Identification of irradiation treatment of spices by thermoluminescence of contaminating minerals

Five spices, cumin, coriander, clove, cinnamon and black pepper were irradiated by gamma-ray doses of 1.0 and 5.0 kGy and thermoluminescence (TL) method was used for identification of the irradiation treatment. The TL response of the minerals isolated from irradiated samples was much higher as compared to the mineral particles from unirradiated control samples. For the normalisation of results the separated minerals were reirradiated to a normalisation dose of 1.0 kGy and the TL glow curve was recorded a second time. By comparing the glow curves of irradiated and unirradiated samples, finding the ratio of the areas of first and second glow curves (TL₁/TL₂) and comparing the shapes of the glow curves, all the irradiated and unirradiated samples were identified correctly.     

The application of different detection methods for irradiated dried anchovy and shrimp

Three different techniques, photostimulated luminescence (PSL), electron spin resonance (ESR) and thermoluminescence (TL) were applied for the detection of dried anchovy and shrimp exposed to electron beam at 0–10 kGy. PSL values for irradiated samples were more than 5000 photon counts/60 s, upper threshold (T₂), whereas those of non-irradiated samples were <700 counts (lower threshold, T₁) in anchovy and intermediate values of T₁–T₂ in shrimp. ESR measurements using both the whole samples did not show any signals specific to irradiation. However, in the case of anchovy it was possible to use bone for ESR detection, showing typical signals (g=2.002, 1.998). Minerals separated from both the samples for TL measurement showed that non-irradiated samples were characterised by glow curves situated at about 300°C with low intensity, while all irradiated samples showed glow peaked at about 200°C and its intensity was high enough to be discriminated from the non-irradiated ones. Furthermore, normalization by a re-irradiation enhanced the reliability of detection results of TL. In conclusion, a multi-step detection using different methods enhances confidence in the detection of irradiated food.     

Thermoluminescence analyses of irradiated dried sea foods using different methods of mineral separation

This research was conducted to find the most suitable parameters to separate minerals from irradiated dried shrimps and mussels (0 and 5 kGy) for thermoluminescence analysis using density separation and modified acid hydrolysis (at 50 °C with continuous agitation) methods. Nonirradiated samples gave TL glow curve of low intensity with peak after 300 °C except dried mussel sample, which gave false positive result. This problem was absent in minerals separated by acid hydrolysis. TL ratios of all nonirradiated samples were <0.1 irrespective of method used for mineral separation. Minerals separated from irradiated samples by density separation showed very high intensity of TL glow peak before 200 °C, where results from irradiated dried shrimp samples were better because of good availability of minerals. The minerals separated from irradiated samples by acid hydrolysis showed slightly low TL intensity and glow curve peak was found at about 200 °C. However, acid hydrolysis method was less laborious and required less sample weight as compared to density separation method. TL ratios of all irradiated samples were >0.1 confirming the quality of minerals on TL discs.     

Characterization of radiation-induced luminescence properties and free radicals for the identification of different gamma-irradiated teas

Two kinds (20 each) of gamma-irradiated (0, 5, and 10 kGy) tea samples, blended powders and packed in sachets (tea bags), were investigated using photostimulated luminescence (PSL), thermoluminescence (TL), and electron spin resonance spectroscopy (ESR) to identify their irradiation status. PSL-based rapid screening was possible for all the control samples except for one packed and two powdered samples. The irradiated samples presented a good dose-dependent PSL count except two powdered samples with very low PSL sensitivity. TL analysis provided the most reliable results, in which all the irradiated samples were identified using a well-defined high-intensity TL glow curve in a temperature range of 150–250 °C. The TL results were also confirmed by determining the TL ratio (TL₁/TL₂), which was <0.1 in all the non-irradiated samples and >0.1 in the irradiated ones. ESR spectroscopy was effective for only 3 packed and 6 powdered samples showing the radiation-induced cellulosic and sugar radical signals, respectively.

Identification of γ-ray irradiated medicinal herbs using pulsed photostimulated luminescence, thermoluminescence, and electron spin resonance spectroscopy

Dried herbal samples consisting of root, rhizome, cortex, fruit, peel, flower, spike, ramulus, folium, and whole plant of 20 different medicinal herbs were investigated using pulsed photostimulated luminescence (PPSL), thermoluminescence (TL), and electron spin resonance spectroscopy (ESR) to identify γ-ray irradiation treatment. Samples were irradiated at 0–50 kGy using a 60Co irradiator. PPSL measurement was applied as a rapid screening method. Control samples of 19 different herbs had photon counts less than the lower threshold value (700 counts 60 s−1). The photon counts of non-irradiated clematidis radix and irradiated evodia and gardenia fruits were between the lower and upper threshold values (700–5,000 counts 60 s−1). TL ratios, i.e., integrated areas of the first glow (TL1)/the second glow (TL2), were found to be less than 0.1 in all non-irradiated samples and higher than 0.1 in irradiated ones providing definite proof of radiation treatment. ESR spectroscopy was applied as an alternative rapid method. In most of the irradiated samples, mainly radiation-induced cellulosic, sugar, and relatively complicated carbohydrate radical ESR signals were detected. No radiation-specific ESR signal, except one intense singlet, was observed for irradiated scrophularia and scutellaria root and artemisiae argyi folium. Figure PPSL can be used as a rapid simple preliminary screening method and a combination of ESR and TL tests for a definite proof of gamma irradiation treatment of medicinal herbs.     

Identification of low amount of irradiated spices (red pepper,garlic, ginger powder) with luminescence analysis

For the identification of irradiated food, current analysis methods have limitations regarding presence and stability of radiation-induced markers. In this study, different spice blends with small quantity of different irradiated (0, 1 and 10 kGy) spice powders, such as red pepper, garlic or ginger, were investigated using PSL and TL techniques. In PSL-based screening analysis, the spice blends containing 10% of irradiated materials (1 or 10 kGy) were determined as intermediate or positive. In TL results, the blends containing 1% of 1 or 10 kGy-irradiated spices showed the typical TL glow curves that could be interpreted as positive. The blends with irradiated garlic powder provided more good results where identification was possible at 0.5% mixing of irradiated sample. However, the TL ratios of all spice blends were <0.1 and only TL glow curve shape and intensity may be used to discriminate the samples having irradiated component.     

Thermoluminescence characteristics of minerals from irradiated potatoes of different origins of production

Thermoluminescence (TL) characteristics were investigated for minerals, which were separated from potatoes irradiated at 0–1 kGy of different origins of production in Korea. The polyminerals analyzed by X-ray diffractometer were mainly composed of quartz and feldspar, and showed varied contents with producing origins, that contributed to typical TL responses to irradiation. The glow curve of irradiated samples at 0.05–1 kGy peaked at approximately 200°C with high intensity, but that of non-irradiated potatoes was observed at approximately 300°C with low intensity. Discrimination between irradiated (more than 0.05 kGy) and non-irradiated samples was possible just on the basis of the first glow curve, however, normalization of results through a re-irradiation step greatly improved their reliability. The signal intensity of TL decreased with the lapse of post-irradiation time under different storage conditions (0±0.5°C/dark room, 25±5°C/dark room and 25±5°C/naturally lighted room) but was still distinguishable from that of the non-irradiated sample even after one year.     

Potential use of the activation energy value calculated from the thermoluminescence glow curves to detect irradiated food

We herein report on the calculation of the activation energy (E _a) from the thermoluminescence (TL) glow curves performed by the initial rise method that allows us to discriminate between irradiated and non-irradiated sesame seeds. E _a values of natural TL (0.68 ± 0.03 eV) and gamma-induced TL (never lower than 0.82 ± 0.02 eV) appear as a complementary criterion to be used differentiating between irradiated and non-irradiated foodstuffs with the position and the intensity of the main peak of the TL emission. In addition, E _a values taken from irradiated sesame samples at different doses (1, 5 and 10 kGy) and stored up to 15 months after being processed were compared to a ‘positive’ Spanish blend (i.e. at least one component was commercially irradiated).     

Gamma-ray induced thermoluminescence emission of green synthesized zinc oxide nanophosphors

The thermoluminescence (Thermally stimulated luminescence) technique has been applied in the field of radiation dosimetry and was found to be highly successful in dating ancient pottery samples. It is also used in the study of biological and biochemical systems. The present study reports the gamma-ray exposed thermoluminescence (TL) emission of ZnO nanophosphors. ZnO nanoparticles were prepared via phyto-mediated green routes according to our previous works. Different analytical techniques such as XRD, FESEM, HRTEM, XPS, EDS, FTIR, and UV-DRS were employed to characterize the samples. The ZnO nanoparticles possess hexagonal wurtzite crystal structure of with 29–71 ​nm particle dimension. TL emission of the samples was recorded with different gamma dosages10-50 Gy at a constant heating rate of 2^oCs^-1. A broad single glow curve above 300 ​°C was exhibited by the samples and good linearity was reserved in integrated TL profiles. The TL emission follows first-order kinetics and the activation energies of the traps located in the samples were determined.     

Photo- and thermally stimulated luminescence of polyminerals extracted from herbs and spices

Ionizing radiation processing is a widely employed method for preservative treatment of foodstuffs. Usually it is possible to detect irradiated herbs and spices by resorting to luminescence techniques, in particular photo- and thermostimulated luminescence. For these techniques to be useful, it is necessary to characterize the response to radiation of each particular herb or spice. In this work, the thermoluminescence (TL) and photostimulated luminescence (PSL) properties of inorganic polymineral fractions extracted from commercial herbs and spices previously irradiated for disinfestation purposes have been analyzed. Samples of mint, cinnamon, chamomile, paprika, black pepper, coriander and Jamaica flower were irradiated from 50 to 400 Gy by using a beta source. The X-ray diffraction (XRD) analysis has shown that the mineral fractions consist mainly of quartz and feldspars. The PSL and TL response as a function of the absorbed dose, and their fading at room temperature have been determined. The TL glow curves have been deconvolved in order to obtain characteristic kinetics parameters in each case. The results of this work show that PSL and TL are reliable techniques for detection and analysis of irradiated foodstuffs.     

Changes in content and composition of dietary fiber in yellow onions and red delicious apples during commercial storage

Changes in pectin composition and solubility are part of the softening process in apples during ripening and postharvest storage. Lignification may also occur with long-term storage. In the United States, apples and onions are harvested once yearly and then stored and marketed for the next 12 months. The changes that occur in the dietary fiber content and composition in Red Delicious apples and yellow Spanish onions during storage were studied, and the loss of fiber in peeled apples was determined. Dietary fiber was extracted by the enzymatic-chemical method of Theander and Westerlund. Storage had no effect on total or insoluble fiber content of apples; Klason lignin concentration was greater in samples stored for 12 months than in those stored for 0, 4, or 8 months. Peeling reduced apple fiber concentration about 25% by decreasing neutral and acidic sugars and Klason lignin in the insoluble fraction. The total fiber content of onions increased with storage, primarily by increasing the insoluble fiber content of uronic acids. The results suggest that the standardized, environmentally controlled storage of apples, as used in Washington State, has little effect on dietary fiber content. In contrast, the less rigorously controlled storage conditions for yellow Spanish onions increases the insoluble fiber fraction and uronic acid content.     

Analysis of shellfish by thermoluminescence and X-ray diffraction methods: Knowledge of gamma-ray treatment and mineral characterization

To investigate the detection of irradiated shellfish, seven kinds of shellfish samples were gamma irradiated at 3 and 6 kGy. The first-glow curves for all the control and irradiated shellfish samples were recorded between temperatures of 50 and 400 °C at a heating rate of 5 °C/s. All the samples, the first glow curves (TL₁) of which have been recorded, were re-irradiated at 1 kGy for the normalization of results. Their second glow curves (TL₂) were obtained at the same conditions in order to achieve the thermoluminescence (TL) ratios (TL₁/TL₂). The TL method proactively identified the whole shellfish samples by using the calcite, aragonite and quartz minerals that are present in the shells. The X-ray diffraction spectroscopy has been used as an analytical tool for the characterization of minerals that are present in the shells as inorganic materials along with biomaterial.     

Identification of irradiated pulses by thermoluminescence of the contaminating minerals

Thermoluminescence (TL) response of contaminating minerals from six samples of pulses commonly consumed in Pakistan has been studied for identification of irradiation treatment. The samples were irradiated by Co-60 gamma rays at 0.3, 0.5 and 1.0 kGy, or by 10 MeV electrons using an accelerator at 0.75 and 2.2. kGy. Generally, the TL intensity for minerals separated from irradiated samples was higher than for unirradiated samples. To normalize the results, separated minerals deposited on stainless steel discs were re-irradiated by a normalizing dose and TL response was redetermined. The ratio of the area of the first glow curve to the second glow curve was more than 0.8 for all irradiated samples and less than 0.33 for most of the unirradiated samples. For those unirradiated samples where the ratio of the glow curves was more then 0.03, the shapes of the glow curves were compared. Taking this criterion into consideration, all 21 unirradiated and irradiated samples of pulses were identified correctly. Therefore, a normalization procedure by re-irradiation of minerals and analysis of TL glow curve shapes lead to unequivocal identification of radiation treatment of pulses.     

Thermoluminescence of contaminating minerals for the detection of radiation treatment of dried fruits

Several types of dry fruits (pistachio nut, dried apricot, almond and raisins) have been investigated for detection of their radiation treatment by gamma rays or electron beam using thermoluminescence (TL) measurements. These samples were irradiated to 1.0–3.0 kGy (gamma rays) or 0.75–3.9 kGy (10 MeV electron beam). Thermoluminescence glow curves for the contaminating minerals separated from the dry fruits were recorded between the temperature range of 50°C and 500°C. In all the cases, the intensity of TL signal for the irradiated dry fruits was 1–3 orders of magnitudes higher than the TL intensity of the corresponding unirradiated control samples allowing clear distinction between the irradiated and unirradiated samples. These results were normalized by re-irradiating the mineral grains with a gamma-ray dose of 1.0 kGy, and a second glow curve was recorded. The ratio of intensity of the first glow curve (TL₁) to that after the normalization dose (TL₂), i.e. (TL₁/TL₂) was determined and compared with the recommended threshold values. These parameters, together with comparison of the shape of the first glow curve, gave unequivocal results about the radiation treatment of the dry fruit samples.     

The identification of irradiated seasoned filefish (Thamnaconus modestus) by different analytical methods

Dried seasoned filefish (Thamnaconus modestus) was irradiated at 0–10 kGy and the identification of irradiation treatment was investigated by analyzing the characteristics of thermoluminescence (TL), hydrocarbon (HC), and 2-alkylacyclobutanone (2-ACB). The TL (TL₁), glow curve of the irradiated samples peaked at approximately 150 °C with high intensity, but that of the non-irradiated samples peaked at about 300 °C with little intensity, thus making it possible to discriminate between irradiated and non-irradiated samples. Moreover, TL ratio (TL₁/TL₂), through normalization steps, enhanced the reliability of the TL₁ results. Six kinds of HCs and three kinds of 2-ACBs quantitatively determined for the samples linearly increased in proportion to irradiation doses. In particular, two HCs like 1-hexadecane and 1,7-hexadecadine, and three ACBs, such as 2-dodecylcyclobutanone, 2-(5′-tetradeceyl)cyclobutanone, and 2-tetradecylcyclobutanone, were identified only in the irradiated samples as radiation-induced markers.     

Optical and thermoluminescence properties of a NaCl single crystal doped with Cd<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript> and exposed to gamma-rays

The thermoluminescense (TL) behavior of solid solutions of cadmium and manganese doped single crystals under γ-irradiation is reported. Various compositions of single crystals of NaCl doped with Cd²⁺ and Mn²⁺ have been irradiated with ionizing radiation. The increase in the glow curve was followed as a function of the F-centers produced by the dose. The analysis shows the potential use of these materials as dosimeters.     

Thermoluminescence analysis for testing the irradiation of spices

Thermoluminescence signals of irradiated and unirradiated spices and herbs are due to inorganic matter grains adhering to the surfaces. This study reports the mineral composition of this dust being, mainly quartz, calcite and philosilicates; it shows the differences between samples exposed and non-exposed to -radiation on the basis of TL signals after long storage periods (1–16 months). A saturation process in the TL signal is found when the samples absorb doses higher than 5 kGy. Finally, the TL glow curve intensities do not suffer significant changes with the dose rate of the -source used in the radiation process.     

Thermoluminescence study of Cu,Ag and Mn doped lithium tetraborate single crystals and glasses

Spectrally resolved thermoluminescence (TL) of non-doped and Ag, Cu^? and Mn-doped lithium-tetraborate (LTB) single crystals revealed that TL emission bands for differently doped samples proved to be at different wavelengths: 272, 370 and 608 nm, respectively. These bands perfectly agree with the photoluminescence (PL) emission bands of Ag⁺, Cu⁺ and Mn²⁺ ions. It strongly points that these dopants are directly involved as recombination centers in the TL process.TL characteristics of non-doped and doped LTB single crystals and the corresponding glassy samples showed that their TL intensities and the structures of the glow curves were apparently different.     

The role of rare earth elements and Mn(2+) point defects on the luminescence of bavenite

Natural fibrous crystals of bavenite (Ca₄Be₂Al₂Si₉O₂₆(OH)₂) collected in intra-granitic pegmatite bodies of Bustarviejo (Madrid, Spain) have been examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron microprobe (EMPA) and inductively coupled plasma-mass spectrometry (ICP-MS). The strong luminescence emissions of bavenite using thermoluminescence (TL), cathodoluminescence (CL) and its thermal stability have been recorded, looking for new physical properties and new phosphor or dosimetric uses. The bavenite luminescence takes place in the 5d electron shell that interacts strongly with the crystal field; the spectra bands assignment are Gd³⁺ (319 nm), Sm³⁺ (562 and 594 nm), Dy³⁺ (572 nm) and Tb³⁺ (495 nm). A Mn²⁺ band at about 578 nm in Ca²⁺ sites is present as a broad band that overlaps with the Dy³⁺, Sm³⁺ and Tb³⁺ bands. Mn²⁺ is a transition metal ion that has an electron configuration of 3d⁵ and interacts strongly with the crystal field (d → d) transition. Stability tests at different temperatures show clearly that the TL glow curves at 400 nm in both irradiated and non-irradiated bavenite samples track the typical pattern of a system produced by a continuous trap distribution. The ICP-MS analyses show concentrations of Yb = 29.7 ppm, Dy = 22.7 ppm, Sm = 9.45 ppm, Nd = 8.95 ppm and Gd = 8.15 ppm in the bavenite lattice.     

TSL and EPR studies of SrBPO5 doped with CeO2 and co-doped with CeO2 and Sm2O3

Thermally stimulated luminescence (TSL) and electron paramagnetic resonance (EPR) investigations were carried out on gamma irradiated SrBPO₅ samples doped with CeO₂ and co-doped with CeO₂ and Sm₂O₃. On gamma-irradiation at room temperature, BO₃ ^2–, O₂ ^– and O^– radicals were produced. It was seen that the O^– radical ion disappeared in the sample annealed at 500 K. It is proposed that the recombination between trapped electrons and O^– radical ions results in transfer of recombination energy to the impurity centre Ce³⁺ resulting in TSL glow peak at 485 K. In the case of co-doped samples energy transfer occurs between Ce³⁺ to Sm³⁺ resulting in increase in the intensity of glow peak at 485 K.The authors are grateful to Dr. V. K. Manchanda, Head, Radiochemistry Division, BARC for his keen interest and encouragement during the course of this work.