摘要 :
Cork presents a range of diverse and versatile properties making this material suitable for several and extremely diverse industrial applications. Despite the wide uses of cork, its antimicrobial properties and potential applicati...
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Cork presents a range of diverse and versatile properties making this material suitable for several and extremely diverse industrial applications. Despite the wide uses of cork, its antimicrobial properties and potential applications have deserved little attention from industry and the scientific community. Thus, the main purpose of this work was the evaluation of the antibacterial properties of cork, by comparison with commercially available antimicrobial materials (Ethylene-Vinyl Acetate copolymer and a currently used antimicrobial commercial additive (ACA)), following the previous development and optimization of a method for such antimicrobial assay. The AATCC 100-2004 standard method, a quantitative procedure developed for the assessment of antimicrobial properties in textile materials, was used as reference and optimized to assess cork antibacterial activity. Cork displayed high antibacterial activity against Staphylococcus aureus, with a bacterial reduction of almost 100% (96.93%) after 90 minutes of incubation, similar to the one obtained with ACA. A more reduced but time-constant antibacterial action was observed against Escherichia coli (36% reduction of the initial number of bacterial colonies). To complement this study, antibacterial activity was further evaluated for a water extract of cork and an MIC of 6 mg mL(-1) was obtained against the reference strain S. aureus.
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Oxygen permeability data is relevant for selecting wine bottles closures. Market available stoppers, two natural and eight microagglomerated corks, were analysed for the oxygen ingress over time in stoppered bottles, under differe...
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Oxygen permeability data is relevant for selecting wine bottles closures. Market available stoppers, two natural and eight microagglomerated corks, were analysed for the oxygen ingress over time in stoppered bottles, under different temperatures (8, 23, and 40 degrees C), with and without contact between cork and wine simulant. Weibull model described well the oxygen ingress. Differences were found between cork types in long-term oxygen pressure (Po) and ingress rates (Tau). For microagglomerated corks, Po increased, and Tau decreased with temperature, following the Arrhenius behaviour, with estimated activation energies of 15.3 and 35.2 kJ mol-1, respectively. Microagglomerated corks exhibited slower initial oxygen ingress but higher long-term oxygen ingress than natural corks. Principal Component Analysis (PCA) showed that factors related to the bottleneckcork interface contributed more to the variance of the system than cork type. Liquid contact reduces oxygen ingress around five times. The temperature impact in the oxygen ingress was lower for natural corks.
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In the industrial production of natural cork stoppers, cork planks are cut transversely into strips and stoppers are bored in the axial direction, therefore with their cylinder axis parallel to the tree axial direction. The influe...
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In the industrial production of natural cork stoppers, cork planks are cut transversely into strips and stoppers are bored in the axial direction, therefore with their cylinder axis parallel to the tree axial direction. The influence of cutting direction of cork planks (transverse or longitudinal), and therefore the orientation of stoppers cylindrical axis (longitudinal or tangential, respectively) on yields, quality profile and porosity characteristics was studied in a random sampling of planks of different quality classes that were bored to produce 45 mm x 24 mm stoppers. The stoppers quality profile and production values were not influenced by the cutting direction, although in good quality planks (1(st)/2(nd)) the longitudinal cut led to a higher proportion of good quality stoppers in comparison to the transversal cut, 32% vs. 23%. Regarding porosity characteristics, pore orientation differed between the two cutting directions but not the porosity coefficient, with the exception of the poor quality classes.
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The kinetics of oxygen ingress into bottles closed with natural cork stoppers was investigated by a nondestructive colorimetric measurement method using the oxidation of an indigo carmine solution. In order to encompass the natura...
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The kinetics of oxygen ingress into bottles closed with natural cork stoppers was investigated by a nondestructive colorimetric measurement method using the oxidation of an indigo carmine solution. In order to encompass the natural variability of cork regarding its oxygen ingress into the bottle, 600 natural cork stoppers from different quality classes and produced from cork planks of different calipers were analyzed. The kinetics of oxygen transfer was similar in all cases and could be adjusted to logarithmic models. A significant variability was found for oxygen ingress into the bottles closed with natural cork stoppers: ingress at 12 months ranged from 0.3 to 4.8 mg; 21% of the stoppers reached the limit of oxygen quantification along the experiment. The results suggest that the variation of oxygen ingress is a consequence of the natural differing features in the cell dimensions and air volume within the stopper's structure.
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During bottling aging, the wine comes into contact with the cork stopper due to the horizontal position of the bottle. The release of compounds, such as cork phenolic compounds, thus take place between the cork and the wine, depen...
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During bottling aging, the wine comes into contact with the cork stopper due to the horizontal position of the bottle. The release of compounds, such as cork phenolic compounds, thus take place between the cork and the wine, depending on the type of cork stopper and the surface treatments applied. Many publications describe the extraction of these phenolic compounds in wine or hydroalcoholic solutions from natural corks, but few address microagglomerated corks, which are increasingly used by winemakers to seal their bottles. The aim of this study was therefore to compare the polyphenols, mainly hydrolysable tannins, transferred from natural and microagglomerated corks treated with supercritical CO2 into hydroalcoholic solutions. For this purpose, polyphenols released in macerates of natural and microagglomerated cork stoppers were identified and quantified by HPLC-DAD-ESI-QQQ. Suberic acid was also quantified. In this study, despite the high intra-“natural cork stopper” variability, significant differences were found between both types of stoppers for all polyphenols, the agglomerated corks releasing significantly less polyphenols; i.e., 25 times less. In contrast, suberic acid was extracted from both types of corks in similar concentrations; therefore, its extractability was not impacted by the type of stopper. A sensory profile was also carried out on the macerates. Macerates of natural cork stoppers were perceived with notes of “cardboard, dust, plank, wood” and “cork taint” significantly higher than supercritical CO2 treated microagglomerated cork stopper macerates. Moreover, the natural cork macerate with the highest content in polyphenol was perceived as being more bitter than that of microagglomerated cork stoppers.
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Champagne cork stoppers are a product made basically from cork, a natural and renewable resource extracted from cork oak forests in western Mediterranean regions. Each stopper is made up of an agglomerated cork body and two natura...
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Champagne cork stoppers are a product made basically from cork, a natural and renewable resource extracted from cork oak forests in western Mediterranean regions. Each stopper is made up of an agglomerated cork body and two natural cork discs. In 2009,60% of the world's champagne cork stoppers were produced in Catalonia, due to the importance of cava, champagne and other sparkling wines in neighbouring areas. The aim of this research was to provide environmental reference data on champagne cork stoppers production, and identify the industrial stages and operations that made the greatest impact. This research was carried out using life cycle assessment (LCA) methodology, and five of the most representative producers were analysed. The system considered all the processes involved in production after the forest management stage and one million champagne cork stoppers were taken as a functional unit (FU). Results showed that 53,886 kg of CO_2 eq. were emitted to produce the FU. It was observed that the champagne cork stopper manufacture stage represented between 57 and 67% of the environmental impact, depending on the category. Specifically, between 25 and 47% of the environmental impacts associated with this stage were caused by the body agglomeration operation, and between 21 and 29% were caused by the gluing of discs. On the other hand, some of the production stages such as the transport of raw cork and intermediate products, cork slab preparation or end of life stages represented a very small part of the total environmental impact of the product, less than 2%. Furthermore, it was observed that a champagne cork stopper produced by the most impacting company presented a higher impact, between 10 and 27% above the sector average, depending on the impact category; while the least impacting company presented between 12 and 32% less impact. These differences indicate that some companies can improve their production by adopting technology and production practices that some of their competitors have already put in place.
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Cork oak forest grows endemically in the coastal regions of the western Mediterranean basin, particularly in the Iberian Peninsula. The cork agro-forestry systems play a key role in ecological processes, and the outer bark, or cor...
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Cork oak forest grows endemically in the coastal regions of the western Mediterranean basin, particularly in the Iberian Peninsula. The cork agro-forestry systems play a key role in ecological processes, and the outer bark, or cork, can be extracted sustainability without damaging the tree or affecting biodiversity. Because of the properties of the cork, an important forestry and industrial structure has been developed around its most valuable goods. This paper describes the current global trade patterns in the Iberian Peninsula, where Portugal and Spain are world leaders. Although these countries bring most of their cork trade flows together with the rest of the world, there are clear differences between these sectors. The aim of this study was to identify these differences and to characterize each analysed sector from an economic perspective. The primary difference between the sectors lies in the characteristics of their supply chain and their capacity to generate wealth from raw cork. Portugal primarily produces and processes raw cork into products with high added value. Spain bases its cork sector on raw material and half-manufactured cork, and it is not able to use the full potential that cork provides. Catalonia is an exception because it is the global leader in the champagne stopper market. To encourage the development of the entire cork sector, every link in the supply chain should be strengthened through the establishment of companies and the generation of employment, and therefore the development of rural areas. Moreover, this industry must establish its own development strategies for the future, thereby increasing its investment in R&D and innovation in relation to the opportunities identified as follows: the potential for diversification beyond the wine market, the improvement potential for forest management and the enhancement of sustainability and eco-efficiency in every link of the cork supply chain. (C) 2015 Elsevier B.V. All rights reserved.
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Cork powder, the most important sub-product of cork processing, combined with thermoplastic matrixes like, high density polyethylene (HDPE), offer a new class of cork-polymer composite (CPC) materials with high added-value. Theref...
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Cork powder, the most important sub-product of cork processing, combined with thermoplastic matrixes like, high density polyethylene (HDPE), offer a new class of cork-polymer composite (CPC) materials with high added-value. Therefore, reinforcing strategies must be considered to increase the mechanical performance, especially when high content of cork powder is added to the formulation. Coconut fibres have several advantages, such as, low density, renewable source, low cost and biodegradability. The use of these fibres on the reinforcement of CPC materials will not only contribute to improve the mechanical performance but also for increasing the amount of natural component present on the final composition. The main goal of this work was to prepare HDPE/cork (50-50 wt.%) composites reinforced with discontinuous coconut fibres (5 and 10 wt.%) with and without the addition of coupling agent (2 wt.%) by extrusion. The developed reinforced cork based composites were characterized regarding its morphology and mechanical performance. Optical micrographs have shown a homogeneous distribution of the fibres. The coupling agent effect on CPC performance was also investigated. The tensile strength and tensile modulus of the reinforced composites were significantly improved with the addition of coupling agent. The use of 10 wt.% of coconut fibres in the presence of coupling agent promote an increase on maximum tensile strength of around 41 % comparing with the HDPE/cork (50-50 wt.%) composites. Scanning electron microscopy (SEM) micrographs of the tensile fractured specimens confirmed that the use of coupling agent promoted the interfacial adhesion between the fibres and the thermoplastic matrix. Since, like cork powder, coconut fibres have good thermal and acoustic properties, we consider that the novel reinforced CPC herein described have high potential to be used in building and construction systems and other structural 3D applications.
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Cork is a natural cellular material with a rather unique set of properties, and its best known application is as stopper for wine bottles. The cork tissue contains structural discontinuities, for example, lenticular channels (LCh)...
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Cork is a natural cellular material with a rather unique set of properties, and its best known application is as stopper for wine bottles. The cork tissue contains structural discontinuities, for example, lenticular channels (LCh), that influence the in-use performance of cork products. X-ray microtomography, in combination with image analysis, has been used for cork characterisation and provided new insights into the three-dimensional location of discontinuities, which are hidden for a visual inspection. It was demonstrated that the presence of LCh is positively correlated with cork density, and the void fraction of LCh in the lower part of a cork stopper is strongly related to the oxygen ingress in the bottle during the first month after bottling. The results contribute to better understanding the natural variation of cork properties.
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Abstract This work presents the evaluation of the porosity by image analysis, the quantitative analysis of the cell morphology from images obtained by scanning electron microscopy (SEM) and the oxygen transmission rate (OTR) of na...
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Abstract This work presents the evaluation of the porosity by image analysis, the quantitative analysis of the cell morphology from images obtained by scanning electron microscopy (SEM) and the oxygen transmission rate (OTR) of natural corks of different visual quality grades. Due to the natural variability of cork stoppers, statistically significant differences could not be established in the porosity of the corks according to their commercial quality. However, the determination of the surface porosity coefficient by image analysis in the tangential and axial sections of the corks allowed us to distinguish between high, medium and low quality classes. The cells in the tangential section were shaped between circular and hexagonal, with very regular perimeters regardless of the cork quality. While the cells of the radial and axial sections showed a square and rectangular shape, with more irregular perimeters, mainly in the lowest quality corks and in the axial section. Corks commercially classified as “flower”, “second” and “third” had the lowest OTR values and presented a similar statistical distribution in their cell perimeters in the axial section. While the corks with higher OTR values (superior and fourth qualities) corresponded with those with greater cell perimeters and greater dispersion in their distribution.
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