Effect of gamma-irradiation on flavour 5′-nucleotides,tyrosine, and phenylalanine in mushrooms (Agaricus bisporus)

The impact of gamma-irradiation on 5′-nucleotides and on the free amino acids tyrosine and phenylalanine in fresh mushrooms was studied. After irradiation the samples were freeze-dried to avoid enzyme induced chemical changes. Three 5′-nucleotides could be detected using HPLC–UV and LC–ESI-MS: adenosine 5′-monophosphate (AMP), guanosine 5′-monophosphate (GMP) and guanosine 5′-diphosphate (GDP). Irradiation significantly reduced (p = 0.05) the GDP concentration (22%). AMP showed a marked reduction (46%) only at 5 kGy. GMP, tyrosine, and phenylalanine were not affected by gamma-irradiation.     

RAFT-mediated polymerization and grafting of sodium 4-styrenesulfonate from cellulose initiated via γ-radiation

Ambient temperature (20 °C) reversible addition fragmentation chain transfer (RAFT) polymerization of sodium 4-styrenesulfonate (SS) conducted directly in aqueous media under γ-irradiation at different dose rates (0.09, 0.03 and 0.02 kGy h⁻¹) proceeds in a controlled fashion (typically, M_w/M_n < 1.25) to near quantitative conversions via 4-cyanopentanoic acid dithiobenzoate (CPADB) mediation. By applying CPADB modified cellulose as a macro chain transfer agent, a graft copolymer with SS was prepared in aqueous media under γ-irradiation. RAFT mediated graft polymerizations provided copolymers with higher graft frequencies compared to those obtained by conventional methods. Thermally initiated grafting of SS from a CPADB-functionalized cellulose surface at 70 °C was also studied which resulted in a reduced graft frequency in comparison to γ-initiated ones.     

Signature of Meyer-Neldel compensation rule in iso-conversional crystallization under the influence of γ-ray irradiation

In the current article, the influence of three different doses of gamma-rays on the thermally assisted crystal growth in a novel ternary chalcogenide glassy Se₇₈Te₂₀Sn₂ semiconductor has been reported in terms of the re-crystallization. The iso-conversional kinetic approach is used in the present study. The variation of crystal growth rate with temperature obeys the Arrhenius relation for all the doses of gamma-rays irradiation. Further analysis confirms that pre-factor K₀ of crystal growth rate and the corresponding energy ΔE involved in thermally governed crystallization follows Meyer-Neldel compensation rule (MNCR). Further, we have observed a linear correlation i.e., Further Meyer-Neldel compensation rule (FMNCR) between Meyer-Neldel pre-factor K₀₀ and Meyer-Neldel energy kT₀. The observed correlations between these significant parameters (MNCR between K₀ & ΔE and FMNCR between K₀₀ & kT₀) may open a new gateway for revealing the external effects on crystal growth rate during the iso-conversional analysis of crystallization kinetics.     

Physicochemical and microbiological changes in irradiated fresh pork loins

The effect of γ-irradiation on the physicochemical and microbiological properties of fresh pork was studied. Radiation treatments were carried out under air on fresh pork loins at doses of 2, 4 and 8 kGy and the loins were evaluated for deamidation, solubility, sulphydryl content and surface hydrophobicity. Deamidation was significantly (p0.05) affected by the treatment with 98% deamidation at a dose of 8 kGy. No significant changes (p > 0.05) were noted in sulphydryl content under the same conditions. The increase in deamidation resulted in a decrease in hydrophobicity and an increase in protein solubility. γ-irradiation also reduced the number of microorganisms in the meat. Mesophiles were more resistant to the irradiation treatment than psychrotrophs and Pseudomonas. All irradiated pork samples (1 or 3 kGy) had a bacterial count lower that 10⁷ CFU/g after 15 days of storage. A minimal dose of 1 kGy was sufficient to increase the shelf life of fresh pork loins although variations in initial pork contamination was found to be the determining factor accounting for the effectiveness of the treatment.     

Development of ESR method for gamma-irradiated lactose powders

In this study, ESR was used to characterize the differences between irradiated lactose and non-irradiated lactose. A multi-component ESR spectrum was observed from most of the non-irradiated commercial lactose powder as well as the gamma-irradiated lactose powder. However, the signal pattern of non-irradiated lactose powder was different from that of irradiated lactose powder. Moreover, the multi-component ESR spectrum intensity of radicals generated by milling was weaker than that by gamma-irradiation. Among the several possible causes of generating radicals such as irradiation, lipid oxidation, protein oxidation, influence of ash or mineral and mechanical radical by grinding, the multi-component ESR spectrum from the non-irradiated lactose powder was shown to have resulted from the generation of mechanical radicals during milling in the manufacturing processes.     

Characterization of poly(vinyl alcohol)/gold nanocomposites obtained by in situ gamma-irradiation method

Gamma-irradiation induced reduction of gold (Au) ions was performed in aqueous poly(vinyl alcohol) (PVA) solution. PVA/Au nanocomposites with different contents of inorganic phase were prepared by solvent evaporation. The colloids and corresponding nanocomposites show visible light absorption with strong excitonic peak in the wavelength range from 520 to 550 nm. Morphological and structural characterizations of gold nanoparticles (Au NPs) and nanocomposites were performed by TEM, XRD, and FTIR measurements. Also, Mie and Maxwell-Garnett theories were applied to calculate optical properties of Au colloids and PVA/Au nanocomposites, respectively. The changes of heat resistance upon the increase of inorganic phase were correlated to the decrease in crystal perfection of polymer. Improvement of thermal stability of nanocomposites, compared with the neat PVA, was observed when the content of inorganic phase exceeds 1 wt %. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Antioxidant properties of Maillard reaction products obtained by gamma-irradiation of whey proteins

The radiation processing of sugar–amino acid solutions results in formation of Maillard reaction products (MRPs). In the present study, the efficacy of gamma-irradiation in the formation of MRPs from whey protein powder was investigated. The formation of MRPs in whey protein suspension was studied by monitoring spectrophotometeric and chemical changes. A dose-dependent increase in UV absorbance and development of fluorescence was observed. Formation of brown pigments was established by increased A_420 nm and Hunter colour upon irradiation. These MRPs exhibited antioxidant activity as measured by 1,1-diphenyl-2-picrylhydrazyl and β-carotene bleaching assays. Reducing power and iron-chelating abilities of MRPs also increased upon irradiation. These MRPs were able to scavenge hydroxyl and superoxide anion radicals under in vitro conditions. Dose-dependent decrease in free amino groups and lactose suggested the formation of glycated proteins upon irradiation treatment. SDS–PAGE analyses indicated formation of crosslinked proteins upon irradiation.     

Influence of temperature and dose rate on the degradation of BiCMOS operational amplifiers during total ionizing dose testing

The degradation of BiCMOS operational amplifiers TLV2451CP under the gamma-irradiation is studied for different dose rates and temperatures during irradiation. It is shown that studied devices are sensitive to both enhanced low dose rate sensitivity and time-dependent effects. Evidently the main reason for degradation of studied devices is build-up of the interface traps. Obtained results show possibility to develop an approach for total ionizing dose testing of BiCMOS devices considering low dose rate effects.     

Effects of gamma- and electron-beam irradiation on semi-rigid amorphous polyethylene terephthalate copolymers

Two semi-rigid amorphous polyethylene terephthalate copolymer materials (in both sheet and powder forms) containing 3% 1,4-cyclohexane dimethanol (CHDM) and 31% CHDM were irradiated at 5, 25 and 50 kGy at ambient temperature with a ⁶⁰Co radiator or an electron-beam accelerator. After irradiation, volatiles were determined using static headspace sampling with capillary gas chromatography and mass selective detection or flame ionization detection (HS/GC/MSD or FID). Non-volatiles were extracted with 10% aqueous ethanol and 100% n-heptane food-simulating solvents, maintained at 40°C for up to 10 days. The non-volatiles in the materials and those migrating into the food-simulating solvents were determined by high-performance liquid chromatography (HPLC) with ultraviolet and/or photodiode array detection. The results obtained from the HS/GC/MSD suggest that no new chemicals were detected by either gamma- or e-beam irradiation when compared with non-irradiated specimens. The major volatiles in the copolymers were acetaldehyde and 2-methyl-1,3-dioxolane. The concentrations of acetaldehyde increased from 1.24-1.96 mg kg^-1 to 1.94-3.65, 3.52-7.23 and 5.45-15.37 mg kg^-1 after exposure to 5, 25 and 50 kGy doses, respectively. The concentrations of 2-methyl-1,3-dioxolane decreased from 2.49-5.26 mg kg^-1 to 2.07-3.13, 1.33-2.14 and 0.64-2.24 mg kg^-1 after exposure to 5, 25 and 50 kGy doses, respectively. The results of analysis of the copolymers for non-volatiles show that irradiation did not produce any new detectable non-volatile chemicals. A 5 kGy dose had no detectable effect on either copolymer. The 25 and 50 kGy doses had slightly different effects with respect to gamma- and e-beam irradiation on low MW oligomers. However, these increased doses did not significantly affect migration. The concentration of most low molecular weight oligomers migrating into 10% ethanol and 100% heptane was ≤2 ng g^-1 of each oligomer for both copolymers. The cyclic trimer migrating from the 3% CHDM copolymer was approximately 4 ng g^-1; it was 3 ng g^-1 for the 31% CHDM copolymer. The overall results suggest that irradiation significantly increased levels of acetaldehyde but had no effect on non-volatile compounds migrating into food simulants.