1. Polysaccharide-based films and coatings for food packaging: A review.Patricia Cazón, Gonzalo Velazquez, Jose A. Ramirez, Manuel Vazquez, 2017, pregledni znanstveni članek Opis: The accumulation of synthetic plastics, mainly from food packaging, is causing a serious environmental problem. It is driving research efforts to the development of biodegradable films and coatings. The biopolymers used as raw material to prepare biodegradable films should be renewable, abundant and low-cost. In some cases, they can be obtained from wastes. This review summarizes the advances in polysaccharide-based films and coatings for food packaging. Among the materials studied to develop biodegradable packaging films and coatings are polysaccharides such as cellulose, chitosan, starch, pectin and alginate. These polysaccharides are able to form films and coatings with good barrier properties against the transport of gases such as oxygen and carbon dioxide. On the other hand, tensile strength and percentage of elongation are important mechanical properties. Desirable values of them are required to maintain the integrity of the packed food. The tensile strength values showed by polysaccharide-based films vary from each other, but some of them exhibit similar values to those observed in synthetic polymers values. For example, tensile strength values of films based on high amylose starch or chitosan are comparable to those values found in high-density polyethylene films. The values of percentage of elongation are the main concern, which are far from the desirable values found for synthetic polymers. Researchers are studying combinations of polysaccharides with other materials to improve the barrier and mechanical properties in order to obtain biopolymers that could replace synthetic polymers. Functional polymers with antimicrobial properties, as that the case of chitosan, are also being studied.
Ključne besede: Cellulose, Chitosan, Starch, Water vapour permeability, Tensile strength, Percentage of elongation at break
Objavljeno v RUNG: 14.12.2020; Ogledov: 2329; Prenosov: 0
Gradivo ima več datotek! Več... |
2. Novel composite films based on cellulose reinforced with chitosan and polyvinyl alcohol: Effect on mechanical properties and water vapour permeabilityPatricia Cazón, Manuel Vazquez, Gonzalo Velazquez, 2018, izvirni znanstveni članek Opis: Novel composite films were prepared by dissolving microcrystalline cellulose (3–5% w/w) in NaOH/urea solution, followed by coagulation in acetic acid solution. The regenerated cellulose films were immersed in chitosan-polyvinyl alcohol solutions at concentrations of 0–1% w/w and 0–4% w/w, respectively. Tensile strength, percentage of elongation at break, Young's modulus and water vapour permeability were measured to assess the effect of each compound on the mechanical and barrier properties. Polynomial models were obtained to evaluate the effect of the formulation on the measured properties. The microstructure was analysed by scanning electron microscopy. Results showed tensile strength values in the range 27.75–78.48 MPa, similar to usual synthetic polymer films. Percentage of elongation at break ranged from 0.98 to 12.82%, increasing when polyvinyl alcohol and chitosan increased. Young's modulus ranged from 2727.04 to 4217.25 MPa, showing higher values than pure chitosan and polyvinyl alcohol films. The highest value was reached combining cellulose and polyvinyl alcohol without chitosan. The water vapour permeability (1.78·10−11-4.24·10−11 g/m s Pa) showed 2 orders of magnitude higher than that of synthetic polymers, but lower than pure chitosan and polyvinyl alcohol films. Results showed that it is feasible to obtain cellulose-chitosan-polyvinyl alcohol composite films with improved mechanical properties and water vapour permeability.
Ključne besede: Regenerated cellulose, Tensile strength, Elongation at break, Young's modulus, Water vapour permeability
Objavljeno v RUNG: 14.12.2020; Ogledov: 2353; Prenosov: 0
Gradivo ima več datotek! Več... |
3. Cellulose-glycerol-polyvinyl alcohol composite films for food packaging: Evaluation of water adsorption, mechanical properties, light-barrier properties and transparencyPatricia Cazón, Manuel Vazquez, Gonzalo Velazquez, 2018, izvirni znanstveni članek Opis: Nowadays consumers are aware of environmental problems. As an alternative to petrochemical polymers for food packaging, researchers have been focused on biopolymeric materials as raw material. The aim of this study was to evaluate mechanical properties (toughness, burst strength and distance to burst), water adsorption, light- barrier properties and transparency of composite films based on cellulose, glycerol and polyvinyl alcohol. Scanning electron microscopy, spectral analysis (FT-IR and UV–VIS-NIR) and differential scanning calorimetry were performed to explain the morphology, structural and thermal properties of the films. Results showed that polyvinyl alcohol enhances the toughness of films up to 44.30 MJ/m3. However, toughness decreases when glycerol concentration is increased (from 23.41 to 10.55 MJ/m3). Water adsorption increased with increasing polyvinyl alcohol concentration up to 222%. Polyvinyl alcohol increased the film thickness. The films showed higher burst strength (up to 12014 g) than other biodegradable films. The films obtained have optimal values of transparency like those values of synthetic polymers. Glycerol produced a UV protective effect in the films, an important effect for food packaging to prevent lipid oxidative deterioration. Results showed that it is feasible to obtain cellulose-glycerol-polyvinyl alcohol composite films with improved properties.
Ključne besede: Cellulose, Toughness, Burst strength, Distance to burst, Water adsorption, Transparency
Objavljeno v RUNG: 14.12.2020; Ogledov: 2431; Prenosov: 0
Gradivo ima več datotek! Več... |
4. Novel composite films from regenerated cellulose-glycerol-polyvinyl alcohol: Mechanical and barrier propertiesPatricia Cazón, Gonzalo Velazquez, Manuel Vazquez, 2019, izvirni znanstveni članek Opis: Cellulose is considered as an alternative for the demand of biocompatible and environmentally friendly food packaging. The aim of this study was to evaluate a composite film from regenerated cellulose combined with polyvinyl alcohol. Glycerol was used as a plasticizer. Mathematical models were used to describe the effect of the film structure on the mechanical (tensile strength, percentage of elongation at break) and barrier properties (water vapour permeability, light-barrier properties and transparency). The morphology, structural and thermal properties were evaluated by spectral analysis (FT-IR and UV-VIS-NIR), scanning electron microscopy and dif- ferential scanning calorimetry. Models predict cellulose-glycerol-polyvinyl alcohol films with tensile strength values from 25.9 to 369 MPa, similar to that of synthetic polymer films. The elongation at break of the developed films (0.89–18.7%) was lower than that of synthetic polymer films. The water vapour permeability obtained (2.32·10−11 - 3.01·10−11 g/s·m·Pa) was higher than that of petrochemical-based plastics. Cellulose films re- inforced with polyvinyl alcohol showed a smooth surface. Results showed that it is viable to accomplish com- posite films from cellulose-polyvinyl alcohol-glycerol with enhanced mechanical properties. The obtained films showed top values of transparency. The addition of glycerol resulted in films with a UV protective effect which could be important in food packaging to prevent lipid oxidative deterioration.
Ključne besede: Regenerated cellulose, Tensile strength, Water vapor permeability, Anti-plasticizer, DSC, UV protection
Objavljeno v RUNG: 14.12.2020; Ogledov: 2319; Prenosov: 0
Gradivo ima več datotek! Več... |
5. Characterization of mechanical and barrier properties of bacterial cellulose, glycerol and polyvinyl alcohol (PVOH) composite films with eco-friendly UV-protective propertiesPatricia Cazón, Gonzalo Velazquez, Manuel Vazquez, 2020, izvirni znanstveni članek Opis: Highly flexible composite films based on bacterial cellulose, glycerol and polyvinyl alcohol (PVOH) with UV barrier properties were developed. The open nanoscale network of bacterial cellulose allowed to combine it with glycerol and polyvinyl alcohol by immersion. This procedure kept intact the bacterial cellulose structure. The interactions among bacterial cellulose, glycerol and PVOH were analyzed using scanning electron microscopy, infrared spectroscopy, thermogravimetry and differential scanning calorimetry. In general, the addition of PVOH reinforced the bacterial cellulose matrix, meanwhile glycerol showed a significant plasticizing effect. Formulations with PVOH and glycerol reached a maximum value of 49.89% of elongation and a good resistance to rupture of 13.78 MPa. The water vapour permeability ranged from 1.87·10−11 to 2.04·10−10 g/m s Pa. The UV-VIS spectral analysis showed that glycerol decreased the transmittance in the UV area and polyvinyl alcohol enhanced the transparency values of the samples in the VIS region. The transmittance in the UV-A, UV-B and UV- C areas for films based on bacterial cellulose with glycerol reached up to 5.59, 2.4 and 0.57%, respectively.
Ključne besede: Acetobacter xylinum, Tensile strength, Percentage of elongation at break, Young's modulus, Eco-friendly film
Objavljeno v RUNG: 14.12.2020; Ogledov: 2145; Prenosov: 0
Gradivo ima več datotek! Več... |
6. MOLECULAR MECHANISMS REGULATING ATP SIGNALING IN MOUSE SENSORY NEURONSTanja Bele, 2015, doktorska disertacija Opis: Coordinated and harmonized neuronal and glial responses to variations in extracellular levels of active soluble mediators such as ATP are essential in controlling neuronal activity. In pathological conditions involving sensory nervous system, elevations in extracellular ATP levels are believed to be one of the main reason for neuronal sensitization.
This notion led us to explore mechanisms of ATP release in sensory ganglia and we found that association among P2X purinergic receptors, their downstream effectors (CASK and CaMKII) and hemichannel Panx1 regulates inhibition of ATP release in basal conditions and that same players are involved in P2X3 receptor evoked-ATP release which globally suggest that even if observed proteins are expressed in different cells, they could be modulated by similar mechanisms and are possibly part of an “ATP-keeper molecular system” that finely regulates extracellular levels of ATP by its sensing and further adjustments of peculiar extracellular concentrations.
Further we showed that P2X3 receptors interact with Panx1 in sensory neurons and that molecular coupling between P2X3, CASK and Panx1 contributes to decoding of the complex purinergic signaling involved in nociception which represents a novel and interesting mechanism of pain regulation that could be precisely targeted in order to alleviate tedious disorders of sensory neurons.
Ključne besede: ATP, ATP release, purinergic signaling, trigeminal ganglion, pain, migraine, P2X3, CASK, Pannexin-1, synaptic strength
Objavljeno v RUNG: 10.12.2015; Ogledov: 5432; Prenosov: 232
 Celotno besedilo (3,75 MB) |
