Irradiation 2231 Introduction

Studies on the effect of ionizing radiation upon living organisms started after the discoveries of X-rays in 1895 and radioactivity in 1896. The first patent for the use of irradiation as a food processing technology was filed in 1905, but sustained effort to use radiation to preserve foods did not begin until the end of World War II. The first commercial use of food irradiation occurred

Electron accelerator

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Product

FIGURE 22.2 Schematic of an electron accelerator.

in 1957 on a spice in Germany [37]. Irradiation is now widely used to inhibit tuber sprouting, delay fruit and vegetable ripening, control insects in fruits and grains, and reduce parasites in products of animal origin [38]. Through the interaction of chemically active species (i.e., free radicals) induced from irradiation and direct damage to microbial DNA caused by high-energy particles, irradiation is also used to reduce or eliminate foodborne microorganisms [39].

Typical ionizing radiation facilities use either gamma rays from the radioactive isotopes 60Co or 137Cs or electron beams as well as X-rays generated in electron accelerators [40]. Strict safety measures are required for gamma ray facilities due to continuous emission from 60Co and 137Cs, such as use of thick concrete walls to construct the irradiation chamber. In contrast, electron accelerators, as shown in Figure 22.2, have few leakage problems because they produce no high-energy electrons when not in use. As recommended by a joint FAO/IAEA/WHO expert committee on food irradiation (JECFI) in 1980, the absorbed dose or amount of energy absorbed by a food product has a limit of 10kGy (1 Gy is a dose equal to 1 J/kg of absorbing material). After reviewing toxicological, nutritional, and microbiological data on foods irradiated at doses over 10 kGy, the committee concluded that foods are both safe and nutritious to consumers when irradiated to any dose adequate to obtain the intended technological objective; however, most foods exposed to dosages above 10kGy will lose sensory quality to some extent [41].

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