Rapid Determination of Phenolic Components in Red Wines from UV-Visible Spectra and the Method of Partial Least Squares

Abstract

Partial least squares regression was applied to the UV-visible spectra of 200 red wine samples at various stages of fermentation and the concentrations of several groups of phenols as determined by the Harbertson-Adams assay. Prediction functions for each of the phenolic classes were obtained using multivariate methods and were then used to estimate the corresponding phenolic measures in 200 independent samples. The correlations between predicted and measured values had coefficients of determination (r²) of 0.88 for anthocyanins, 0.86 for tannins, 0.82 for nontannin iron-reactive phenols, 0.88 for total phenols, 0.82 for small polymeric pigments, 0.41 for large polymeric pigments, and 0.76 for total polymeric pigments. The method has the potential for the rapid determination of these color and phenol components during the fermentation of red wines.