Phytosanitary irradiation is a treatment that uses

ionizing radiation Ionizing (ionising) radiation, including Radioactive decay, nuclear radiation, consists of subatomic particles or electromagnetic waves that have enough energy per individual photon or particle to ionization, ionize atoms or molecules by detaching ...

on commodities, such as

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

s and

vegetable Vegetables are edible parts of plants that are consumed by humans or other animals as food. This original meaning is still commonly used, and is applied to plants collectively to refer to all edible plant matter, including edible flower, flo ...

s to inactivate pests, such as

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s. This method is used for international food trade as a means to prevent spread of non-native organisms. It is used as an alternative to conventional techniques, which includes

heat treatment Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are a ...

, cold treatment,

pesticide Pesticides are substances that are used to control pests. They include herbicides, insecticides, nematicides, fungicides, and many others (see table). The most common of these are herbicides, which account for approximately 50% of all p ...

sprays, high pressure treatment, cleaning, waxing or chemical fumigation. It is often used on

spice In the culinary arts, a spice is any seed, fruit, root, Bark (botany), bark, or other plant substance in a form primarily used for flavoring or coloring food. Spices are distinguished from herbs, which are the leaves, flowers, or stems of pl ...

s, grains, and non-food items. It inhibits the species reproduction cycle by destroying nuclear material primarily, whereas other methods are measured by species mortality. Each country has different effective approved dosages, although most follow guidelines established by the IPPC which has issued guidelines referred to as the International Standards for Phytosanitary Measures (ISPM). The most commonly used dose is 400 Gy (as a broad spectrum, generic treatment) based on USDA-APHIS guidelines.

History

The foundations of ionizing radiation was first discovered in 1895 by

Wilhelm Röntgen Wilhelm Conrad Röntgen (; 27 March 1845 – 10 February 1923), sometimes Transliteration, transliterated as Roentgen ( ), was a German physicist who produced and detected electromagnetic radiation in a wavelength range known as X-rays. As ...

through discovery of

x-ray An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

s. In the following year,

Henri Becquerel Antoine Henri Becquerel ( ; ; 15 December 1852 – 25 August 1908) was a French nuclear physicist who shared the 1903 Nobel Prize in Physics with Marie and Pierre Curie for his discovery of radioactivity. Biography Family and education Becq ...

discovered natural

radioactivity Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is conside ...

, another form of

. Soon after the discovery of ionizing radiation, therapeutic use and

bactericide A bactericide or bacteriocide, sometimes abbreviated Bcidal, is a substance which kills bacteria. Bactericides are disinfectants, antiseptics, or antibiotics. However, material surfaces can also have bactericidal properties based solely on their p ...

treatments were proposed. Research in the early 1900s demonstrated that X-rays can destroy and hinder the development of the egg, larval and adult stages of cigar beetles. Application of irradiation as a disinfestation procedure for fruit flies was suggested in 1930, however, it was only in 1986 that irradiation up to 1kGy was approved by the

FDA The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

as a method to disinfest

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s in food. Before approval in the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

Hawaii Hawaii ( ; ) is an island U.S. state, state of the United States, in the Pacific Ocean about southwest of the U.S. mainland. One of the two Non-contiguous United States, non-contiguous U.S. states (along with Alaska), it is the only sta ...

petitioned for permission of irradiation on

papaya The papaya (, ), papaw, () or pawpaw () is the plant species ''Carica papaya'', one of the 21 accepted species in the genus '' Carica'' of the family Caricaceae, and also the name of its fruit. It was first domesticated in Mesoamerica, within ...

s in 1972. The FDA finally approved the use of 1 kGy for use on arthropods in fruits and vegetables in 1986. In that same year, the first case of commercial phytosanitary irradiation occurred with

Puerto Rica Puerto, a Spanish word meaning ''seaport'', may refer to: Places *El Puerto de Santa María, Andalusia, Spain *Puerto, a seaport town in Cagayan de Oro, Philippines *Puerto Colombia, Colombia *Puerto Cumarebo, Venezuela *Puerto Galera, Oriental Mi ...

mango A mango is an edible stone fruit produced by the tropical tree '' Mangifera indica''. It originated from the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South and Southeast As ...

es imported to the

Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...

market. Three years later, Hawaii received approval for irradiation of papayas at 150 Gy for shipment to mainland U.S. In 2004,

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

and

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

opened their markets to phytosanitary irradiation. In 2007,

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

sent a shipment of mangoes to the U.S., followed by fruit from

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...

, and

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. Australia continues to broaden their irradiated exports with new markets in

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

Malaysia Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...

and Vietnam.

Mode of action

Ionizing radiation such as

gamma rays A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

electron beam Since the mid-20th century, electron-beam technology has provided the basis for a variety of novel and specialized applications in semiconductor manufacturing, microelectromechanical systems, nanoelectromechanical systems, and microscopy. Mechani ...

X-rays An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays. Roughly, X-rays have a wavelength ran ...

can be used to provide phytosanitary treatment. The direct effect of these high energy photons and electrons, as well as the free radicals they produce result in sufficient damage to large organic molecules such as

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

and

RNA Ribonucleic acid (RNA) is a polymeric molecule that is essential for most biological functions, either by performing the function itself (non-coding RNA) or by forming a template for the production of proteins (messenger RNA). RNA and deoxyrib ...

resulting in

sterilization Sterilization may refer to: * Sterilization (microbiology), killing or inactivation of micro-organisms * Soil steam sterilization, a farming technique that sterilizes soil with steam in open fields or greenhouses * Sterilization (medicine) render ...

morbidity A disease is a particular abnormal condition that adversely affects the structure or function of all or part of an organism and is not immediately due to any external injury. Diseases are often known to be medical conditions that are asso ...

or mortality of the target pests. The sources of irradiation for gamma rays are Cobalt 60 and Cesium 137. X-rays are produced by accelerating electrons at metal sources such as

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

and

s are produced via an electron accelerator.

Commercial use

Phytosanitary irradiation is used to control the spread of non-native species from one geographical area to another. Global trade allows for the procurement of seasonal produce all year round from all over the world, however, there are risks involved due to the spread of invasive species. Irradiation is highly effective as a phytosanitary measure and as a non-thermal treatment, also helps maintain quality of fresh produce. The most commonly used generic dose is 400 Gy to cover most pests of concern except

pupae A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...

and adults of the order

Lepidoptera Lepidoptera ( ) or lepidopterans is an order (biology), order of winged insects which includes butterflies and moths. About 180,000 species of the Lepidoptera have been described, representing 10% of the total described species of living organ ...

, which includes

moth Moths are a group of insects that includes all members of the order Lepidoptera that are not Butterfly, butterflies. They were previously classified as suborder Heterocera, but the group is Paraphyly, paraphyletic with respect to butterflies (s ...

s and

butterflies Butterflies are winged insects from the lepidopteran superfamily Papilionoidea, characterized by large, often brightly coloured wings that often fold together when at rest, and a conspicuous, fluttering flight. The oldest butterfly fossi ...

. Generic doses are the dose level used for a specific group of pests and/or products. Irradiation treatment levels depend upon the pests of concern.

Advantages

A key advantage of phytosanitary irradiation is that treatment doses are tolerated by many commodities without adverse effects on their sensory and physicochemical profiles. Conventional methods of phytosanitation, such as hot water dips and

fumigation Fumigation is a method of pest control or the removal of harmful microorganisms by completely filling an area with gaseous pesticides, or fumigants, to suffocate or poison the pests within. It is used to control pests in buildings (structural ...

with

methyl bromide Bromomethane, commonly known as methyl bromide, is an organobromine compound with chemical formula, formula Carbon, CHydrogen, H3Bromine, Br. This colorless, odorless, nonflammable gas is Bromine cycle, produced both industrially and biologically ...

, can affect sensory quality and damage the fruit. Compared to the doses used for

microorganism A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...

s, the doses for phytosanitation are considerable lower and adverse effects are minimal. In some climacteric fruit, irradiation delays ripening which extends shelf life and allows the fruit to maintain quality for the long distance shipment between harvest and consumption. Since 2000, phytosanitary irradiation has seen a 10% increase every year. This is in part due to increased restrictions on conventionally used chemicals and the effectiveness in a wide variety of produce. In certain fruits such as

rambutan Rambutan ( ; ; ''Nephelium lappaceum'') is a medium-sized tropical tree in the family Sapindaceae. The name also refers to the edible fruit produced by this tree. The rambutan is native to Southeast Asia. It is closely related to several other ed ...

, irradiation is the only method capable of treatment without extensive deterioration as seen from commercial methods. In addition, temperature based phytosanitation methods and chemical fumigation are not entirely reliable. Import inspections still find live pests in commodities treated with these methods.

Disadvantages

Some fruit, such as certain varieties of

citrus ''Citrus'' is a genus of flowering trees and shrubs in the family Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, mandarins, lemons, grapefruits, pomelos, and limes. ''Citrus'' is nativ ...

and

avocado The avocado, alligator pear or avocado pear (''Persea americana'') is an evergreen tree in the laurel family (Lauraceae). It is native to Americas, the Americas and was first domesticated in Mesoamerica more than 5,000 years ago. It was priz ...

s have a low tolerance to irradiation and show symptoms of phytotoxicity at low irradiation levels. Sensitivity to irradiation depends on many factors, such as irradiation dose, commodity, and storage conditions. In addition,

organic food Organic food, also known as ecological or biological food, refers to foods and beverages produced using methods that comply with the standards of organic farming. Standards vary worldwide, but organic farming features practices that cycle resou ...

industries prohibit the use of irradiation on organic products. Lack of communication and education regarding phytosanitary irradiation can hamper its use. Since this treatment causes reproductive sterilization, pests may be present during commodity inspection. The presence of live pests conflict with current inspection standards and there is no clear marker of treatment efficacy. Some other challenges in relation to the commercialization and acceptance of this technology can be attributed to lack of sufficient facilities, cost and inconvenience of treatment, lack of approved treatment for certain pests and concerns about its technology by the key decision makers (traders, shippers, packers). Lack of harmonization of regulations across countries is also a factor that limits its use. Although phytosanitary irradiation has seen an increase in use globally, lack of consumer acceptance in the

European Union The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia. It constitutes the southern half of the Korea, Korean Peninsula and borders North Korea along the Korean Demilitarized Zone, with the Yellow Sea to the west and t ...

, and

Taiwan Taiwan, officially the Republic of China (ROC), is a country in East Asia. The main geography of Taiwan, island of Taiwan, also known as ''Formosa'', lies between the East China Sea, East and South China Seas in the northwestern Pacific Ocea ...

limits its use in countries for which these are major export markets.

References