High-resolution NMR and diffusion-ordered spectroscopy of port wine

The use of high-resolution NMR and high-resolution diffusion-ordered spectroscopy (DOSY) for the characterization of selected Port wine samples of different ages with the aim of identifying changes in composition is described. Conventional 1D and 2D NMR methods enabled the identification of about 35 compounds, including minor components such as some medium-chain alcohols, amino acids, and organic acids. High-resolution (HR) DOSY extended sample characterization, increasing the number of compounds identified and NMR assignments made, by providing information on the relative molecular sizes of the metabolites present. Port wines of different ages were found to differ mainly in their content of (a) organic acids and some amino acids, (b) an unidentified possible disaccharide, and (c) large aromatic species. The relative amount of these last high Mw aromatics is seen to decrease significantly in the oldest wine, as expected from the known formation and precipitation of anthocyanin-based polymers during red wine aging.     

不同品种红葡萄酒花色苷高效液相色谱指纹图谱识别

利用高效液相色谱法建立了9个品种葡萄酒的花色苷指纹图谱,对不同品种葡萄酒进行识别。HPLC检测：采用反相C18柱,调整流动相pH值1.6,二元梯度洗脱,检测波长518 nm。指纹图谱建立方法：计算HPLC色谱峰的相对保留时间和相对峰面积,按相对保留时间排列相对应的相对峰面积。采用夹角余弦法计算相关系数,并使用SPSS11.0统计分析软件对指纹图谱进行系统聚类分析。结果表明：不同品种葡萄酒花色苷的HPLC指纹图谱存在着差异,山葡萄种及杂种葡萄酒具有区别于欧亚种葡萄酒的特征色谱峰;不同品种葡萄酒花色苷指纹图谱的相似性不同,不同种间品种葡萄酒相似性较差;系统聚类分析初步建立了不同品种葡萄酒花色苷识别模式,对葡萄酒进行了较好的识别。指纹图谱技术结合聚类分析是识别不同酿造品种葡萄酒的有效方法之一。     

Tannin quantification in red grapes and wine: comparison of polysaccharide- and protein-based tannin precipitation techniques and their ability to model wine astringency

Quantification of red grape tannin and red wine tannin using the methyl cellulose precipitable (MCP) tannin assay and the Adams-Harbertson (A-H) tannin assay were investigated. The study allowed for direct comparison between the repeatability of the assays and for the assessment of other practical considerations such as time efficiency, ease of practice, and throughput, and assessed the relationships between tannin quantification by both analytical techniques. A strong correlation between the two analytical techniques was observed when quantifying grape tannin (r(2) = 0.96), and a good correlation was observed for wine tannins (r(2) = 0.80). However, significant differences in the reported tannin values for the analytical techniques were observed (approximately 3-fold). To explore potential reasons for the difference, investigations were undertaken to determine how several variables influenced the final tannin quantification for both assays. These variables included differences in the amount of tannin precipitated (monitored by HPLC), assay matrix variables, and the monomers used to report the final values. The relationship between tannin quantification and wine astringency was assessed for the MCP and A-H tannin assays, and both showed strong correlations with perceived wine astringency (r(2) = 0.83 and r(2) = 0.90, respectively). The work described here gives guidance to those wanting to understand how the values between the two assays relate; however, a conclusive explanation for the differences in values between the MCP and A-H tannin assays remains unclear, and further work in this area is required.     

Chemometric classification of Apulian and Slovenian wines using 1H NMR and ICP-OES together with HPICE data

High-performance ion chromatography exclusion, inductively coupled plasma emission spectroscopy, and nuclear magnetic resonance (NMR) measurements were carried out in combination with chemometrics on 33 wine samples coming from three Slovenian wine-growing regions and from Apulia (southern Italy). The chemometric classification of wines according to their geographical origin was obtained with a nearly 100% degree of achievement. The discriminating potential of the (1)H NMR and of the other analytical determinations has been estimated separately. The best prediction of wines has been obtained with NMR data.     

Identification of amino acids in wines by one- and two-dimensional nuclear magnetic resonance spectroscopy

Amino acids are minor compounds in wines, but they have a profound influence on wine quality, and amino acids composition can be used to differentiate wines according to the vine variety, geographical origin, and year of production. The NMR signals of amino acids in NMR spectra are overlapped by the signals of other compounds present and especially by the signals of dominant compounds such as water, ethanol, and glycerol. In this work we used 1D (1)H and (13)C, 2D homonuclear COSY, TOCSY, and 2D heteronuclear HSQC and HMQC pulse sequences, also with an incorporated WET pulse sequence element that allows the simultaneous suppression of several frequencies. Complete (1)H and (13)C NMR assignments for 17 amino acids commonly present in wine and of gamma-aminobutyric acid at pH 3 have been achieved in wine sample of Sauvignon from the Coastal wine-growing region of Slovenia, vintage 1994.     

Potent aroma compounds of two red wine vinegars

Gas chromatography olfactometry (GCO) was used to determine key aroma compounds of two red wine vinegars. Sensory analysis was performed to choose the best neutralization agent of acetic acid (NaOH or MgO) and to test representativeness of four extracts obtained by different methods (dichloromethane extraction, XAD-2, mixture of XAD-2 and XAD-7, and Extrelut resins extraction). Neutralization with NaOH followed by dichloromethane extraction was selected to extract volatile compounds of vinegars. Key odorant compounds were determined by GCO based on detection frequency with 13 people. In the two red wine vinegars, 13 odors were perceived by at least 70% of the panelists, and 8 compounds among the 13 were identified: acetic acid, 3-methylbutyric acid, 2-phenyl-1-ethanol, 2, 3-butanedione, butyric acid, 2-methylbutyric acid, mixture of 2- and 3-methyl-1-butanol, and two newly identified compounds in vinegar, 3-hydroxy-2-pentanone and 3-(methylthio)-1-propanal. Quantification of all the volatile compounds was performed by GC-FID, and 10 other compounds were identified for the first time in wine vinegar.     

A comparison of four different raw humus types in Norway using chemical degradations and CPMAS 13C NMR spectroscopy

Crust, felty, greasy and granular raw humus were analysed by wet chemical methods and by ¹³C NMR. The amounts of amino acids, monosaccharides and aliphatic dicarboxylic acids were determined and the yields compared with the ¹³C NMR spectra. Protein carbon constitutes 9–13%, polysaccharide carbon 8–19% dicarboxylic acids 1–2% and free carboxylic acid groups 2–4% of the total sample carbon. Degradation of greasy raw humus yields half the amount of monosaccharides and twice the amount of aliphatic dicarboxylic acids found in the other raw humus types. This result is confirmed by ¹³C NMR. Forty to fifty percent of the soil carbon is unaccounted for among the degradation products identified. Based on estimates of ¹³C NMR data, the unknown part consists of aliphatic carbon, where the C:O ratio ranges between 1 1.1:1 and 1.8:1. All data indicate great similarity between crust and felty raw humus, whereas greasy raw humus differs clearly from those two. Granular raw humus gives approximately the same amount of degradation products as crust and felty raw humus but differs in its ¹³C NMR spectrum. The relative proportions of all compounds identified, including aliphatic dicarboxylic acids, are approximately constant, indicating a difference in degree rather than kind of the four raw humus types.     

Development of a rapid "fingerprinting" system for wine authenticity by mid-infrared spectroscopy

This paper reports on the development of a rapid and simple method for red wine authenticity confirmation during transport and processing; namely, a wine "fingerprinting" system. When wine is transported between two sites, a sample is taken and a mid-infrared (MIR) spectrum is obtained. One hundred sixty-one (n = 161) samples of three main red wine varieties grown in Australia, Shiraz, Cabernet Sauvignon, and Merlot, were collected from six commercial wineries across Australia and scanned in transmission on two MIR spectrophotometers located at The Hardy Wine Company's main site at Reynella, South Australia (Foss WineScan FT 120) (926-5012 cm-1). A similarity index (SI) method was used as a tool to classify wine samples on the basis of their spectral data. The results showed that high rates of classification were obtained when wine samples scanned in different instruments were analyzed. The SI has been proven to provide an acceptable measurement for authentication of red wine integrity during transportation. In five of the six winery data sets, the SI correctly classified 98% of the wines. It was also observed that less than 1% of wines were misclassified between the different wineries investigated. Further studies are needed in order to test the applicability of the SI in a commercial situation and to evaluate its potential as a rapid quality control tool for routine use to authenticate wine samples during transport.     

Fining treatments of white wines by means of polymeric adjuvants for their stabilization against browning

Browning and maderization represent important problems for white wine stability. Essentially, this is due to polyphenol oxidation in the wine. The problem has been remedied by adsorption of polyphenol compounds with polymeric adjuvants (chitosans, scleroprotein, and polylactic acid) not used traditionally in wine-making. In particular, some chitosans reduced the polyphenol content and stabilized two Italian white wines (Trebbiano and Albana) to the same extent as did potassium caseinate, an adjuvant normally used in enology. Moreover, chitosans could be reused after a simple regeneration process.     

Direct method for determining seed and skin proanthocyanidin extraction into red wine

A method was developed for determining the amount of seed and skin proanthocyanidin extraction into wines by direct measurement. This method was based upon the analysis of proanthocyanidin cleavage products after acid catalysis in the presence of excess phloroglucinol. On the basis of the analysis of proanthocyanidin extracts from grape tissues, two observations were made as follows: (i) the seed and skin proanthocyanidin extension subunit compositions were considerably different from each other, and (ii) their composition did not vary with extraction time. Thus, by comparing the proportional extension subunit composition of proanthocyanidins in wine relative to their proportional composition in corresponding grape seed and skin, it was possible to determine the contribution of each to wine. To provide additional information, the procedure was used to investigate seed and skin proanthocyanidin extraction during commercial-scale fermentations that had undergone 4 or 10 day low temperature prefermentation skin contact prior to the onset of fermentation. The results for both fermentations indicated that the proportion of skin tannin declined during fermentation and also showed that at the end of fermentation the amount and proportion of skin tannin were the same.     

Multivariate analysis of CPMAS 13C-NMR spectra of soils and humic matter as a tool to evaluate organic carbon quality in natural systems

A series of humic and fulvic acids isolated from different sources, size‐fractions separated from a humic acid, and three soils of different origin were subjected to CPMAS ¹³C‐NMR spectroscopy to obtain the distribution of their carbon contents. The relative areas of chemical shift regions in NMR spectra were used to apply a principal component analysis (PCA) to the three sets of samples. The multivariate analysis was successful in efficiently differentiating samples on the basis of the quality of their organic carbon content. The PC biplots based on two principal components distinguished objectively among samples as accurately as it was possible to do by subjective qualitative evaluation of the original spectra. In the case of the soils, a discriminant analysis (DA) was applied to build a classification model that allowed the validation of the three soils according to their origin. Percentage of validation in the classification model is expected to increase when a large number of NMR spectra are accumulated and/or the concentration of organic carbon in samples is enhanced. The multivariate analyses described are likely to become a useful tool to increase the importance of CPMAS ¹³C‐NMR spectra in the appraisal of natural organic matter variations in heterogeneous natural systems.     

Investigations of La Rioja terroir for wine production using 1H NMR metabolomics

In this study, La Rioja wine terroir was investigated by the use of (1)H NMR metabolomics on must and wine samples. Rioja is a small wine region in central northern Spain which can geographically be divided into three subareas (Rioja Alta, Rioja Baja, and Rioja Alavesa). The winemaking process from must, through alcoholic and malolactic fermentation, was followed by NMR metabolomics and chemometrics of nine wineries in the Rioja subareas (terroirs). Application of interval extended canonical variate analysis (iECVA) showed discriminative power between wineries which are geographically very close. Isopentanol and isobutanol compounds were found to be key biomarkers for this differentiation.     

基于GF-6卫星影像多特征优选的酿酒葡萄精准识别

多源遥感信息和特征优选是提高农作物识别精度的重要支撑,高分六号（GF-6）卫星作为首次引入红边波段的国产卫星,其丰富的光谱信息为作物识别提供了新的思路和解决途径。该研究基于宁夏回族自治区银川市永宁县2018年6月-2019年3月的GF-6数据,充分利用红边优势提取光谱特征、纹理特征和植被指数特征,构建多种特征组合方案,并根据随机森林算法对特征重要性进行度量,选取最优特征组合对酿酒葡萄进行精准识别。结果表明,与单一特征相比,多源遥感特征的增加显著改善了酿酒葡萄分类效果,其中,植被指数贡献程度最大,光谱特征次之;基于随机森林的优选特征组合分类效果最佳,其中,总体分类精度为94.15%,酿酒葡萄用户精度为94.23%,制图精度为92.59%;以实地调查的4个酒庄为验证区,将酿酒葡萄提取结果与统计数据进行对比,面积相对精度均在70%以上,其中优选特征结果相对精度在90%以上,研究结果将为国产卫星红边波段在植被分类和识别方面的应用提供数据参考。     

Electrochemical sensing of total antioxidant capacity and polyphenol content in wine samples using amperometry online-coupled with microdialysis

This work describes the method for total antioxidant capacity (TAC) and/or total content of phenolics (TCP) analysis in wines using microdialysis online-coupled with amperometric detection using a carbon microfiber working electrode. The system was tested on 10 selected wine samples, and the results were compared with total reactive antioxidant potential (TRAP), oxygen radical absorbance capacity (ORAC), and chemiluminescent determination of total antioxidant capacity (CL-TAC) methods using Trolox and catechin as standards. Microdialysis online-coupled with amperometric detection gives similar results to the widely used cyclic voltammetry methodology and closely correlates with ORAC and TRAP. The problem of electrode fouling is overcome by the introduction of an electrochemical cleaning step (1-2 min at the potential of 0 V vs Ag/AgCl). Such a procedure is sufficient to fully regenerate the electrode response for both red and white wine samples as well as catechin/Trolox standards. The appropriate size of microdialysis probes enables easy automation of the electrochemical TAC/TCP measurement using 96-well microtitration plates.     

Synergetic activity of catechin and other antioxidants.

The antioxidant synergy between (+)-catechin and other wine or biological antioxidants (Trolox, ascorbate, SO(2), uric acid) was measured in vitro using the Folin-Ciocalteu (FC) and metmyoglobin assays. Although the two assays are based on very different reagents (i.e., metal salts versus organic and biochemical reagents), the individual antioxidants showed similar relative activities in both systems. In addition, interaction studies showed simple additive effects in all cases except with the (+)-catechin/SO(2) mixture, which showed a remarkable synergetic effect in both assays.     

NMR-based metabolic profiling of rice wines by F(2)-selective total correlation spectra

In this study, we performed NMR-based metabolic profiling of major rice wines (Japanese sake, Chinese Shaoxing wine, and Korean makgeolli). In the (1)H NMR spectra, the rice wines showed broad resonances in the region of about 7.9-9.0 ppm. These resonances showed many and complex correlations with approximately 0.5-4.5 ppm in the F(2)-selective TOCSY (total correlation spectroscopy) spectra, and these correlations were attributed mainly to peptides. These spectral patterns were characteristic of individual rice wines, and the combination of F(2)-selective TOCSY spectra and principal component analysis enabled us to classify the rice wine species. Furthermore, it also provided information about raw materials, namely, what type of koji (rice koji or wheat koji) was used. These spectra may be useful as a new "fingerprint" for quality control or food authentication.     

Lignin modification during Eucalyptus globulus kraft pulping followed by totally chlorine-free bleaching: a two-dimensional nuclear magnetic resonance, Fourier transform infrared, and pyrolysis-gas chromatography/mass spectrometry study

Chemical modification of eucalypt lignin was investigated during kraft pulping and chlorine-free bleaching by comparing milled wood lignin, kraft lignin, and pulp enzymatic residual lignins. The syringyl-to-guaiacyl ratio (S/G) from analytical pyrolysis slightly changed during pulping and bleaching (S/G, 3-4) but was higher in the kraft lignin. Semiquantitative heteronuclear single quantum correlation (HSQC) nuclear magnetic resonance (NMR) showed that the relative amount of beta-O-4' (around 80% side chains) and resinol type substructures (15%) was slightly modified during pulping and oxygen delignification. However, a decrease of resinol substructures (to only 6%) was found after alkaline peroxide bleaching. The relative amount of surviving linkages in the highly phenolic kraft lignin was dramatically modified; resinols were predominant. Oxygen delignification did not change interunit linkages, but a relative increase of oxidized units was found in the HSQC aromatic region, in agreement with the small increase of pyrolysis markers with oxidized side chains. NMR heteronuclear multiple bond correlations showed that the oxidized units after oxygen delignification bore conjugated ketone groups.     

Impact of concentration of ellagitannins in oak wood on their levels and organoleptic influence in red wine

Some wood substances such as ellagitannins can be extracted during wine aging in oak barrels. The level of these hydrolyzable tannins in wine depends of some parameters of oak wood. Their impact on the organoleptic perception of red wine is poorly known. In our research, oak staves were classified in three different groups according to their level of ellagitannins estimated by NIRS (near infrared spectroscopy) online procedure (Oakscan). First, the ellagitannin level and composition were determine for each classified stave and an excellent correlation between the NIRS classification (low, medium and high potential level of ellagitannin) and the ellagitannin content estimated by HPLC-UV was found. Each different group of NIRS classified staves was then added to red wine during its aging in a stainless tank, and the extraction and evolution of the ellagitannins were monitored. A good correlation between the NIRS classification and the concentration of ellagitannins in red wine aging in contact with the classified staves was observed. The influence of levels of ellagitannins on the resulting wine perception was estimated by a trained judge's panel, and it reveals that the level of ellagitannins in wine has an impact on the roundness and amplitude of the red wine.     

Method for measuring antioxidant activity and its application to monitoring the antioxidant capacity of wines.

A novel method for measuring the antioxidant activity using N, N-dimethyl-p-phenylenediamine (DMPD) was developed. The radical cation of this compound gives a stable colored solution and a linear inhibition of color formation can be observed in the presence of 0. 2-11 microg of TROLOX. The experimental protocol, which is rapid and inexpensive, ensures sensitivity and reproducibility in the measure of antioxidant activity of hydrophilic compounds. The effectiveness of the DMPD method on real foods was verified by evaluating the antioxidant ability of wine samples coming from different areas of Campania, Italy. Antioxidant capacity of wines is strictly related to the amount of phenolic compounds. The results obtained by the DMPD method are very similar to those obtained on the same samples when the radical cation of 2, 2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (Miller et al., 1996) was used.