Effect of gamma irradiation on the thiamine, riboflavin and vitamin B6 content in two varieties of Brazilian beans

The effect of ⁶⁰Co gamma rays on the content of several B-vitamins in two varieties of Brazilian beans has been studied. Carioca (Phaseolus vulgaris L. var. Carioca) and Macaçar beans (Vigna unguiculata L. Walp, var. Macaçar) were irradiated at doses of 0, 0.5, 1.0, 2.5, 5.0 and 10 kGy, and subsequently stored at ambient temperature for 6 months. The content of vitamin B₁, B₂ and B₆ was analysed by HPLC. In addition, the optimum cooking time was established for each dose and bean variety. A taste panel evaluated sensory properties. Only slight changes were measured for thiamine and riboflavin, whereas a dose-dependent decrease was noted for pyridoxine, which, however, was significant only at the highest doses of 5 and 10 kGy. Cooking time was considerably reduced with increasing radiation dose, but accompanied by a loss of the sensory quality. However, at the disinfestation dose up to 1 kGy, acceptable ratings were obtained for the sensory evaluation. In conclusion, for insect disinfestation of Brazilian beans radiation processing is a promising technology.     

Application of different techniques to identify the effects of irradiation on Brazilian beans after six months storage

Four different techniques to detect the effect of irradiation in beans were investigated. Two types of Brazilian beans, Phaseolus vulgaris L., var. carioca and Vigna unguiculata (L.) Walp, var. macaçar, were irradiated using a ⁶⁰Co source with doses ranging from 10.0 kGy. After 6 months storage at ambient temperature the detection tests were carried out. Firstly, germination tests showed markedly reduced root growth and almost totally retarded shoot elongation of irradiated beans as compared to non-irradiated beans. Secondly, DNA fragmentation was studied using a microgel electrophoresis. Irradiated cells produced typical comets with DNA fragments migrating towards the anode. DNA of non-irradiated cells exhibited a limited migration. Thirdly, electron spin resonance for detection of cellulose radicals was tested, since it was expected that these free radicals are quite stable in solid and dry foods. However, only in beans irradiated with 10 kGy a small signal could be detected. Fourtly, thermoluminescence, a method to analyze mineral debris adhering to food, turned out to be a good choice to detect irradiation effects in beans, even after 6 months of storage. The results indicate that three of these four techniques proposed, can be used to detect the effect of irradiation in these two varieties of Brazilian beans at a dose level useful for insect disinfestation (1 kGy).     

Effect of irradiation on anti-nutrients (total phenolics, tannins and phytate) in Brazilian beans

The Brazilian bean varieties Phaseolus vulgaris L. var. Carioca and Vigna unguiculata (L.) Walp var. Macaçar were irradiated with doses of 0.5, 1.0, 2.5, 5.0 and 10 kGy and subsequently stored at ambient temperature for 6 months. The anti-nutrients phenolic compounds, tannins and phytate were determined to be 0.48 mg g⁻¹ dry basis, 1.8 mg g⁻¹ dry basis and 13.5 μmol g⁻¹ dry basis in the raw non-irradiated Carioca beans and 0.30 mg g⁻¹ dry basis, 0.42 mg g⁻¹ dry basis and 7.5 μmol g⁻¹ dry basis in the raw non-irradiated Macaçar beans. After soaking and cooking a higher content of phenolic compounds and a lower phytate content was observed in both bean varieties. Tannin content was not affected by soaking and cooking of Carioca beans, but higher after soaking and cooking of Macaçar beans. Using radiation doses relevant for food did not effect the content of the anti-nutrients under investigation in both bean varieties.     

Effect of gamma irradiation on the microbiological quality and on the functional properties of proteins in dry red kidney beans (Phaseolus vulgaris)

Gamma-irradiation was found to affect the physicochemical properties of dry red kidney beans. The highest dose used (8 kGy) significantly (P0.05) modified the extent of deamidation, the number of sulfhydryl groups, as well as the solubility and the hydrophobicity of the protein. Deamidation, protein solubility and hydrophobicity all increased with the irradiation dose while the number of sulfhydryl groups was reduced by the treatment. Furthermore, irradiation also affected the outgrowth of natural filamentous fungi contaminants present on the dry beans. A dose of 1.5 kGy reduced the number of filamentous fungi by 2 log cycles immediately after treatment. However, the highest dose used (3 kGy) did not eliminate the filamentous fungi completely. Moreover, the filamentous fungi population was a lot less diversified on the irradiated samples. Species of Aspergillus sp. and Penicillium sp. were more abundant on the unirradiated beans while the beans irradiated at 3 kGy contained were predominantly infected by species of Rhizopus sp. , Cladosporium sp. and Alternaria sp.     

DNA comet assay: A simple screening technique for identification of some irradiated foods

DNA Comet Assay method was carried out to detect irradiation treatment of some foods like meat, spices, beans and lentils. The fresh meat of cow and duck were irradiated up to radiation doses of 3 kGy, the spices (cardamoms and cumin black) were irradiated to radiation doses of 5, 10, 15 and 20 kGy while the beans (black beans and white beans) and lentils (red and green lentils) were irradiated to 0.5 and 1 kGy. All the foods were then analyzed for radiation treatment using simple microgel electrophoresis of single cells or nuclei (DNA Comet Assay). Sedimentation, lysis and staining times were adjusted to get optimized conditions for correct and easy analysis of each food. Using these optimized conditions, it was found out that radiation damaged DNA showed comets in case of irradiated food samples, whereas in non-treated food samples, round or conical spots of stained DNA were visible. Shape, length and intensity of these comets were also radiation dose dependent. Screening of unirradiated and irradiated samples by Comet Assay was successful in the case of all the foods under consideration under the optimized conditions of assay. Therefore, for different kinds of irradiated foods studied in the present study, the DNA Comet Assay can be used as a rapid, simple and inexpensive screening test.     

Detection of radiation treatment of beans using DNA comet assay

A simple technique of microgel electrophoresis of single cells (DNA Comet Assay) enabled a quick detection of radiation treatment of several kinds of leguminous beans (azuki, black, black eye, mung, pinto, red kidney and white beans). Each variety was exposed to radiation doses of 0.5, 1 and 5 kGy covering the permissible limits for insect disinfestation. The cells or nuclei from beans were extracted in cold PBS, embedded in agarose on microscope slides, lysed between 15 and 60 min in 2.5% SDS and electrophoresis was carried out at a voltage of 2 V/cm for 2–2.5 min. After silver staining, the slides were evaluated through an ordinary transmission microscope. In irradiated samples, fragmented DNA stretched towards the anode and the damaged cells appeared as a comet. The density of DNA in the tails increased with increasing radiation dose. However, in non-irradiated samples, the large molecules of DNA remained relatively intact and there was only minor or no migration of DNA; the cells were round or had very short tails only. Hence, the DNA comet assay provides an inexpensive, rapid and relatively simple screening method for the detection of irradiated beans.     

Sensorial analysis evaluation in cereal bars preserved by ionizing radiation processing

Gamma-rays utilized as a food-processing treatment to eliminate insect contamination is well established in food industries. Recent troubles in Brazilian cereal bars commercialization require a special consumer's attention because some products were contaminated by insects. To solve the problem, food-irradiation treatment was utilized as a safe and effective solution. The final product was free of insect contamination. The aim of this study was to determine the best radiation dose processing utilized to disinfestations and detect some change on sensorial characteristic by sensorial analysis in cereal bars. In this study, three different kinds of cereal bars were purchased in São Paulo (Brazil) in supermarkets and irradiated with 1.0, 2.0 and 3.0 kGy at “Instituto de Pesquisas Energéticas e Nucleares” (IPEN-CNEN/SP). The samples were treated with ionizing radiation using a ⁶⁰Co gamma-ray facility (Gammacell 220, A.E.C.L.). That radiation doses were used successfully as an anti-insect treatment in the cereal bars, since in some food industries doses up to 3.0 kGy are used to guarantee at least a dose of 1.0 kGy in internal cereal bars package. Sensorial analysis was necessary since cereal bars contain ingredients very sensitive to ionizing radiation process.     

Evaluation of microbial loads,physical characteristics,chemical constituents and biological properties of radiation processed Fagonia arabica

Whole plant of Fagonia arabica with 3 different particle sizes (30, 50 and 70 mesh) were exposed to gamma radiation doses of 1–10 kGy from a Cobalt 60 source. A series of tests was performed in order to check the feasibility of irradiation processing of the plant. The applied radiation doses did not affect (P<0.05) pH and antimicrobial activities of the plant. The total weight of the dry extracts in methanol as well as water was found increased with irradiation. The irradiated samples showed significant increase in phenolic content and free radical scavenging activity using DPPH. Shortly after irradiation (on the day of radiation treatment) high amounts of free radicals were detected in the irradiated plant samples and the chemiluminescence measurements were generally found to be dose dependent. Maximum luminescence intensity was observed in case of samples with mesh size of 30 for all the radiation doses applied. After a period of one month the chemiluminescence signals of the irradiated samples approximated those of the controls. The study suggests that gamma irradiation treatment is effective for quality improvement and enhances certain beneficial biological properties of the treated materials.     

Effects of (60)Co gamma radiation on thylakoid membrane functions in Anacystis nidulans

In photosynthetic organisms oxidative stress is known to result in photoinactivation of photosynthetic machinery. We investigated effects of ⁶⁰Co γ radiation, which generates oxidative stress, on thylakoid structure and function in cyanobacteria. Cells of unicellular, non-nitrogen fixing cyanobacterium Anacystis nidulans (Synechococcus sp.) showed D₁₀ value of 257 Gy of ⁶⁰Co γ radiation. When measured immediately after exposure, cells irradiated with 1500 Gy (lethal dose) of ⁶⁰Co γ radiation did not show any differences in photosynthetic functions such as CO₂ fixation, O₂ evolution and partial reactions of photosynthetic electron transport in comparison to unirradiated cells. Incubation of irradiated cells for 24 h in light or dark resulted in decline in photosynthesis. The decline in photosynthesis was higher in the cells incubated in light as compared to the cells incubated in dark. Among the partial reactions of electron transport, only PSII activity declined drastically after incubation of irradiated samples. This was also supported by the analysis of membrane functions using thermoluminescence. Exposure of cyanobacteria to high doses of ⁶⁰Co γ radiation did not affect the thylakoid membrane ultrastructure immediately after exposure as shown by electron microscopy. The level of reactive oxygen species (ROS) in irradiated cells was 20 times higher as compared to control. In irradiated cells de novo protein synthesis was reduced considerably immediately after irradiation. Treatment of cells with tetracycline also affected photosynthesis as in irradiated cells. The results showed that photoinhibition of photosynthetic apparatus after incubation of irradiated cells was probably augmented due to reduced protein synthesis. Active photosynthesis is known to require uninterrupted replenishment of some of the proteins involved in electron transport chain. The defective thylakoid membrane biogenesis may be leading to photosynthetic decline post-irradiation.     

Improvement of microbiological safety of sous-vide meals by gamma radiation

Experimental batches of smoked-cured pork in stewed beans sauce were inoculated with spores of psychrotrophic Bacillus cereus, more heat and radiation resistant than spores of non-proteolytic C. botulinum. After vacuum packaging, the meals were treated with combinations of pasteurizing heat treatments and gamma irradiation of 5 kGy. Prior and after treatments, and periodically during storage at 10°C, total aerobic and total anerobic viable cell counts, and selectively, the viable cell counts of B. cereus and sulphite-reducing clostridia have been determined. The effects of the treatment order as well as addition of nisin to enhance the preservative efficiency of the physical treatments were also studied. Heat-sensitization of bacterial spores surviving irradiation occurred. The quality-friendly sous-vide cooking in combination with this medium dose gamma irradiation and/or nisin addition increased considerably the microbiological safety and the keeping quality of the meals studied. However, approx. 40% loss of thiamin content occurred as an effect of combination treatments, and adverse sensorial effects may also limit the feasible radiation doses or the usable concentrations of nisin.     

Design,Synthesis, Biological Evaluation and SARs of Anthranilic Diamide Derivatives Containing Pyrrole Moieties

In order to find a new variety of ryanodine receptor(RyR) regulator with greater biological activity, a series of anthranilic diamide derivatives possessing pyrrole structure was designed and synthesized in this study. The pyrrole derivatives were evaluated for their insecticidal activity against Mythimna separata and Plutella xylostella. As indicated by the preliminary biological activities, compounds 12h-12j and 12l-12n exhibited a remarkable insecticidal activity against M. separata at 0.25 mg/L. Compared to control chlorantraniliprole, compound 12j exhibited more excellent insecticidal activity at 0.1 mg/L. Meanwhile, compounds 12c, 12h, 12i, 12j, 12l, and 12m were selected to test the insecticidal activity against P. xylostella, which led to the desirable insecticidal activity at 1×10^-3 mg/L. Notably, compound 12l demonstrated 47% insecticidal activity at 5×10^-6mg/L over the control. In addition, the biological mechanism of action of compound 12j was investigated by means of insect electrophysiology experiment.     

Application of thermoluminescence measurements to detect low dose gamma-irradiated table grapes

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.     

Effect of gamma radiation on microbial population of natural casings

The high microbial load of fresh and dry natural casings increases the risk of meat product contamination with pathogenic microorganisms, agents of foodborn diseases.

The aim of this work is to evaluate the killing effect of gamma radiation of the resident microbial population of pork and beef casings, to improve their hygiene and safety.

Portions of fresh pork (small intestines and colon) and dry beef casings were irradiated in a Cobalt 60 source with with absorbed doses of 1,2,5 and 10 kGy.

The D₁₀ values of total aerobic microorganisms in the pork casings were 1.65 kGy for colon and 1.54 kGy for small intestine. The D₁₀ value found in beef dry casings (small intestine) was 10.17 kGy. Radurization with 5 kGy was able to reduce, at least, 6 logs the coliform bacteria in pork casings. The killing effect over faecal Streptococci was 4 logs for pork fresh casings and 2 logs for beef dry casings. Gamma radiation with 5 kGy proved to be a convenient method to reduce substantially the microbial population of pork fresh casings. Otherwise, the microbial population of beef dry casings still resisted to 10 kGy.     

The effect of irradiation in the quality of the avocado frozen pulp

The quality of frozen avocado pulp irradiated with ⁶⁰Co gamma rays at doses of: 0.5, 1.0, 1.5, and 2.5 kGy, was studied. These are possible doses for reducing the content of bacteria Listeria monocytogenes by 1–4 log cycles. The study principally consisted of weekly evaluations of damages caused in lipids and chlorophyll pigment over a period of one year. No significant differences were found in either hydrolysis rancidity or in the oxidative rancidity for any of the doses. The concentrations of fatty acids and peroxides were below those established by Codex Alimentarius. This means that the quality of the oil in the frozen avocado pulp remains acceptable. The kinetic model for the oxidative rancidity is of first order and the shelf life of the product is of about 120 weeks. The concentrations of the fatty acids and of malondialdehyde were not high enough to produce off-flavors. It was also determined that the radiation doses did not influence the chemistry of the chlorophyll. The results were confirmed by the panelists, who accepted irradiated frozen pulp at the highest radiation dose.     

Effects of irradiation on trans fatty acids formation in ground beef

In order to give the consumer the assurance that meat processed by irradiation is a safe product, a great deal of research has been developed in the world. The effect of irradiation on the hygienic quality of meat and meat products is considered as related to the control of meat-borne parasites of humans; elimination of pathogens from fresh meat and poultry; and elimination of pathogens from processed meat. Lipid oxidation and associated changes are the major causes of the quality deterioration of meat during storage. Irradiation of lipids induces the production of free radicals, which react with oxygen, leading to the formation of carbonyls, responsible for alterations in food nutritional and sensorial characteristics. Trans fatty acids are present in ground beef and can also be formed during its processing. Interestingly, the trans fatty acids, due to their chemical and physical characteristics, show more resistance to the oxidizing process. This property motivated us to investigate the level of the trans fatty acids, as well as the level of oxidation in irradiated ground beef. Irradiation of ground beef was performed by gamma rays from a ⁶⁰Co source. The applied radiation doses were 0; 1.0; 2.0; 3.0; 4.0; 5.0; 6.0; 7.0 and 8.0 kGy. Lipid peroxidation in terms of TBA number and carbonyl content was monitored during storage. The sample characteristics and trans fatty acids composition were measured, following irradiation and after 60 and 90 days of storage at –10°C.     

Effects of gamma irradiation on the shoot length of Cicer seeds

The effects of radiation on the shoot and root lengths of germinated seedling of irradiated seeds of Cicer species, i.e. three kabuli types and four desi types of cultivated chickpea (Cicer arietinum Ladiz.) and 2 annual wild types (C. reticulatum Ladiz. and C. bijugum K.H. Rech.) were investigated. The seeds were irradiated with a ⁶⁰Co gamma source using 0, 200, 300 and 400 Gy doses at 1.66 kGy h⁻¹. At 200 Gy minor effects could be observed, but at 400 Gy an obvious depression of shoot length was observed. The kabuli types were more affected than the desi ones. The critical dose that prevented the shoot and root elongation varied among species and also ranged from genotypes to genotype within species.     

Orchid flowers tolerance to gamma-radiation

Cut flowers are fresh goods that may be treated with fumigants such as methyl bromide to meet the needs of the quarantine requirements of importing countries. Irradiation is a non-chemical alternative to substitute the methyl bromide treatment of fresh products. In this research, different cut orchids were irradiated to examine their tolerance to gamma-rays. A 200 Gy dose did inhibit the Dendrobium palenopsis buds from opening, but did not cause visible damage to opened flowers. Doses of 800 and 1000 Gy were damaging because they provoked the flowers to drop from the stem. Cattleya irradiated with 750 Gy did not show any damage, and were therefore eligible for the radiation treatment. Cymbidium tolerated up to 300 Gy and above this dose dropped prematurely. On the other hand, Oncydium did not tolerate doses above 150 Gy.     

Effect of gamma-ray irradiation on the mechanical strength of polystyrene-ferrocene composite

Thin films of polystyrene-ferrocene (PS---Fe) composite were irradiated with various doses of gamma irradiation ranging from 4·1 to 25·3 Mrad. The Vickers hardness number (H_v) was calculated for pure and irradiated specimens. It was used to analyse mechanical strength at a saturation load of 100 g. The mechanical strength was found to increase with irradiation dose up to 12 Mrad. Brittleness of the composite PS-Fe was found to occur at a higher dose of 25 Mrad as compared to 15 Mrad for polystyrene. Further, fracture toughness, brittleness index and yield strength were calculated for various irradiated specimens consequent to crack propagation in the specimens.     

The effect of the short wavelength ultraviolet radiation. An extension of biological dosimetry to the UV-C range

Polycrystalline uracil thin layer can be used as biological dosimeter for assessing exposure to UV radiation. The dimerization and reversion efficiency of the ultraviolet radiation in the UV-B and the UV-C range were quantified on polycrystalline uracil thin layers irradiated with quasi-monochromatic radiation using interference filters of 10nm bandwidth. The dimer formation and monomerization (reversion) dose-effect relations were determined by optical spectroscopy. The decrease of the OD value of the uracil thin layer at 288 nm was taken as a measure of the dimer formation, while the increase of the OD of a completely irradiated (until reaching the saturation level) uracil layer was taken as the sign of the monomerization. The two processes in the UV-B and the UV-C range take place simultaneously, the individual characterization of the dimerization efficiency was performed from the initial slope of the dimerization dose-effect function and an action spectrum for dimerization was constructed in the UV-C range too. The reversion efficiency was found to be practically the same with all of the investigated wavelengths: 200 nm, 210 nm, 220 nm, 230 nm, 240 nm The possible biological relevance of the reversion of dimers are discussed.     

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.