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Study on the Characteristics of Fluorescence Spectroscopy of Ningxia Wines

Author: ChenFeng
Tutor: LiHua
School: Northwest University of Science and Technology
Course: Grapes and wine ,
Keywords: Ningxia wines Fluorescence Spectroscopy Chemometrics
CLC: TS262.6
Type: Master's thesis
Year: 2011
Downloads: 121
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Abstract

Several techniques for discriminating wines have been used, but these methods are time-consuming, expensive, require highly skilled operators. Hence an urgent demand exists for inexpensive, rapid and precise methods for differentiating wines. In this study, the Synchronous fluorescence spectra (SFS) and three dimensional Fluorescence spectra (EEM)of wines from Ningxia have been investigated, since there are few publications reported about wine differentiation and classification using Synchronous fluorimetry, and study on using three dimensional Fluorescence spectroscopic technique to discriminate wines is limited to preliminary research. Chemometrics were applied in this study to differentiate and classify wines by type, brewery and vintage. The result as follow:1. Study on the method and preprocessing of samples using Synchronous fluorimetryWine samples were diluted by ultrapure water into different concentrations and with different pH, SFS were then collected in the excitation wavelength range of 220 to 550 nm using offsets (Δλ) of 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100 nm between excitation and emission wavelengths. The results showed that concentration of (1:100, wine: water) is optimal for white wine and (1: 60, wine: water) for red wines and pH is a critical factor which affect the SFS dramatically. It is vital to keep the samples in good condition without being affected. By analyzing the SFS at variousΔλ, best discrimination was obtained whenΔλ=90nm.2. Synchronous Fluorescence spectra and three dimensional Fluorescence spectra of wines from NingxiaSFS of Chardonney showed two bands with maxima at about 228 nm and 269 nm, while there were three bands with maxima at about 233 nm, 271 nm and 320 nm of red wines (Cabernet Sauvignon and Merlot). EEM of Chardonney have two fluorescent peaks centered at approximately 225 nm(Ex)/365 nm(Em) and 280 nm/365 nm and three peaks located at about 260 nm/385 nm, 290nm /385 nm and 325 nm/430 nm were observed of red wines(Cabernet Sauvignon and Merlot). It is clear that white wine is characterized of two SFS bands and two EEM peaks while red wine shows three SFS bands and EEM peaks.3. Analysis of SFS of wines from Ningxia using ChemometricsWine samples of various variety, brewery and vintage can be correctly discriminated by SFS combined with Principal Component Analysis (PCA) and discriminant analysis (DA).4. Characteristic of fluorescence spectra of wine influenced by variety, brewery and vintageCorrect classification of variety reach to 91.3% and 95.65% by using synchronous fluorimetry and three dimensional fluorescence spectroscopic technique respectively. No clear classification of brewery and vintage were obtained, however better classification of brewery was observed than that of vintage. It shows that synchronous fluorescence spectra of wine are best characterized by variety, then followed by brewery and vintage.5. Comparison of Synchronous fluorimetry and three dimensional fluorescence spectroscopic technique in wine analysesIt is clear that both synchronous fluorimetry and three dimensional fluorescence spectroscopic technique can discriminate wines by variety, brewery and vintage.Though better classification was achieved by applying three dimensional fluorescence spectroscopic technique, synchronous fluorimetry is quicker than three dimensional fluorescence spectroscopic technique in collecting fluorescence spectra of wine samples and much easier in analyzing the data. It is concluded that synchronous fluorimetry is promising approach to fingerprint wines aiming to discriminate wines, which can be a alternative choice to three dimensional fluorescence spectroscopic technique.

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