Laura Martins Fonseca

Action of ginger essential oil ( Zingiber officinale ) encapsulated in proteins ultrafine fibers on the antimicrobial control in situ

The ultrafine fibers were produced using a polymeric blend of soy protein isolate (SPI), polyethylene oxide (PEO), and zein at a ratio of 1:1:1 (v/v/v) by electrospinning. The ginger essential oil (GEO) was encapsulated in the ultrafine fibers and the morphology, Fourier-Transform Infrared Spectroscopy (FTIR) analysis, thermal properties and relative crystallinity were evaluated. The antimicrobial activity of ginger essential oil was evaluated against five bacteria (Listeria monocytogenes, Staphylococcus aureus, Escherichia coli 0157:H7, Salmonella typhimurium, and Pseudomonas aeruginosa). Based on the preliminary tests, the concentration of GEO selected to add in the polymer solution was 12% (v/v; GEO/polymer solution). The fiber produced with 12% (v/v) GEO was used for antimicrobial analysis and in situ application (in fresh Minas cheese) against L. monocytogenes by micro-atmosphere. The ultrafine fibers produced, regardless the concentration of the essential oil, presented homogeneous morphology with cylindrical shape without the presence of beads. The application of the active fibers containing 12% GEO showed high potential to be applied in food packaging to reduce microbial contamination.

Mechanical Analysis of Biodegradable Films from Native and Chemically Modified Potato Starches

The production of biodegradable films has been studied to be a substitute of conventional plastics. The use of starch in biodegradable films are of great interest and starch modification improves an increase to the mechanical properties the film. The mechanical properties were evaluated by Dynamic Mechanical Analysis (DMA). The aim of this study is to determine the mechanical properties of biodegradable films produced from native and chemically modified potato starch. The starch was extracted and subjected to chemical modification by oxidation in different concentrations of active chlorine. The biodegradable films were prepared with starch and glycerol as plasticizer, and were observed with an optical microscope to evaluate the morphology and their relationship with the strength. The tensile tests were performed at 80oC to evaluate the mechanical properties by means of stress-strain curves. The morphology of biodegradable potato starch films shows that the starch granules were partially gelatinized during the film formation. As the elastic modulus is a property which determines the stiffness of the material, by means of he DMA analysis it can be seen that oxidation results in beneficial changes in the mechanical properties of the films, because the modulus increased from 346.70 MPa for the native starch to 651.75 MPa to oxidized starch with 1.5% of active chlorine, respectively.

Development of Coating to Metallic Surfaces with Capacitive Capabilities for Applications in Electronics

The capacitive properties on aluminum alloy coated by sol-gel are evaluated in this work. The samples were anodized in a H2SO4 solution for three different times (15, 20 and 30 min) and subsequently covered by a sol-gel. The capacitance of the samples was evaluated by electrochemical impedance spectroscopy (EIS). Firstly the capacitance of the anodizing samples was evaluated. The second condition was the evaluation of the anodized samples coated by sol-gel. The better capacitance results obtained in the first condition was observed in the blank samples and by the 15 min anodized samples. After the sol-gel deposition, the influence of coating on the overall capacitance was observed. Their stability during the immersion time of the evaluation was observed as well.

Evaluation of Green Corrosion Inhibitors for Applying in Food Packaging

In this study, the inhibitor effect of Solidago chilensis extract as green corrosion inhibitor for anodized aluminum alloy samples was evaluated in NaCl 3%wt solution. This study was carried out for application on cans for pack of foods. The procedure of the surface treatment of the samples was done by anodizing followed by sealing in a solution containing the inhibitor. Essays of potentiostatic polarization and electrochemical impedance spectroscopy were done to evaluate the inhibitor effect. The mechanical analyses were performed on anodized samples to evaluate the influence of the thickness of anodization on the mechanical resistance of the samples. The potentiostatic essays indicated that a cathodic inhibitor effect occurs only in non-anodized samples and that the anodic effect of the inhibitor not appears on the anodized samples. The calculated efficiency of the inhibitor was 96 %. The EIS results indicated that the higher values of polarization resistance (16 kΩ) occur on anodized samples containing inhibitor after 72 hours of immersion in NaCl 3%wt. The mechanical essays indicated a non – significant difference between anodized and non – anodized samples.