Thermal properties and radical monitoring after gamma, X-ray, and electron beam irradiation in polyamides.

Ionizing radiation induced transformations in materials were monitored through tracking of the generation and degradation processes of radical species. Consequently, the types and quantities of radicals were determined by electron spin resonance (ESR). Subsequently, differential scanning calorimetry (DSC) was utilized to assess the impact of irradiation on the material crystallinity. The effects of gamma rays, X-rays, and electron beams were investigated on different polyamides, which exhibit an ESR signal up to 60 days. DSC results showed no significant effect of irradiation on the melting peak temperature of the materials, indicating that the amount of radicals generated was not large enough to induce a significant alteration of the material's macrostructure.

Toward Enhanced Machine-Based Release in X-ray Sterilization.

Trends toward the use of irradiator parameter release (also called machine-based release) put pressure on equipment manufacturers to guarantee accuracy and reliability of monitored process parameters. In the specific case of X-ray processing, relevance of these monitored parameters is questionable due to the additional difficulty coming from the fact that the X-ray converter does not have associated parameters or a monitored feedback mechanism. To bridge this gap, this article presents a novel method to verify in real-time consistency of certain X-ray field properties. It covers the description of an X-ray flux monitor and its experimental characterization. The proposed detector can be used as a control and monitoring tool in addition to the conventional "passive" dosimetry per ISO 11137-1 and ISO 11137-3. It can detect photon flux deviation on the order of magnitude of 1%. Its performance would allow real-time monitoring of each pallet being processed and ensure that the correct X-ray beam is directed to the product. Further, the known response of the detector to a product can serve as a validation that the correct product is in front of the beam. Moreover, a detector of this type could contribute to moving from the current dosimetric release to irradiator parameter release. Compared with current practices, benefits would include an increased number of control points used to verify process conformity, real-time information on the radiation field (process output validation), limited manual handling of dosimeters, and verification that the product treated is the same as the performance qualification dose-mapped product.

Guidelines on reporting treatment conditions for emerging technologies in food processing.

In the last decades, different non-thermal and thermal technologies have been developed for food processing. However, in many cases, it is not clear which experimental parameters must be reported to guarantee the experiments' reproducibility and provide the food industry a straightforward way to scale-up these technologies. Since reproducibility is one of the most important science features, the current work aims to improve the reproducibility of studies on emerging technologies for food processing by providing guidelines on reporting treatment conditions of thermal and non-thermal technologies. Infrared heating, microwave heating, ohmic heating and radiofrequency heating are addressed as advanced thermal technologies and isostatic high pressure, ultra-high-pressure homogenization sterilization, high-pressure homogenization, microfluidization, irradiation, plasma technologies, power ultrasound, pressure change technology, pulsed electric fields, pulsed light and supercritical CO2 are approached as non-thermal technologies. Finally, growing points and perspectives are highlighted.

Effects of a metallic implant on radiotherapy planning treatment-experience on a human cadaver.

BACKGROUND: Metallic implants (MIs) complicate radiotherapy planning. Several studies have worked on tissue-equivalent phantoms as experimental models to estimate dose distributions in this context. The application of these results to clinical practice remains disputable because the inhomogeneity of human tissue densities is a difficult factor to integrate into dose calculation software. In this work, we evaluate the impact of human tissue inhomogeneities by assessing the discrepancies between treatment planning system (TPS) dose calculations and measured delivered doses on a human cadaver with hip prostheses. METHODS: A total of 143 alanine dosimeters were positioned in contact with the prostheses (bones group), soft tissues (soft tissues group), skin surfaces (skin group) and natural cavities (cavities group) of a human cadaver. The planning target volume (PTV) corresponded to a standard endometrial cancer treatment. The irradiation was performed with 6 MV X-ray tomotherapy at the one fraction-dose of 10 Gy. RESULTS: A total of 140 dosimeters were analyzed. After applying a temperature correction coefficient to the measured doses, the global analysis of all dosimeters showed a significant difference between the calculated doses and the measured doses (P<0.001). For dosimeters of the bones, soft tissues, skin and cavities groups, this difference was also significant (P<0.001 for each group). The mean measured doses were 21.9% lower than the mean calculated doses in the global analysis and 17.0%, 21.2%, 33.0% and 19.0% lower for the bones, soft tissues, skin and cavities groups, respectively. CONCLUSIONS: This study showed that the received doses were significantly lower than the calculated doses and suggested the need to improve the understanding of this discrepancy.

Detection of irradiated ingredients included in low quantity in non-irradiated food matrix. 1. Extraction and ESR analysis of bones from mechanically recovered poultry meat.

Protocol EN 1786 for the detection of irradiated food by electron spin resonance (ESR) spectroscopy was not conceived for the detection of irradiated bone-containing ingredients included in low concentration in non-irradiated food. An enzymatic hydrolysis method, realized at 55 degrees C, has been developed for the extraction of the bone fraction. When followed by a purification of the extracts by an aqueous solution of sodium polytungstate, this method made possible the detection of irradiated mechanically recovered poultry meat at very low inclusions (0.5%, wt/wt by ESR) in various meals (quenelles and precooked meals).

Detection of irradiated ingredients included in low quantity in non-irradiated food matrix. 2. ESR analysis of mechanically recovered poultry meat and TL analysis of spices.

Protocols EN 1786 and EN 1788 for the detection of irradiated food by electron spin resonance spectroscopy (ESR) and thermoluminescence (TL) were not conceived for the detection of irradiated ingredients included in low concentration in nonirradiated food. An enzymatic hydrolysis method, realized at 55 degrees C, has been developed for the extraction of silicate minerals and bone fragments. When followed by a purification of the extracts by an aqueous solution of sodium polytungstate, this method made it possible to detect very low inclusions of irradiated spices (0.05%, wt/wt by TL) included in various meals (cheeses and precooked meals). Even for food containing together two ingredients (spices and mechanically recovered meat), it was possible to detect and identify them simultaneously.

Freeze-drying of enzymes in case of water-binding and non-water-binding substrates.

Enzymes typically have a critical instability, which dominates both formulation and process development. In this paper, the ability to preserve the enzyme activity during freeze-drying was investigated for both water-binding and non-water-binding substrates. For this purpose, acid phosphatase was used as model protein. In addition, a procedure for the fast development of a freeze-drying cycle is shown. For the secondary drying part, the effect of processing temperature and time on enzyme activity was investigated. The enzyme activity decreased continuously during secondary drying, with a dramatic drop associated with processing temperatures higher than 293 K. Besides product temperature, the residual moisture level and water mobility are also important. As the residual moisture level and water mobility depend on the product formulation, the stabilizing effect against the enzyme deactivation was studied for a number of formulations which contain different additives, that is, sucrose, lactose, mannitol, and poly-vinylpyrrolidone, with a dramatic activity loss associated with crystallizing excipients. This study also confirmed that not all water-binding substrates can successfully protect the enzyme against deactivation. In fact, water-binding substrates containing reducing sugars (lactose) showed the highest loss of activity.

Irradiation stability of folic Acid in powder and aqueous solution.

This study attempts to examine the folic acid stability after irradiation treatment, under different physical states, pH values, and atmosphere conditions. Aqueous folic acid samples, folic acid in powder, and wheat flour fortified with folic acid were irradiated by an electron beam (E-beam) between 0 (control) and 10.0 kGy. It was realized that the physical state of folic acid plays an important role on its stability toward E-beam processing, being largely unstable in solution, no matter the pH and atmosphere conditions assayed. Otherwise, folic acid in powder showed huge irradiation stability, even when mixed in a dry food matrix, such as fortified wheat flour samples.