Radiation detection, food

K is a (3 -emitting nuclide that is the predominant radioactive component of normal foods and human tissue. Due to the 1460-keV 7 ray that accompanies the (3 decay, it is also an important source of background radiation detected by 7-ray spectrometers. The natural concentration in the body contributes about 17 mrem/y to the whole body dose. The specific activity of 40K is approximately 855 pCi/g potassium. Despite the high specific activity of 87Rb of 2400 pCi/g, the low abundance of rubidium in nature makes its contribution to the overall radioactivity of the environment small. 

The microstructure of bread and other microporous foods can be conveniently studied by applying synchrotron radiation X-ray microtomography (X-MT) (Falcone et al., 2004a Maire et al., 2003) to centimeter- or millimeter-sized samples (Lim and Barigou, 2004). X-MT application only requires the presence of areas of morphological or mass density heterogeneity in the sample materials. The use of this technique for food microstructure detection is of recent date. It was traditionally used for the analysis of bone quality (Peyrin et al., 1998, 2000 Ritman et al., 2002). 

A. The success of medical support effort depends to a great degree on the adequacy of prewar logistical planning and preparation. Logistical plans should provide not only for medical supplies and equipment but also general supplies, food, clothing, water purification apparatus, radiation detection and measurement instruments, communications equipment, and modes of transportation. 

An improved HPLC-photohydrolysis-colorimetry method was validated for twenty-eight reference nitrosamines. These were separated by HPLC and photolytically cleaved by UV radiation. The resulting nitric oxide was oxidized and hydrolyzed to nitrite ions, which were derivatized into an azo dye with Griess reagent and measured spectrophoto-metrically. The method was applied to separate and detect hitherto unknown nonvolatile nitrosamines in biological fluids and food extracts591. 

One of the standardized methods, electron spin resonance (ESR) technique, permits identification of food that contains a hard, dry matrix, e.g., bone. When food containing bone is irradiated, free radicals are produced and trapped in the crystal lattice of the bone, which can be detected by ESR spectroscopy [137]. Thermoluminescence of contaminating minerals for detection of radiation treatment of, e.g., spices and dried fruits can be successfully applied [138, 139]. Another standardized method that has been developed for identification of irradiated fat-containing foods is the mass-spectrometric detection of radiation-induced 2-alkylcyclobutanones after gas-chromatographic separation [140]. The... 

Borsa, J. Chu, R. Sun, J. Linton, N. Hunter, C. Radiat. Phys. Chem. 2002, 63, 271. Murray, C.H., Stewart, E.M., Gray, R., Pearce J. Eds. Detection Methods for Irradiated Foods—Current Status) The Royal Society of Chemistry, Information Services London, 1996. Delincee, H. Radiat. Phys. Chem. 2002, 63, 455. 

Drug residues in foods that strongly fluoresce can be more efficiently detected by fluorescence detectors. Typically, fluorescence sensitivity is 10-1000 times higher than that offered by a UV detector for strong UV-absorbing materials (125). Using a fluorescence detector, it has been possible to detect the presence of even a single analyte molecule in an LC flow cell. This type of detection is very versatile because of its ability to measure the intensity of the fluorescent radiation emitted from analytes excited by UV. 

When bone is treated with ionising radiation, free radicals are trapped in the crystal lattice of the bone (Gordy etal., 1955) and consequently can be detected by EPR spectroscopy. Prior to its application for the identification of irradiated food, the technique was used to date archaeological specimens (Ikeya and Miki, 1980) and as an in-vivo dosimeter to determine the level of human exposure to radiation (Pass and Aldrich, 1985). 

Delincee, H. (1993). Control of irradiated food Recent developments in analytical detection methods. Radiat. Phvs. Chem. 42. 351. 

Schreiber, G.A., Helle, N. and Bogl, K.W. (1993a). Detection of irradiated food - Methods and routine applications. Int, J, Radiat. Biol. 63. 105. 

Radiations with energies above 10 m.e.v. induce detectable levels of radioactivity in food products (83). However, radiations in the energy range proposed for food irradiation, 0.1-10 m.e.v., lose their energy almost exclusively by transferring it to the electrons of the irradiated material, producing electronically excited or ionized molecules. 

Polyatomic molecules have more complex microwave spectra, but the basic principle is the same any molecule with a dipole moment can absorb microwave radiation. This means, for example, that the only important absorber of microwaves in the air is water (as scientists discovered while developing radar systems during World War II). In fact, microwave spectroscopy became a major field of research after that war, because military requirements had dramatically improved the available technology for microwave generation and detection. A more prosaic use of microwave absorption of water is the microwave oven it works by exciting water rotations, and the tumbling then heats all other components of food. 

Extensive animal feeding studies designed to detect the potential presence of toxic substances in various irradiated foods have been carried out since the 1950s, mostly in USA and Europe. None of the studies carried out under the auspices of the IFIP (24 involved countries, 67 technical reports published in 12 years) showed any indication that the irradiated foods contained radiation-produced carcinogens or other toxic substances. In a French study, for example, nine chemical compounds that had been identified in irradiated starch were fed daily to rats in amounts calculated to be 800 times the amounts the animals might be expected to consume from a normal daily intake of irradiated starch. No toxic effect was found even at this exaggerated rate of intake (chapter 8 of [1 ]). 

Vitamin D can be obtained from some foods, but its major source is through the action of ultraviolet radiation, which converts 7-dehydrocholesterol to cholecalciferol in the skin. Hydroxylation of this compound in the liver produces 25-hydroxycholecalciferol, which is then converted in the kidney to 1,25-hydroxycholecalciferol, the active form of vitamin D. Vitamin D plays a major role in promoting absorption of calcium and maintaining bone mineralization. Recently, research has focused on immunosuppressive effects of vitamin D. The vitamin D receptor has been detected in lymphocytes and the thymus, and vitamin D plays a role in T cell-mediated immune response (Deluca Cantoma, 2001). 

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