Qualitative and quantitative assessment of cork anomalies using near infrared spectroscopy (NIRS)

Abstract

Abstract The aim of this study was to develop applications of near infrared spectroscopy (NIRS) to detect certain anomalies in cork used in the manufacture of stoppers for wine bottling. 326 spectra of cork planks were used in a qualitative analysis to evaluate the feasibility of NIRS to discriminate between pure cork, yellow stain and lignified cork. Classification and validation errors varied between 0 % and 11.4 %. In addition, 360 spectra of cork granulate were used in a quantitative analysis to determine the percentage of yellow stain and corkback. A root mean standard error of cross validation (RMSECV) of 1.50 % was obtained for yellow stain percentage (R² = 99.62 %). For corkback percentage RMSECV was 2.96 % (R2 = 98.53 %). These results show that NIRS technology has potential, alongside traditional methods, to determine the quality of cork used to manufacture stoppers.