Discrimination of juice press fractions for sparkling base wines by a UV-Vis spectral phenolic fingerprint and chemometrics

The feasibility of an ultraviolet-visible (UV-Vis) spectral phenolic fingerprint (SPF), combined with principal component analysis (PCA), is evaluated as a rapid, simple, and reliable technique for the discrimination of grape juice press fractions destined for the production of sparkling white wines. Juice press fractions of Vitis vinifera L. Chardonnay and Pinot noir grapes comprising free-run (i.e., juice released during the loading of press), cuvée (i.e., first press fraction), and taille (i.e., subsequent press fraction), were analyzed by SPF combined with multivariate data analysis. Two trials were carried out, a laboratory and a commercial scale trial. In both trials, cuvée and taille of Chardonnay and Pinot noir grapes were clearly separated in their corresponding PCA plots based on their SPF. The proposed method enables a rapid and objective discrimination of juice press fractions, which can be obtained using relatively inexpensive UV-Vis spectrophotometric equipment. Insights arising from this research suggest a future possibility of objective, real-time discrimination of juice quality that could liberate the winemaker from tasting juice at the press.