Development of active and nanotechnology-based smart edible packaging systems: physical-chemical characterization

This work aims at characterising polysaccharide-based films without (GA) and with the incorporation of free natamycin (GA-NA) and natamycin-loaded in a smart delivery device consisting in poly(N-isopropylacrylamide) nanohydrogels (GA-PNIPA). Transport properties (water vapour, oxygen and carbon dioxide permeabilities), mechanical properties (tensile strength and elongation-at-break), opacity, water sensitivity (moisture content and contact angle) and thermal properties (differential scanning calorimetry and thermogravimetric analyses) were evaluated. Chemical interactions were studied by means of Fourier transform infrared spectroscopy and scanning electron microscopy was used to verify the presence of natamycin and nanohydrogel particles in the film matrix. The results show that natamycin and natamycin-loaded poly(N-isopropylacrylamide) (PNIPA) nanohydrogels can be successfully added to edible films without changing their main packaging properties. However, tensile strength decreased (p < 0.05) when both natamycin and natamycin-loaded PNIPA nanohydrogels were incorporated (from 24.44 to 17.02 and 16.63 MPa, for GA-NA and GA-PNIPA, respectively). GA-NA and GA-PNIPA films are more opaque and showed to be more sensitive to water (i.e. higher values of moisture content and decrease of contact angle) than GA films. Scanning electron microscopy images confirmed the presence of natamycin and poly(N-isopropylacrylamide) nanohydrogels in the films’ matrix. Since natamycin could be successfully released from polysaccharide-based films, the system could be used as active packaging ingredient when used free in the matrix or as smart packing when loaded with PNIPA nanohydrogels.Miguel A. Cerqueira (SFRH/BPD/72753/2010) is a recipient of a fellowship from the Fundacao para a Ciencia e Tecnologia (FCT, POPH-QREN and FSE Portugal). The support of EU Cost Actions FA0904 and FA1001 is gratefully acknowledged

Photoluminescence and structure properties from mu c-Si:H and mu c-Si:H-PS samples

Microcrystalline and Porous on Microcrystalline Silicon thin films were produced. The photoluminescence characteristics of Porous on Microcrystalline Silicon were studied and compared with those from Microcrystalline and Porous Silicon grown on Silicon wafers. Under steady state it is possible to excite these samples with visible light at room temperature. This excitation gives rise to a red photoluminescence band, which is similar to that of Porous Silicon excited under the same conditions. MicroRaman and transmission spectroscopy shows that the Porous Silicon layer was produced below the Microcrystalline Silicon thin film that acts as a shield for excitation and emission of radiation with wavelength smaller than 500 nm. Sample thickness, crystallite size and crystallinity are determined. The results are discussed in terms of the theoretical framework based in the fluctuating quantum wire model for Porous Silicon.FCT-Praxis XX

Natamycin-loaded poly(n-isopropylacrylamide) nanohydrogels for smart edible packaging : development and characterization

The development of new formulations for antimicrobial agents release has attracted great attention due to the possibility of using such formulations in several applications (e.g. food packaging and surface treatments in biomedical devices). Smart packaging appears in the last years as one of the most promissory application to food packaging in order to enhance the capacity to maintain food quality and safety. Moreover, edible packaging, using edible and biodegradable biopolymers, has been stated as one of the promises in packaging science (e.g. fresh-cut products, cheese, fruits, fish). Based on this and in the fact that no work has been reported with the incorporation of smart nanohydrogels in edible packaging, a smart delivery device consisting in poly(N-isopropylacrylamide) nanohydrogels and polysaccharide- based films was developed. Polysaccharide-based films with and without the incorporation of natamycin-loaded poly(N-isopropylacrylamide) nanohydrogels were charactherized in terms of: transport (water vapour, oxygen and carbon dioxide permeabilities) and mechanical properties (tensile strength and elongation-at-break), opacity, water sensitivity (moisture content and contact angle) and thermal properties (differential scanning calorimetry - DSC and thermogravimetric analyses - TGA). Chemical interactions were studied by means of Fourier Transform Infrared Spectroscopy (FTIR) and scanning electron microscopy was used to verify the presence of nanohydrogel in the film matrix. [...

Subtle local structural variations in oxygen deficient niobium germanate thin film glasses as revealed by x-ray absorption spectroscopy

6 págs.; 4 figs.; 2 tabs. 16th International Conference on X-ray Absorption Fine Structure (XAFS16) ; Open Access funded by Creative Commons Atribution Licence 3.0The local electronic and crystal structure of niobium-lead-germanate, Nb2O5-PbO- GeO2 (NPG), glass thin films on silicon substrates were probed by XANES and EXAFS. NPG glasses are promising candidates for applications in nonlinear optical devices because they exhibit interesting optical characteristics such as high nonlinear third order optical susceptibility. In this work NPG glasses were prepared with pulsed laser deposition method with varying oxygen partial pressure to induce thin films with different oxygen stoichiometry. Previously, it was shown that oxygen stoichiometry has a very important effect to produce unusual high optical susceptibility. Detailed EXAFS and XANES analyses in a series of NPG thin films revealed the subtle variations in the local environment around Nb atoms and the Nb oxidation states caused by oxygen deficiencies. Published under licence by IOP Publishing LtdPeer Reviewe

Utilização de revestimentos/filmes edíveis para aplicações alimentares

A indústria alimentar procura constantemente novas estratégias para aumentar o tempo de prateleira dos alimentos. Nos últimos anos, os filmes e revestimentos edíveis têm sido considerados uma das tecnologias com potencial para alcançar tais objectivos, assegurando a segurança microbiológica e a protecção dos alimentos da influência de factores externos. Surgem constantemente inovações significativas na área das embalagens alimentares, sempre com o propósito de criar um sistema mais efectivo de conservação da qualidade dos alimentos, tornando-os mais atractivos para o consumidor. Uma das maiores preocupações no desenvolvimento de revestimentos/filmes é o uso de materiais provenientes de fontes renováveis, tais como hidrocolóides de origem biológica, e a incorporação de ingredientes funcionais que podem ser usados, por exemplo, como agentes antioxidantes e antimicrobianos. Tendo em consideração os mais recentes desenvolvimentos, o principal objectivo desta revisão é proporcionar aos leitores uma visão do estado-da-arte na área dos sistemas de filmes e revestimentos edíveis baseados em hidrocolóides, com um ênfase particular nos trabalhos realizados pelo grupo do Centro de Engenharia Biológica da Universidade do Minho. São discutidos os aspectos mais importantes desta tecnologia tais como as propriedades físicas, químicas, térmicas e mecânicas; as propriedades de transporte, em particular as relacionadas com as trocas de vapor de água, oxigénio e dióxido de carbono; a incorporação de compostos bioactivos (por exemplo antimicrobianos e antioxidantes) e a aplicação em produtos alimentares

Beta-carotene loaded oleogels’ texture and disintegration behaviour during in-vitro digestion

Food products are digested in different ways ; rigidity and different textures are characteristics that will influence how digestion will occur. Absorption of lipids and lipid-soluble components from food is quite complex and factors like lipid composition, breakdown of food matrices, emulsion droplet size and lipid solubilization within mixed micelles of bile salts will influence the digestive process (Dickinson, 2014) . In this work, two types of edible oleogels loaded with beta-carotene (0.01 % w/w) have been developed. The oleogels were produced through the gelling process of long chain triglycerides (oil phase) with a sterol-mix (formed by gamma-oryzanol and beta-sitosterol) or beeswax as the two oil gelators. We report on the morphological and textural characteristics, as well as on the cytotoxicity and digestive behaviour of the oleogels during a digestion simulation (i.e. mouth, stomach and small intestine) using a static harmonized in-vitro digestion method (Minekus et al., 2014). Textural results showed that sterol-based oleogels have an average hardness of 0.6 N, which is approximately 4 times higher than the values recorded for beeswax oleogels. Both gels presented adhesiveness values without significative differences. In-vitro digestion allowed concluding that both types of oleogels showed structural disintegration, namely during the final two steps that correspond to gastric and intestinal phase (as evaluated by visual inspection and fluorescence microscopy analysis). In addition, beeswax oleogels’ structure was less resilient than oryzanol oleogels. Cytotoxicity tests, using a human epithelial cell line (Caco-2) with PrestoBlue assay, showed that both undigested sterol-and beeswax-based oleogels (without beta-carotene) were not cytotoxic, up to 48 hours of contact . Beeswax-based oleogels loaded with beta-carotene showed the same non-toxic behaviour under the same conditions. Future work will be performed aiming at establishing the rel ationship between gels’ disintegration and beta-carotene bioavailabilityinfo:eu-repo/semantics/publishedVersio

GMOS-IFU Spectroscopy of 167-317 (LV2) Proplyd in Orion

We present high spatial resolution spectroscopic observations of the proplyd 167-317 (LV2) near the Trapezium cluster in the Orion nebula, obtained during the System Verification run of the Gemini Multi Object Spectrograph (GMOS) Integral Field Unit (IFU) at the Gemini South Observatory. We have detected 38 forbidden and permitted emission lines associated with the proplyd and its redshifted jet. We have been able to detect three velocity components in the profiles of some of these lines: a peak with a 28-33 km/s systemic velocity that is associated with the photoevaporated proplyd flow, a highly redshifted component associated with a previously reported jet (which has receding velocities of about 80-120 km/s with respect to the systemic velocity and is spatially distributed to the southeast of the proplyd) and a less obvious, approaching structure, which may possibly be associated with a faint counter-jet with systemic velocity of (-75 +/- 15) km/s. We find evidences that the redshifted jet has a variable velocity, with slow fluctuations as a function of the distance from the proplyd. We present several background subtracted, spatially distributed emission line maps and we use this information to obtain the dynamical characteristics over the observed field. Using a simple model and with the extinction corrected Halpha fluxes, we estimate the mass loss rate for both the proplyd photoevaporated flow and the redshifted microjet, obtaining (6.2 +/- 0.6) x 10^{-7} M_sun/year and (2.0 +/- 0.7) x 10^{-8} M_sun/year, respectively.Comment: 26 pages, 10 figures (6 are in colors), accepted by A