ABSTRACT
In order to promote barrier against ultraviolet radiation and increase of mechanical characteristics performance, nanocomposites of recycled polycarbonate/nano-zinc oxide (rPC/nZnO) with different nZnO content were prepared and submitted to doses of gamma-radiation (1050 kGy). The nanocomposites were also exposed to Xenon light source in a weather chamber viewing to evaluate the action of nZnO against ultraviolet light. The rPC/nZnO nanocomposites were characterized by thermogravimetry (TGA), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and infrared spectrometry (FT-IR). There was a progressive reduction of the glass transition temperature (T g) and degradation temperatures, T onset and T max, as function of gamma-radiation dose and nano-zinc oxide content. The lowering of the thermal properties was attributed to the alcoholysis reaction between hydroxyl groups onto the nZnO surface and carbonate linkages of the rPC during the molten state. WAXD revealed a possible chains arrangement (induction of crystallinity) and/or segregation of chains size (scission of rPC chains generating oligomers) associated to the alcoholysis reaction. The action of gamma-radiation as crosslinking agent was not effective. The degree of swelling is zero on account of the stabilization of rPC radicals by oxygen during gamma-radiation exposure. Before exposure to UV light the carbonyl index (CI) show trend to decreasecorroborating the scission of the rPC carbonate bonds. After 100 hours of exposure a recovering of the CI was noticed. The result was associated to the free radicals recombination and esterification reactions. In some extent the combined action of nZnO and gamma-radiation as barrier to UV light was successful.
ABSTRACT
A adequada manipulação do pescado desde sua captura até seu processamento tecnológico, além da manutenção das condições higiênico-sanitárias, o que inclui a qualidade da água utilizada na cadeia, influencia na carga microbiana inicial apresentada. A fim de retardar o processo de deterioração, diminuir as perdas e os riscos iminentes à saúde coletiva, como a propagação de agentes etiológicos de doenças alimentares, são empregados diferentes métodos de conservação. Os feixes de elétrons são utilizados em vários países e levam à destruição dos microrganismos por alterações em suas estruturas, as quais ocorrem pela remoção de elétrons de seus átomos. Objetivou-se, no presente trabalho, contribuir para a avaliação da eficiência da irradiação por feixe de elétrons na qualidade microbiológica de filés de corvina (M. furnieri) refrigerados, desembarcados no município de Niterói - RJ, Brasil. Foram realizadas contagem de bactérias heterotróficas aeróbias mesófilas, de bactérias heterotróficas aeróbias psicrotróficas e enumeração de Enterococcus spp. e, posteriormente, comparadas as amostras do grupo controle com as dos grupos irradiados a doses de 0,7 e 1,0kGy. Os peixes inteiros foram adquiridos no cais de Itaipu, filetados no mercado, embalados a vácuo e mantidos a ±4°C. Embora não tenha sido encontrada diferença estatisticamente significativa entre os três grupos (P>0,05) em nenhuma das análises, concluiu-se que o processamento utilizado foi eficaz na redução do crescimento das três bactérias pesquisadas no dia zero de ambos os grupos irradiados.
The proper handling of fish from capture to technological processing, as well as maintenance of sanitary conditions and the quality of water, can influence the initial microbial load presented. In order to slow down the deterioration process, the reduction of losses and eminent risk to public health as the spread of etiological agents of foodborne illness are different methods used for storage. Electron beams are used in several countries and lead to the destruction of microorganisms by changes in their structures, which occur by removing electrons from their atoms. The objective in the present study contributes to the evaluation of electron beam irradiation efficiency in microbiological quality of chilled croaker fillets (M. furnieri), landed in Niterói - RJ, Brazil. Were performed Bacteria Count Heterotrophic aerobic mesophilic, psychrotrophic bacteria Heterotrophic Aerobic and enumeration of Enterococcus spp. and subsequently compared to the control group of samples with the groups irradiated at doses of 0.7 and 1.0kGy. Whole fish were purchased from the Itaipu pier, threaded on the market, vacuum packed and kept at ±4°C. Although there was no statistically significant difference among the three groups (P>0.05) in any of the analyzes, it was concluded that the application of this technology was effective in reducing the growth of the three bacteria surveyed on day zero of both irradiated groups.
