This paper reports the antibacterial effect and physico-chemical characterization of films containing silver nanoparticles for use as food packaging. Two masterbatches (named PEN and PEC) con- taining silver nanoparticles embedded in distinct carriers (silica and titanium dioxide) were mixed with low-density polyethylene (LDPE) in different compositions and extruded to produce plain films. These films were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetric analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR). The morphology of the films showed the formation of agglomerates of nanoparticles in both PEN and PEC composites. X-ray analyses confirmed the presence of SiO2 in PEN samples and TiO2 in PEC samples. Thermal analyses indicated an increase in thermal stability of the PEC compositions. The antimicrobial efficacy was determined by applying the test strain for Escherichia coli and Staphylococcus aureus, according to the Japanese Industrial Standard Method (JIS Z 2801:2000). The films analyzed showed antimicrobial properties against the tested microorganisms, presenting better activity against the S. aureus than E. Coli. These findings suggest that LDPE films with silver nanoparticles are promising to provide a significant contribution to the quality and safety of packaged food.

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Several mutagenic agents may be present in substances released in the environment, which may cause serious environmental impacts. Among these substances, there is a special concern regarding the widespread use of silver nanoparticles (AgNP) in several products due to their widely known bactericidal properties, including in the medical field and the food industry (e.g., active packaging). The assessment of the effects of AgNP released in the environment, having different concentrations, sizes, and being associated or not to other types of materials, including polymers, is therefore essential. In this research, the objective was to evaluate the genotoxic and cytotoxic effects of AgNP (size range between 2 and 8 nm) on root meristematic cells of Allium cepa (A. cepa). Tests were carried out in the presence of colloidal solution of AgNP and AgNP mixed with carboxymethylcellulose (CMC), using distinct concentrations of AgNP. As a result, when compared to control samples, AgNP induced a mitotic index decrease and an increase of chromosomal aberration number for two studied concentrations. When AgNP was in the presence of CMC, no cytotoxic potential was verified, but only the genotoxic potential for AgNP dispersion having concentration of 12.4 ppm.

Active food packaging containing antimicrobial additive goes beyond traditional functions of packaging, once it can extend food shelf life maintaining its quality, safety and reducing postharvest losses by controlling food spoilage. Among several antimicrobial additives employed in polymeric films for packaging, metallic nanoparticles outstand due to its facility for synthesis, low-cost of production, and intense antimicrobial properties. In this work, extruded plain films of low-density polyethylene (LDPE) containing silver nanoparticles (AgNPs) embedded in SiO 2 and TiO 2 carriers (namely MS and MT, respectively) were produced and used as active packaging for maintaining the physicochemical and microbiological quality of carrots (Daucus Carota L. cv. Brasília). The neat (LDPE) and composite films containing MS and MT were characterized by scanning electron microscopy and permeability to oxygen and used for packaging fresh-cut sliced carrots stored at 10°C for 10 days. After the storage time, the physicochemical properties of carrots were characterized, while the antimicrobial properties of films and AgNP migration were investigated. Our results revealed that both MT and MS packages showed antimicrobial activity even for films containing low concentration of AgNP. In addition, AgNP antimicrobial activity demonstrated to be carrierdependent, once MT-LDPE showed improved performance compared to MS-LDPE. Regarding the physicochemical properties of packaged carrot, lower soluble solids and weight loss and higher levels of ascorbic acid were observed for carrots packaged with MT-LDPE films (compared to MS-LDPE), leading to a better postharvest quality conservation. Such differences observed in physicochemical properties of carrots are related to the distinct antimicrobial and film permeability properties for each composite film. In addition, under the conditions employed in this study, AgNP migration from the packages to fresh-cut carrot was not observed, which is highly desirable for food packaging safety, indicating the potential of such active packages for food preservation application.

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A portable flow board system was developed in the present study with the aim to fa cilitate lab-scale experiments of controlled atmosphere (CA) with fruits and vegetables. This sturdy flow board combines ease fabrication, low cost and gas economy. Its functionality is provided by manifolds and gas mixers. Each gaseous component is supplied by a gas cylinder through a differential valve of adjusted pressure control, generally at 6 kPa, and forced through 13 standardized restrictors coupled to each manifold output. Controlled atmospheres are then formed with one, two or three gases in 13 gas mixers affixed to the flow board base, which are further conducted through flexible tubes to storage mini-chambers that can also be used to study metabolic consumption and production of gaseous components. The restrictors used in the flow gaseous components were manufactured from microhematocrit test-type capillary glass tubes following the hot forming method under continuous air flow. The portable flow board showed to be low cost and simple post-harvest equipment that allows preparing controlled atmospheres in open systems with stable composition and flow, in a manner similar to traditional flow boards with control of gas escape by barostats. KEYWORDS:Flow-board, Flux control, Gas flow, Method, Gas mixer, Restriction. FLUXCENTRO PORTÁTIL PARA EXPERIMENTOS COM ARMAZENAMENTO EM ATMOSFERA CONTROLADA DE FRUTAS E HORTALIÇAS EM MINI-CÂMARASRESUMO: Para facilitar os ensaios de atmosfera controlada em laboratórios que estudam condições experimentais de armazenagem de frutas e hortaliças, desenvolveu-se o fluxcentro portátil de restrições, que agrega facilidade de confecção, baixo custo e economia no uso de gases. Sua funcionalidade é propiciada pelos distribuidores e misturadores de gases. Cada componente gasoso proveniente de um cilindro de gás através de uma válvula diferencial de controle da pressão é regulado, geralmente a 6 kPa, e forçado através de 13 restrições padronizadas acopladas a cada saída do distribuidor. A seguir, em 13 misturadores afixados na base, formam-se as atmosferas controladas com 1, 2 ou 3 componentes, que são conduzidas por tubo flexível a minicâmaras de armazenamento, que servem também para estudos de consumo e produção metabólica de componentes gasosos. As restrições para aplicar os mencionados fluxos especificados de componentes gasosos foram produzidas a partir de tubos capilares de vidro para exame de microhematócrito, pelo método da moldagem a quente sob fluxo continuado. O fluxcentro portátil é um equipamento simples e de baixo custo, que possibilita a preparação de atmosferas controladas em sistema aberto de composição e fluxos estáveis, de maneira similar aos tradicionais fluxcentro de controle com escape de gás através de barostatos.

␤-Galactosidase catalyzes the hydrolysis of lactose to glucose and galactose. The hydrolysis of lactose is a promising process in the food industry for the development of new products with no lactose in their composition. The elimination of lactose allows the consumption of milk for the great percentage of the world population (about 70%) which suffers of lactose intolerance. Also, cheese whey is an abundant subproduct of the dairy industry that contains 50 g/L of lactose. After hydrolysis, it may be used in the food industry for development of new products with no lactose contents. The immobilization of the enzyme allows its use in continuous process and the reuse of the enzyme, what may reduce costs in the lactose hydrolysis process. Therefore, in this work, ␤-galactosidase from Kluyveromyces fragilis was immobilized on different activated supports. The best derivative was obtained by immobilizing the enzyme on chitosan coagulated with KOH and activated with glutaraldehyde, both steps carried out at 50 • C. The immobilization yield and recovered activity were 100%. The pH and temperature of maximum activity was similar of the soluble enzyme (pH 7 and 45 • C). An enzyme load as high as 247 mg of protein per gram of support could be reached. The operational stability of the immobilized enzyme was higher than the soluble one. After four cycles of lactose hydrolysis (20 minutes each), at 40 • C and pH 7; the immobilized enzyme lost only 17% of the initial activity.D-Hydantoinase (EC 3.5.2.2, dihydropyrimidinase) catalyses the hydrolytic opening of DL-5-substituted hydantoins to Ncarbamoyl-D-amino acids. Immobilization and stabilization of enzymes may allow their reuse in many cycles of the reaction, decreasing the process costs. In this work, commercial D-hydantoinase from Vigna angulares was immobilized by multipoint covalent attachment on organic supports chitosan and agarose using different strategies. The best derivatives were obtained by immobilizing the enzyme at 25 • C and pH 10.05 for 24 hours, in the presence of Zn 2+ or Mg 2+ ions. Using agarose activated with glyoxyl groups, all offered enzyme was immobilized and 58% of that was measured in the derivative (recovered activity). The immobilized enzyme was 89-fold more stable than the soluble enzyme at 70 • C and pH 9.0. By immobilizing the enzyme on the hybrid gel chitosan-alginate activated with epoxy groups, it was achieved recovered activity of 40% and stabilization factor of ca. 27. These best derivatives and soluble enzyme were used in the hydrolysis of phenylhydantoin to Ncarbamoyl-D-phenylglycine, achieving 99% of conversion after 3, 9 and 15 hours of reaction using soluble enzyme, glyoxyl-agarose and epoxy-chitosan-alginate enzyme derivatives, respectively. The high enantioselectivity of the soluble enzyme was maintained after immobilization in both supports.We present a multilayer microfluidic device to simultaneously conduct distinct experiments. The concept is based on the decoupling of pressure drop from residence time. The device is fabricated...

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