Definition of quality classes for champagne cork stoppers in the high quality range (original) (raw)
Related papers
Natural variability of surface porosity of wine cork stoppers of different commercial classes
OENO One, 2012
The aim of this study was to characterize the variability and to quantify the surface porosity of wine cork stoppers of different quality classes. Methods and results : The porosity of 300 cork stoppers was characterized by image analysis on the lateral surface and tops. Porosity coefficient was 2.4 %, 4.0 % and 5.5 % for premium, good and standard stoppers, respectively. The lateral surface of stoppers was heterogeneous with respect to porosity features: the tangential regions presented higher porosity while the radial regions had larger pores. Conclusion : The quality classes of cork stoppers can be differentiated by the mean values of the main porosity features of their surface. There is a natural heterogeneity of the porosity features over the external surface of cork stoppers that can be traced back to the biological basis of cork formation and the production process. Significance and impact of the study: Natural cork stoppers are the premium product of the cork industry, with worldwide recognition of quality and performance as wine sealant. Due to the large sampling and detailed observation, the results presented in this study may be used for reinforcing quality requirements, e.g., with definition of standards to improve the classification system. A better understanding of cork intrinsic variability and of the anisotropy of porosity features shown by cork stoppers is important for performance development.
The porosity of natural cork stoppers
Natural cork stoppers are the premium product of the cork industry with worldwide recognition of quality and performance as wine sealant. The occurrence of negative evolution of bottled wines has often been attributed to cork stoppers as a result of their intrinsic variability. One of the main characteristics of cork stoppers is their surface porosity which is the determining factor for their commercial quality grading. Although several studies have analysed the porosity of cork stoppers, the results have been limited to rather small samplings and the anisotropy of porosity was not studied in detail. In this study, the porosity of 600 natural cork stoppers was characterized by image analysis on the lateral surface and tops. Porosity coefficient was 2.4%, 4.0% and 5.6%, respectively for premium, good and standard stoppers. Tops (transverse section) have a lower porosity coefficient and much less pores per unit area (about 60%) in relation to the lateral surface. Moreover, pores in the tops are more elongated than in the lateral surface. The detailed observation of the lateral surface of stoppers showed its heterogeneity in relation to porosity features. The tangential regions present higher porosity (3.1%, 4.9% and 6.2% for, respectively, premium, good and standard quality) while radial regions had larger pores and higher largest pore area. The shape-type variables presented mean values similar for the entire lateral surface, with slightly higher shape factor in the tangential section than in the radial section. The anisotropy of porosity features shown by cork stoppers is a consequence of the biological development of cork and of the method of production i.e. the cutting orientation. Understanding this variation is a relevant component in the analysis of stoppers performance as wine sealants and can lead to improvements in cork quality classification algorithms used in the automated systems.
Food and Bioproducts Processing, 2013
The natural cork stoppers are commercially graded into quality classes according with the homogeneity of the external surface. The underlying criteria for this classification are subjective without quantified criteria and standards defined by cork industry or consumers. Image analysis was applied to premium, good and standard quality classes to characterize the surface of the cork stoppers and stepwise discriminant analysis (SDA) was used to build predictive classification models. The final goal is to analyze the contribution of each porosity feature and propose an algorithm for cork stoppers quality class classification. This study provides the knowledge based on a large sampling to an accurate grading of natural cork stoppers.
Analysis of mechanical properties of cork stoppers and synthetic closures used for wine bottling
Journal of Food Engineering, 2008
There is an increasing interest towards synthetic closures as an alternative to cork stoppers for sealing wine bottles. In this preliminary study, a set of testing conditions using the TA-HDI Texture Analyzer were implemented to measure selected mechanical parameters for the characterization of wine closures (natural and technical corks, co-extruded and injected synthetic closures in terms of compression force, extraction force and resilience. The results showed the presence of significant differences among the closures for the parameters tested. Injected closures were characterized by the highest weight (range = 6.8–7.2 g), whereas the corks showed wide variability (SD = 0.23–0.57 = 4.4–15.3%). The force required to pull-out the closure from the bottle ranged between 176 and 421 N and the extreme values were found on natural (196 ± 20 N) and technical cork (329 ± 39 N). The force of compression was highest for corks (1006–1046 N), whereas lowest values were found for the synthetic closures (566–639 N). The Principal Component Analysis grouped the synthetic closures according to the technology process, i.e. injected and co-extruded, whereas the corks broadened aside with a little dispersion of technical cork compared to the natural cork.
2012
We attempted to predict the performance of cylindrical stoppers by evaluating their inner morphology. the same white wine lots were stored for eighteen months under controlled humidity and temperature conditions. stopper cellulation was analysed using scanning electron microscopy. the results show that the wine-browning kinetics were significantly different for each stopper used and were related to the regularity of stopper cellulation. combining our observations regarding the inner closure morphology with data on browning kinetics, we propose an arbitrary scale for classifying stopper quality. this scale can be practically applied during pre-bottling operations to choose the most efficient cylindrical closure.
Journal of the Science of Food and Agriculture, 2007
Quality classification of wine natural cork stoppers is related to presence of discontinuities in the cork tissue. Automated image analysis of stoppers based on black and white cameras is used industrially for commercial classification but recently color has been introduced in image processing. This paper compares the performance of three image vision systems regarding classification accuracy of cork stoppers of good, medium and inferior quality: black and white, three-band RGB color and manual detection by digitalization in color image. A canonical discriminant analysis approach was used to compare the discriminating power between cork stopper quality in each vision system. Good discriminant results were obtained with the area of pores expressed either in total or as ratio, mean or maximum value. The use of color slightly enlarges the range of cork inspection systems and automated systems have a similar accuracy of classification to visual inspection.
The Evaluation of the Quality of Cork Planks by Image Analysis
hfsg, 1996
The quality evaluation of cork planks in relation to porosity may use image analysis techniques. Results are presented on the number, dimensions, form and orientation of the lenticular channels in tangential, transverse and radial sections of cork planks of different thickness and qualities. The porosity coefficient (% pore area in relation to total area) varied between 1.1%-I8.9% and 2.1%-16.4%, respectively in tangential and transverse/radial sections and is determined mostly by the number of pores larger than 0.8mm 2 and by their average area, The porosity may be used to define cork quality classes. Due to the heterogeneous porosity distribution in cork plunks, an assessment of quality made on small cork samples will give a result with a large error. For an error below 15%, the observation in the tangential section should be made on a sample with a minimum area of 225cm 2 (e.g. 15 cm 15cm) and in the transverse and radial sections on a sample with a minimum length of 15cm.
Quality grading of cork planks with classification models based on defect characterisation
Holz als Roh- und Werkstoff, 2000
A quality grading system for cork planks is presented using a classi®cation model based on data obtained from the image analysis of transverse and tangential sections of cork planks and taking into account different types of defects. Three types of defects may be distinguished in cork by their geometrical parameters: pores (lenticular channels), physiological anomalies (nail, clay and``bofe'') and pathogenic anomalies (insect galleries of Coroebus undatus (F.) and Crematogaster scutellaris Ol.). A discriminant analysis was used to construct the classi®cation model: the variable with the highest discriminant power was the total porosity in the transverse section, and the other variables were transformations of the speci®c width in the tangential section and the aspect ratio in the transverse section. The model classi®ed two thirds of the samples in accordance with the manual classi®cation currently used in the industry and all cases of disagreement referred to changes between contiguous quality classes. Klassifizierung von Korkplatten mittels automatisierter Fehlererkennung Ein Klassi®zierungsmodell fu Èr Korkplatten wird vorgestellt, das auf Ergebnissen einer Bildanalyse beruht, wobei verschiedene Fehlertypen in Quer-und Tangentialschnitten beru Ècksichtigt werden. Drei Fehlertypen ko Ènnen unterschieden werden aufgrund ihrer geometrischen Parameter: Poren (Kana Èle zwischen den Lentizellen), physiologische Anomalien und pathogene Anomalien (z.B. Insektenfraû). Eine Diskriminanten-Analyse wurde eingesetzt, um ein Klassi®zierungsmodell zu entwickeln. Die Variable mit dem sta Èrksten Ein¯uû auf die Klassi®zierung war die gesamte Porosita Èt, gemessen am Querschnitt. Die andern Variablen betreffen Transformationen der spezi®schen Breite der Poren im Tangentialschnitt und ihr Aspekt-Verha Èltnis im Querschnitt. Das Modell klassi®ziert zwei Drittel der Proben in U È bereinstimmung mit der in der Industrie u Èblichen visuellen Klassi®kation. In allen anderen Fa Èllen beziehen sich die Abweichung auf jeweils benachbarte Klassen.
Yield and quality in the production of cork stoppers
Holz als Roh- und Werkstoff, 1994
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 x 24 mm (length x 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/m 2. 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. xst 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.