Eber Antonio Alves Medeiros

Zinc Oxide Nanoparticles: Synthesis, Antimicrobial Activity and Food Packaging Applications

Zinc oxide (ZnO) is an inorganic compound widely used in everyday applications. ZnO is currently listed as a generally recognized as safe (GRAS) material by the Food and Drug Administration and is used as food additive. The advent of nanotechnology has led the development of materials with new properties for use as antimicrobial agents. Thus, ZnO in nanoscale has shown antimicrobial properties and potential applications in food preservation. ZnO nanoparticles have been incorporated in polymeric matrices in order to provide antimicrobial activity to the packaging material and improve packaging properties. This review presents the main synthesis methods of ZnO nanoparticles, principal characteristics and mechanisms of antimicrobial action as well as the effect of their incorporation in polymeric matrices. Safety issues such as exposure routes and migration studies are also discussed.

Edible Films from Methylcellulose and Nanoemulsions of Clove Bud (Syzygium aromaticum) and Oregano (Origanum vulgare) Essential Oils as Shelf Life Extenders for Sliced Bread

Consumers are increasingly demanding foods with lower synthetic preservatives. Plant essential oils are natural compounds with remarkable antimicrobial properties and may be incorporated as emulsions into water-soluble polymers to form antimicrobial films. Coarse emulsions (diameters of 1.3-1.9 μm) and nanoemulsions (diameters of 180-250 nm) of clove bud (Syzygium aromaticum) and oregano (Origanum vulgare) essential oils were produced through low-speed mixing and ultrasonication, respectively. Methylcellulose was added for film-forming purposes. Both essential oils reduced the rigidity and increased the extensibility of the methylcellulose films, effects that were even more pronounced for nanodroplets. Both essential oils lessened the counts of yeasts and molds in sliced bread during 15 days, and droplet size reduction provided a further improvement in antimicrobial properties. Due to increased bioavailability, less preservative content might be used and still deliver the same antimicrobial efficiency if encapsulated in smaller particles.

Physical–mechanical and antimicrobial properties of nanocomposite films with pediocin and ZnO nanoparticles

This work aimed to develop nanocomposite films of methyl cellulose (MC) incorporated with pediocin and zinc oxide nanoparticles (nanoZnO) using the central composite design and response surface methodology. This study evaluated film physical-mechanical properties, including crystallography by X-ray diffraction, mechanical resistance, swelling and color properties, microscopy characterization, thermal stability, as well as antimicrobial activity against Staphylococcus aureus and Listeria monocytogenes. NanoZnO and pediocin affected the crystallinity of MC. Load at break and tensile strength at break did not differ among films. NanoZnO and pediocin significantly affected the elongation at break. Pediocin produced yellowish films, but nano ZnO balanced this effect, resulting in a whitish coloration. Nano ZnO exhibited good intercalation in MC and the addition of pediocin in high concentrations resulted crater-like pits in the film surfaces. Swelling of films diminished significantly compared to control. Higher concentrations of Nano ZnO resulted in enhanced thermal stability. Nanocomposite films presented antimicrobial activity against tested microorganisms.

Use of allyl isothiocyanate and carbon nanotubes in an antimicrobial film to package shredded, cooked chicken meat

We developed antimicrobial packaging incorporated with allyl isothiocyanate (AIT) and carbon nanotube (CNT), and this packaging was used for shredded cooked chicken meat inoculated with Salmonella Choleraesuis. The following parameters were analysed during the 40 days of storage: microbial counts, colour characteristics and changes in the oxidation of the meat as well as changes in the mechanical properties of the film, the structure of the antimicrobial film and the diffusion of the antimicrobial agent into the food. The incorporation of AIT into the films increased the elongation at the break (E) value of the films and decreased the tensile strength (TS) value of the films. The CNT was important to retain the AIT which is a volatile substance in the film. The diffusion of the AIT from the film into the chicken reduced the microbial contamination, controlled oxidation and reduced the colour changes. Thus, these packages were effective for the 40 days of storage.

Development of chitosan/montmorillonite nanocomposites with encapsulated α-tocopherol.

Nanocomposites of chitosan (CS) were developed and characterized in a full factorial design with varying levels of montmorillonite (MMTNa) and encapsulated tocopherol (toc-encap). The structural properties (XRD, FTIR), morphology (TEM), hygroscopic properties (water vapour permeability, hydrophobicity, sorption isotherms) and optical properties (haze, CIELab parameters) of the resulting materials were evaluated. Toc-encap contents up to 10% influenced the intercalation of MMTNa in the CS matrix, resulting in films with reduced water vapour permeability (3.48×10(-11)(g/msPa)), increased hydrophobicity (ΔGHydroph |7.93-59.54|mJm(-2)) and lower equilibrium moisture content (EMC), thus showing potential for active food packaging materials. At levels above 10%, toc-encap agglomerates occurred, which deteriorated the properties of the resulting films, as shown with the TEM. As the toc-encap content increased, the films became slightly more yellow, more irregular and less transparent, with a higher haze index.

Antimicrobial edible coating in post-harvest conservation of guava

This study aimed to develop an antimicrobial edible coating and to evaluate its efficiency in preserving guava. Guava samples were submitted to five treatments: without coating, coating of cassava starch, coating of cassava starch added with acetic acid, coating of cassava starch added with 1.0% and 1.5% chitosan. The following characteristics were analyzed: color of pulp and peel, texture, mass loss, total soluble solids, filamentous fungi and yeast counting. Peel green color of the fruits treated with antimicrobial coatings was preserved and the pulp color of all treatments changed from pink to intense red during the storage. Fruits treated with antimicrobial coatings presented lower mass loss, when compared with the control fruits. There was a decrease in the total soluble solid values of the control group during storage, whereas in the other treatments, the sugar content was preserved until the 8th day. Fruits treated with 1.0% and 1.5% of chitosan showed the lower filamentous fungi and yeast counting when compared with the control. The use of antimicrobial edible coatings contributes to the preservation of guava, reducing microbial growth and increasing its post-harvest life.

Application of PCDA/SPH/CHO/Lysine vesicles to detect pathogenic bacteria in chicken

During the course of infection, Salmonella must successively survive the harsh acid stress of the stomach and multiply into a mild acidic compartment within macrophages. Inducible amino acid decarboxylases are known to promote adaptation to acidic environments, as lysine decarboxylation to cadaverine. The idea of Salmonella defenses responses could be employed in systems as polydiacetylene (PDA) to detect this pathogen so important to public health system. Beside that PDA is an important substance because of the unique optical property; that undergoes a colorimetric transitions by various external stimuli. Therefore 10,12-pentacosadyinoic acid (PCDA)/Sphingomyelin(SPH)/Cholesterol(CHO)/Lysine system was tested to determine the colorimetric response induced by Salmonella choleraesuis. PCDA/SPH/CHO/Lysine vesicles showed a colour change even in low S. choleraesuis concentration present in laboratory conditions and in chicken meat. Thus, this work showed a PCDA/SPH/CHO/Lysine vesicle application to simplify routine analyses in food industry, as chicken meat industry.

Starch, cellulose acetate and polyester biodegradable sheets: Effect of composition and processing conditions

The production of biodegradable plastic materials using natural resources has aroused increased attention due to environmental concerns. This study aimed to manufacture novel, commercially feasible, biodegradable sheets by flat die extrusion-calendering process produced with thermoplastic starch/plasticized cellulose acetate (TPS/PCA) and thermoplastic starch/plasticized cellulose acetate/poly (butylene adipate-co-terephthalate) (TPS/PCA/PBAT) blends, and to investigate the effects of composition and processing conditions, morphological characteristics, and thermal properties. The results showed that TPS/PCA and TPS/PCA/PBAT biodegradable sheets properties were highly dependent upon both composition and processing temperature. The morphological characteristics and thermal properties of the sheets demonstrated the good compatibility between TPS and PCA in TPS/PCA blends, mainly at higher processing temperatures, whereas TPS/PCA/PBAT sheets present a heterogeneous structure due to the poor compatibility between the components. TPS/PCA biodegradable sheets presented suitable processability and handleability characteristics that allow them to be considered as a novel eco-friendly, economically feasible alternative to conventional plastic materials.

Optical and structural properties of biodegradable whey protein isolate nanocomposite films for active packaging

ABSTRACT Films of whey protein isolate/sodium montmorillonite/citric acid nanocomposites were developed by casting. The objective of this study was to evaluate the effect of the sodium montmorillonite clay (MMT) and citric acid (CA) content on the water vapor barrier, optical, morphological and structural properties of whey protein isolate (WPI) films. The interaction between MMT (3 g/100 g of WPI) and CA (5 g/100 g of WPI) showed lower water vapor permeability (WVP). The addition of CA and MMT caused small alterations in the optical properties without affecting appearance, in more opaque films, in relation to the WPI. The scanning electron microscopy (SEM) showed possible dispersion results for films with 1% MMT, and 5 and 10% CA. Infrared Spectroscopic peaks (FTIR) showed interaction between CA, MMT and WPI.

Development of active packaging for the preservation of lyophilized pulp fruit

Innovative technologies are needed to maintain food freshness, quality and safety, while reducing concentrations of chemical additives. This work aimed the development of an active packaging material to preserve lyophilized tropical fruits pulp powder and to study the stability provided by the active packaging.