宁夏原产地葡萄酒荧光光谱法研究

宁夏原产地葡萄酒荧光光谱法研究

STUDY ON THE CHARACTERISTICS OF FLUORESCENCE SPECTROSCOPY OF NINGXIA WINES

作者：陈　锋　　导师：李　华

西北农林科技大学　　葡萄与葡萄酒学2011届硕士

摘　要

目前用于葡萄酒区分与鉴别的方法比较多，尽管一些方法十分准确，但高昂的成本、繁琐的样品处理及较慢的测定速度不利于其广泛应用，因此探索一种低成本、快速准确的新方法具有重要的意义。本论文对同步荧光光谱测定葡萄酒的方法进行了研究，分析了宁夏原产地葡萄酒的同步荧光光谱、三维荧光光谱和等高线光谱特征，并结合主成分分析、判别分析和聚类分析对葡萄酒进行了区分与分类。研究结果如下：

1.　葡萄酒同步荧光光谱测定方法

通过分析赤霞珠和梅尔诺干红葡萄酒、霞多丽干白葡萄酒在不同的稀释梯度和不同的pH值时荧光光谱特征，综合考虑荧光图谱的荧光强度及荧光峰数量特征，确定测定霞多丽干白葡萄酒的同步荧光光谱时样品稀释100倍为最佳，测定赤霞珠和梅尔诺干红葡萄酒的同步荧光光谱时，样品稀释60倍为最佳。样品同步荧光光谱受pH的影响较大，因此测定葡萄酒样品时，保证葡萄酒样品的稳定、防止葡萄酒pH发生改变十分重要。

测定了波长差Δλ＝Em-Ex分别为10、20、30、40、50、60、70、80、90和100 nm时的同步荧光光谱，通过主成分分析荧光光谱发现Δλ=90 nm时对葡萄酒的区分效果最佳。

2.　宁夏原产地葡萄酒同步荧光光谱和三维荧光光谱特征比较

根据葡萄酒样品的同步荧光光谱，干白葡萄酒在228 nm和269 nm左右具有两个荧光峰，干红葡萄酒在233 nm和269 nm或271 nm左右具有两个明显的荧光峰，个别样品在320 nm左右出现第三个荧光峰。由葡萄酒样品的三维荧光光谱和等高线光谱，发现霞多丽干白葡萄酒只有两个荧光峰，位于激发波长(nm)/发射波长(nm)为225nm/365nm和280 nm/365 nm左右；梅尔诺和赤霞珠干红葡萄酒都具有三个荧光峰，位于260 nm/385 nm，290 nm/385 nm和325 nm/430 nm左右。不论是同步荧光光谱还是三维荧光光谱和等高线图，霞多丽干白葡萄酒都要比赤霞珠和梅尔诺干红葡萄酒少一个荧光峰。

3.　化学计量法分析宁夏原产地葡萄酒的同步荧光光谱

通过对同一品种同一生产者不同年份、同一生产者同一年份不同品种和同一品种同一年份不同生产者的葡萄酒同步荧光光谱进行主成分分析和判别分析，能够完全区分不同品种、生产者和年份的葡萄酒样品。

4.　葡萄酒品种、生产者和年份对葡萄酒荧光光谱的影响

对所有样品按品种聚类时同步荧光光谱法正确率为91.3%，三维荧光光谱法正确率为95.65%。在对生产者和年份分类时，两种荧光光谱法对生产者的分类的正确率都要高于对年份的聚类。说明品种是葡萄酒最主要和典型的特征，对葡萄酒影响最大，其次是生产者或酿造工艺，最后是年份。

5.　同步荧光光谱法与三维荧光光谱法的比较

对两种荧光光谱法进行比较，发现结合化学计量学方法两种荧光光谱法都能很好区分不同的葡萄酒样品，而且能够正确地对葡萄酒按品种、生产者和年份进行分类。

三维荧光光谱法在对葡萄酒进行聚类时正确率相对高一些，说明三维荧光光谱法能较好地提取葡萄酒的特征信息，但同步荧光光谱法相对于三维荧光光谱法更快速些，数据分析也相对容易，因此可以作为三维荧光光谱法的替代方法，用来建立葡萄酒的同步荧光光谱指纹图谱来进行葡萄酒的鉴别。

关键词　宁夏原产地葡萄酒　荧光光谱　化学计量学

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 fluorimetry

Wine 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 various Δλ,best discrimination was obtained when Δλ=90nm.

2.　Synchronous Fluorescence spectra and three dimensional Fluorescence spectra of wines from Ningxia

SFS 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 Sauvignonand Merlot). EEM of Chardonneyhave 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 Sauvignonand 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 Chemometrics

Wine 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 vintage

Correct 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 analyses

It 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.

Key words　Wines from Ningxia　Fluorescence spectroscopy　Chemometrics