This comprehensive book describes cork as a natural product, as an industrial raw-materials, and as a wine bottle closure. From its formation in the outer bark of the cork oak tree to the properties ...that are of relevance to its use, cork is presented and explained including its physical and mechanical properties. The industrial processing of cork from post-harvest procedures to the production of cork agglomerates and composites is described. Intended as a reference book, this is the ideal compilation of scientific knowledge on state-of-the-art cork production and use. * Presents comprehensive coverage from cork formation to post-harvest procedures * Explains the physical properties, mechanical properties and quality of cork * Addresses topics of interest for those in food science, agriculture and forestry
•It has been detected a deterioration of cork quality in the sampled stands.•Cerambycidae and Coroebus undatus are prevalent in the sampled stands.•Stands with good growing state showed a higher ...presence of Coroebus undatus.•It is advisable to extend the stripping cycle duration for obtaining good cork.•The same trees should be monitored in each consecutive cork sampling plan.
Good knowledge of the factors that influence cork quality and the health of forests is essential when making decisions regarding the management of productive cork oak forests. The quality of cork planks depends on: plank thickness, plank porosity and the presence of anomalies. So far, no studies have evaluated cork quality based on cork anomalies, partly due to the difficulty of obtaining adequate data. In 1985, it was developed the first Cork Quality Field Assessment Plan (CQFAP) to provide information about the quality of harvested cork by collecting data of very high quality. This work analyzes the anomalies present in 2049 cork sampling units collected from ten stands under the CQFAP for the period 1986–2012 in three consecutive cork stripping cycles. Data on diseases, pests and stripping damages are also analyzed in the 654 trees where cork sampling units were collected in the third stripping cycle. Additionally, mean monthly temperature and precipitation values for the 35 years covering the three stripping periods were calculated. A progressive deterioration of cork quality was observed in the sampled cork oak stands. It was found a positive relationship between cork thickness and temperature indicating that the cork growing period could be extended when temperatures are moderate. Sampled cork oaks were more affected by Cerambycidae attacks and Coraebus undatus indicating their prevalent nature. The presence of Coraebus undatus were higher in stands with good health status. The studied diseases were Biscogniauxia mediterranea, Phytophthora sp. and fungi of the family Botryosphaeriaceae, finding a not previously reported correlation between the presence of Crematogaster scutellaris and the three studied diseases. Stripping damages increase with smaller cork thickness but climate is not a decisive factor for a proper stripping. Although having room for improvement, the CQFAP is proving to be an effective tool for assessing the quality of cork, the health status of cork oak forests and the evolution of these forests over time. The information provided could be also used to identify places worthy of further studying. The main recommendation for improving the CQFAP would be to monitor the same trees in each consecutive sampling for properly monitoring cork thickness and the presence of defects to be used as a proxy for tree health. Regarding forest management, the main recommendations would be to extend the length of stripping cycles to enhance cork production, and to use the new tools and systems for cork stripping to reduce damage.
Currently, the selection of the trees to be removed in a thinning, carried out in a young cork oak plantation, is determined by a systematic rule to reach a predefined tree density value, in ...combination with simple criteria regarding individual tree sanitary conditions and stem shape. Since no criteria regarding the cork are available, thinnings can result in the removal of individuals that would later produce high quality secondary cork, leaving tree producers with lower quality cork. This study aims to test the feasibility of using CIELAB colour space coordinates and porosity values, measured in virgin cork samples, as predictors of the industrial cork quality and porosity obtained in secondary cork, thereby providing additional information usable for the classification of trees prior to the first thinning implementation. The L* and b* colour coordinates, measured in the transverse direction, depicted three main cork quality groups. Other L* and b* colour parameters, measured in the radial direction or in the cork back surface, have also shown statistically different average values while measured in different quality cork samples. Cork porosity from virgin and secondary cork showed a positive moderate monotonic relationship. A hyperbolic model for the prediction of secondary cork porosity was developed based on the virgin cork porosity, with one parameter expressed as a function of virgin cork colour coordinates (R2 =0.445). Results were successful in confirming the hypothesis raised. They may be used for the classification of trees prior to thinning.
•Virgin cork colour average values allow to predict main secondary cork quality groups.•L* and b* parameters measured in the transversal section were the most relevant.•Increase L* in virgin cork was associated to lower quality of the secondary cork.•Increase b* in virgin cork was associated to higher quality of the secondary cork.•Virgin and secondary cork porosity present a moderate positive monotonic relationship.
Natural cork stoppers, renowned for their sealing efficacy in wine bottles, face challenges in gas-tightness due to cork surface irregularities. This study investigates the impact of lubricant ...coatings (silicone or paraffin emulsions), on cork stopper gas-tightness. These coatings facilitate cork conformity to glass, minimizing gaps at the interface and significantly improving sealing capacity. A small amount of lubricant leads to a two-order-of-magnitude reduction in gas flow. However, careful control of coating is crucial to ensure reliable sealing. Additionally, water absorption by cork is proposed to contribute to sealing by generating expansion forces and softening the cork, enhancing conformity to glass.
This study emphasizes that natural cork stoppers should be viewed as both sealants and membranes. These findings shed light on the importance of surface treatments and water interaction in achieving reliable sealing in cork stoppers, ultimately ensuring the preservation and quality of bottled wine.
•Gas-tightness of cork stoppers in wine bottles can be compromised by cork-glass interface leakage.•Paraffin and silicone coatings mitigate leaks at the cork-glass interface.•Water absorption by cork contributes to sealing by facilitating its conformation to the glass surface.•A small amount of lubricant can significantly improve the sealing capacity of cork stoppers.•Surface treatments and water interaction are key parameters in achieving reliable sealing in cork stoppers.
•Algerian Aleppo pine wood have two different values of thermal conductivity in the parallel and perpendicular directions and Algerian black agglomerated cork is a good insulator.•Sandwich assemblies ...of Wood-cork are a good insulators that can be used in the field of construction.•The value of the thermal conductivity is influenced by sample moisture.•Because of its honeycomb structure, we note that the cork is a good absorber of heat comparing to the wood.•Thermal diffusivity of sandwiches assemblies is very small comparing with other scientists researches.
This paper presents an experimental study of the thermal conductivity, thermal resistance, specific heat and thermal diffusivity of wood, cork and their composites. The first part is devoted to the determination of the thermal resistance of composite materials elaborated from solid Aleppo Pine wood, laminated timber wood and black agglomerated cork. From experimental results, we can predict the values of the thermal conductivity, specific heat using a modulated differential scanning calorimetry (MDSC) of different samples. For the thermal conductivity, we use two different methods: the flow meter and a thermal conductivity meter (TC meter) at laboratory conditions (23°C, 50% RH). However, we have the possibility to calculate the thermal resistance and the thermal diffusivity and make comparison between the two methods. The results have been compared with other experimental researches and usual building materials. Furthermore, the aim of this study is to show the influence of the moisture on the values of the thermal properties of wood and cork which has been performed in a climatic chamber (23°C, 80% RH). The results indicate that increasing the mass of the samples leads to an increase of the value of the thermal conductivity and a decrease in thermal resistance of sandwich structures.
To provide information on the identification and quality evaluation of Q. variabilis virgin cork from Korea, the qualitative anatomical characteristics of the virgin cork were observed by optical and ...scanning electron microscopy and compared with those of Q. suber reproduction cork from Portugal. Q. variabilis showed a narrower growth ring than Q. suber. A dark-brown zone with sclereids was found only inQ. variabilis cork. The lenticular channel in Q. variabilis is larger than that in Q. suber. Q. variabilis virgin cork showed a distinct growth ring boundary and an abrupt transition from earlycork to latecork with a few rows of latecork cells. Q. suber reproduction cork showed an indistinct growth ring with a gradual transition from one to two rows of latecork cells. In the earlycork, Q. suber showed mild corrugation, while Q. variabilis displayed significant corrugation with collapsed and distorted cork cells. The lenticular channel in Q. variabilis virgin cork was surrounded by thick-walled cells filled with compact lenticular filling tissue. Q. suber reproduction cork had an opening with loose lenticular filling tissue surrounded by thick-walled cells. Prismatic crystals, thick-walled sclereid cells, and fiber-sclereids were found only in Q. variabilis. A few trabeculae were found in both cork samples.
This study investigated the potential of a novel biomass-derived cork as a suitable catalyst after its modification with Fe@Fe2O3 for in-situ application in heterogeneous electro-Fenton (HEF) process ...for benzoquinone (BQ) elimination from water. No attempts on the application of modified granulated cork (GC) as a suspended heterogeneous catalyst in the HEF process for water treatment have been published yet. GC was modified by sonification approach in a FeCl3 + NaBH4 solution to reduce the ferric ions to metallic iron in order to obtain Fe@Fe2O3-modified GC (Fe@Fe2O3/GC). Results clearly demonstrated that this catalyst exhibited excellent electrocatalytic properties, such as a high conductivity as well as relatively high redox current and possessed several active sites for water depollution applications. Using Fe@Fe2O3/GC as catalyst in HEF, 100% of BQ removal was achieved in synthetic solutions by applying 33.3 mA cm−2 after 120 min. Different experimental conditions were tested to determine that best possible conditions can be as follow: 50 mmol L−1 Na2SO4 and 10 mg L−1 of Fe@Fe2O3/GC catalyst using Pt/carbon-PTFE air diffusion cell by applying 33.3 mA cm−2. Nevertheless, when Fe@Fe2O3/GC was used in the HEF approach to depollute real water matrices, no complete BQ concentration was removal achieved after 300 min of treatment, achieving between 80 and 95% of effectiveness.
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•Fe@Fe2O3/GC can electro-Fenton activate H2O2 to .•OH.•Homogeneous and surface Fe3+/Fe2+ couples activate H2O2 to .•OH.•Fe@Fe2O3/GC-electro-Fenton mineralizes BQ solution better than EF and EO.
Cork powder and granules are the major subproducts of the cork industry, one of the leading economic activities in Portugal and other Mediterranean countries. Many applications have been envisaged ...for this product, from cork stoppers passing through the incorporation in agglomerates and briquettes to the use as an adsorbent in the treatment of gaseous emissions, waters and wastewaters. This paper aims at reviewing the state of the art on the properties of cork and cork powder and their application in adsorption technologies. Cork biomass has been used on its original form as biosorbent for heavy metals and oils, and is also a precursor of activated carbons for the removal of emerging organic pollutants in water and VOCs in the gas phase. Through this literature review, different potential lines of research not yet explored can be more easily identified.
► Outline of cork powder and granules' chemical and physical properties. ► Overview of the application of cork powder and granules in biosorption. ► Review of previously reported methods for activated carbon preparation from cork. ► Summary of the main applications of cork-based activated carbons in adsorption.
The annual growth and the thickness of cork are known to be highly variable between trees located in the same geographical location. Researching how climate variables affect different trees within ...the same site is a step forward for the management of cork production since current knowledge focusses only on the average tree response. Quantile regression methodology was applied for the first time to a large data set containing measurements of cork growth, sampled in 35 stands across the cork oak distribution area in Portugal. This methodology proved to be useful for testing the hypothesis raised: does climate affect differently the annual cork growth, and ultimately cork thickness of individual trees located in the same stand? Estimating the amount of cork produced by one stand that has the required thickness for the production of natural cork stoppers is essential to support cork oak management. However, no model, before this work, had been developed to provide managers with this information. A downward parabolic relationship between annual cork growth and annual precipitation was determined for all quantiles, with optimum annual average precipitation value ranging from 1103 to 1007 mm. April to August monthly temperatures, spring average temperature or summer average temperature, showed a negative relationship with annual cork growth, in particular for lower quantiles. Maximum annual temperature was shown to negatively affect annual cork thickness, in particular for the trees under the 6th quantile. The ratio between annual precipitation and average temperature, that define the Lang index (LI), showed a downward parabolic relationship with annual cork growth. Best cork growth conditions are found for Lang index values around 60, corresponding for the transition between semi-arid climate and humid climate. The application of the final model developed for estimating cork thickness of an eight years’ cork growth period allowed the prediction and mapping of the percentage of cork suitable for natural cork stopper production. It showed that higher values are expected in the Southern and Central coastal regions and along the Tagus River basin. The Northern coastal and mountain regions, characterised by Lang index values higher to 60 (humid climates), present lower estimated values for the percentage of cork suitable for natural cork stopper production. The estimated values are expected to be reduced under climate change scenarios in the Southern and Central coastal regions.
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