Adam Gilmore,* A. Mehmedovic, Q. Sui, T. Hayes, and M. T. Cleary  
*HORIBA Instruments Inc., 3880 Park Ave., Edison, NJ 08820 (adam.gilmore@horiba.com)

Both the color and phenolic composition of grape juice and wine are recognized as key quality characteristics associated with visual perception, taste and mouthfeel. Because the phenolic composition indicates fruit ripeness, it can be used to optimize viticulture during the veraison period, then throughout the winemaking process to establish quality control guidelines. Conventional chromatographic analyses of colored and phenolic compounds are costly, slow, and labor intensive; reagent based colorimetric assays are also slow, and importantly, do not provide compound discrimination. This study presents practical application examples of a new rapid method for discriminatory phenolic compound analysis. The method involves a patented purely optical instrument capable of simultaneous absorbance, transmission, and fluorescence excitation-emission mapping (ATEEM) spectroscopy. The ATEEM method provides both the transmission information for a complete International Commission on Illumination (CIE) tristimulus analyses and the absorbance information needed for the hue, intensity, and various other parameters considered to be conventional in the wine industry. Importantly, the study demonstrates the effective and unique synergistic capacity of simultaneously analyzing the complete multi-dimensional ATEEM data set. Results are presented using unsupervised multivariate component analyses and calibrated least squares regression methods for precise sample classification and phenolic quantification, respectively. The new application examples are evaluated with respect to characterizing and classifying juice and wine samples as a function of ripening varietal and process related parameters, including possible screening for adulteration and storage issues, such as oxidation and microbial spoilage.

Funding Support: Horiba Instruments Inc.