Identifying irradiated oysters by luminescence techniques (TL & PSL)

This study shows an exhaustive comparison of different methods, based on luminescence techniques, to identify X-ray irradiated oysters at five different dose levels in the range 0.1-2 kGy and suggests a simple, fast and sequential routine analysis protocol. A total number of 50 oysters from North Sea, including 10 control samples, were analysed by using two photo-stimulated luminescence (PSL) methods (named A and B) and three thermoluminescence (TL) methods (named C, D and E), either on constituents or contaminating minerals from shells and intestines. Setting a lower threshold value T1 (1000 counts/60s) all of control specimens gave negative screening results while photo counts from irradiated samples were found to be higher than upper threshold T2 (4000 counts/60s), except at the lowest dose level 0.1 kGy for procedure A. All PSL calibrated analysis were successful and a sensitivity index was also determined to better classify obtained data according to the revised European Standard (EN 13751:2009). TL ratios, Glow 1 over second Glow 2, the latter after irradiating at 1 kGy and remeasuring the same minerals for each sample, showed values less than 0.1 related to untreated samples or higher than 0.1 for irradiated ones. Reported procedures were also tested over 60 days, longer than oyster shelf life confirming the applicability and feasibility of the proposed methods.     

Applicability of different analytical methods for the identification of γ-irradiated fresh mushrooms during storage

Photostimulated luminescence (PSL), thermoluminescence (TL), and electron spin resonance (ESR) analyses were performed to identify γ-irradiated (0, 1,2, and 3 kGy) fresh mushrooms (oyster, king oyster, and shiitake mushrooms) during storage at 5°C. PSL analysis gave negative results [<700 photon counts (PCs)] for the nonirradiated and intermediate (700–5,000 PCs) or positive results (>5,000 PCs) for the irradiated samples. The shape, intensity, and occurrence of TL glow curve in a typical temperature range (150–250°C) along with TL ratio (TL₁/TL₂) provided sufficient information to confirm the irradiation history of samples. Storage resulted in a negligible fading effect on PSL and TL characteristics. X-ray diffraction analysis showed the abundance of feldspar and quartz minerals in the separated dust from mushrooms. In detailed ESR analysis employing different sample pre-treatments, all samples were silent for radiation-specific ESR signals giving only a central signal (g=2.005) that showed an increase in intensity upon irradiation.     

Changes in thermoluminescence properties of minerals separated from irradiated potatoes and garlic during long-term storage under different light conditions

The effect of different light conditions on the specificity and reliability of thermoluminescence (TL) analysis to detect irradiated samples (potatoes and garlic) during 2?years of storage was investigated. The silicate minerals separated from the nonirradiated samples provided a low-intensity TL glow curve with a maximum peak after 300?°C demonstrating the absence of an irradiation history. The TL glow curve from the irradiated samples provided easy discrimination with TL glow curves of high intensity and maximum peak in temperatures range of 160?C185?°C. The results were also confirmed by calculating the TL ratio (TL₁/TL₂) through normalization (re-irradiation) step. The key parameters of the TL analysis including the TL intensity, TL glow curve shape, and the TL ratio exhibited a time-dependent change. The bleaching effect of different light conditions was also significant, which was most prominent in the case of natural light with a prominent decrease in the TL intensity and ratio. The maximum TL glow peak also showed a shift towards the higher temperature. However, all irradiated samples, irrespective of the storage conditions and time, were easily discernable from the nonirradiated ones considering the shape and intensity of the TL glow curve.     

Effect of γ-irradiation on physical quality attributes and identification properties of different sauces

Gamma-irradiated (0, 1, and 10 kGy) ketchup (KTP), barbeque sauce (BBQ), and sweet chili sauce (SWC) were identified using photostimulated-luminescence (PSL) and thermoluminescence (TL) analysis and characterized for physical properties like Brix, consistency, and color. PSL-based screening showed negative results for all nonirradiated samples, while intermediated results were found for irradiated samples. Routine density separation method for mineral extraction provided better TL results; however, alkaline and acid hydrolysis could ease the process with acceptable results. A slight decrease in consistency of all the samples was observed. Brix of KTP remained unchanged, while increase of same was obvious in BBQ and SWC following irradiation. The Hunter L* value of the γ-irradiated sauces decreased except SWC samples, and the a* and b* values showed a general increase compared to the non-irradiated samples. The studied methods have potential to successfully identify and characterize the irradiated sauces for technical and regulatory requirements.     

Effect of Drying Treatment on Physical Identification Characteristics of Irradiated Seasonings

The effect of different drying treatments such as spray drying and vacuum drying on the sensitivity of physical detection methods (photostimulated luminescence (PSL), electron spin resonance (ESR), and thermoluminescence (TL)) was investigated for four types of irradiated seasonings. The slurry feed of each seasoning was exposed to γ-ray irradiation at doses of 0, 5, 10 kGy before being subjected to drying process. Spray drying was applied to beef and soybean seasoning while garlic and broth seasoning were exposed to vacuum drying according to routine protocols adopted in the industry. The samples were analyzed by PSL as a rapid screening method followed by validated methods including ESR spectroscopy and TL analysis. The PSL photon counts drastically dropped in all irradiated samples after both drying processes. No ESR signal was obtained from any of the irradiated seasonings before or after the drying applications. All the irradiated seasoning samples produced typical TL glow curves between the specific temperature range of 150–250 °C. However, the shape, peak, and intensity of TL glow curves were greatly affected particularly after the spray drying treatment. In conclusion, the dry treatment can significantly affect the irradiation detection characteristics in seasoning samples.     

Comparison of three methods for detection of herbal food supplement irradiation

A survey for irradiation of 106 herbal food supplements was carried out in Denmark in 2003. The results from three methods, two screening methods and a specific method, were compared: Direct epifluorescent filter technique/aerobic plate count (DEFT/APC), photostimulated luminescence (PSL) and thermoluminescence (TL) standardised by Comité Européen de Normalisation (CEN). Forty samples screened positive with the DEFT/APC method. However, the TL method could only confirm irradiation of 15 samples, 11 samples wholly irradiated and 4 samples with a minor irradiated ingredient. Thus, the DEFT/APC method gave a large number of false positive results, although the number of false negative results probably was very low. Only 7 of the 15 confirmed irradiated samples screened positive with the PSL screening method, the samples with low photon counts escaping detection. For 10% of the samples also the TL method was lacking in sensitivity, as not enough minerals could be isolated to get a signal over the minimum detection level. For such clean herbal food supplements no suitable method exists at all among the CEN standardised methods for irradiation detection.     

Detection Properties of Irradiated Ostrich Meat by DNA Comet Assay and Radiation-induced Hydrocarbons

ABSTRACT: Detection of irradiated ostrich meat with doses of 1 to 10 kGy using the DNA comet assay and hydrocarbon determinations by gas chromatography-mass spectrometry was investigated. The irradiated ostrich meat showed comets with long tails whereas nonirradiated controls showed intact cells only slight comets. Concentrations of radiation-induced hydrocarbons increased with irradiation dose. Radiation-induced hydrocarbons in ostrich meat were detected at doses of 1 kGy or more; however, they were not detected in nonirradiated controls. The prominent radiation-induced hydrocarbons included 14:1, 15:0, 16:2, 16:3, 17:1, and 17:2, with 16:2 the most abundant.     

Identification of a gamma-irradiated ingredient (garlic powder) in Korean barbeque sauce by thermoluminescence analysis

Thermoluminescence (TL) analysis was applied to identify gamma-irradiated garlic powder in Korean barbeque sauce before and after pasteurization (85 °C, 30 min), when blended in different ratios (1%, 3%, and 5%). The sauce sample with nonirradiated garlic powder gave a background glow curve. However, the sample blended with irradiated ingredient (1 and 10 kGy) showed typical TL glow curves at temperatures of 150 to 200 °C. The identification properties of sauce samples were more influenced by blending ratios than by irradiation doses, showing that 3% and 5% added samples produced glow curves at 150 to 250 °C. After pasteurization of the samples containing the irradiated ingredient, TL glow intensity decreased but did not change its shape or temperature range. As a result, the pasteurization of Barbeque sauces containing irradiated ingredients had reduced TL glow intensity, but the shape and temperature range of glow curve were still able to provide information required for confirming irradiation treatment. PRACTICAL APPLICATION: To monitor the irradiated food in international market, thermoluminescence (TL) analysis is considered most promising identification technique because of its sensitivity and long-term stability. In this study the applicability of TL analysis to detect an irradiated ingredient (garlic powder) added in low quantity to a food matrix (sauce) was investigated. The effect of processing (pasteurization) on TL results was also evaluated.     

Potential Chemical Markers for the Identification of Irradiated Sausages

Abstract: Hydrocarbons, gas compounds, and off‐odor volatiles were determined for irradiated (0 or 5 kGy) commercial sausages with different fat contents (16% and 29%) during a 60‐d storage period at 4 °C. Total of 4 hydrocarbons (C14:1, C15:0, C16:2, and C17:1) were detected only in irradiated sausages: the amount of C16:2 was the highest, followed by C17:1, C14:1, and C15:0. The concentrations of hydrocarbons decreased significantly (P < 0.05) with storage, but were still detectable at the end of 60‐d storage. Irradiated sausages produced significantly higher amounts of CO than the nonirradiated ones. CH₄ was detected only in irradiated sausages. Dimethyl disulfide was detected only in irradiated sausages and its concentration decreased significantly (P < 0.05) with storage. Fat content of sausages showed a significant effect on the production and retention of hydrocarbons, gas compounds, and sulfur volatiles in irradiated sausages during storage. Some hydrocarbons (C16:2, C17:1, C14:1, and C15:0), CH₄, and dimethyl disulfide were only found in irradiated sausages indicating that these compounds can be used as potential markers for irradiated sausages.     

Quality and Microbial Population of Cornish Game Hen Carcasses as Affected by Electron Beam Irradiation

ABSTRACT:  We evaluated the chemical and microbiological quality of Cornish game hen carcasses irradiated up to 7 kGy with a 10 MeV linear accelerator (dual beam configuration). Eighty frozen and vacuum packaged (approximately 0.45 kg) Cornish game hens ( Gallus domesticus ) were irradiated and stored in low-density polyethylene bags at 4 ± 1 °C for 21 d; nonirradiated chickens served as controls. Fat oxidation (in terms of malonaldehyde content) increased with storage time and dose for all chicken parts analyzed (breast, thigh, and skin). As expected, the skin had the highest level of fat oxidation while the breast samples had the lowest. Oxidation level in all samples exposed to 2 kGy reached a maximum on day 14. Sensory evaluation showed that irradiation caused significant textural toughening, and increased the redness of raw chicken meat. In terms of overall quality and aroma, lipid oxidation was not a major problem since it was not detected by the panelists. Irradiation significantly reduced the total viable microbial counts (TVC) in the breast and thigh samples. Exposure to 3-kGy dose decreased the TVC by 0.3-log cycles on the surface of the skin. In less than 14 d, the nonirradiated chicken carcasses had counts greater than 6 log CFU/50 cm², while the 2 and 3 kGy irradiated samples reached these numbers only after 21 d of storage. Samples irradiated at 7 kGy had consistently the lowest counts (2.5 log CFU/50 cm²) throughout storage time.This study shows that irradiation up to 7 kGy and refrigerated storage (4 °C) inhibits microbial growth and extends shelf life of Cornish game hens without affecting consumers' acceptability.     

茶叶辐照的热释光分析研究

不采用二次辐照,将TL 分析法应用于辐照茶叶的定性鉴定。分离并收集茶叶中黏附的硅酸盐,采用热释光剂量仪测量获得硅酸盐的热释光发光曲线,比较未辐照与辐照不同剂量茶叶的热释光发光曲线的积分强度、峰值和峰值温度等特征参数。未辐照茶叶的热释光发光曲线的积分强度小于50、峰值小于0.4、峰值温度大于260℃;反之,辐照茶叶的热释光发光曲线的积分强度大于50000、峰值大于600、峰值温度位于160～190℃。TL 分析法能判别出茶叶的辐照与否,尤其对不能满足参比剂量辐照条件的样品很有帮助。     

Analysis of irradiated jujube (Zizyphus jujuba) by photostimulated luminescence and electron spin resonance spectroscopy

Possibility of photostimulated luminescence (PSL) and electron spin resonance (ESR) to detect γ-irradiation of jujube (Zizyphus jujuba) was investigated. The jujube samples were exposed to γ-irradiation at doses of 1, 3, 5, and 10 kGy. The PSL results showed that jujube exposed to at 1 kGy or more had a photon count of greater than 5,000 count/60 sec (positive), while the non-irradiated jujube yielded a photon count of less than 700 photon count/60 sec (negative). However, physical parameters (light exposure, storage, and thermal treatment) of irradiated jujube samples gave a strong effect on the PSL signal, resulting in decrease of the photon counts from the initial counts. ESR spectroscopy analysis of irradiated jujube revealed specific signals derived from cellulose radicals, and irradiation caused a significant increase in the ESR signal intensity of the jujube samples without any changes in the spectral patterns. Light exposure, storage, and thermal treatment of jujube resulted in significant decreases in the ESR signal intensities of cellulose radicals.     

Pulsed photostimulated- and thermo-luminescence investigations of γ ray-irradiated herbs

In this study, physical detection methods like pulsed photo-stimulated luminescence (PPSL) and thermoluminescence (TL) were investigated to indentify γ-ray irradiation treatment of some medicinal herbs. Dried herbal samples consisting of root, rhizome, cortex, fruit, seed, flower, spike, ramulus, folium and whole plant of nineteen different herbs were irradiated using a 60Co irradiator at 0–50 kGy. Fifteen non-irradiated control samples had photon counts (PCs) less than the lower threshold value (700 counts/60 s). The photon counts of four non-irradiated samples (roots of osterici, angelica gigas, liriope, and whole plant of taraxaci herba) were between the lower and upper threshold values (700–5000 counts/60 s). However, PCs of all the irradiated samples were found to be higher than the upper threshold value (5000 counts/60 s), clearly screening them out from the non-irradiated ones. Even after 12 weeks of storage PPSL signals of all irradiated samples were observed to be higher than the upper threshold value, making it possible to distinguish them from the non-irradiated control samples. The first TL glow curves (TL₁) for the non-irradiated samples were of very low intensity at about 250–300 °C. Irradiated samples (5–50 kGy) showed a higher peak at around 150–250 °C. TL ratios [ratio of the integrated areas of the first (TL₁) and second (TL₂) glow], measured after re-irradiation for the TL₁-tested samples at 1 kGy, were found to be less than 0.1 for the non-irradiated samples and higher than 0.1 for the irradiated ones. TL ratios for all irradiated samples measured after 12 weeks of storage under dark condition at (23 ± 2 °C) were apparent for distinguishing them from the non-irradiated controls.     

An Improved Approach to Identify Irradiated Spices Using Electronic Nose,FTIR, and EPR Spectroscopy

Changes in cumin and chili powder from India resulting from electron‐beam irradiation were investigated using 3 analytical methods: electronic nose (E‐nose), Fourier transform infrared (FTIR) spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. The spices had been exposed to 6 to 14 kGy doses recommended for microbial decontamination. E‐nose measured a clear difference in flavor patterns of the irradiated spices in comparison with the nonirradiated samples. Principal component analysis further showed a dose‐dependent variation. FTIR spectra of the samples showed strong absorption bands at 3425, 3007 to 2854, and 1746 cm^?1. However, both nonirradiated and irradiated spice samples had comparable patterns without any noteworthy changes in functional groups. EPR spectroscopy of the irradiated samples showed a radiation‐specific triplet signal at g = 2.006 with a hyper‐fine coupling constant of 3 mT confirming the results obtained with the E‐nose technique. Thus, E‐nose was found to be a potential tool to identify irradiated spices.     

Effect of low-dose radiation on microbiological, chemical, and sensory characteristics of chicken meat stored aerobically at 4 degrees C

The effect of gamma-radiation (0.5, 1, and 2 kGy) on the shelf life of fresh skinless chicken breast fillets stored aerobically at 4 degrees C was evaluated. Microbiological, chemical, and sensorial changes occurring in chicken samples were monitored for 21 days. Irradiation reduced populations of bacteria, i.e., total viable bacteria, Brochothrix thermosphacta, lactic acid bacteria (LAB), and the effect was more pronounced at the highest dose (2 kGy). Pseudomonads, yeasts and molds, and Enterobacteriaceae were highly sensitive to gamma-radiation and were completely eliminated at all doses. Of the chemical indicators of spoilage, thiobarbituric values for nonirradiated and irradiated aerobically packaged chicken samples were in general low (<1 mg of malonaldehyde per kg of muscle) during refrigerated storage for 21 days. With regard to volatile amines, both trimethylamine nitrogen (TMA-N) and total volatile basic nitrogen (TVB-N) values for nonirradiated aerobically packaged chicken increased steeply, with final values of ca. 20.3 and 58.5 mg N/100 g of muscle, respectively. Irradiated aerobically packaged chicken samples had significantly lower TMA-N and TVB-N values (P < 0.05) of ca. 2.2 to 3.6 and 30.5 to 37.1 mg N/100 g of muscle, respectively, during refrigerated storage for 21 days. Of the biogenic amines monitored, only putrescine and cadaverine were detected in significant concentrations in both nonirradiated and irradiated chicken samples, whereas histamine formation was noted only in nonirradiated samples throughout storage. On the basis of sensorial evaluation, low-dose irradiation (0.5 and 1.0 kGy) in combination with aerobic packaging extended the shelf life of fresh chicken fillets by ca. 4 to 5 days, whereas irradiation at 2.0 kGy extended the shelf life by more than 15 days compared with that of nonirradiated chicken.     

Hydrocarbons detected in irradiated pork,bacon and ham

Hydrocarbons produced by γ-radiation of pork, bacon and ham were analyzed to determine how irradiation affects the production of the hydrocarbons and whether the hydrocarbons can be used for identifying post-irradiation of pork, bacon and ham. Hydrocarbons were determined by a sequential procedure of lipid extraction by hexane, Florisil column chromatography and gas chromatography. Hydrocarbons C17:1, C16:2, C17:2 and C16:3 were detected in pork, bacon and ham irradiated at 0.5 kGy or higher, but not in non-irradiated ones except C17:1. The detection levels in all the irradiated samples were in the order of C16:2, C17:1, C17:2 and C16:3 from the highest to the lowest.     

Electron seed dressing of barley—aspects of its verification

Seeds (e.g. cereal grains) are treated with low energy electrons for seed dressing to inactivate phytopathogenic organisms on their surface and in the seed coat. To verify the electron treatment of barley by e-ventus^® technology, three physical detection methods were investigated: photostimulated luminescence (PSL), thermoluminescence (TL) and electron spin resonance (ESR). Influencing factors such as storage time and temperature, geographic origin of samples and light exposure were studied. All three detection methods proved to be suitable, with PSL being the most convenient. But also ESR by measuring the barley husks offered a simple and rapid verification. Although TL was more laborious to perform, it was highly reliable. PSL was able to classify electronically dressed seeds after storage times of at least 12–13 months independent of storage temperatures, assayed in the range of 5–23 °C. The applicability of ESR after storage was dependent on the measuring system used and on storage temperature. At room temperature the advanced E-Scan? spectrometer allowed verification of treatment for at least 7.5 months, whereas the EMS 104 spectrometer was applicable only up to 2 months of storage. Storage temperatures of 5 °C markedly prolonged the verifiability of treatment. Using TL, treated samples stored at room temperature could be easily verified for at least 13 months. Fading of the PSL signal of treated barley was observed under the influence of light, the extent of fading being influenced by illuminance but not by treatment of the samples with high or low energy electrons. Contrary to PSL, TL and ESR were found to be still applicable for the detection of treated barley exposed to light.     

Effect of freezing, irradiation, and frozen storage on survival of Salmonella in concentrated orange juice

Six strains of Salmonella (Anatum F4317, Dublin 15480, Enteritidis 13076, Enteritidis WY15159, Stanley H0588, and Typhimurium 14028) were individually inoculated into orange juice concentrate (OJC) and frozen to -20 degrees C. The frozen samples were treated with 0 (nonirradiated), 0.5, 1.0, or 2.0 kGy of gamma radiation and held frozen for 1 h, and the surviving bacterial population was assessed. The strains showed significant variability in their response to freezing and to freezing in combination with irradiation. The response was dose dependent. Relative to the nonfrozen, nonirradiated control, the reduction following the highest dose (2.0 kGy) ranged from 1.29 log CFU/ml (Salmonella Typhimurium) to 2.17 log CFU/ml (Salmonella Stanley). Samples of OJC inoculated with Salmonella Enteritidis WY15159 and irradiated were stored at -20 degrees C for 1, 2, 7, or 14 days, and the surviving population was determined. Relative to the nonfrozen, nonirradiated control, after 14 days, the population was reduced by 1.2 log CFU/ml in the nonirradiated samples and by 3.3 log CFU/ml following treatment with 2.0 kGy. The combination of frozen storage plus irradiation resulted in greater overall reductions than either process alone.     

Sensorial and chemical quality of gamma-irradiated fresh-cut iceberg lettuce in modified atmosphere packages

A study was conducted to investigate the effects of various doses of irradiation on the quality of fresh-cut iceberg lettuce and to determine a suitable maximum dose. Fresh-cut iceberg lettuce packaged in film bags was exposed to 0, 1, 2, 3, and 4 kGy of gamma radiation and stored at 3 degrees C for 14 days. CO2 levels were higher and O2 levels were lower in packages containing irradiated lettuce than in those containing nonirradiated lettuce for most of the storage period. Comparison with nonirradiated lettuce indicated that total ascorbic acid (ascorbic acid plus dehydroascorbic acid) content and firmness were not significantly influenced by irradiation at 1 or 2 kGy. The overall visual appearance was best for lettuce irradiated at 1 or 2 kGy. This improved quality may be related to the high CO2 and low O2 levels observed for the irradiated samples. Electrolyte leakage for lettuce increased with higher radiation doses and was correlated (R2 = 0.99) with a soggy appearance. The leakage for lettuce irradiated at > or = 2 kGy was significantly more extensive than that for nonirradiated lettuce. The irradiation of fresh-cut lettuce in modified atmosphere packages at doses of 1 kGy and perhaps 2 kGy for safety enhancement and quality improvement is feasible.     

Lipid oxidation, color changes and volatiles production in irradiated pork sausage with different fat content and packaging during storage

Effects of irradiation on lipid oxidation, color and volatiles production in pork sausages with different fat content and packaging were determined. Sausages (with 4.7, 10.5 and 15.8% fat content) were sliced and vacuum-packaged either in oxygen-permeable or impermeable bags, irradiated (0 or 4.5 kGy) and stored at 4°C for 7 days. Lipid oxidation, color and volatiles productions were analyzed at 0, 3 and 7 days of storage. TBARS (2-thiobarbituric acid reactive substances) values of cooked pork sausages increased with the increase of fat content regardless of storage, irradiation or packaging types. Irradiated samples had higher TBARS than nonirradiated at 0 day but the difference disappeared during storage in both packaging types. Lightness of sausages (Hunter L-value) increased with the increase of fat content and storage time but was not affected by irradiation. In aerobic packaging, irradiation reduced Hunter a-values of pork sausages at 0 day but irradiation effect on a-value disappeared during storage. In vacuum packaging, however, irradiated samples had higher Hunter a-values than nonirradiated samples. Irradiation increased 1-heptene and total volatiles, but the amount of 1-heptene was not associated well with TBARS values of pork sausages. In both irradiated and nonirradiated pork sausages, aerobic packaging produced more volatiles than vacuum packaging during storage. It was concluded that irradiation and fat content had significant effects on lipid oxidation, color and volatiles production of cooked pork sausages during storage but that oxygen availability had a stronger effect than irradiation and fat content.