No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
An electron resonance study of gamma-irradiated grapes
Abstract
The ESR spectra of the seeds, skins and stalks of unirradiated and γ-irradiated Cape black grapes have been obtained. In the spectra of all parts of the grape a single line (g ca. 2.004) is observed both before and after irradiation. New spectral features are observed after irradiation with doses of between 2 and 10 kGy. Some of these features decline in intensity over a period of several days. However, in the case of stalks, new spectral features are readily observed over the shelf-life of the fruit and in samples irradiated to a dose of only 2kGy.
... Different scientists reported the effectiveness of ESR spectroscopy in irradiated food of a plant origin targeting cellulose radicals. [6,7] The irradiation of food containing cellulose produces two peaks (g = 2.020 and g = 1.985) with a mutual distance of approximately 6 mT in the ESR spectrum. ESR technique can be applied easily to dried food materials without any laborious pretreatment. ...
... Similar ESR signals due to organic radicals [21] from different foods of plant origins were also reported. [6][7][8]10,13] Mainly, semiquinone radicals, which are produced by the oxidation of polyphenolic compounds in the plant matrix, are considered responsible for these results. [22,23] There was a significant difference in the intensities of the signals from different parts of the same vegetable, where the effect of different sample pretreatments was also prominent. ...
makes every effort to ensure the accuracy of all the information (the "Content") contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at
... Some researchers (Tabner & Tabner, 1991.;Maloney, Tabner, & Tabner, 1992) carry out more detailed studies of EPR spectroscopy for seeds, stems and skins of grapes that confirm the appearance of radiation-induced signals. ...
Irradiation of food in the world is becoming a preferred method for their sterilization and extending their shelf life. For the purpose of trade with regard to the rights of consumers is necessary marking of irradiated foodstuffs, and the use of appropriate methods for unambiguous identification of radiation treatment. One-third of the current standards of the European Union to identify irradiated foods use the method of the Electron Paramagnetic Resonance (EPR) spectroscopy. On the other hand the current standards for irradiated foods of plant origin have some weaknesses that led to the development of new methodologies for the identification of irradiated food. New approaches for EPR identification of radiation treatment of herbs and spices when the specific signal is absent or disappeared after irradiation are discussed. Direct EPR measurements of dried fruits and vegetables and different pretreatments for fresh samples are reviewed.
... The best fi t has been obtained for linear function determined by the highest R-square coeffi cients which for bananas are R 2 = 0.9299, for papaya R 2 = 0.8749, while for fi g R 2 = 0.9132. The linear relationship of EPR signal intensity vs. dose has been observed earlier for irradiated dried grapefruits [16] and dried candied fruits, the components of diet supplements [17]. ...
The dominating carbohydrates in fruits are monosaccharides like fructose, glucose, sorbose and mannose. In dehydrated fruits, concentration of monosaccharides is higher than in fresh fruits resulting in the formation of sugar crystallites. In most of dried fruits, crystalline fructose, and glucose dominate and appear in proportion near to 1:1. Irradiation of dried fruits stimulates radiation chemical processes resulting in the formation of new chemical products and free radicals giving rise to multicomponent EPR signal which can be detected for a long period of time. For that reason, it is used as a marker for the detection of radiation treatment of dried fruits. It has been found that EPR spectra recorded in dried banana, pineapple, papaya, and fig samples resemble the EPR spectrum obtained by computer addition of fructose and glucose spectra taken in proportion 1:1. The decay of radiation induced EPR signals proceeds in dried fruits fast during the first month of observation and becomes much slower and almost negligible after prolonged storage. However, it remains intense enough for EPR detection even one year after processing. The radiation induced EPR signal is easily detected in dried fruits exposed to 0.5 kGy of gamma rays. Thus, the EPR method of the detection of irradiated fruits can be used for the control of dried fruits undergoing quarantine treatment with 200-300 Gy of ionizing radiation.
... A single central signal (g=2.0040) was observed in all nonirradiated samples irrespective of sample type and pretreatment (Fig. 1). Various researchers also reported similar central signals in different foods of plant origins131415161718 and were attributed to organic (semiquinone) radicals [13,192021. Upon different sample pretreatments, the intensity of this signal was the lowest in alcoholic extracted samples while the highest in water treated samples, however qualitative appearance was the same without any change in g-value (g=2.0040). ...
Fresh (raw roots), white (dried), and red (steamed-drid) ginseng samples were gamma-irradiated at 0 to 7 kGy. Electron spin resonance (ESR) technique was used to characterize the irradiation status of the samples, targeting the radiation-induced cellulose radicals after different sample pretreatments. All non-irradiated samples exhibited a single central signal (g=2.006), whose intensity showed significant increase upon irradiation. The ESR spectra from the radiation-induced cellulose radicals, with two side peaks (g=2.0201 and g=1.9851) equally spaced (±3 mT) from the central signal, were also observed in the irradiated samples. The core sample analyzed after alcoholic-extraction produced the best results for irradiated fresh ginseng samples. In the case of irradiated white and red ginseng samples, the central (natural) and radiation-induced (two-side peaks corresponding to cellulose radical) signal intensities showed little improvement on alcoholic-extraction. The water-washing step minimized the effect of Mn(2+), but reduced the intensity of side peaks making them difficult to indentify. The effect of different origins was negligible, however harvesting year showed a clear effect on radiation-induced ESR signals.
... Recently, ESR spectra of ␥-irradiated fresh fruits have been reported [14][15][16][17]. Although previous studies have recorded the time course of signal intensities, the precise response between signal intensities and irradiation doses have not been examined [14][15][16][17][18][19][20][21][22]. Some papers have shown "cellulose-like" satellite signals in some fruits, except for the mango that has shown a singlet after irradiation [15]. ...
An electron spin resonance (ESR) spectroscopic study of radicals induced in irradiated fresh mangoes was performed. Mangoes in the fresh state were irradiated with gamma-rays, lyophilized and then crushed into a powder. The ESR spectrum of the powder showed a strong main peak at g=2.004 and a pair of peaks centered at the main peak. The main peak was detected from both flesh and skin specimens. This peak height gradually decreased during storage following irradiation. On the other hand, the side peaks showed a well-defined dose-response relationship even at 9 days post-irradiation. The side peaks therefore provide a useful means to define the irradiation of fresh mangoes.
Two different groups of dried fruits of white mulberry (Morus Alba L.) sold in Turkish markets were investigated by the X-band ESR spectroscopy technique for irradiation detection purposes. No resonance signals were detected in the ESR spectra of the un-irradiated samples. After irradiation, identical multi-line resonance signals were induced in the ESR spectra of both types of samples, except for the intensities. At doses of 2 and 10 kGy, the long-term stabilities of the radiation-induced radicals at room temperature were investigated over a storage period of about 100 days. The results obtained show that the ESR technique can be used to distinguish irradiated white mulberry fruits from un-irradiated ones.
Photostimulated luminescence (PSL) or thermo-luminescence (TL) analysis and electron spin resonance (ESR) spectroscopy were performed to detect radiation-induced markers in various trading fruits, such as oranges, grapefruits, mandarins, lemons, limes, bananas, and pineapples. All the unknown samples were identified as non-irradiated fruits, and gamma irradiation at 1 kGy permitted dose by Codex and US FDA was applied to investigate radiation-induced markers. The photon counts for all calibrated PSL samples revealed higher than 5000 (positive) except banana. The ESR triplet signals were detected as a radiation-induced marker resulting from cellulose existing in irradiated fruits excluding banana. The unambiguous identification of irradiated banana was impossible by both techniques. However, isolated minerals from all fruit samples showed radiation-induced typical TL glow curves through the normalization step, confirming the feasible application of TL analysis for identifying irradiation status of all the subjected trading fruits.
Objective: To study the effects of gamma irradiation (10 and 25 kGy) on volatile oil constituents, total phenolic content, and free radical scavenging activity of cassumunar ginger rhizomes. Moreover, the effects on toxicity were investigated on both non-irradiated and irradiated samples, and accompanied by measurements of free radical content. Methods: Electron paramagnetic resonance spectroscopy (EPR) and GC-MS were used to determine free radicals and active compounds in essential oils, respectively. Toxicity was estimated using Toxi-Chromo Test. Total phenolic content and Antioxidant properties were determined using the Folin-Ciocalteu and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, respectively. Results: Irradiation at the doses of 10 and 25 kGy significantly (P < 0.05) increased free radicals in cassumunar ginger rhizomes. However, the volatile oils, total phenolic content, antioxidant activity and toxicity were not significantly (P > 0.05) affected by the irradiation doses. Conclusion: The present results suggest that gamma irradiation at the doses up to 25 kGy can safely be used to sanitize dried cassumunar ginger rhizomes.
In order to detect irradiated grapes by electron spin resonance(ESR)spectroscopy, the grape skins, grape stalks and grape seeds were used as test materials to study the feature changes of ESR spectrum and the relationship between ESR intensity and irradiation dose in the range of 0 to 10 kGy. The results showed that the ESR spectra of grape skins, grape stalks and grape seeds were obviously different before and after irradiation, the intensity of ESR signal increased with the increasing of the absorbed dose. The grape stalks which had the minimum detection limit (0.25 kGy) could be used as an ideal experimental material to identify whether or not grapes had been irradiated. By comparing the dose effect curves of grape skins, grape stalks and grape seeds, it was concluded that grape stalk curves showed the most accurate (R2=0.9943). The ESR intensity of three kinds of irradiated samples all decreased during the storage time (15 d), grape skins showed severest attenuation (attenuation 80%). The results could provide the technical basis for the application of ESR spectroscopy in detecting irradiated grapes.
Electron spin resonance (ESR) spectroscopy of gamma-irradiated fresh broccoli and kimchi cabbage was conducted to identify their irradiation history. Different pretreatments, such as freeze-drying (FD), oven-drying (OD), alcoholic-drying (ALD), and water-washing and alcoholic-drying (WAD) were used to lower the moisture contents of the samples prior to ESR analysis. The non-irradiated samples exhibited a single central signal (=2.0007) with clear effect of , especially in kimchi cabbage. Upon irradiation, there was an increase in the intensity of the central signal, and two side peaks, mutually spaced at 6 mT, were also observed. These side peaks with (left)=2.023 and (right)=1.985 were attributed to radiation-induced cellulose radicals. Leaf and stem in broccoli, and root and stem in kimchi cabbage provided good ESR signal responses upon irradiation. The signal noise was reduced in case of ALD and WAD pretreatments, particularly due to signals. The ALD treatment was found most feasible to detect the improved ESR spectra in the irradiated samples.
An improved detection of radiation-induced paramagnetic faults was developed to identify the irradiation status of basil and clove. The effectiveness of different sample pretreatments, including freeze-drying (FD), oven-drying (OD), alcoholic-extraction (AE), and water-washing and alcoholic-extraction (WAE), were examined. All non-irradiated samples showed a single central signal (=2.006), whereas radicals representing two additional side peaks (=2.023 and =1.986) with a mutual distance of 6 mT were detected in the irradiated samples. AE and WAE produced the best results for irradiated clove in terms of intensities of radiation-specific ESR signals and their ratios to the central signal. However, FD provided the highest intensities of radiation-specific ESR signals for basil, whereas their ratios to the major signal were better in the cases of AE and WAE. Signal noise, particularly due to signals, was observed, whereas it decreased in AE and WAE pretreatments. Based on our results, AE and WAE can improve the detection conditions for radiation-specific ESR signals in irradiated samples.
In this work we use paramagnetic defects induced by radiation in the fruit pulp to identify gamma-irradiated kiwi, papaya and tomato. Pulp without seed, peels or stalks are treated by alcoholic extraction in order to remove water, soluble fractions and solid residue. The ESR spectra of pulp samples of irradiated fruit is composed of species A (g = 2.0045) and species C (g = 2.0201 and g = 1.9851), which are also observed in irradiated stalks and skins. In comparison with samples which are not submitted to alcoholic extraction, species C is stable enough to be used as a dose marker. Furthermore, the species C signal can be detected perfectly even in pulp samples irradiated with doses as low as 200 Gy. Irradiation doses of fruit, exposed to 200–900 Gy of a gamma rays, were estimated with an overall uncertainty of 15% using dried pulp samples. These results indicate that radicals induced in pulp have potential to be used in the identification and absorbed dose determination of irradiated fruit.
Peanuts were analyzed by electron spin resonance (ESR) spectroscopy and gas chromatography (GC) before and after gamma irradiation. Using European protocols, the validity and effectiveness of these two techniques were compared with regard to sample preparation, sample and solvent consumption and dose–response curves after irradiation. The results showed the possibility of using ESR and GC for distinguishing between irradiated and unirradiated peanuts. A radiation dose of 0.1kGy could be detected by ESR but not by GC. The results also indicated that GC is an effective method for qualitative analysis of irradiated peanut, while ESR is suitable for the rapid detection of irradiated peanuts.
Gamma-irradiated (0, 1, 5 and 10 kGy) spaghetti sauce samples were identified using photostimulated luminescence (PSL), thermoluminescence (TL) and electron spin resonance (ESR) techniques. PSL technique was used as a screening method for irradiated sauce samples, where the improved results of PSL method were observed for the freeze-dried and alcoholic-extracted samples. TL technique, through the density separation step of silicate minerals from irradiated samples, gave specific shape, intensity and occurrence of TL glow curve in a typical temperature range as well as TL ratio (TL 1/TL 2) to identify the irradiation treatment. The ESR method employed for the freeze-dried samples, showed radiation-specific cellulose signals for 5 and 10 kGy-treated samples, and the results were comparable with oven-dried samples. In general, TL technique was found the most sensitive and reliable for the identification of irradiated spaghetti sauces.
The safety of food irradiation is well documented; however, this technique lacks international consensus for general applicability. Validated identification methods have prime importance for the application of different regulations regarding the international trade of irradiated food. This study comprehensively investigated the potential of different available techniques for the identification of irradiated sauce samples. Liquid samples were treated with different modified methods to find the improved identification results. The presented results may be useful for different regulatory authorities to identify or monitor irradiated spaghetti sauces.
The ESR spectra of the stalks and skins of a selection of unirradiated and γ-irradiated citrus fruits have been obtained. The spectra from the stalks and skins of unirradiated fruits exhibit only a single line, the intensity of which varies markedly from fruit to fruit. The spectra from irradiated stalks exhibit extra features which can be used to detect irradiation, particularly at higher doses. The spectra obtained from the skins of the irradiated fruits also exhibit radiation-induced features which can easily be used to detect irradiation even at the lowest dose examined (2 kGy). The spectra from the irradiated skins show a high degree of reproducibility from fruit to fruit. These observations suggest that ESR spectroscopy could form the basis of a viable test to determine the radiation history of these fruits.
Summary In this work we use paramagnetic defects induced by radiation in the fruit pulp to identify gamma-irradiated kiwi, papaya and tomato. Pulp without seed, peels or stalks are treated by alcoholic extraction in order to remove water, soluble fractions and solid residue. The ESR spectra of pulp samples of irradiated fruit is composed of species A (g = 2.0045) and species C (g = 2.0201 and g = 1.9851), which are also observed in irradiated stalks and skins. In comparison with samples which are not submitted to alcoholic extraction, species C is stable enough to be used as a dose marker. Furthermore, the species C signal can be detected perfectly even in pulp samples irradiated with doses as low as 200 Gy. Irradiation doses of fruit, exposed to 200–900 Gy of a gamma rays, were estimated with an overall uncertainty of 15% using dried pulp samples. These results indicate that radicals induced in pulp have potential to be used in the identification and absorbed dose determination of irradiated fruit.
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.
The ESR spectra of the seeds, skins and stalks of unirradiated and γ-irradiated Chilean white grapes have been obtained and the results compared to those previously reported for Cape black grapes. The high degree of reproducibility of the spectra obtained from the stalks of different varieties of grapes suggest that ESR spectroscopy could form the basis of a viable test to determine their irradiation history. The condition of the stalk prior to irradiation has been found to have little effect on the resulting spectra. The spectra from the stalks, skins and seeds of unirradiated and γ-irradiated apples, peers and cherries have also been examined. Although most of the spectra from irradiated components exhibit extra features, they are sometimes short-lived and restrict the development of ESR as a viable test.
The ESR spectra of the flesh of a selection of unirradiated and γ-irradiated citrus fruits have been obtained. When dried, the flesh from unirradiated fruits gives rise to virtually no ESR spectrum. However, the flesh of irradiated fruits exhibit a strong spectrum with radiation induced features which show a high degree of reproducibility within the fruits examined. These features have been previously observed in spectra from the intact skin and skin components of irradiated citrus fruits. It is believed that this is the first time that radicals have been observed by ESR in the flesh of irradiated fruits.
This article's purpose primarily is to review the scientific literature on the development of analytical methods for the identification of irradiated foods over the past decade. The main modalities currently being employed or developed (e.g. physical vs. chemical vs. biological) are introduced, and their advantages and disadvantages discussed. Radiation/free radical chemistry and electron spin resonance (ESR) spectroscopy are presented in the most depth. Some recent food irradiation/ESR research from the authors' laboratories is included. Finally, it is hoped that this review will shed some light on the current status and prospects for food irradiation practices world-wide.
ESR signals were recorded from irradiated papaya at liquid nitrogen temperature (77 K), and freeze-dried irradiated papaya at room temperature (295 K).Two side peaks from the flesh at the liquid nitrogen temperature indicated a linear dose response for 3–14 days after the γ-irradiation. The line shapes recorded from the freeze-dried specimens were sharper than those at liquid nitrogen temperature.
ESR spectra of the hard seed cover and kernel coating of irradiated orange and tangerine fruits were obtained under different sample drying conditions to analyze the effect of treatment on ESR line at g = 2.0033 (line A). The spectra shows almost the same lines that appear in stalks, achenes, seeds and skins of fresh fruit. The peak-to-peak intensity of the line A of the spectra shows a linear variation with dose in the range studied (up to 5 kGy) under controlled sample preparation. Q-band ESR spectra shows that this line is composed for three different lines from different species. A1, A2 and A3. The A2 and A3 lines are associated with dose but grow also during drying of the sample and are probably due to 'cellulosic' components of the seed cover. The A1 line appears only when sample is dried and is probably associated with the quinones of the internal kernel coat.
One variety (Aple) of Libyan dry dates (Phoenix dactylifera L.) was irradiated in a 60Co source to absorbed doses of 0.8, 1.0, 1.5 and 2.0 kGy. Unirradiated date stone contains a radical with a single line g = 2.0045, feature A. Irradiation to a dose of 2.0 kGy (the recommended dose for fruits in U.K.) induces the formation of additional radicals with signals g = 1.9895 and 2.0159, feature C. The single line having g = 2.0045 decays in both unirradiated and irradiated samples whereas the additional signals g = 1.9895 and 2.0159 remain almost unchanged over a period of time 15 months stored at room temperature and 4 degrees C.
This review gives a brief outline of the principles of the EPR detection method for irradiated foods by food type. For each food type, the scope, limitations and status of the method are given. The extensive reference list aims to include all which define the method, as well as some rarely cited works of historical importance.
The international commerce of vegetable products is often dependent on the quarantine protections that are imposed by the importing countries because of the fear of contamination by fruit flies. The use of ionizing radiation as a treatment for these products can be used to remove this problem and a real proof of irradiation can contribute to the implementation of the international commerce. ESR measurement on the pulp of vegetable products can be used as a proof of irradiation using the species introduced in cellulose that are found uniquely in irradiated products. The stability of these species are compatible with the life of the products analyzed. The pulp signal intensity is sufficient to identify products irradiated with doses as low as 100 Gy for some fruits.
Nine spice and aromatic herb samples (i.e., basil, bird pepper, black pepper, cinnamon, nutmeg, oregano, parsley, rosemary, and sage) were gamma-irradiated at a dose of 10 kGy according to commercial practices. The effects of the disinfection treatment on the content of organic radicals and some nutrients (namely, vitamin C and carotenoids) in the samples were investigated by chromatographic and spectroscopic techniques. Irradiation resulted in a general increase of quinone radical content in all of the investigated samples, as revealed by electron paramagnetic resonance spectroscopy. The fate of these radicals after storage for 3 months was also investigated. The cellulose radical was clearly observed in a few samples. Significant losses of total ascorbate were found for black pepper, cinnamon, nutmeg, oregano, and sage, whereas a significant decrease of carotenoids content was observed for cinnamon, oregano, parsley, rosemary, bird pepper, and sage.
EPR spectra of dry, sugar containing fruits--raisins, sultanas, figs, dates, peaches, blue plums and chokeberry recorded before and after irradiation with gamma-rays, are reported. It is shown that weak singlet EPR line with 2.0031+/-0.0005 can be recorded before irradiation of seeds, stones or skin of chokeberry, figs and raisins as well as flesh of blue plum, raisins and peaches. EPR signals of various shape are distinguished after irradiation in different parts of the fruits, as well as in randomly cut pieces of them: As a result, randomly cut pieces of dry fruits suitable for EPR studies, containing various constituents, exhibit different in shape and intensity EPR spectra. Kinetic studies followed for 1 year on the time stability of all reported EPR signals indicate that intensity ratio between the simultaneously appearing EPR signals in particular fruit varies from 1:20 immediately after irradiation to 1:0.5 at the end of the period. These observations open a new possibility for identification of irradiated fruits - using the magnitude of the intensity ratio to find the approximate date of radiation processing in the first ca. 30-100 days.
Electron spin resonance spectra of the m‐dinitrobenzene anion radical and several of its derivatives have been examined under a variety of conditions in order to study the alternating linewidth effect and, for the first time, the associated dynamic second‐order frequency shifts. More detailed information about the molecular motions was obtained in this way than is otherwise possible. The m‐dinitrobenzene anion, the 3,5‐dinitromesitylene anion, the 3,5‐dinitrophenolate dianion, and the 3,5‐dinitrobenzoate dianion radicals were obtained by electrolytic generation in solvents such as tetrahydrofuran (THF), 1,2‐dimethoxyethane (DME), and N,N‐dimethylformamide (DMF). Except for the benzoate dianion in DMF, the data are well represented by a two‐state model with two 14N splitting constants, aI and aII. The two different splittings probably arise because the nitro groups are complexed with the solvent or with cations. Even the spectra showing a rapid exchange between the two states have values of aI and aII that are approximately the same as those found for the single species that are obtained in the presence of alkali‐metal cations, and which correspond to the static limit. The correlation times τc observed in the spectra showing the alternating linewidth effect were in the range from 0.4–0.9×10−9 sec, while those corresponding to the static limit are greater than about 10−6 sec. Spectra of the 3,5‐dinitrobenzoate dianion radical obtained in DMF with and without added water could not be analyzed by a two‐state model; a more appropriate model is probably one in which the carboxylate group in addition to the two nitro groups can interact with the solvent or the cations. A few spectra were carefully studied to obtain data on the g‐tensor and electron‐nuclear anisotropic dipolar interactions as well as those arising from modulations of the isotropic splittings, and this complete analysis made it possible to estimate values of the spectral densities for the latter interaction. In most cases studied in this way, it was found that there was complete out‐of‐phase correlation of the splittings at the two nitrogen nuclei.
Electron paramagnetic resonance (EPR) spectroscopy was used to measure the production of free radicals induced by 60Co γ-rays in shrimp exoskeleton, mussel shells, and fish bones. The EPR spectrum for irradiated shrimp shell was dose dependent and appeared to be derived from more than one radical. The major component of the radiation-induced spectrum resulted from radical formation in chitin, assigned by comparison with irradiated N-acetyl-D-glucosamine. Other measurements include the total yield of radicals formed as a function of dose and the longevity of the radiation-induced EPR signal. Similar measurements were made for mussel shells and fish bones, and the results are compared and discussed. It was concluded that irradiated shrimp (with shell attached) could definitely be identified by this technique; however, precise determination of absorbed dose was less straightforward. Positive identification of irradiated fish bones was also clearly distinguishable, and dosimetry by EPR appeared to be feasible.
Electron spin resonance (ESR) spectroscopy was used to measure the production of free radicals induced by 60Co γ-rays in chicken bones. It was found that the radiation-induced ESR signal in bone could easily be distinguished from the endogenous ESR signal Long-term (4 months) stability studies at 20°C showed no decay of the radiation-induced ESR signal. A linear relationship was observed between the radiation-induced ESR signal intensity (peak-to-peak amplitude) and the absorbed dose (1-5 kGy). It was concluded that ESR measurements of bones can be used to determine whether the bone-containing meat has been irradiated and also at approximately what dose. The measurements indicate the feasibility of postirradiation dosimetry (PID) of meats when bones are present.
Electron spin resonance (ESR) spectroscopy has been used to examine components from γ-irradiated fish, meat and fruit produce in order to identify areas in which the technique may be of use in detecting an irradiation history.
Results show that, in the studied samples of the flesh of meat, fish and fruit, stable radical species are not formed on irradiation, thus indicating that ESR will have no applications for determining a radiation history of such specimens. However, stable ESR signals are obtained in components where radical centres can be stabilised within a crystalline or protein matrix. Thus bone from meat or fish yields a characteristic ESR signal at levels likely to be used commercially, although signal intensity appears to be related to the degree of crystallinity of the hydroxyapatite. This would be a complicating factor in determining quantitative radiation exposure measurements. Similarly a radiation-induced ESR signal can be observed in scampi shell. The signal appears to be associated with the chitin component and thus cooking, either before or after irradiation, can result in a major decrease in signal intensity as a result of chitin degradation. Several radical species were observed in irradiated animal fat, one of which had spectral parameters similar to those obtained from organic peroxy radicals. These species were of limited stability restricting any practical ESR determination to within a few days of treatment. Stable free radical centres are produced in the seeds of fruit, but their spectra generally resemble those of the naturally occurring melanin-type pigments. Since the concentrations of the latter may vary considerably as a result of natural factors such as exposure to sunlight, ESR has limited applications in the diagnosis of an irradiation history in such materials. With irradiated grapes a weak spectral component that was not present in unirradiated specimens was observed in the seeds. It is possible, therefore, that the ESR method could be useful for detecting irradiated grapes.
Results are presented giving details of the effect of six different methods of sample preparation on the free radical concentration in irradiated chicken drumsticks. Comparisons were made using electron spin resonance spectroscopy. Freeze drying and grinding was found to be the preferred method of sample preparation.
Two-hundred pairs of chicken bones (drumsticks) were irradiated at 2.5, 5.0, 7.5 and 10.0 kGy and stored for 0, 7, 14, 21 and 28 days at −20°C or + 5°C thus giving five replicates per treatment. Five unirradiated pairs of bones were stored at 5°C, one sample being analysed at each storage time. The samples were fragmented, freeze dried and ground prior to determination of the free radical concentration using electron spin resonance (ESR) spectroscopy. ESR signal strength increased significantly as irradiation dose increased, and decreased with storage time. Temperature alone had no significant effect on free radical concentration but, as the storage time increased, the bones stored at 5°C showed a significantly greater reduction in free radical concentration than those stored at −20°C. Correction of the ESR signal to a standard P or Ca concentration did not significantly reduce the variability of the results but did eliminate the interaction between storage temperature and storage time.
Gamma-radiation of powdered tumeric, black pepper, dry mustard, cinnamon and paprika, at dosage of 30 kGy, at 30°C, produced free radicals detectable by EPR. The intensities of the EPR signals were proportional to the total irradiation dose up to a saturation dose. The signal decayed most significantly in the first four-postirradiation days, but could be detected even after 34 days. The paramagnetic signal was unaffected by the presence of oxygen, but decayed rapidly in water. Similar observations were made for spray-dried fruit powder.
ESR provides an excellent method for the identification of irradiated foods containing bone or calcified cuticle, even in the absence of unirradiated controls. It also shows promise for strawberries.
Roasted coffee gives free-radical electron paramagnetic resonance (EPR) signals in any solid roasted form (beans) or powder). This signal persists to some extent in solution. Tea leaves and instant tea powder also give free-radical EPR signals. In contrast to coffee, the signals are drastically reduced in intensity, or are absent altogether, in tea infusions. Work is in progress to identify the persistent free radicals in coffee solutions. Coffee is traditionally considered to pose a greater health risk than tea. The present results may indicate one reason: free radicals.
Peroxy radical formation in raw coffee beans of different qualities and origins from all over the world has been studied with electron spin resonance (ESR) analysis. The gamma-ray equivalent absorbed dose (ED) which creates the same concentration of radicals is obtained by the additive gamma-ray irradiation of the coffee beans. The ED and the cup quality is somewhat inversely related suggesting that the peroxidation of the unsaturated fatty acid is somewhat indicative of the degree of the aromatic decomposition and rancidity.
Electron spin resonance (ESR) spectral analysis of different parts (bones, scales, jaw, etc.) from ionized (irradiated) frozen frogs' legs and fishes (brown trout and sardine) were recorded. There is always present, after treatment, a signal due to the irradiation. ESR and ENDOR experiments lead us to assign it to h1 centers from hydroxyapatite, as in the case of other irradiated meat bones. The use of ESR to prove whether one of these foods has been irradiated or not is discussed.
Previous work has shown that the calcified tissues in several foods give rise to characteristic ESR spectra on irradiation. Further foods have now been examined. Mussel and crab shells give large signals, compared with bones of poultry, beef or frog, while prawn cuticle gives a smaller signal. The limits of detection of irradiation vary between species but are below the doses likely to be used commercially. Quantitative estimation of dose can be achieved by re-irradiation and extrapolation to zero signal.
Agric. Food chenl. 36,601 Appl. Radiat. Zsot. 40, 1211. Evans J. C. and Rowlands C. C. (1989) Spectrosc. World 33
- H M S O London
- M F Desrosiers
- M F Desrosiers
- W L Mclaughlin
- N J F Dodd
- A J Swallow
- F J Ley
- N J F Dodd
- J S Lea
- A J Swallow
- R J Faber
- G E Stevenson
- M H Gray
- R G C Yang
- M M Mossoba
Report on the Safety and Wholesomeness of Irradiated Foods. H.M.S.O., London. Desrosiers M. F. (1989) J. Agric. Food Gem. 37, 96. Desrosiers M. F. and McLaughlin W. L. (1989) R&at. Phys., Chem. 34, 895. Desrosiers M. F. and Simic M. G. (1988) J. Agric. Food chenl. 36,601. Dodd N. J. F., Swallow A. J. and Ley F. J. (1985) Radiut. Phys. Chem. 26, 451. Dodd N. J. F., Lea J. S. and Swallow A. J. (1989) Appl. Radiat. Zsot. 40, 1211. Evans J. C. and Rowlands C. C. (1989) Spectrosc. World 33. Faber R. J. and Fraenkel G. E. (1967) J. Chem. Phys. 47, 2462. Goodman B. A., McPhail D. B. and Duthie D. M. L. (1989) J. Sci. Food Agric. 47, 101. Ikeya M., Baffa F. 0. and Mascarenhas S. (1989) Appl. Radial. Isot. 40, 1219. RaEi J. and Agnel J. P. L. (1989) Radiat. Phys. Chem. 34, 891. Raffi J. J., Agnel J. P. L., Buscarlet L. A. and Martin C. C. (1988) J. Chem. Sot. Faraaby Trans. I 84, 3359. Raffi J., Evans J. C., Agnel J. P. L., Rowlands C. C. and Lesgards G. (1989) Appl. Radiat. Isot. 40, 1215. Stevenson M. H. and Gray R. (1989a) J. Sci. Food Agric. 48, 269. Stevenson M. H. and Gray R. (1989b) J. Sci. Food Agric. 48, 261. Swallow A. J., (1988) Chem. Bit. 24, 102. Troup G. J., Pilbrow J. R., Hutton D. R., Hunter C. R. and Wilson G. L. (1989) Appl. Radiat. Isot. 40, 1223. Yang G. C., Mossoba M. M., Met-in U. and Rosenthal I. (1987) J. Food Qual. 10, 287.
- Raffi