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Thermoluminescent Dust for Identification of Irradiated Spices
Abstract
It is shown that most of the natural products contain minute amounts of wind blown or intruding dust which can be separated and used to identify irradiated spices by measuring its thermoluminescence (TL). The method has several advantages over the use of the whole grains of spices. There is no spurious signal due to oxidation of the organic components, therefore the samples can be heated to higher temperatures at which more stable TL peaks are accessible. As a consequence, the method provides (1) high reliability in identification, (2) an access to a quantitative assessment of the administered dose even after some years, (3) determination of the time elapsed between the food irradiation and the TL readout. Thermoluminescent dust obtained from cumin, green pepper, sage, rosemary, mugwort, lovage, thyme, dill weed, oregano, savory, marjoram and basil is investigated.
... One of the main aspects in irradiated foodstuffs is their identification (4)(5)(6)(7)(8), and this can be done using the phenomenon of thermoluminescence (TL). The TL phenomenon has been widely used for the detection of many kinds of irradiated foods (9)(10)(11)(12)(13). Sanderson et al. and Göksu et al. (9,11) have reported that the TL signal from irradiated foods comes from inorganic dust adhering to the organic part. ...
... The TL phenomenon has been widely used for the detection of many kinds of irradiated foods (9)(10)(11)(12)(13). Sanderson et al. and Göksu et al. (9,11) have reported that the TL signal from irradiated foods comes from inorganic dust adhering to the organic part. Indeed, the inorganic mineral content in herbs and spices such as black pepper (Piper nigrum L.) permits the identification of irradiated samples by thermally stimulated luminescence (TL) (14)(15)(16)(17)(18) and can also relate the TL emission with the received dose. ...
The inorganic mineral fraction extracted from black pepper (Piper nigrum L.) has been analysed using a thermoluminescence (TL) method, investigating the glow curve structure, including an evaluation of the kinetic parameters. Different grain sizes, i.e. 10, 74, and 149 μm, were selected from commercial black pepper. The X-ray diffraction of the inorganic fraction shows that quartz is the main mineral present in it. The samples were exposed to 1–25 kGy doses by gamma rays of 60Co in order to analyse the thermally stimulated luminescence response as a function of the delivered dose. The glow curves show a complex structure for different grain sizes of the pepper mineral samples. The fading of the TL signal at room temperature was obtained after irradiation, and it was observed that the maximum peaks of the glow curves shift towards higher values of the temperature when the elapsed time from irradiation increases. It seems that the fading characteristic may be related to a continuous trap distribution responsible for the complex structure of the glow curve. Similar glow curves structure behaviour was found under ultraviolet irradiation of the samples. The activation energy and the frequency factor were determined from the glow curves of different grain sizes using a deconvolution programme because of the evident complexity of the structure.
... Several physical and chemical techniques have been developed for detection of irradiated food and to ensure the desired absorbed dose to the food commodities with uniform distribution of radiation dose (Bögl 1989;Beneitez et al. 1994;Khan et al. 1998;Goksu et al. 1990). These techniques have also been used to compliment the labeling requirement of irradiated food as well as to ensure regulatory compliances in domestic and/or international trade. ...
Thermo-luminescence (TL) method was employed to identify irradiated garlic or ginger powder mixed at different proportions into the food base. The identification of irradiation was carried out by analyzing the shapes of the glow curves and the TL ratios in the temperature ranges of 150–250 °C. Four independent laboratories participated in the study. Garlic or ginger powder was irradiated at 1 or 10 kGy with gamma ray and mixed into a non-irradiated single food base at ratios 0, 0.5, 1, 5, and 10 % for analysis. Detectable TL glows were observed for the samples containing more than 5 % of irradiated ginger or garlic powder. However, the TL ratios of the samples containing more than 5 % were not always positive. In order to identify irradiation in complicated food matrices, garlic or ginger powder irradiated at 10 kGy was added to curry powder and black bean sauce powder at different ratios, namely, 0, 5, 10, 15, and 20 %. In case of curry powder, identification of irradiated garlic and ginger was possible for samples containing more than 5 and 15 %, respectively. On the other hand, identification was possible for black bean sauce powder containing more than 5 % irradiated garlic and 10 % irradiated ginger. The results showed that the detection sensitivity of the TL method decreased substantially in complicated food matrices. In addition, the observed detection limits were too high as compared to the commercial food products. The study showed that the identification of irradiated food ingredients by the TL method was dependent on the irradiation dose, food type, and proportion of irradiated ingredients mixed with the food. Further study is required on how to reduce the variance of the detection limit of irradiated materials in food mixtures.
... Significant progress has been made in the development of detection methods for irradiated foods [9][10][11][12]. Thermoluminescence (TL) is one of the most important physical techniques for examining spices, herbs, and dried fruits [13][14][15]. There is an increasing interest among researchers in extending the use of this technique to different types of food commodities because of its sensitivity and efficiency in detecting irradiation after prolonged storage. ...
Identification of irradiated fruits is of paramount importance to address the limitation of irradiation technology because of varying national and international regulations. Thermoluminescence (TL) analysis was carried out to identify oranges irradiated with gamma-ray, electron beam and X-ray. Non-irradiated samples exhibited background TL signals, but all the irradiated samples showed defined TL glow curves characterized by a prominent peak at 158-163 A degrees C. Characterizations of the irradiated standard minerals showed that feldspars were the major contributors to the TL emission and stable TL signals revealed a successful detection of irradiated oranges even after a prolonged storage.
... The fine grain sedimented layer was used for the salt and dust measurements. Details of the sample preparation and evaluation can be found elsewhere (Gbksu et al., 1990(Gbksu et al., , 1993. All measurements were performed with a Chance Pilkington HA3 heat absorbing filter. ...
The radiation response of natural materials and domestic articles was investigated by EPR and TL to select suitable materials for retrospective dose assessment in accident dosimetry. The thermal stability and the influence of UV-exposure to the radiation-induced EPR centres were investigated. Based on a required precision of ±20% for dosimetry the lower limits of applicability of the materials were determined. The lowest dosimetry limits of 0.5 Gy were found using sugar, boiler scale and egg shells by EPR and 0.3 Gy by using TL with boiler scale. A list of materials found not to be applicable for retrospective radiation accident EPR dosimetry is also given.
The aim of the study was to investigate whether it is possible to detect low-dose irradiation in dried fruits using the thermoluminescence (TL) method. Selected dried fruits: strawberries, cherries, black currants, two types of raisins, mulberries, apricots, figs, dates and plums were irradiated with doses of 0.1 kGy, 0.3 kGy and 0.5 kGy.
Thermoluminescence (TL) method was investigated for detection of radiation treatment of black pepper (Piper nigrum), irradiated to gamma ray doses of 1.0 kGy and 5.0 kGy. The TL response of the minerals isolated from irradiated samples was much higher as compared to that of un-irradiated control samples. For the normalisation of results the separated minerals were re-irradiated to a normalisation dose of 1.0 kGy and TL glow curve recorded a second time. By comparing the glow curves of irradiated and unirradiated samples, it was possible to separate the irradiated samples from unirradiated ones. For laboratories having re-irradiation facilities, more accurate detection was possible by finding the ratio of the areas of first and second (re-irradiated) glow curves (TL1/TL2), which was confirmed by comparing the shapes of the glow curves of irradiated and un-irradiated samples.
Black pepper and cumin samples were analyzed for identification of irradiation treatment. Thermoluminescence (XL) signals of irradiated and unirradiated spices were due to inorganic dust particles adhering to the surfaces. All X-ray diffraction - characterized dust samples revealed the presence of at least 2 common minerals; quartz and feldspars. The samples were irradiated by 60Co gamma - rays at 1, 3, 5 and 10 kGy. Results indicated a clear detectable difference in the shape of glow curves from irradiated and unirradiated samples, and glow curves from irradiated ones with a characteristic shape. The TL effect due to radiation treatment differs from spice to spice and package to package. The TL integrated areas of irradiated spices were higher than their controls. Irradiation can be detected more reliably by comparing the first (original B TL1) glow curve with the reirradiated one (TL2). The ratio of the area of the first glow curve (before re-irradiation) to the second glow curve (after re-irradiation) was > 1.30 for all irradiated samples and < 0.01 for unirradiated samples. Quantitative estimation of absorbed dose can be achieved by re-irradiation and extrapolation to zero signal. Based on the observations made it is possible to distinguish irradiated black pepper and cumin after 365 days post-irradiation.
This study was carried out to determine whether detection of minerals separated from irradiated mussel could be could be done by thermoluminescence (TL) method. After the minerals were separated by sodium polytungstate solution (2.0 g/mL) from irradiated mussel, organic compounds remaining in the minerals were removed by acid-base treatment and dried at 50°C overnight, and then the minerals were measured through TL. The TL intensities of separated minerals at different irradiation doses during storage conditions of room and darkroom were obtained. TL intensity of first glow curves for minerals separated from irradiated mussel showed linear increase from the control to 5 kGy and slight increase from 5 kGy to 10 kGy. Since glow curve ratios of G2, G3 and G4, calculated from re-irradiated minerals measured immediately after irradiation and after storage of three months were over 0.5, detection of irradiation was possible. G1, which showed the glow curve ratios above 0.1, was classified as non-irradiated samples because the unique first glow curve was not found within the recommended temperature interval (150-230°C). Hence, on the basis of TL intensity, and glow curve ratio and shape, it is possible to correctly identify irradaited mussels after mineral separation during storage.
The presence of silicates in many personal objects suggests their potential use at low dose as fortuitous dosimeter in an accidental radiological exposure, when conventional dosimetry is not available. The goal of the present work is the dosimetric characterization of mineral silicates extracted from the plant Hibiscus Sabdariffa L, known as Jamaica flower, in the dose range 0.5–5 Gy. By studying the radiation-induced signal in time, the temperature integration region between 210 °C and 250 °C was found to be the most stable and also reduced the effects of thermal fading in the dose reconstruction process; the dose response curve was linear between 0.5 Gy and 5 Gy. By checking the change in sensitivity after repeated exposures to ionizing radiations and to high temperature heating, no variation in the glow curve shape or peak intensities were detected. To eliminate a pre-existing background signal, all the characterization measurements were performed with aliquots “annealed” by a preliminary readout of the TL.
Eight types of spices and herbs or their mixtures of Asian origin have been investigated for detection of irradiation treatment using thermoluminescence (TL) of insoluble mineral contaminants adhering to the samples. These samples were irradiated by 60Co γ-rays (at absorbed doses 1, 5 and 10 kGy) as well as by 10-MeV electrons using an accelerator (at a dose of 5.4 kGy). The integrated TL intensities of glow curves from the irradiated samples were found to be much higher than those from unirradiated samples. These results were normalized by administering a re-irradiation γ-ray dose of 1 kGy and calculating the ratio of the integral of the first glow curve (of unirradiated or irradiated samples) to that of the second glow curve (after re-irradiation). This ratio is less than 0.02 for all unirradiated samples and more than 0.3 for all irradiated samples (more than 1 for samples irradiated to 5 kGy or at higher doses), thereby making discrimination between irradiated and unirradiated samples possible. If one also compares the different temperature regions of the glow-curve maxima of unirradiated and irradiated samples, unequivocal discrimination is achieved for those previously irradiated to doses equal to or greater than 1 kGy.
This work investigates the feasibility of using silicates contained in dust for retrospective individual dosimetry in case of a radiation accident or a radiological attack involving people not wearing physical dosimeters. It is well known that minerals (silicates) can be used for dosimetry and dust already plays an important role in the field of food irradiation detection using luminescence techniques as described in the European Standards (EN 13751 and EN 1788). This paper explores the feasibility of conducting retrospective personal dosimetry on the basis of thermoluminescence analysis of silicates extracted from dust on objects that people usually wear (e.g. jewelry, watches, keys and coins). The primary objective was to evaluate if the method is sufficiently sensitive for detection of dose levels at the order of several grays. The results were encouraging in the sense that most of the objects investigated contained sufficient silicates to reveal a TL signal well distinguishable from the natural background after irradiation in the laboratory with a dose of 10 Gy. However, it was also found that the radiation-induced signal varied by a factor of 10 among different objects as a consequence of differences in intrinsic luminescence sensitivity of the silicates. Additional studies are needed to more accurately assess the minimum detectable dose and to confirm the general applicability of the method for accidental situations.
Thermoluminescence (TL) method has been successfully applied for
detecting the irradiation of dried and powdered foodstuffs.
Identification investigations on whole samples succeeded but TL response
strongly depended on material-as it was confirmed by interlaboratory
tests. TL intensity was several order greater in measurements on
contaminant minerals-mainly quartz and feldspar-separated from the
samples. Therefore, these studies can be considered to be problems of
solid-state physics, and the dosimeter is not the whole product any
longer. The structure of electron traps-responsible for TL
phenomenon-may be different according to inorganic or organic samples
(in separated minerals or protein-containing products). Detailed
investigations were done on silicate minerals isolated from paprika
powders, and the conditions of mineral separation were also examined. In
the case of food-industrial products, a quantitative detection of the
degree of irradiation seems to be possible, after clearing up the
background of TL phenomenon.
The sale of irradiated food in the UK has been legal since the start of 1991 with the proviso that it must be labelled as such. At present there are no methods sufficiently accurate and reliable for the routine detection of irradiated food of all varieties. The current state of development of different physical, chemical and biological methods available is reviewed. These comprise electron paramagnetic resonance, luminescence, viscosity changes, detection of radiation-induced chemical species such as volatile hydrocarbons and o-tyrosine by chromatographic-mass spectrometric techniques, changes to DNA and changes in microflora.
A major factor hampering the introduction of ionizing radiation as an alternative quarantine treatment to chemical fumigation for fruit and vegetables is the lack of reliable, simple and inexpensive post-treatment methods to confirm this low dose irradiation treatment. Considering this purpose, thermoluminescence (TL) measurements of the wind blown dust naturally adhered to the surface of table grapes, was surveyed. Two doses, 0.5 and 1.0 kGy, were studied, applied to the main Chilean table grape export varieties: Thompson Seedless and Flame Seedless.TL measurements were carried out over 78 days for Thompson Seedless and 62 days for Flame Seedless varieties, both stored at 1 ± 1°C (usual handling of this fruit). TL response fading of dust samples stored at room temperature was also followed over 125 days. The TL response values obtained from the irradiated samples exceeded at least 3 times the highest ones obtained from the unirradiated counterparts. The treatment, even for the lower γ-radiation dose applied, could be properly detected well above the shipping and marketing time for this Chilean export fruit (2–8 weeks). This method also has the advantage of using relatively inexpensive equipment.
A study was carried out to establish a detection method for irradiated chickpea and corn by thermoluminescence (TL) method. The leguminous were packed in polyethylene bags and then the packets were irradiated at room temperature at different doses by 60Co gamma source at 1, 4, 8 and 10 kGy. Minerals extracted from the leguminous were deposited onto a clean aluminum disc and TL intensities of the minerals were measured by TL. It was observed that the extracted samples from both leguminous exhibit good TL Intensity and the TL intensity of glow curves of them increased proportionally to irradiation doses. The TL glow curve of both irradiated leguminous presents a single broad peak below 400 °C. The TL trapping parameters glow peaks were estimated by the additive dose (AD), Tm(Ea)–Tstop and computerized glow curve deconvolution (CGCD) methods. The fading characteristics of glow curves were also recorded up to 6 months.
Study was made of factors influencing the thermoluminescence (TL) intensity of feldspars separated from irradiated foods. Autoradiography and optical densitometry with application of digital image processing was found to be a suitable method for determining the mineral specific differences in irradiated feldspars. Alteration of K feldspar was observed to reduce the luminescence intensity. A structural change from unaltered mineral to fully seriticized form without marked change in element composition was accompanied by a decrease in TL from very intensive to nonobservable. Likewise increase in FeO concentration during alteration was accompanied by decrease in the TL intensity. Thermoluminescence of plagioclase increased with the CaO/Na2O ratio.
Data from import control of irradiated seafood were collected from 300 batches of seafood. Thermoluminescence (TL) analysis of the seafood, based on measurement of thermoluminescent minerals separated from intestinal tract, was carried out with a Risø TL-DA-10 instrument. As identified by X-ray diffraction and SEM/EDS analysis, four main categories of minerals were extracted: tectosilicates, phyllosilicates, carbonates and sulphates. Detection of irradiation was reliable when based on the TL of tectosilicate minerals, i.e. quartz and feldspar. Suitable minerals were found in most seafood: only about five percent of all samples could not be successfully analysed because no minerals or only non-thermoluminescent clays or carbonates were found. False positive results were never obtained. A false negative decision results if analyses are based on hydrous clays or carbonates in the form of aragonite.
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.
In the recent years, increasing attention has been given to irradiation as a method of food preservation. Since the treatment of foods with radiation has to include dose limits, this requires the development of appropriate and reliable method for determining whether a particular food has been irradiated or not and, if possible, at what dose. Various methods are possible depending on the nature of the food. Only electron spin resonance (ESR) and thermoluminescence (TL) detection will be considered here. Studies were carried out on green lentils and encouraging results were obtained.
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.
Research studies reported by various authors have shown that a few methods one of which is thermoluminescence technique- may be suitable for identification of some certain irradiated spicies and food containing bones. This study is an application of the thermoluminescence technique for identifying the irradiated samples. The investigation was carried out on different types of foodstuffs such as onions, potatoes and kiwi. Measurements show that the technique can be applied as a reliable method to distinguish the irradiated food products from non-irradiated ones. The results demonstrate also that it is possible to use this method for determining the absorbed dose of irradiated samples from the established dose-effect curve.
Irradiated foods can be detected by thermoluminescence (TL) of contaminating inorganic dust particles. In this study, black peppers were irradiated with gamma rays at doses of 1, 3, 5 and 10 kGy. The inorganic dust particles collected from irradiated black pepper are investigated. This study reports the mineral composition of this dust being, mainly quartz, feldspar and little amount clay minerals. The TL detection method is clearly able to distinguish irradiated and non-irradiated black peppers at the doses ranging from 1 to 10 kGy. The paper provides a detailed calculation of the activation energy (E), frequency factor (s) and the order of kinetics of the 240 °C TL identification peak in polymineral dust material. The experimental and computerized deconvolution results are consistent with the presence of a closely overlapping second-order TL peaks in the identification peak at 240 °C. The TL kinetic parameters of overlapping peaks were estimated by computerized deconvolution method. The computer deconvolution shows the existence of four well-defined TL peaks at 118, 210, 270 and 305 °C. These four peaks probably due to the combined TL of quartz and feldspar minerals.
The thermoluminescence properties of the inorganic dust extracted from the Chile Guajillo (paprika) Mexicano, were studied in order to verify the possibility of using the TL technique to discriminate between irradiated and non irradiated peppers. The inorganic dust was found to consist of quartz 60%, albite (NaAlSi(3)O(8)) 30%, and ortose (KAlSi(3)O(8)) 10%. Its thermoluminescence dose response covers the wide dose range of 1 Gy--10 kGy, which was attributed mainly to feldspars. Its high sensitivity and its stability over 10 irradiation-readout cycles allow the application of a single grain--single aliquot regeneration dosimetry in Chile Guajillo (paprika). Evaluations based on trapping parameters show that thermal fading at room temperature for glow-peaks above 180 degrees C, is not a problem in the dosimetry of paprika.
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