Gamma irradiation of protein-based textiles for historical collections decontamination

In order to investigate the effect of gamma rays on cultural heritage materials, samples of silk and wool fabrics were subjected to accelerated ageing testing and then irradiated with different gamma-ray doses: 10 and 25 kGy. In the data analysis, combining thermal analysis (TG and DTG), infrared spectroscopy (FTIR-ATR) and mechanical tests allowed us to explore the changes in physical and chemical features for silk and wool, in relationship to the radiation doses. This analytical protocol offers a way to examine the behaviour of the textiles made of wool and silk within museum collections and their response to gamma-rays irradiation treatment. An exposure to a dose of 10 kGy did not cause significant changes in the tested properties; however, higher doses initiated irreversible loss in the physical and chemical stability of protein-based fabrics. Increasing the irradiation dose above 10 kGy has drastic effects in the loss of elasticity and the mechanical resistance of the tested yarns.     

Microbiological decontamination of natural honey by irradiation

Degree of microbiological decontamination, organoleptic and physico-chemical properties of natural honeys were investigated after radiation treatment. Seven kinds of honeys were irradiated with the beams of 10 MeV electrons from a 10 kW linear accelerator “Elektronika 10-10” at the dose 10 kGy.

It was shown, that after irradiation, the total count of aerobic and anaerobic bacteria and moulds decrease by 99%. The antibiotic value in investigated honeys increased in turn from 1.67 to 2.67 after irradiation. Such factors and parameters of investigated honeys as their consistency, content of water and saccharose, acidity, the diastase and 5-HMF values were not changed significantly after irradiation.

Decontamination by irradiation is a process which allows us to obtain high microbiological purity of honeys. It is especially needed, when honeys are used in surgical treatment of injuries and in nutrition of babies with food deficiency.     

The decontamination effects of gamma irradiation on the edible gelatin

The decontamination effects of gamma irradiation on the edible gelatin were studied. The results indicated that the bacterium and mold in the gelatin decreased significantly with the dose of 5 kGy treatment. However, the content of crude protein, microelement, amino acid in the gelatin remained unchanged under the irradiation of 4 and 8 kGy. The viscosity of the gelatin decreased with the increase of the irradiation dose, but the gelatin with a dose of 5 kGy treatment still accorded with the standard of the second-order class. These results suggested that the optimum irradiation dose for edible gelatin for the purpose of decontamination was in the range 3–5 kGy.     

The decontamination of industrial casein and milk powder by irradiation

The efficacy of gamma radiation decontamination of industrial casein, a milk protein utilized as a component of many food and non-food products has been studied. Low-fat milk powder was also included with a purpose to study the microflora survival in protein-rich materials. Microbial analysis of the samples prior to irradiation showed that the initial total viable count was higher than 6.0 log cfu g⁻¹ in both casein and milk powders. The contamination of casein with moulds and yeasts was found to be equal to 3.56 log cfu g⁻¹. The counts of coliforms have not exceeded the value of 2.48 log cfu g⁻¹. Radiation processing of casein and milk powder has substantially reduced the microbial population of all samples. The dose of 5 kGy was sufficient to reduce the total microflora and coliforms counts to the level permitted for food products. Survivals of microorganisms were analyzed by the generalized exponential equation, SF=exp[−D/D_o)^α]. Values of an exponent, α, standing for the dispersion parameter, were equal to 0.65 and 0.70 for microorganisms contaminating casein and milk powders, respectively. The numerical value of the dispersion parameter α<1 indicates the concave dependence of a logarithm of surviving fraction versus radiation dose. No difference in microflora survival in irradiated samples tested immediately and in samples stored for 1-month after irradiation has been noticed.     

The pharmacological activity of medical herbs after microbiological decontamination by irradiation

In the Institute of Nuclear Chemistry and Technology research on microbiological decontamination of medicinal herbs by irradiation has been carried out since 1996. It was shown that using ionizing radiation (a dose of 10 kGy) can obtain satisfactory results of microbiological decontamination of these products. The content of essential biologically active substances such as essential oils, flavonoids, glycosides, anthocyans, antra-compounds, poliphenoloacids, triterpene saponins, oleanosides and plants mucus did not change significantly after irradiation. Pharmacological activity of medicinal herbs has been found satisfactory after microbiological decontamination by irradiation.     

Suitability of sterin dose indicators for control of certain food irradiation processes

Sterin indicator, a new label dosimeter was evaluated for reliability and suitability as a device for discriminating and monitoring radiation treatment. Two versions, Sterin-125 and Sterin-300 were irradiated with gamma rays at dose ranges of 75–175 Gy and 200–400 Gy respectively. The irradiated samples were evaluated subjectively using Multiple Comparison Difference technique and their stability was tested under dark and differing light and temperature conditions. The results showed that these Sterin labels are generally reliable and useful but are affected by doses lower than designated threshold and by extended exposure to light sources.     

Effect of gamma irradiation on microbial decontamination,and chemical and sensory characteristic of lycium fruit

Lycium fruit, popular traditional Chinese medicine and food supplement generally is ingested uncooked, was exposed to several doses of gamma irradiation (0–14 kGy) to evaluate decontamination efficiency, changes in chemical composition, and changes in sensory characteristic. In this study, lycium fruit specimens contained microbial counts of 3.1×10³–1.7×10⁵ CFU/g and 14 kGy was sufficient for microbial decontamination. Before irradiation, the main microbe isolated from lycium fruit was identified as a strain of yeast, Cryptococcus laurentii. After 10 kGy of irradiation, a Gram-positive spore-forming bacterium, Bacillus cereus, was the only survivor. The first 90% reduction (LD₉₀) of C. laurentii and B. cereus was approximately 0.6 and 6.5 kGy, respectively, the D₁₀ doses of C. laurentii and B. cereus was approximately 0.6 and 1.7 kGy, respectively. After 14 kGy irradiation, except the vitamin C content, other chemical composition (e.g., crude protein, β-carotene, riboflavin, fructose, etc.) and the sensory characteristic of lycium fruit specimens did not have significant changes. In conclusion, 14 kGy is the optimal decontamination dose for lycium fruit for retention of its sensory quality and extension of shelf life.     

Use of some organic dyes in gamma irradiation dose determination

In the present work, the radiation-induced color bleaching of Remazol brilliant blue (RBB), Wegocet orange (WO), Methyl green (Me G) and Thioflavine S (Th S) dyes solutions was studied. Solutions of these dyes in different solvents were found to obey Beer’s law within certain concentration levels. The % color bleaching occurring in different dye solutions on using different gamma irradiation doses was determined and the data obtained showed the existence of good linear relationships among them in the four dye systems used. The linear sections lines were used as calibration curves for evaluating unknown gamma irradiation doses. From the obtained results, it was concluded that RBB in water, WO in ethanol, Me G in butanol and Th S in 60% ethanol–water mixture could be used for dose evaluation within the dose ranges 5–25 kGy for RBB, 20–90 kGy for WO, 10–70 kGy for Me G and 5–160 kGy for Th S. The sensitivity of the systems towards gamma radiations has been also reported.     

The application of high dose food irradiation in South Africa

During the 1950s to the end of the 1970s the United States Army developed the basic methodology to produce shelf-stable irradiated meat, seafood and poultry products. These products are normally packed without gravy, sauce or brine, as liquid is not required to sterilize the product as in the canning process. This leads to the distinctive “dried cooked” taste normally associated with roasts opposed to the casserole taste usually associated with tinned meats. The Biogam group at the Atomic Energy Corporation of South Africa is currently producing shelf-stable irradiated meats on a commercial basis. The meats are cooked, chilled, portioned, vacuum packed and irradiated to the required minimum dose of 45 kGy at a temperature of between −20 and −40°C to ensure absolute sterility even under tropical conditions. The product is packaged in a high quality four layer laminate pouch and will therefore not rust or burst even under adverse weather conditions and can be guaranteed for more than two years as long as the integrity of the packaging is maintained. Safari operators in remote parts of Africa, mountaineers, yachtsmen, canoeists and geological survey teams currently use shelf-stable irradiated meat products produced in South Africa.     

Lateritic minerals for decontamination of radionuclides

Naturally available lateritic minerals (LM) have been used on laboratory scale for the removal of Ce, Gd and Lu radionuclides from nuclear industry and reactor effluents. The adsorption behavior using radiotracers is reported, describing factors such as the nature and strength of acids, particle size, temperature and equilibration time which influence the adsorption mechanism. The interference of various anions and organic complexing agents on sorption of these radiotracers has also been considered. The optimized physico-chemical conditions and high loading capacities suggest an, effective use of LM for the isolation of the radionuclides from industrial and reactor effluents. Leaching studies made on pelletized LM loaded with the radionuclides indicate their potential for disposal in reduced solid form for a longer period.     

Use of CT scans and treatment planning software for validation of the dose component of food irradiation protocols

The challenging problem of estimating the dose delivered to heterogeneous products by radiation modalities of limited penetration can be readily handled by using technologies developed for, and widely used in, radiation therapy applications. In particular, combining CT scanning with radiation treatment planning programs can simulate radiation processing with either photons or electrons, and can provide detailed, high resolution and accurate dose maps for any arbitrary product and package configuration. Such dose maps are an essential part of process validation. Comparison of the simulated dose distributions with measured dose maps verifies the soundness of this approach. The present communication presents results obtained with the simulation technique for a variety of common food items which are likely candidates for radiation processing.     

Microbial quality evaluation and effective decontamination of nutraceutically valued lotus seeds by electron beams and gamma irradiation

Lotus seeds are nutraceutically valued natural plant produce, which succumbs to microbial contamination, predominantly to toxigenic moulds. Results of the present study revealed seed coat portion to harbor higher proportion of microbial load, particularly fungi than cotyledon portion. Among the mycotoxins analyzed, aflatoxins (B₁, B₂, G₁ and G₂) were below detectable limits, while the seeds were devoid of Ochratoxin-A (OTA). Application of different doses of electron beam and gamma irradiation (0, 2.5, 5, 7.5, 10, 15 and 30 kGy) for decontamination purpose revealed significant dose-dependent decrease in the fungal contaminants (P<0.05). However, the contaminant yeasts could survive up to 10 kGy dose, which could be completely eliminated at 15 kGy. From the results obtained, a dose range between 10 and 15 kGy is recommended for complete decontamination, as these doses have also been shown earlier to have minimal effects on nutritional and functional properties of lotus seeds.     

Twin column chromatography for industrial-scale decontamination processes

A frontal chromatographic unit was devised consisting of a column-detector-column array. The unit is either equipped with identical columns (identical twins) or with columns of varying length (fraternal twins). Due to the finite nature of the columns, a prerun is formed at the column walls following the same regularities as the main stream. These regularities are used for the identification of the process termination below the detection limits of the monitor. For the implementation, a clear preference is given to the employment of fraternal twins, as the feed assay can be integrated into the separation process.     

Thermogravimetric and calorimetric study of cellulose paper at low doses of gamma irradiation

The study of the behaviour of cellulose materials at low doses of ionizing radiation regained the interest because of the recent results showing that physical properties of the paper have less or no changes for absorbed doses below 10 kGy, despite the high decrease of the degree of polymerization. The understanding of the relationship among molecular, microscopic and macroscopic changes in cellulose materials may change the current opinion that irradiation of paper is not the best choice for conservation of cultural heritage. The aim of this study is to reveal the changes in gamma-irradiated pure cellulose paper by simultaneous TG/DSC analysis. For cellulose fibres, the thermal decomposition parameters depend on the cellulose degree of polymerization. For high irradiation doses, there is established a relationship between the absorbed dose and the degree of polymerization. However, a direct relationship between absorbed dose and the parameters of cellulose thermal decomposition for low irradiation doses was not established either in the literature or in our study. By using a peak separation technique, we studied the changes in the region of water loss (70–150 °C) and physical ageing (160–300 °C) for Whatman paper with low initial water content (<1 %), previously gamma irradiated at doses between 0 and 30 kGy. We concluded that strength of the hydrogen bond structure is increasing up to a point when the stress produces fractures in the fibrilar structure. This may explain the results reported for mechanical tests at low dose irradiation and it is in agreement with scanning electron microscopy pictures showing changes in fibril structure at high irradiation doses. Cellulose irradiated at low doses maintains its original hydrogen bond structure despite the decrease of the degree of polymerization.     

Depth dose dependence of the mouse bone using kilovoltage photon beams: A Monte Carlo study for small-animal irradiation

This study investigated the dose enhancement due to the presence of mouse bone irradiated by the kilovoltage (kV) photon beams. Dosimetry of the bone associated with soft and lung tissue was determined by Monte Carlo simulations using the EGSnrc-based code in millimeter scale. Two inhomogeneous phantoms with 2 mm of bone layer sandwiched by: (1) water and lung (bone–lung phantom); and (2) water (bone–water phantom), were used. Relative depth doses along the central beam axes in the phantoms and dose enhancement ratios (bone dose in the above inhomogeneous phantoms to the dose at the same point in the water phantom) were determined using the 100 and 225 kVp photon beams. For the 100 kVp photon beams, the depth dose gradient in the bone was significantly larger compared to that in a water phantom without the bone. This is due to the beam hardening effect that some low-energy photons were filtered out in the deeper depth, resulting in less photoelectric interactions and hence energy depositions in the bone. Moreover, dose differences between the top and downstream (bottom) bone edges at depths of 1–5 mm were 168–192% and 149–166% for the bone–lung and bone–water phantom, respectively. These differences were larger than 21–27% (bone–lung) and 12–23% (bone–water) for the 225 kVp photon beams. The maximum dose enhancement ratio in the bone for the bone–lung and bone–water phantoms in various depths was about 5.7 using the 100 kVp photon beams. This ratio was larger than two times of that (2.4) for the 225 kVp photon beams. It is concluded that, apart from the basic beam characteristics such as attenuation and penumbra, which are related to the photon beam energy in the mouse irradiation, the bone dose is another important factor to consider when selecting the beam energy in the small-animal treatment planning, provided that the bone dose enhancement is a concern in the preclinical model.     

Special requirements for calculation methods for soil decontamination processes

Soil decontamination is one of the major problems of industrialized nations. Various soil purification processes together with their characteristic attributes are discussed. Some transport and equilibrium phenomena of the contaminant/soil system are covered and some research needs are outlined which will facilitate better process design and significantly reduce clean-up costs.     

Effect of isotacticity on radiation stability of polypropylene under lower dose irradiation

Relationship between radiation stability and isotacticity of polypropylene was studied. It was found that the higher the isotacticity, the better the radiation stability under lower dose irradiation. Special PP power with higher isotacticity can keep the melting index change less after γ-irradiation in air. Furthermore, the special PP powder with higher isotacticity has lower intention of branching after 1 kGy γ-irradiation in vacuum and has lower intention of degradation after 5 kGy γ-irradiation in vacuum.