Identification of irradiated wheat by germination test, DNA comet assay and electron spin resonance

In several countries, there has been an increase in the use of radiation for food processing thus improving the quality and sanitary conditions, inhibiting pathogenic microorganisms, delaying the natural aging process and so extending product lifetime. The need to develop analytical methods to detect these irradiated products is also increasing. The goal of this research was to identify wheat irradiated using different radiation doses. Seeds were irradiated with a gamma ⁶⁰Co source (Gammacell 220 GC) in the Centro de Energia Nuclear na Agricultura and the Instituto de Pesquisas Energéticas e Nucleares. Dose rate used were 1.6 and 5.8 kGy/h. Applied doses were 0.0, 0.10, 0.25, 0.50, 0.75, 1.0, and 2.0 kGy. After irradiation, seeds were analysed over a 6 month period. Three different detection methods were employed to determine how irradiation had modified the samples. Screening methods consisted of a germination test measuring the inhibition of shooting and rooting and analysis of DNA fragmentation. The method of electron spin resonance spectroscopy allowed a better dosimetric evaluation. These techniques make the identification of irradiated wheat with different doses possible.     

Thermal analysis applied to irradiated propolis

Propolis is a resinous hive product, collected by bees. Raw propolis requires a decontamination procedure and irradiation appears as a promising technique for this purpose. The valuable properties of propolis for food and pharmaceutical industries have led to increasing interest in its technological behavior. Thermal analysis is a chemical analysis that gives information about changes on heating of great importance for technological applications. Ground propolis samples were ⁶⁰Co gamma irradiated with 0 and 10 kGy. Thermogravimetry curves shown a similar multi-stage decomposition pattern for both irradiated and unirradiated samples up to 600°C. Similarly, through differential scanning calorimetry , a coincidence of melting point of irradiated and unirradiated samples was found. The results suggest that the irradiation process do not interfere on the thermal properties of propolis when irradiated up to 10 kGy.     

Radiation effect studies on anticancer drugs, cyclophosphamide and doxorubicin for radiation sterilization

Two anticancer drugs, cyclophosphamide (CPH) and doxorubicin hydrochloride (DOXO), in powder form were exposed to a range of doses of ⁶⁰Co gamma and electron beam radiation to study the effects of ionizing radiation. Pharmacopoeia tests, discolouration, degradation products, effect of irradiation temperature and dose rate were investigated. CPH undergoes less than 2% degradation at 30 kGy. Chromatographic studies revealed formation of several trace level degradation products, discolouration and free radicals in the irradiated CPH. N,N-bis (2-chloroethyl) group in the molecule is particularly sensitive to radiation degradation. Irradiation to 5 kGy at low temperature (77 K) did not result in significant changes. DOXO was observed to be quite radiation resistant and did not undergo significant changes in its physico-chemical properties and degradation product profile. It can be radiation sterilized at normal sterilization dose of 25 kGy.     

The effect of irradiation of fresh pork loins on the protein quality and microbiological changes in aerobically—or vacuum-packaged

The effect of γ-irradiation on the physico-chemical, organoleptic and microbiological properties of pork was studied, during 43 d of storage at 4°C. Irradiation treatments were carried out under air or vacuum packaging on fresh pork loins at a dose of 6 kGy, at two dose-rates: 2 and 20 kGy/h. Regardless of the type of packaging and dose-rate of irradiation, all irradiated pork samples were prevented from bacterial spoilage during 43 d. Meat redness and texture of irradiated loins were well preserved during storage especially when samples were stored under vacuum. The physico-chemical and organoleptic changes in pork loins appeared to be relatively little affected by the 6 kGy dose.     

Gamma radiation for preservation of biologically damaged paper

Samples of nine different papers in use in the library, including two mould-contaminated papers, were irradiated with 14.4 kGy in a Co-60 facility. Five of the samples were subsequently subjected to an accelerated UV-ageing process. mechanical (tensile energy absorption and stretch) and optical properties were measured on control and irradiated samples, before and after ageing.

For most samples, the effect of ageing on mechanical properties turned out to be larger than that of irradiation. Irradiated and control samples were similarly affected by the accelerated ageing. Mould contaminated samples were still in acceptable conditions of use after irradiation. No discoloration effect was observed after irradiation and/or ageing.     

Antimicrobial properties of natural substances in irradiated fresh poultry

This study was undertaken to determine if a combined treatment (marinating in natural plant extracts or vacuum) with irradiation could have a synergetic effect, in order to reduce the dose required for complete elimination of Salmonella on fresh poultry. The effect of these combined treatments on the shelf-life extension was also evaluated. The fresh chicken legs were irradiated at 0, 3 and 5 kGy. The poultry underwent microbial analysis(mesophilic and Salmonella detection). For each treatment, the total microbial count decreased with increase of irradiation dose. The marinating treatment have a synergistic effect with irradiation treatment to reduce the total microbial count and controlling the proliferation during storage at 4°C. Irradiation of fresh chicken pieces with a dose of 3 kGy appears to be able to extend the microbial shelf-life by a factor of 2. When the chicken is marinating and irradiated at 3 kGy or when irradiated at 5 kGy without marinating, the microbial shelf-life is extended by a factor of 7 to 8. No Salmonella was found during all the experiment in the chicken in air and marinated. However, a presence of Salmonella was found in samples irradiated at 5 kGy under vacuum, in unirradiated samples and samples irradiated at 3kGy in air and under vacuum.     

Identification of low level gamma-irradiation of meats by high sensitivity comet assay

The detection of low levels of irradiation in meats (pork, beef, and chicken) using the new comet assay was investigated in order to assess the capability of the procedure. The new assay includes a process that improves its sensitivity to irradiation and a novel evaluation system for each slide (influence score and comet-type distribution). Samples used were purchased at retailers and were irradiated at 0.5 and 2 kGy at 0°C. The samples were processed to obtain comets. Slides were evaluated by typing comets, calculating the influence score and analyzing the comet-type distribution chart of shown on the slide. Influence scores of beef, pork, and chicken at 0 kGy were 287(SD=8.0), 305 (SD=12.9), and 320 (SD=21.0), respectively. Those at 500 Gy, were 305 (SD=5.3), 347 (SD=10.6), and 364 (12.6), respectively. Irradiation levels in food were successfully determined. Sensitivity to irradiation differed among samples (chicken>pork>beef).     

The effects of gamma irradiation on the microbiological, physical and sensory qualities of diced tomatoes

Diced Roma tomatoes were treated with gamma irradiation and evaluated for changes in microbial, physical, chemical and sensory properties. Dosages for Trial 1 were 0.0, 0.39, 0.56 and 1.82 kGy and in Trial 2, 0.0, 0.50, 1.24 and 3.70 kGy. Irradiation at 3.70 kGy resulted in no aerobic populations through day 12 and significantly fewer colonies through day 15 whereas yeast and mold populations experienced a 2 log reduction through day 12. Color, titratable acidity, and °Brix were not significantly affected by irradiation. Tissue firmness decreased with increasing dose but not with storage time. Treatment with 3.7 kGy decreased firmness by 50% and 20% with 0.5 kGy, however, the reduced firmness induced by 0.50 kGy was undetected by a 9 member trained sensory panel. A significant (p0.05) inverse correlation between changes in texture and water-soluble pectin (WSP) was determined while total pectin remained relatively constant and oxalate soluble pectin content decreased slightly with irradiation dose. The significant inverse correlation between the loss of firmness and WSP indicates that the changes in WSP play an important role in the tissue softening of tomatoes, This study indicates that irradiation at 0.5 kGy can reduce microbial counts substantially to improve microbial shelf life without adverse effects on sensory qualities.     

Effect of high-dose irradiation on quality characteristics of ready-to-eat chicken breast

High-dose (higher than 30 kGy) irradiation has been used to sterilize specific-purposed foods for safe and long-term storage. The objective of this study was to investigate the effect of high-dose irradiation on the quality characteristics of ready-to-eat chicken breast in comparison with those of the low-dose irradiation. Ready-to-eat chicken breast was manufactured, vacuum-packaged, and irradiated at 0, 5, and 40 kGy. The populations of total aerobic bacteria were 4.75 and 2.26 Log CFU/g in the samples irradiated at 0 and 5 kGy, respectively. However, no viable cells were detected in the samples irradiated at 40 kGy. On day 10, bacteria were not detected in the samples irradiated at 40 kGy but the number of bacteria in the samples irradiated at 5 kGy was increased. The pH at day 0 was higher in the samples irradiated at 40 kGy than those at 0 and 5 kGy. The 2-thiobarbituric acid reactive substance (TBARS) values of the samples were not significantly different on day 0. However, on day 10, the TBARS value was significantly higher in the samples irradiated at 40 kGy than those at 0 and 5 kGy. There was no difference in the sensory scores of the samples, except for off-flavor, which was stronger in samples irradiated at 5 and 40 kGy than control. However, no difference in off-flavor between the irradiated ones was observed. After 10 days of storage, only the samples irradiated at 40 kGy showed higher off-flavor score. SPME-GC–MS analysis revealed that 5 kGy of irradiation produced 2-methylbutanal and 3-methylbutanal, which were not present in the control, whereas 40 kGy of irradiation produced hexane, heptane, pentanal, dimethly disulfide, heptanal, and nonanal, which were not detected in the control or the samples irradiated at 5 kGy. However, the amount of compounds such as allyl sulfide and diallyl disulfide decreased significantly in the samples irradiated at 5 kGy and 40 kGy.     

Detection of irradiated fresh fruits treated by e-beam or gamma rays

Since about 1990, the amount of commercially irradiated food products available worldwide has increased. Commercial irradiation of foods has been allowed in Brazil since 1973 and now more than 20 different food products are approved. Among these products are a number of fresh fruits which may be irradiated for insect disinfestation, to delay ripening and to extend shelf-life. Today, there is a growing interest to apply radiation for the treatment of fruits instead of using fumigation or e.g. vapour-heat treatments, and an increased international trade in irradiated fruits is expected. To ensure free consumer choice, methods to identify irradiated foods are highly desirable. In this work, three detection methods for irradiated fruits have been employed: DNA Comet Assay, the half-embryo test and ESR. Both electron-beam (e-beam) and gamma rays were applied in order to compare the response with these two different kinds of radiation. Fresh fruits such as oranges, lemons, apples, watermelons and tomatoes were irradiated with doses in the range 0, 0.50, 0.75, 1.0, 2.0 and 4.0 kGy. For analysis, the seeds of the fruits were utilized. Both DNA Comet Assay and the half-embryo test enabled an easy identification of the radiation treatment. However, under our conditions, ESR measurements were not satisfactory.     

Thermal analysis of some phytotherapeutic products irradiated with electron beam

The purpose of the present work deals with the evaluation of the electron beam irradiation effects on some natural products based on thermal analysis. Some natural products with therapeutic contributions (artichoke, sea buckthorn, common sage, stonebreaker and cloves) were irradiated with doses up to 9 kGy using accelerated electron beam. The thermal profiles lead to identify three phenomena: dehydration — volatilization, irreversible degradation — molecular reorganization and residue decomposition. The radio-induced degradations determine slight shifts of the temperatures where these phenomena occur. The energetic value of the studied products is affected by e-beam treatment depending on irradiation dose.     

Reduction of Escherichia coli 0157:H7 in shredded iceberg lettuce by chlorination and gamma irradiation

Lettuce was inoculated with a six-strain cocktail of acid-adapted Escherichia coli 0157:H7 at a level of 1×10⁷ CFU/g. Following chlorination at 200 μg/ml, the lettuce was irradiated at 0.15, 0.38, or 0.55 kGy using a ⁶⁰Co source. Survival of E. coli 0157:H7, aerobic mesophiles and yeast and molds were measured over a period of 10 days. For quality analysis, chlorinated lettuce was subjected to irradiation at 0.33 and 0.53 kGy and stored at 1.0°C, 4.0°C or 7.0°C. Changes in texture and color were determined by instrumental means and changes in flavor, odor, and visual quality were determined by sensory testing.

Chlorination plus irradiation at 0.55 kGy produced a 5.4−log reduction in E. coli 0157:H7 levels. Chlorination alone reduced the E. coli 0157:H7 counts by 1–2 logs. Irradiation at 0.55 kGy was also effective in reducing standard plate counts and yeast and mold counts. Irradiation at this level did not cause softening of lettuce and sensory attributes were not adversely affected. In general, appearance and flavor were affected more by the length of storage than by temperature conditions. The 5+log reduction in E. coli counts and lack of adverse effects on sensory attributes indicate that low-dose irradiation can improve the safety and shelf-life of fresh-cut iceberg lettuce for retail sale or food service.     

A study of the physiological changes and the nutritional qualities of irradiated apples and the effect of irradiation on apples stored at room temperature

The effects of γ-irradiation on the metabolism and nutritional qualities of cold Delicious apples and on the lethality of verticillate pathogenic fungi have been studied. The storage effect of irradiation on apples at room temperature has been observed. The results showed that the respiratory intensity of irradiated apple at 0.3–0.5 kGy was near or lower than that of unirradiated apple after 15 days irradiation. The amount of ethylene release was obviously inhibited when fruits were irradiated with 0.3–0.7 kGy. The flesh firmness of apple irradiated with 0.3–0.9 kGy was higher than that of unirradiated apple with the increasing of storage time. The negative correlations between the flesh firmness and the activities of pectinesterase (PE), polygalacturonase (PG) were observed when the dosage was lower than 1.5 kGy. The 2.0 kGy irradiation damaged the ultrastructure of cells, induced the softening of apple. When apples were irradiated with 0.7–2.0 kGy, the contents of 4 important volatile components of apple would be decreased. However, the dosage mentioned above had no effects on the pure chemicals. The studies showed that there was no significant effect of irradiation with 0.3–2.0 kGy on the nutritional qualities of apples and this dosage range could effectively control the verticillate pathogenic fungi. The result of storage experiments showed that the rotting fruits were obviously decreased by 0.3–0.9 kGy irradiation.     

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

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

Effect of gamma-irradiation on the foaming behavior of ethylene-co-octene polymers

Ethylene-co-octene polymers containing different branching levels were irradiated in air and under vacuum at 25, 50 and 100 kGy. Gel fraction measurements, thermal analysis and rheology were used to assess the effect of the treatment on polymer structure modifications. The copolymer with 24 wt% octene was shown to be more sensitive to gamma rays and degradation was observed in some cases. Cross-linking in the amorphous phase also occurred as a consequence of irradiation and affected the foaming behavior of these materials.     

Electric properties of non-irradiated and gamma-irradiated keratin

Dielectric measurements as a function of temperature and frequency are reported for non-irradiated and γ-irradiated keratin, the irradiation doses being 5 and 50 kGy. The effect of γ-irradiation on the dielectric permittivity of keratin is not observed up to 190°C. In this temperature range, the values of the relaxation time and dipole moment are similar for non-irradiated and irradiated keratin at the same temperature. The influence of irradiation is manifested as a shift of the parameter (_s−_∞) peaks associated with the process of denaturation, towards lower temperatures. This fact is supported by lower values of the dipole moment for irradiated than for non-irradiated keratin, as a result of a decrease in the number of polar groups in the side and main chains of the macromolecule in the irradiated samples.     

Gamma irradiation improves the antioxidant activity of Aloe vera (Aloe barbadensis miller) extracts

Aloe has been widely used in food products, pharmaceuticals, and cosmetics because of its aromatic and therapeutic properties. In the present study, the ethanolic extracts of aloe gel were gamma-irradiated from 10 to 100 kGy. After gamma irradiation, the color of the ethanolic extracts of aloe gel changed to red; this color persisted up to 40 kGy but disappeared above 50 kGy. Liquid chromatography/mass spectrometry analysis demonstrated the production of a new, unknown compound (m/z=132) after gamma irradiation of the ethanolic extracts of aloe gel. The amount of this unknown compound increased with increasing irradiation up to 80 kGy, and it was degraded at 100 kGy. Interestingly, it was found that gamma irradiation significantly increased the antioxidant activity, as measured by the 1,1-diphenyl-2-picrylhydrazyl-radical scavenging capacity. The antioxidant activity of aloe extract was dramatically increased from 53.9% in the non-irradiated sample to 92.8% in the sample irradiated at 40 kGy. This strong antioxidant activity was retained even at 100 kGy. These results indicate that gamma irradiation of aloe extract can enhance its antioxidant activity through the formation of a new compound. Based on these results, increased antioxidant activity of aloe extracts by gamma rays can be applied to various industries, especially cosmetics, foodstuffs, and pharmaceuticals.     

Post electron-beam irradiation oxidation of orthopaedic UHMWPE

The mechanisms and products of the oxidation process induced by electron-beam irradiation of UHMWPE were thoroughly investigated in the present study. The e-beam technique has the peculiarity of dispensing the whole radiation dose in a very short time and it allows following the post-irradiation oxidation process at room temperature, which represents a major advantage for the present purpose.Thin sections of orthopaedic grade UHMWPE GUR 1050 were irradiated at doses ranging from 5 to 100 kGy in vacuum, air or pure oxygen, depending on the aim of the following analyses. After irradiation, the samples were stored in liquid nitrogen until the measurements began. Chemical and physical changes caused to the polymer by irradiation were investigated by FTIR, derivatisation techniques and spectral subtractions.As reported in the literature, secondary hydroperoxides and ketones were found to be the main oxidation products, along with carboxylic acids and alcohols. Nevertheless, in our case, the kinetics of formation of oxidation products were inconsistent with previously reported mechanisms. An alternative oxidation mechanism, including the simultaneous formation of hydroperoxides and ketones, is proposed. The thermal stability of hydroperoxides is also discussed in detail and the similarities between the post-irradiation oxidation process and the thermal oxidation process are highlighted.     

Pectin- and gelatin-based film: effect of gamma irradiation on the mechanical properties and biodegradation

Agricultural by-products, pectin and gelatin, were used to prepare a biodegradable film. The film casting solution including the pectin and gelatin was irradiated at 0, 10, 20, and 30 kGy to investigate the irradiation effect on the mechanical properties of the film. The tensile strength of the 10 kGy-irradiated film was the highest among the treatments but the elongation at break, water vapour permeability, and swelling ratio were the lowest. Hunter color L^*- and a^*-values decreased but the b^*-value increased as the irradiation dose increased. The total organic carbon content produced from the Paenibacillus polymyxa and Pseudomonas aeruginosa also showed that the film of 10 kGy-irradiated was lower than those of 0, 20, and 30 kGy-irradiated films. In conclusion, irradiation of the film casting solution at 10 kGy increased the mechanical properties of the pectin and gelatin based film. To manufacture the film by agricultural by-products, however, the irradiation dose of the film casting solution should be determined to achieve better mechanical properties.