Growing Interest In Food Irradiation

Acceptance of any new technology by society depends on there being a genuine need for the benefits offered by that technology. In recent years there has been a veritable explosion of consumer interest in, and concern with, food-borne illness. There is a growing realization that such illness constitutes a very real problem around the world, with significant costs inflicted on the personal as well as national levels. Food irradiation is increasingly viewed as a technology that has much to offer in the ongoing battle against foodborne illness. Responsible public health agencies are urging adoption of irradiation as an additional means of protecting the safety of our food supply. The net effect of all these developments is that there now is an unprecedented level of interest in food irradiation.

TECHNICAL ASPECTS Definition of Food Irradiation

Food irradiation is a process involving the exposure of food to a field of ionizing energy (radiation) for the purpose of effecting some desired benefit. Hence, in respect to purpose, radiation processing of food is similar to the processing of food by more conventional methods.

Energy Considerations. Food processing of any type involves energy transfer into, or out of, the food substance being treated. The form of energy involved can differ and can include thermal, chemical, mechanical, microwave, pressure, or ionizing energy (synonymous with radiation). Thus, at this basic level, food irradiation differs from more conventional forms of food processing in the form of energy involved. However, it should be noted that at this level, the conventional forms of food processing differ from one another as well.

Types of Ionizing Energy. Ionizing energy is any form of energy whose individual quanta (discrete packets of energy) are energetic enough to create ions by ejecting electrons from the atoms within a material absorbing that energy. Such energy can be photonic (pure electromagnetic energy, with no physical particles involved) or particulate (real particles involved). Examples of the former type include y-rays, spontaneously given offby certain radioactive elements (like cobalt-60 or cesium-137) and X rays (produced by X-ray generating machines). Beams of high-energy electrons, generated by special machines called electron accelerators, constitute the most common form of particulate radiation. Any of these types of ionizing energy can be used for processing materials. However, to avoid potential induction of radioactivity in the treated material, electron energies must be kept below 10 MeV, while photons must not exceed 5 MeV.

Radiation as Processing Energy. Ionizing energy, in its various forms, possesses several characteristics that make it extremely useful as a form of processing energy (2). These include its versatility in effecting a variety of technical end points in a wide variety of materials, its ability to penetrate through the bulk of the product being treated, its ability to effect treatment without significantly increasing the temperature of the material being treated, its controllability, its flexibility, its convenience, its low cost, its environmental friendliness and its lack of residues in the treated product. Figure 1 illustrates the general concept of radiation processing. As shown in Figure 1, radiation processing of any material gives rise to change(s) in the physical, chemical, and biological properties of the treated substance. One or more of these changes in material properties constitute the purpose of the treatment. It is worth noting that radiation processing is no stranger to our daily lives. Although most consumers are generally not aware of it, there already is widespread use of consumer products whose manufacture is associated with radiation processing in one way or another, reflecting the great utility and versatility of this type of industrial processing. Some familiar examples of such products include electrical insulation, automobile tires, personal hygiene products, bandages, cosmetics, plastic films and coatings, baby soothers, packaging materials for juices and other liquids, advanced composites used in aircraft manufacture, cellulosic products (eg, fabrics) derived from plant biomass, medical devices, and even jewelry.

Process of Food Irradiation

Conceptually, the process of food irradiation is very simple. The essential elements include a shielded chamber containing a field of ionizing energy, and appropriate equipment for conveying foodstuffs through the facility. In operation, the food material is transported into the irradiation chamber, kept there for an appropriate length of time during which the desired amount of ionizing energy is absorbed, and then removed from the chamber. Upon removal from the chamber, the food material is ready for immediate utilization, which could involve consumption, further processing, or storage, as appropriate. In actual practice, the irradiation facility operator must pay attention to a lot of detail to ensure that the process is carried out properly, but that detail is invisible to both the facility client and the end user of the treated product.

X-rays Electrons

Commodity

y-rays

Processed commodity

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