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kGy Dose (kgy + dose)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

GAMMA IRRADIATION ON FROZEN AND PACKAGED HEADED SHRIMP

JOURNAL OF FOOD QUALITY, Issue 4 2009
V.K.G. ABREU
ABSTRACT The objective of this work was to evaluate the effects of , irradiation (0, 2, 4 and 6 kGy doses), applied on frozen and packaged headed shrimps, on pathogenic Vibrio cholerae O1 and Salmonella enteritidis bacteria, as well as on some of the physical and sensory characteristics of this kind of food. The 6 kGy dose was highly efficient in inhibiting V. cholerae O1 and S. enteritidis and in decreasing lipid oxidation in shrimps compared with the nonirradiated product. Shrimp texture was not affected by any of the irradiation doses studied, but the lightness of the surface color increased in shrimps irradiated with 6 kGy compared with those irradiated with 2 kGy. Shrimps irradiated with 6 kGy showed lower overall acceptability than those irradiated with 2 kGy or were nonirradiated. The application of , irradiation in doses up to 6 kGy on frozen and packaged headed shrimps could improve the microbiological quality of this commodity. PRACTICAL APPLICATIONS The use of , irradiation has the potential to ensure safety effectively by inactivating bacteria, increasing shelf life and maintaining food quality without significant chemical changes in the food matrix. Besides, this process can be applied to frozen and packaged products. Thus, irradiation of frozen and packaged shrimps could benefit the local processing industry, which could offer the international market a high-quality product, with an additional safety treatment. [source]

Biodegradable Water Absorbent Synthesized from Bacterial Poly(amino acid)s

MACROMOLECULAR BIOSCIENCE, Issue 3 2004
Masao Kunioka
Abstract Summary: Biodegradable hydrogels prepared by , -irradiation from microbial poly(amino acid)s have been studied. pH-Sensitive hydrogels were prepared by the , -irradiation of poly(, -glutamic acid) (PGA) produced by Bacillus subtilis and poly(, -lysine) (PL) produced by Streptomyces albulus in aqueous solutions. When the , -irradiation dose was 19 kGy or more, and the concentration of PGA in water was 2 wt.-% or more, transparent hydrogels could be produced. For the 19 kGy dose, the produced hydrogel was very weak, however, the specific water content (wt. of absorbed water/wt. of dry hydrogel) of this PGA hydrogel was approximately 3,500. The specific water content decreased to 200, increasing when the , -irradiation dose was over 100 kGy. Under acid conditions or upon the addition of electrolytes, the PGA hydrogels shrunk. The PGA hydrogel was pH-sensitive and the change in the volume of the hydrogel depended on the pH value outside the hydrogel in the swelling medium. This PGA hydrogel was hydrodegradable and biodegradable. A new novel purifier reagent (coagulant), made from the PGA hydrogels, for contaminated turbid water has been found and developed by Japanese companies. A very small amount of this coagulant (only 2 ppm in turbid water) with poly(aluminum chloride) can be used for the purification of turbid water. A PL aqueous solution also can change into a hydrogel by , -irradiation. The specific water content of the PL hyrdogel ranged from 20 to 160 depending on the preparation conditions. Under acid conditions, the PL hydrogel swelled because of the ionic repulsion of the protonated amino groups in the PL molecules. The rate of enzymatic degradation of the respective PL hydrogels by a neutral protease was much faster than the rate of simple hydrolytic degradation. [source]

Spectroscopic and thermal studies of poly[(N -vinylimidazole)- co -(maleic acid)] hydrogel and its quaternized form

POLYMER INTERNATIONAL, Issue 4 2008
Nursel Pekel
Abstract BACKGROUND: In this study, poly[(N -vinylimidazole)- co -(maleic acid)] (poly(VIm/MA)) hydrogels were prepared by ,-irradiation of ternary mixtures of N -vinylimidazole,maleic acid,water using a 60Co ,-source. Spectroscopic and thermal analyses of these hydrogels as a function of protonation showed that the results are consistent with the existence of an H-bridged complex when the imidazole rings are partially protonated. Finally, the efficiency and binding trends of Cu2+, Co2+, Cd2+ and Pb2+ ions with both protonated and unprotonated poly(VIm/MA) hydrogels were determined. RESULTS: Gelation of 90% was reached at around 180 kGy dose at the end of irradiation. The poly(VIm/MA) hydrogels synthesized were further protonated in HCl solutions with different concentrations. Hydrogels originally showed 450% volumetric swelling; this ratio reached 1900% after protonation at pH = 5.0. Fourier transform infrared spectral changes in the +NH stretching region (3200,3600 and 1173 cm,1) and the ring mode deformation at 915 cm,1 are consistent with the formation of an H-bridged complex between the protonated and unprotonated imidazole rings upon partial protonation. Similar changes were obtained from NMR spectra of both the protonated and unprotonated forms of the hydrogels. CONCLUSION: Protonated and unprotonated hydrogels have been used in heavy metal ion adsorption studies for environmental purposes. Adsorption decreased with decreasing pH value due to the protonation of the VIm ring. The adsorption of Me2+ ions decreased in the order Cu2+ > Co2+ > Cd2+ > Pb2+, which is related to the complexation stability as well as the ionic radius of the metal ions. These results show that P(VIm/MA) hydrogels can be used efficiently to remove heavy metal ions from aqueous solutions. However, the protonated form is a bad choice for heavy metal ion adsorption due to electrostatic repulsion forces; it can nevertheless be assumed to be a good choice for anion adsorption from environmental waste water systems. Copyright © 2007 Society of Chemical Industry [source]