Fluorescence spectroscopy for discrimination of botrytized wines

Abstract

Some botrytized wines with “protected designation of origin” have a high market price, thus they are prone to adulteration with cheaper alternatives. This work presents the use of fluorescence spectroscopy combined with chemometrics as a relatively fast and inexpensive tool to discriminate botrytized wines according to two classification criteria: (1) distinguishing between botrytized wines of different quality, namely four-, five-, and six butt wines, and essence; and (2) distinguishing between unadulterated and adulterated samples. Various emission and synchronous fluorescence spectra were recorded and compressed by principal component analysis (PCA) and then linear discriminant analysis (LDA) was performed. The best PCA-LDA results (the percentage of correct classification for each wine category in the prediction step) were obtained with fluorescence spectra recorded on raw samples. Regarding wines of different quality, four- and five butt wines as well as essences were 100% correctly classified, while six butt wine samples were 80% correctly classified using emission spectra excited at 390 or 460 nm as well as synchronous fluorescence spectra recorded at wavelength difference of 100 nm. Regarding unadulterated and adulterated samples, the percentages of correct classification were 60, 80, 80 and 100% for four-, five-, and six butt wines and essence, respectively, while adulterated samples were 100% correctly classified, in all cases, using synchronous fluorescence spectra recorded at wavelength difference of 100 nm.