Cork Stoppers Research Articles

CORA - an automated method for the evaluation and comparison of the microbial activity in cork and cork stoppers

A new method for quantitative evaluation of the microbial load of cork and cork stoppers, coded CORA (Cork Activity Assay) is described. It is based on measurement by gas chromatography of dimethylsulfide (DMS) evolving from the reduction of dimethylsulfoxide (DMSO) by microbial activity. The method is accurate, gives results within 48 h and can be automated. Test results for various types of cork, sampled before, during and after the manufacturing process of bottle closures, are provided. The use of CORA as a tool for the development of better production processes to limit cork infection by micro‐organisms and for advanced microbiological quality control is discussed.

Cork quality classification system using a unified image processing and fuzzy-neural network methodology

Cork is a natural material produced in the Mediterranean countries. Cork stoppers are used to seal wine bottles, Cork stopper quality classification is a practical pattern classification problem. The cork stoppers are grouped into eight classes according to the degree of defects on the cork surface. These defects appear in the form of random-shaped holes, cracks, and others. As a result, the classification cork stopper is not a simple object recognition problem. This is because the pattern features are not specifically defined to a particular shape or size. Thus, a complex classification form is involved, Furthermore, there is a need to build a standard quality control system in order to reduce the classification problems in the cork stopper industry. The solution requires factory automation meeting low time and reduced cost requirements. This paper describes a cork stopper quality classification system using morphological filtering and contour extraction and following (CEF) as the feature extraction method, and a fuzzy-neural network as a classifier. This approach will be used on a daily basis. A new adaptive image thresholding method using iterative and localized scheme is also proposed, A fully functioning prototype of the system has been built and successfully tested. The test results showed a 6.7% rejection ratio, It is compared with the 40% counterpart provided by traditional systems. The human experts in the cork stopper industry rated this proposed classification approach as excellent.

Mycobiota in Portuguese ‘normal’ and ‘green’ cork throughout the manufacturing process of stoppers

The compounds responsible for the so-called 'cork taint' include, among others, some microbial metabolites which can be produced by the microbial population colonizing the unprocessed cork and stoppers. This study was intended to obtain information on the mycobiota associated with Portuguese cork throughout the manufacturing process of stoppers. Samples of barks and stoppers of both 'normal' and 'green' cork were examined. Moulds were isolated from 'normal' and 'green' cork throughout the entire cork stopper manufacturing process. Yeasts were rarely detected in the corks. Fungal contamination was not detected in finished stoppers from the company under study.

Cork-borne bacteria and yeasts as potential producers of off-flavours in wine

Bacteria and yeasts were found to be present within cork lenticels, covered by mucous or fibrous substances. They survived heating, peroxide treatment and contact with the alcohol and sulfur dioxide of wine. 187 bacteria and 36 yeast strains were isolated from cork stoppers of wine bottles and, during various stages of production, from corkwood and new cork stoppers. After culturing, a number of isolates showed the ability to modify the aroma of model systems consisting of dilute or full strength wine and pulverised cork. The aromas produced by isolates of varying cork origin are tabled. A small number of isolates methylated 2,4,6-trichlorophenol, yielding 2,4,6-trichloroanisole, responsible for the typical cork taint. During the boiling of cork slabs, the internal temperature on the inside of a box made from cork slices did not exceed 87°C.

Toward Adopting Cork Alternatives for Fine Wines: A Review

Cork stoppers may taint as many as one in 33 bottles of all domestic US wines. Yet, because tradition is thought to play such an important role in shaping expectations regarding acceptable premium wine packaging, marketers have felt little need to test whether cork closures are indeed a critical consumer expectation. This paper serves as a guide toward understanding the obstacles which must first be overcome by those producers who wish to adopt cork substitutes for fine wines. This paper also offers insight into grappling with the implementation of problem solutions; shows why desirable solutions may not always be practical; and provides insight into why conflicting intrafirm departmental viewpoints, consumer expectations, and the competitive environment in which the firm or industry operates, can combine to lead the marketer to reject money‐saving superior product innovations. Preliminary work indicates that consumers reject label message conditions as a means of achieving acceptance of cork alternatives. The main objective of future research should therefore be to provide specific findings on how much positive and negative impact is likely to occur by changing the product design.

Determination of Oxalates in Cork Stoppers by HPLC with Electrochemical Detection

For oxalate quantification in cork stoppers an automated HPLC method using an ion exchange organic acid column and an electrochemical detector was performed. The study was conducted on cork stoppers in three steps of their manufacture: untreated cork stopper (corresponding to natural cork), whitened stopper, and final stage (ready for commercial delivery). The oxalate determinations may be performed in a linear range from 0.1 µg/mL (detection limit) to 20 µg/mL. The identification of the chromatographic peak corresponding to oxalic acid was proved by the specific action of oxalate oxidase. Satisfactory recovery for the extraction procedure (recoveries of oxalic acid in the additions method between 92.85% ± 3.70% and 103.65% ± 7.70%) and precision for the over-all procedure (relative standard deviation between 5.90% and 8.20%), and low time consuming (30 min for the HPLC analysis) were observed. It makes this procedure suitable for monitoring residual oxalates in cork stoppers either by the industry itself or by government quality control. Quantification of oxalic acid in 60 randomly obtained samples from the market gave the value of 173.8 ± 15.4 µg/g (X ± SE).

Yield and quality in the production of cork stoppers

Bottle stoppers of natural cork are produced from cork planks as cylinders which are bored in the axial direction. The process was followed for the production of 38 mm×24 mm (length×diameter) stoppers, using cork planks of different quality grades. The mass yield is on average 24% of the initial cork with net productions of 98 stoppers/kg and 747 stoppers/m2. The net yields are higher when using the best quality raw-material due to an increasing number of refused stoppers with the decrease in quality of the cork planks. The quality profiles of the stoppers are determined by the quality of the raw-material: i.e. ist grade cork planks produce 82% of high quality stoppers (superior and 1st class) and 5th grade planks only 22%. The results obtained allowed to establish correlations between the number of stoppers produced and raw-material parameters, namely the area and dry weight, which can be used to estimate production from a given lot of cork planks.

Cork and corks

The common cork stopper takes advantage of the peculiar properties of the bark of the cork oak. This has very low permeability to both gases and liquids due to suberin and waxes; the cellular structure makes possible the deformation that gives a secure fit in the bottle neck.

Determination of copper, iron, aluminium, lead and cadmium in cork stoppers by electrothermal atomic absorption spectrometry

Methods for the determination of five elements (Cu, Fe, Al, Pb and Cd) in cork stoppers by electrothermal atomic absorption spectrometry (ETAAS) with a stabilized temperature platform furnace are described. A previous acid digestion of the cork stoppers in HNO3–HCl–HF in poly(tetrafluoroethylene) apparatus, was required owing to the specific and characteristic nature of cork. The digests were evaporated to dryness and the residue was dissolved in HNO3 for subsequent measurement by ETAAS. Depending on the metal, a suitable chemical modifier was added when necessary, i.e., Mg(NO3)2 for Al and Fe, a mixture of Mg(NO3)2 and Pd(NO3)2 for Pb and NH4H2PO4 for Cd. The linear ranges for determination were 0.6–50, 0.8–50, 1.5–50, 1.1–75 and 0.4–2.0 µg l–1 for Cu, Fe, Al, Pb and Cd, respectively, after appropriate dilution. For precision and recovery studies, several determinations (from six to ten) for each of the five metals were conducted on different aliquots of the same sample, using the standard additions method at three specific concentrations. The relative standard deviations were 11.4, 9.4, 15.0, 9.5 and 7.1% for Cu, Fe, Al, Pb and Cd, respectively, which makes this method satisfactory and suitable for routine analysis.

Analysis of solid samples by ICP-mass spectrometry

ICP-Mass spectrometry is typically used as a technique for very rapid multielement analysis at trace and ultra-trace levels of solutions by continuous sample aspiration and nebulization. However, ICP-MS is well suited to be used as a detector for other sample introduction devices. For the analysis of solid samples laser sampling and electrothermal vaporization accessories may be used as sample introduction devices for ICP-MS. Laser sampling permits the analysis of many different types of solid materials. For solid sampling ETV-ICP-MS analysis it is of advantage to reduce the sample to a fine powder prior to analysis. For automated analysis powders may be introduced as slurries into the graphite furnace by means of a slurry sampling device. Since appropriate certified solid reference materials are not always available for calibration, or since they are not certified for all analyte elements of interest, the analyses discussed in this contribution were performed semiquantitatively. The instrument response function was established using reference materials which were similar in their composition to the samples. The results of semiquantitative bulk analyses of glass (NIST 612) and geological material (USGS GXR-3) by laser sampling ICP-MS are in good agreement with the certified values. The concentrations of the analytes determined in the glass sample were in the range of 10 μg/g to 80 μg/g. The lowest analyte concentration in the geological sample was 0.4 μg/g (Eu) and the highest was approximately 186 mg/g (Fe). The precision achieved was in the order of 5% to 15%. Laser sampling ICP-MS is not only suitable to bulk analysis but also to analyses where spatial information is required. As an example for such an application the determination of Pb in a wine bottle cork stopper is dicussed. The slurry sampling technique was used for the semiquantitative analysis of NIST coal reference samples by electrothermal vaporization ICP-MS. The accuracy achieved with this approach was within a factor of ±2 of the reference values.

Cork products: a potential source of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans

4 samples of cork stoppers and 1 sample of cork wallpaper were analysed for the content of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs). The cork stoppers contained trace amounts of PCDDs/PCDFs between 0,18 and 2,6 ng TE/kg, the wallpaper contained 12,9 ng TE/kg. Theoretical evaluations show that the human intake of PCDDs/PCDFs via cork stoppers is neglectible compared to the total daily intake of PCDDs/PCDFs. Wallpaper might contribute to the indoor air and dust contamination with PCDDs/PCDFs.

The Portuguese gamma irradiation facility

A Gamma Radiation Facility was built up in the National Laboratory of Industrial Technology and Engineering (LNETI), Lisbon, Portugal. This plant (UTR GAMA-Pi) is a Cobalt-60 dry storage continuous facility with a nominal capacity of 1.5X10 16 Bq. The initial activity is 1.1X10 16 Bq and the troughput capacity 10 3 ton/year for product with a bulk density of 0.2 g/cm 3 treated with a minimum absorbed dose of 25 kGy. Complementary control devices were installed: ventilation system, closed water refrigeration circuit, internal TV system, detection and extinction fire system and emergency power group. It must be emphasized that the best attention was given to the conception and efficiency of the interlock safety systems. This facility will be utilized mainly for radiosterilization of medical articles and decontamination of wine cork stoppers.

Searching for a strategy to gamma-sterilize Portuguese cork stoppers — preliminary studies on bioburden, radioresistance and sterility assurance level

A gamma radiation plant will start running next year in Portugal, to sterilize medical devices and wine cork stoppers. As Portugal is the first world producer, manufacturer and exporter of wine cork stoppers, an efficient sterilizing procedure is required to overcome moulding from long term shipping. Preliminary research on cork stoppers bioburden and microflora radioresistance allowed to establish reliable D 10 and Sterility Assurance Level (SAL) values. Studied samples showed an initial average contamination of about 10 4 c.f.u. per cork stopper. The determined D 10 values for fungi were not higher than 2 kGy. In these conditions, a SAL of 10 -4 can be expected when the product is treated at a minimum absorbed dose of 15 kGy.

Hot-Water Dip for Control of Fuller Rose Beetle Eggs, 1986

Abstract Fuller rose beetle eggs were obtained by allowing beetles to oviposit between layers of wax paper. Egg masses on wax paper, 0-7 days old, were randomized and placed in stainless steel screen cages (6 cm long × 18 mm diam) closed with cork stoppers. The cages contained an average of 505 eggs/each and were submerged in a water bath at several temperatures (±0.5°C) and durations as shown in the table. Posttreatment conditions were 27°C at 85% RH. Mortality counts made 1 mo after treatment consisted of fully developed embryos and hatched eggs versus undeveloped eggs. Each test was replicated 3 times. Embryos with clearly defined head capsules and body segmentations were considered fully developed.

Development of applications of a cobalt-60 irradiation unit

The determination of isodoses in a facility, which enables the gamma irradiation of samples with good reproducibility and uniformity, is described. Two examples of applications, with catheters and cork stoppers, are presented.

Laboratory Evaluation of Chemicals for Postharvest Control of Fuller Rose Beetle, 1986

Abstract Eggs (0-7 days old) oviposited on wax paper were placed in stainless steel screen cages 6 cm long × 18 mm diam closed with cork stoppers. Cages with eggs were dipped in test compounds at recommended strengths for 3 min, drip dired for 1 min, rinsed in tap water for 1 min, and air dried for 30 min. The tap water rinse was omitted for Dimilin. Treated eggs were held at 27°C and 85% RH for 30 days and examined for mortality. There was an average of 387 eggs/replicate, and each test was replicated 3 times. All data were corrected using Abbott's formula (1925).

Stress relaxation and creep of cork

The stress relaxation and creep behaviour of cork under compression were characterized in tests done with the compression axis parallel to each of the three principal directions in the tree (radial, tangential and axial). All stress relaxations lead to a linear variation of stress with the logarithm of time, the slopes being nearly independent of stress and direction of compression. Creep stresses in the range 0.36 to 1.72 MPa were used. The strain rate continuously decreases during creep, from initial values around 10−4sec−1 to ∼ 10-7 sec−1 after 8 h, but its dependence on the creep stress and direction of compression is not simple, mainly because different deformation regimes may operate during a single creep test. Compression loading-relaxation-unloading cycles were imposed on specimens, with compression either in the radial or in the tangential direction, with the purpose of simulating the performance of a cork stopper. A “work softening” is observed, i.e. the resistance decreases in successive compressions, particularly between the first two. This is explained in terms of an increased undulation of the cell walls produced in the first compression.

Wire-loop application of liquid emulsion to slides for autoradiography in light microscopy.

This is an adaptation of procedures used to prepare autoradiographs for electron microscopy to light microscopy. A rectangular wire loop slightly larger than the slide is used. The liquid emulsion is prepared by mixing 1 volume of a 0.1% solution of Dreft or Ivory Snow with 2 volumes of Kodak NTB3 nuclear track emulsion. The slide to be coated is placed on a cork stopper supported by a glass plate 61 cm from the safelight. The loop was withdrawn from the liquid emulsion, with the plane of the loop parallel to the surface of the liquid, placed directly over the slide and slowly lowered so that the film (in the sol state) was broken by the slide. If desired, the film can be allowed to gel before application to the slide by waiting approximately 40 sec after the loop is removed from the liquid emulsion. That the developed emulsion is consistently uniform was indicated by a thickness of 0.4 ± 0.02 μm. Diluted emulsion can be stored after use for 1–2 wk at 2–8 C and used a second time before discarding. The id...

Some Techniques for the Preparation, Study, and Storage in Microvials of Insect Genitalia2

Sodium hydroxide in the form of household flake lye is a substitute which is more gentle on delicate tissues than potassium hydroxide. Several types of small dishes and cavity plates are convenient containers in which to study genitalic preparations. Suggestions are made for the storage of genitalia in glycerine within microvials, especially the avoidance of too much glycerine and the need to slant the vials to keep the corks dry when they are pinned. Plastic microvials and synthetic rubber stoppers are suggested as substitutes for glass microvials and cork stoppers.

Unsaponifiable lipids of Taenia taeniaeformis and Moniezia sp.

The experiments presented above show that in Taenia taeniaeformis and in Moniezia sp. cholesterol is by far the most prevalent unsaponifiable substance. In the former tapeworm it amounted to at least 98% of total unsaponifiable material, in the latter to approximately 85%. The fact that a search for friedelin in Taenia taeniaeformis was negative strengthens the assumption by Cmelik and Bartl, 1956 that the friedelin found in Taenia saginata did originate from cork stoppers. Our finding of 7-ketocholesterol in the Moniezia sample requires a comment. It is known that hot alkaline saponification of 7-ketocholesterol ester produces cholesta-3, 5-diene-7-one. 3 3 We refluxed a mixture of 7-ketocholesterol and 2% methanolic potassium hydroxide solution for one hour, i.e., under considerably milder conditions than employed by us in the saponification of the acetone soluble lipids and isolated predominantly cholesta-3,5-diene-7-one. Milburn et al., 1956 Mauthner and Suida, 1896. Since the latter compound was not present in our sample, it may be concluded that the 7-ketocholesterol was not originally present, but was formed during isolation and storage of the unsaponifiable material 4 4 Fieser et al. 1957 have isolated 7-ketocholesterol from aged and air-oxidized cholesterol. from the Moniezia sp. No trace of 7-ketocholesterol could be isolated from the unsaponifiable material of the Taenia taeniaeformis.