Application of image analysis and NIRS technology to the evaluation of the porosity of planks, sheets and cork stoppers, and its relation with the industrial quality

The quality of cork is one of the most important issues for the cork industry. It is a complex process that requires evaluating many factors and simultaneously handles continuous and discrete variables, sometimes with a high degree of subjectivity. There are two objectives, in first place to establish the relationship between the commercial quality of the cork and the porosity measured by image analysis at different stages of industrial processing (planks, sheets, and stoppers), and in second place, to evaluate the potential of NIRS technology as a method of assessing the porosity and, therefore, the industrial quality. For this, there has been used a sample group formed by 479 planks, 176 sheets and 90 one piece natural cork stoppers, classified industrially into 4, 2 and 3 quality classes, respectively. The coefficient of porosity was evaluated into two and three classes of color by using image analysis techniques. NIRS spectra were obtained in the transverse section (planks and stoppers), in the tangential section (sheets and stoppers) and in the radial section (stoppers), with a spectrophotometer Foss NIRSystems 6500 SY II, by remote reflectance mode. Statistical analysis of the relationship between quality and coefficient of porosity, measured by image analysis, discriminates two quality classes for planks and sheets, and three classes for stoppers. Classifying the image into a larger number of clusters improves the results. Best NIRS calibrations were obtained measuring the porosity into 3 classes of color, matching the results obtained by image analysis. This allow to discriminate two quality classes in planks (refuse and race), the two classes in sheets (R2=0.83; r2 =0.78) and the three classes for stoppers (R2=0.67; r2=0.53). Due to the difficulties of automated image analysis in the early stages of industrial processing, NIRS technology could be an objective tool to evaluate the porosity and to differentiate two classes of quality in planks and sheets, and three classes in stoppers.

Bibliographic Details

Main Authors:	Gómez-Sánchez, I., García de Ceca, J. L., García-Olmo, J., Lara-Buil, L., López-Luque, R., Prades, C.
Format:	journal article biblioteca
Language:	eng
Published:	2013
Online Access:	http://hdl.handle.net/20.500.12792/1814
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