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Resumo: Uma blenda de polietileno de alta densidade e polietileno de baixa densidade (PEAD/PEBDL) comumente utilizada em filmes de embalagem foi modificada com argila montmorilonita organofílica comercial para obter nanocompósitos com melhores propriedades de barreira. Amostras com 5 e 7,5% de argila (em massa) foram estudadas em diferentes condições de processamento. Filmes produzidos com os nanocompósitos foram avaliados quanto à dispersão da argila por difração de raio X e Microscopia Eletrônica de Transmissão. As propriedades de barreira dos filmes foram determinadas pelas medições de permeabilidade ao oxigênio e ao vapor d'água. As propriedades mecânicas e ópticas também foram determinadas. Observou-se uma estrutura com a argila parcialmente esfoliada e intercalada. A permeabilidade ao oxigênio diminuiu significativamente enquanto a permeabilidade à água foi pouco influenciada. As propriedades mecânicas e a transparência dos filmes foram pouco alteradas. O modelo de Nielsen foi aplicado para os dados de permeabilidade relativa e demonstrou ser um ótimo recurso para a avaliação do grau de esfoliação da argila para as diferentes amostras, que foram confirmadas pelas análises realizadas em microscopia eletrônica de transmissão. Palavras-chave: Nanocompósitos, blendas poliméricas, propriedades de barreira, montmorilonita. PEAD/PEBDL Composites -Evaluation of the Exfoliation of Organophilic Clay Using the Nielsen Model and of the Mechanical, Optical and Permeability PropertiesAbstract: A typical high density polyethylene and linear low density polyethylene (HDPE/LLDPE) blend used in flexible packaging was modified with commercial organophylic montmorilonite clay to obtain nanocomposites with superior barrier properties. Samples with 5 and 7.5% of clay were prepared under different processing conditions. Films produced from the nanocomposites were evaluated in terms of oxygen and water vapor permeation and also by X-ray diffraction and Transmission Electron Microscopy. Tensile and optical properties were also evaluated. The clay showed to be intercalated and partially exfoliated. The oxygen permeation was mainly reduced and the vapor permeation was weakly modified. The mechanical properties and transparency did not change significantly. Nielsen's model was applied considering the relative permeability coefficient. This method was able to give an estimate of the exfoliation state of the samples, supported by the transmission electron microscopy.

SUMMARYThe performance of oxygen scavengers can be infl uenced by several conditions, such as temperature (T) and relative humidity (RH), which are considered to be the two major factors. Therefore, the development of new scavengers requires the study of their performance, with these conditions varied. In this paper, the response surface methodology (RSM) was used to study the performance of a newly developed oxygen scavenger sachet and to model the infl uences of T and RH and their interaction on the absorption capacity and rate constant of the developed sachet. Commercial oxygen scavenger sachets were used for comparison purposes. The oxygen absorption capacity and rate constant were evaluated with a 2 2 factorial design with a central point. The results showed that each absorber sachet presented a different behaviour and there were signifi cant interactions between T and RH; so, the RSM was the most appropriate for these studies. The developed sachet presented a better performance compared with the commercial ones at 23°C and 53% RH, which represents the condition for commercialization at room temperature of foods of intermediary water activity, while in the extreme conditions (100% RH and 37°C) all sachets present a similar absorption capacity.

SUMMARYWest Indian cherry (Malpighia glabra L.) and pineapple (Ananas comosus (L.) Meer) juice clarification by cross-flow UF, using polysulphone hollow fiber and ceramic tubular membranes with, respectively, nominal molecular weight cut off values of 100kDaltons and average pore diameters of 0.01µm, were studied. The influence of enzymatic treatment using enzyme concentrations of 20, 100 and 300mg/L, a time of 90min and a temperature of 40ºC for depectinization was verified. The juices were then clarified in a laboratory scale filtration unit, with an effective filtration area of 0.12m 2 for the polysulphone hollow fiber membrane and of 0.005m 2 for the ceramic tubular membranes. The influence of enzymatic treatment on viscosity, turbidity and total pectin of the juice, before ultrafiltration, is reported. Membrane performance was evaluated in terms of flow rate and clarity of the permeate. The permeate flow rate of depectinized pineapple juice was higher (30 -60%) for both membranes. Depectinized West Indian cherry juice presented a lower permeate flow rate for the polysulphone hollow fiber membrane. The increase in permeate flow rate, with the use of the 300mg/L and 100mg/L enzyme concentration was not significant, so it is economically advantageous to ultrafilter depectinized juice, treated with an enzyme concentration of 20mg/L.

The electrospinning of cellulose acetate (CA) was investigated to develop biodegradable nanostructured membranes for the controlled release of drugs used to treat skin wounds. CA nanofibers were successfully prepared via the electrospinning in the four mixed solvents acetic acid : water; acetone : water; DMAc : acetone; DMAc : acetone : water. Design of experiments (DOE) was applied to see what combinations of parameters could affect the production of electrospun microfibers and nanofibers to optimize the process. The results of this work indicated that both the processing parameters and the solvent mixtures were responsible for the fiber diameter and nanostructure membrane appearance. The optimized condition for each solvent mixture was obtained and compared with each one of the others. The best conditions achieved were dimethylacetamida (DMAc) : acetone with 17% of CA, which provided homogeneous and free bead fibers with an average diameter of 295 nm. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

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O presente estudo teve como objetivo apresentar as mais recentes tendências do setor de embalagens alimentícias no mercado nacional e internacional. Foram abordados os conceitos de embalagens ativas e inteligentes, assim como suas funções, a composição, o formato, as reações químicas envolvidas, a forma de atuação de alguns tipos de embalagens, aplicações e os benefícios da sua utilização pela indústria de alimentos. Essas embalagens são planejadas e permitem interações com os alimentos a fim de manter a qualidade, a integridade, o frescor e a segurança do produto embalado. As inovações tecnológicas já são estabelecidas e bem aceitas em alguns países e conferem benefícios à conservação de grande variedade de alimentos. No Brasil, essas embalagens são tecnologias emergentes que estão em fase de adaptação no mercado nacional e de desenvolvimento por meio da pesquisa de novos mecanismos que podem ser empregados nas mais diversas aplicações.

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