Near infrared reflectance spectroscopy and multivariate analysis in enology: Determination or screening of fifteen parameters in different types of wines Original Research Article

A study of the feasibility of near infrared reflectance spectroscopy (NIRS) for analytical monitoring in wineries is presented, in which equations for the determination or screening of the commonest enological parameters are proposed. The training and validation sets to develop NIR general equations were built with samples (180) from different apellation d’origine, different wine types, etc. By the calibration step (partial least squares regression and cross-validation were used for multivariate calibration), major components such as ethanol, volumic mass, total acidity, pH, glycerol, colour, tonality and total polyphenol index are accurate determined by the proposed equations as compared with the reference data obtained by the official and standard methods—determination coefficients (R2) were higher than 0.800 (and higher than 0.900 most times) and standard error cross-validation (SECV) values were close to those of the reference methods. The proposed method also offers screening capability for components such as volatile acidity (R2 = 0.481), organic acids (R2 = 0.432 for malic acid, R2 = 0.544 for tartaric acid, R2 = 0.541 for gluconic acid)—with the exception of the accurate determination of lactic acid (0.860 and 0.35 g l−1 for R2 and SECV, respectively)—reducing sugars (R2 = 0.705) and total sulphur dioxide (R2 = 0.615). In equations validation, the correlation between the reference and NIRS methods was tested, and slope and bias values statistically not different from 1 and 0, respectively, were obtained for most parameters.