 and caesium-137, which are derived by neutron bombardment of cobalt-59 and as a nuclear source by-product, respectively.[54] Cobalt-60 is the most common source of gamma rays for food irradiation in commercial scale facilities as it is water insoluble and hence has little risk of environmental contamination by leakage into the water systems.[54] As for transportation of the radiation source, cobalt-60 is transported in special trucks that prevent release of radiation and meet standards mentioned in the Regulations for Safe Transport of Radioactive Materials of the International Atomic Energy Act.[58] The special trucks must meet high safety standards and pass extensive tests to be approved to ship radiation sources. Conversely, caesium-137, is water soluble and poses a risk of environmental contamination. Insufficient quantities are available for large scale commercial use. An incident where water-soluble caesium-137 leaked into the source storage pool requiring NRC intervention[59] has led to near elimination of this radioisotope. Cobalt 60 stored in Gamma Irradiation machine Gamma irradiation is widely used due to its high penetration depth and dose uniformity, allowing for large-scale applications with high through puts.[54] Additionally, gamma irradiation is significantly less expensive than using an X-ray source In most designs, the radioisotope, contained in stainless steel pencils, is stored in a water-filled storage pool which absorbs the radiation energy when not in use. For treatment, the source is lifted out of the storage tank, and product contained in totes is passed around the pencils to achieve required processing.[54] Electron beam Edit See also: Electron beam processing Treatment of electron beams is created as a result of high energy electrons in an accelerator that generates electrons accelerated to 99% the speed of light.[54] This system uses electrical energy and can be powered on and off. The high power correlates with a higher throughput and lower unit cost, but electron beams have low dose uniformity and a penetration depth of centimeters.[54] Therefore, electron beam treatment works for products that have low thickness. Irradiated Guava: Spring Valley Fruits,Mexico X-ray Edit X-rays are produced by bombardment of dense target material with high energy accelerated electrons(this process is known as bremsstrahlung-conversion), giving rise to a continuous energy spectrum.[54] Heavy metals, such as tantalum and tungsten, are used because of their high atomic numbers and high melting temperatures.Tantalum is usually preferred versus tungsten for industrial, large-area, high-power targets because it is more workable than tungsten and has a higher threshold energy for induced reactions.[60] Like electron beams, x-rays do not require the use of radioactive materials and can be turned off when not in use. X-rays have high penetration depths and high dose uniformity but they are a very expensive source of irradiation as only 8% of the incident energy is converted into X-rays.[54] Cost Edit Efficiency illustration of the different radiation technologies (electron beam, X-ray, gamma rays) The cost of food irradiation is influenced by dose requirements, the food's tolerance of radiation, handling conditions, i.e., packaging and stacking requirements, construction costs, financing arrangements, and other variables particular to the situation.[61] Irradiation is a capital-intensive technology requiring a substantial initial investment, ranging from $1 million to $5 million. In the case of large research or contract irradiation facilities, major capital costs include a radiation source, hardware (irradiator, totes and conveyors, control systems, and other auxiliary equipment), land (1 to 1.5 acres), radiation shield, and warehouse. Operating costs include salaries (for fixed and variable labor), utilities, maintenance, taxes/insurance, cobalt-60 replenishment, general utilities, and miscellaneous operating costs.[51][62] Perishable food items, like fruits, vegetables and meats would still require to be handled in the cold chain, so all other supply chain costs remain the same.

Public perception Edit

Negative connotations associated with the word "radiation" are thought to be responsible for low consumer acceptance. Several national expert groups and two international expert groups evaluated the available data and concluded that any food at any dose is wholesome and safe to consume.[63] Irradiation has been approved by many countries. For example, in the U.S. the FDA has approved food irradiation for over fifty years. However, in the past decade the major growth area is for fruits and vegetables that are irradiated to prevent the spread of pests. In the early 2000s in the US, irradiated meat was common at some grocery stores, but because of lack of consumer demand, it is no longer common. Because consumer demand for irradiated food is low, reducing the spoilage between manufacturer and consumer purchase and reducing the risk of food borne illness is currently not sufficient incentive for most manufacturers to supplement their process with irradiation.[21] Nevertheless, food irradiation does take place commercially and volumes are in general increasing at a slow rate, even in the European Union where all member countries allow the irradiation of dried herbs spices and vegetable seasonings but only a few allow other foods to be sold as irradiated.[64] Although there are some consumers who choose not to purchase irradiated food, a sufficient market has existed for retailers to have continuously stocked irradiated products for years.[65] When labeled irradiated food is offered for retail sale, these consumers buy it and re-purchase it, indicating that it is possible to successfully market irradiated foods, therefore retailers not stocking irradiated foods might be a major bottleneck to the wider adoption of irradiated foods.[65] It is however, widely believed that consumer perception of foods treated with irradiation is more negative than those processed by other means[4] and some industry studies indicate the number of consumers concerned about the safety of irradiated food decreased between 1985 and 1995 to levels comparable to those of people concerned about food additives and preservatives.[66] Even though is it is untrue "People think the product is radioactive," said Harlan Clemmons, president of Sadex, a food irradiation company based in Sioux City, Iowa.[67] Because of these concerns and the increased cost of irradiated foods, there is not a widespread public demand for the irradiation of foods for human consumption.[21] Irradiated food does not become radioactive.

Standards & regulations Edit

Irradiated food supply Edit

As of 2010, the quantities of foods irradiated in Asia, the EU and the US were 285,200, 9,300, and 103,000 tons.[86] Authorities in some countries use tests that can detect the irradiation of food items to enforce labeling standards and to bolster consumer confidence.[87][88][89] The European Union monitors the market to determine the quantity of irradiated foods, if irradiated foods are labeled as irradiated, and if the irradiation is performed at approved facilities. Irradiation of fruits and vegetables to prevent the spread of pest and diseases across borders has been increasing globally. In 2010, 18,446 tonnes of fruits and vegetables were irradiated in six countries for export quarantine control. 97% of this was exported to the United States.[86] In total, 103 000 tonnes of food products were irradiated on mainland United States in 2010. The three types of foods irradiated the most were spices (77.7%), fruits and vegetables (14.6%) and meat and poultry (7.77%). 17 953 tonnes of irradiated fruits and vegetables were exported to the mainland United States.[86] Mexico, the United States' state of Hawaii, Thailand, Vietnam and India export irradiated produce to the mainland U.S.[86][90][91] Mexico, followed by the United States' state of Hawaii, is the largest exporter of irradiated produce to the mainland U.S.[86] In total, 6 876 tonnes of food products were irradiated in European Union countries in 2013; mainly in four member state countries: Belgium (49.4%), the Netherlands (24.4%), Spain (12.7%) and France (10.0%). The two types of foods irradiated the most were frog legs (46%), and dried herbs and spices (25%). There has been a decrease of 14% in the total quantity of products irradiated in the EU compared to the previous year 2012 (7 972 tonnes).[92] United States Edit The U.S. Food and Drug Administration and the U.S. Department of Agriculture have approved irradiation of the following foods and purposes: Packaged refrigerated or frozen red meat [93] — to control pathogens (E. Coli O157:H7 and Salmonella) and to extend shelf life. [94]

— to control pathogens (E. Coli O157:H7 and Salmonella) and to extend shelf life. Packaged poultry — control pathogens (Salmonella and Camplylobacter). [94]

Fresh fruits, vegetables, and grains — to control insects and inhibit growth, ripening and sprouting. [94]

Pork — to control trichinosis. [94]

Herbs, spices and vegetable seasonings [95] — to control insects and microorganisms. [94]

— to control insects and microorganisms. Dry or dehydrated enzyme preparations — to control insects and microorganisms. [94]

White potatoes — to inhibit sprout development. [94]

Wheat and wheat flour — to control insects. [94]

Loose or bagged fresh iceberg lettuce and spinach [96]

Crustaceans (lobster, shrimp, and crab) [3]

Shellfish (oysters, clams, mussels, and scallops)[3]

Timeline of the history of food irradiation Edit

See also Edit

Notes Edit

References Edit