Trace metal studies of selected white wines: an alternative approach

A number of white wines from vineyards outside the metropolitan region of Melbourne were analyzed for the trace metals copper, iron, potassium, sodium, magnesium and calcium by atomic absorption spectrometry (AAS). The 24 wines analyzed included Chardonnay, Sauvignon Blanc, Riesling, Gewürztraminer and Pinot Gris. In addition, preliminary transmission near infrared (NIR) spectrometric analyses for these metals in the above wines indicated, using both multiple linear regression (MLR) and partial least squares (PLS), that promising results may be obtained for some metals. The squared correlation coefficients (R²) and the ratios of the standard error of cross validation (SECV) and the standard deviation (S.D.) for the calibration models for potassium, sodium, magnesium and calcium were acceptable, however those for iron and copper were not. Although, only a small number of wines were used in this study, the preliminary data indicated that NIR spectrometry may provide a suitable, rapid method for analysis for some metals in white wines, and warrants a further investigation using a larger number of white wines over a wider range of locations.     

Varietal discrimination of Australian wines by means of mid-infrared spectroscopy and multivariate analysis

This study outlines the use of mid-infrared (MIR) spectroscopy combined with principal component analysis (PCA) and linear discriminant analysis (LDA) for the varietal classification of commercial red and white table wines. Three red varieties (Cabernet Sauvignon, Shiraz and Merlot) and four white varieties (Chardonnay, Riesling, Sauvignon Blanc and Viognier) were sourced from different wine regions in Australia. Wine samples were scanned in transmission on a FOSS WineScan FT 120 from wave numbers 926 to 5012 cm⁻¹. All samples were sourced from the 2006 vintage and had not been blended with any other variety or wine from other regions. Spectral data were reduced to a small number of principal components (PCs) and LDA was then performed to successfully separate the wines into the different varieties. To test the robustness of the LDA models developed for the red wines, a set of red wines scanned in 2005 were used. Correct classification of over 95% was achieved for the validation set.     

中国不同产区赤霞珠干红葡萄酒香气成分数据的可视化分析

可视化技术被引入葡萄酒香气成分数据的分析,以达到鉴别区分不同产区葡萄酒的目的。葡萄酒分析样品是2005年赤霞珠干红葡萄酒产品。5个产区是河北昌黎、新疆玛纳斯、云南弥勒、宁夏贺兰山东麓和河北沙城。香气成分用二氯甲烷连续萃取,有机相真空浓缩之后进行GC-MS分析检测。共鉴定并半定量分析出5个产区赤霞珠干红葡萄酒中68种香气成分,对原始色谱分析数据进行标准归一化处理,将信息映射到[0,1]之间的灰度图空间,然后根据数据可视化原理,用Vc 构建含多种香气成分信息的二维灰度图,直观表征不同产地赤霞珠干红葡萄酒的香气成分信息。研究结果是一种反映葡萄酒化学信息的条形码技术,该技术转换葡萄酒香气成分色谱数据之后得到二维灰度图,能够良好区分不同产区的赤霞珠干红葡萄酒。     

Simultaneous determination of levodopa and carbidopa by synchronous fluorescence spectrometry using double scans

The aim of this study was to investigate the potential use of a direct headspace-mass spectrometry electronic nose instrument (MS e_nose) combined with chemometrics as rapid, objective and low cost technique to measure aroma properties in Australian Riesling wines. Commercial bottled Riesling wines were analyzed using a MS e_nose instrument and by a sensory panel. The MS e_nose data generated were analyzed using principal components analysis (PCA) and partial least squares (PLS1) regression using full cross validation (leave one out method). Calibration models between MS e_nose data and aroma properties were developed using partial least squares (PLS1) regression, yielding coefficients of correlation in calibration (R) and root mean square error of cross validation of 0.75 (RMSECV: 0.85) for estery, 0.89 (RMSECV: 0.94) for perfume floral, 0.82 (RMSECV: 0.62) for lemon, 0.82 (RMSECV: 0.32) for stewed apple, 0.67 (RMSECV: 0.99) for passion fruit and 0.90 (RMSECV: 0.86) for honey, respectively. The relative benefits of using MS e_nose will provide capability for rapid screening of wines before sensory analysis. However, the basic deficiency of this technique is lack of possible identification and quantitative determination of individual compounds responsible for the different aroma notes in the wine.     

Comparison on phenolic compounds and antioxidant properties of cabernet sauvignon and merlot wines from four wine grape-growing regions in china

The antioxidant activities in the Cabernet Sauvignon and Merlot wines from four wine grape-growing regions in China were measured by different analytical assays: 2,2-diphenyl-1-picrylhydrazyl (DPPH·), cupric reducing antioxidant capacity (CUPRAC), superoxide radical-scavenging activity (SRSA) and the contents of total phenols, total flavonoids, total flavanols and total anthocyanins were determined. The results showed that the contents of phenolic compounds and the levels of antioxidant activity in the wine samples greatly varied with cultivar and environmental factors of vine growth. The contents of phenolic compounds and antioxidant activities in Cabernet Sauvignon and Merlot wines from the Yuquanying region of Ningxia were significantly higher than other three regions, followed by the wines from Shacheng region of Hebei, and these parameters were the lowest in Cabernet Sauvignon and Merlot wines from the Changli regions of Hebei and Xiangning region of Shanxi. Taken together, a close relationship between phenolic subclasses and antioxidant activity was observed for the wine samples. Moreover, there were significant discrepancies in the individual phenolic composition and content of four regional Cabernet Sauvignon and Merlot wines, among which the individual phenolic compounds (catechin, epicatechin, cinnamic acid, quercetin-3-O-glucuronide, quercetin-3-O-glucoside, laricitrin-3-O-glucoside and isorhamnetin-3-O-glucoside) revealed a significant correlation (p < 0.05) with the antioxidant capacity in present study, especially for catechin and epicatechin.     

Determination of glutathione content in grape juice and wine by high-performance liquid chromatography with fluorescence detection

A modified preparation of sample was developed for the determination of glutathione content in grape juice and wine by high-performance liquid chromatography with fluorescence detection, using on-line pre-column derivatization. Ice-cold deoxygenated methanol was used to deactivate the oxidation enzymes in juices or wines and keep the glutathione stable. The optimum recovery of glutathione content in grape juice and wine was obtained when either the sample of grape juice or wine was mixed in ice-cold deoxygenated methanol in the ratio 10:90 (v:v) and further diluted in sodium acetate buffer in the ratio 1:1 (v:v). The optimized method was validated for linearity, limit of detection, limit of quantification, precision and uncertainty. According to the validation data the method is appropriate for the determination of glutathione content in grape juice and wine. Glutathione contents in grape juices made from White Muscat grapes and Sauvignon Blanc wines were analysed. The average glutathione content in 28 young Sauvignon Blanc wines was 12.5 mg L⁻¹.     

Geographical classification of some Australian wines by discriminant analysis using HPLC with UV and chemiluminescence detection

HPLC with UV and acidified potassium permanganate chemiluminescence detection, combined with multivariate data analysis techniques, were used for the geographical classification of some Australian red (Cabernet Sauvignon) and white (Chardonnay) wines from two regions (Coonawarra and Geelong). Identification of the wine constituents prominent in the chromatography was performed by mass spectrometry. Principal components analysis and linear discriminant analysis were used to classify the wines according to region of production. Separation between regions was achieved with both detection systems and key components leading to discrimination of the wines were identified. Using two principal components, linear discriminant analysis with UV detection correctly classified 100% of the Chardonnay wines and, overall 91% of the Cabernet Sauvignon wines. With acidified potassium permanganate chemiluminescence detection, 75% of the Chardonnay wines and 94% of the Cabernet Sauvignon wines were correctly classified using two factors.     

Identification of potent odourants in wine and brewed coffee using gas chromatography-olfactometry and comprehensive two-dimensional gas chromatography

Volatile constituents in wine and brewed coffee were analyzed using a combined system incorporating both GC-olfactometry (GC-O) and comprehensive two-dimensional GC-flame ionization detection (GC×GC-FID). A column set consisting of a 15m first dimension ((1)D; DB-FFAP (free fatty acid phase)), and a 1.0m (2)D column (DB-5 phase) was applied to achieve the GC×GC separation of the volatile extracts isolated by using solid phase extraction (SPE). While 1D GC resulted in many overlapping peaks, GC×GC allowed resolution of co-eluting compounds which coincided with the odour region located using GC-O. Character-impact odourants were tentatively identified through data correlation of GC×GC contour plots across results obtained using either time-of-flight mass spectrometry (TOFMS), or with flame photometric detection (FPD) for sulfur speciation. The odourants 2-methyl-2-butenal, 2-(methoxymethyl)-furan, dimethyl trisulfide, 2-ethyl-5-methyl-pyrazine, 2-octenal, 2-furancarboxaldehyde, 3-mercapto-3-methyl-1-butanol, 2-methoxy-3-(2-methylpropyl)-pyrazine, 2-furanmethanol and isovaleric acid were suspected to be particularly responsible for coffee aroma using this approach. The presented methodology was applied to identify the potent odourants in two different Australian wine varietals. 1-Octen-3-ol, butanoic acid and 2-methylbutanoic acid were detected in both Merlot and a Sauvignon Blanc+Semillon (SV) blend with high aroma potency. Several co-eluting peaks of ethyl 4-oxo-pentanoate, 3,7-dimethyl-1,5,7-octatrien-3-ol, (Z)-2-octen-1-ol, 5-hydroxy-2-methyl-1,3-dioxane were likely contributors to the Merlot wine aroma; while (Z)-3-hexen-1-ol, β-phenylethyl acetate, hexanoic acid and co-eluting peaks of 3-ethoxy-1-propanol and hexyl formate may contribute to SV wine aroma character. The volatile sulfur compound 2-mercapto-ethyl acetate was believed to contribute a fruity, brothy, meaty, sulfur odour to Australian Merlot and SV wines.     

Multi-Year Study of the Chemical and Sensory Effects of Microwave-Assisted Extraction of Musts and Stems in Cabernet Sauvignon,Merlot and Syrah Wines from the Central Coast of California

Microwave technology (MW) was applied to musts and stems over three consecutive vintages in Cabernet Sauvignon, Merlot and Syrah wines from California (USA). Stems were added to musts at a rate of 50 and 100% (50% Stems and 100% Stems), either as untreated or after MW (50% MW Stems and 100% MW Stems). Stem additions lowered ethanol (up to 1.15% v/v reduction), but increased pH (up to 0.16 units) and the tannin content of the wines. In 2016, tannins increased by 103% (100% Stems), and 124% (100% MW Stems). In 2017, tannins increased by 39% in stem-added Merlot wines and by 63% (100% Stems) and 85% (100% MW Stems) in Syrah wines. In 2018, tannins in Syrah wines increased by 250% (100% MW Stems) and by 743% (100% Stems). Wines made with 50% Stems exhibited intermediate tannin contents. Must MW increased flavonols (up to 278% in Syrah wines), monoglucosylated, acylated and anthocyanin-derived pigments. Stem additions reduced wine color and polymeric pigment formation in Syrah. Must MW decreased the perception of coarseness and herbaceous flavors in Merlot, whereas stem additions increased herbaceous aromas in Syrah. Despite higher tannin contents in stem-added wines, no concomitant increases in astringency were observed.     

Rapid analysis of grape aroma glycoconjugates using Fourier-transform infrared spectrometry and chemometric techniques

The varietal aroma of most wines from non-aromatic grapes is partly dependent on the qualitative and quantitative composition of glycosidic precursors in grapes. The only rapid method to assess these glycoconjugates (Red-Free Glycosyl-Glucose (G-G) method) allows only their total quantitation. We developed a new method using Fourier-transform infrared spectrometry (FT-IR) and chemometric techniques allowing these glycosidic precursors to be determined more finely. Vitis vinifera cv. Melon B. grapes grown in different areas of Muscadet vineyard (Northwest France) and harvested at different maturity stages were used to demonstrate the potentiality of this analysis method. Predictive partial least squares (PLS) regressions were established using 39 samples, representative of the glycoside variability. These models allowed the total levels of C13-norisoprenoidic and monoterpenic glycoconjugates, the most relevant aroma glycoconjugates for Muscadet wines, to be determined with a predictive error of 14 and 15%, respectively, and the total levels of the other classes of glycoconjugates with predictive errors ranging from 22% for volatile phenols to 36% for aliphatic and aromatic alcohols.     

Development of a mixed-mode solid phase extraction method and further gas chromatography mass spectrometry for the analysis of 3-alkyl-2-methoxypyrazines in wine

A new method for analysing 3-isopropyl-2-methoxypyrazine, 3-sec-butyl-2-methoxypyrazine and 3-isobutyl-2-methoxypyrazine in wine has been developed and applied to wine. The analytes are extracted from 25 mL of wine in a solid-phase extraction cartridge filled with 60 mg of cation-exchange mixed-mode sorbent. Analytes are recovered with triethylamine in dichloromethane and the organic extract is analysed by GC-SIM-MS using 3-isopropyl-2-ethoxypyrazine as internal standard. The detection limits of the method are in all cases under 1 ng/L, below the olfactory thresholds of the compounds in wine. The repeatability of the method is around 15% for levels in wine of 2 ng/L. Linearity is satisfactory and recoveries are in all cases close to 100% with RSD between 13% and 20%. The method has been applied to the analysis of 12 Chilean white and 8 Spanish red wines. The levels found suggest that 3-alkyl-2-methoxypyrazines can exert a significant sensory contribution to the aroma of Chilean Sauvignon Blanc wines, while most likely they play a nearly negligible role on traditional Ribera and Rioja Spanish red wines.     

Effect of Hanseniaspora uvarum–Saccharomyces cerevisiae Mixed Fermentation on Aroma Characteristics of Rosa roxburghii Tratt,Blueberry, and Plum Wines

Hanseniaspora uvarum, a non-Saccharomyces cerevisiae species, has a crucial effect on the aroma characteristics of fruit wines, thus, attracting significant research interest in recent years. In this study, H. uvarum–Saccharomyces cerevisiae mixed fermentation was used to ferment Rosa roxburghii Tratt, blueberry fruit wine, and plum fruit wines using either a co-inoculated or a sequentially inoculated approach. The three fruit wines’ volatile aroma characteristics were analyzed by headspace–solid-phase microextraction–gas chromatography-mass spectrometry (HS–SPME–GC–MS). The results showed that the mixed inoculation of H. uvarum and S. cerevisiae reduced the alcoholic content of Kongxinli fruit wine. Moreover, H. uvarum–S. cerevisiae fermented Rosa roxburghii Tratt, blueberry, and plum fruit wines and further enriched their flavor compounds. The overall flavor characteristics of sequentially inoculated fruit wines differed significantly from those fermented with S. cerevisiae alone, although several similarities were also observed. Sequential inoculation of H. uvarum and S. cerevisiae positively affected the mellowness of the wine and achieved a better harmony of the overall wine flavors. Therefore, H. uvarum–Saccharomyces cerevisiae mixed fermentation can improve the complexity of the wines’ aromatic composition and empower them with a unique identity. In particular, H. uvarum–Saccharomyces cerevisiae blueberry wine produced by mixed fermentation had the widest variety and content of aroma compounds among the fermented wines. Therefore, H. uvarum–Saccharomyces cerevisiae mixed-fermentation inoculation in the three fermented fruit wines significantly increased the aroma compound variety and content, thus, enriching their aroma richness and complexity. This study is the first comparative evaluation of the aroma characteristics of different fruit wines fermented with a mixed inoculation of H. uvarum and S. cerevisiae and provides a preliminary guide for these fruit wines produced with non-Saccharomyces yeast.     

Determination of furaneol (4-hydroxy-2,5-dimethyl-3(2H)-furanone) in some wines from Italian native grapes by Gas-Chromatography-SIM/MASS spectrometry

Gas Chromatography-Mass Spectrometry (GC-MS) analysis by Selective Ion Monitoring (SIM) was applied to quantify 4-Hydroxy-2,5-dimethyl-3(2H)-furanone (HDMF) in both red and white wines obtained from some Italian cultivar of Vitis vinifera. Wines were extracted by liquid-liquid extraction performed with 1,1,2-trichlorotrifluoroethane (Freon 113). The ion m/z 128 was used for quantification while the ion m/z 129 as qualifier. Precision, linearity and accuracy of the method resulted satisfactory. Results showed a significant variation in the concentration of furaneol in wine with grape variety. Generally, HDMF concentrations in white wines were lower than in red wines. Among white wines, Chardonnay resulted characterized by the highest concentration of HDMF. Among red wines the highest concentrations of HDMF were detected in Primitivo and Refosco varieties.     

Comparison of the volatile aroma components in noble rotted grape berries from two different locations of the Tokaj wine district in Hungary

The most famous wine type of Hungary is Tokaji Aszú. Noble rotted botrytised (Aszú) grape berries and a specific vinification technology give its unique delicious aroma and taste. The present work compares volatile aroma components of noble rotted Aszú grape berries from two different locations in the Tokaj wine district. Aszú grape berries have been soaked in 10% ethanol-containing water solutions and thereafter extracted with Freon 11. Volatile components were determined by gas chromatography-mass spectrometry (GC-MS). The total ion chromatograms contained 220-260 components. More than 80 components are identified, among them alcohols, aldehydes, acids, acetals, esters, epoxides, nitrils, furan derivatives and lactones. The compositional differences between the two Aszú grape samples are analysed according to the different component classes. The differences are quantitative rather than qualitative. Some δ-lactones are identified for the first time in noble rotted berries from Tokaj. These substances have very characteristic odor notes such as coconut, chocolate, peach, fruity. Together with the identified γ-lactones they seem to be characteristic aroma components of Tokaji Aszú wines.     

Development of a routine analysis of 4-mercapto-4-methylpentan-2-one in wine by stable isotope dilution assay and mass tandem spectrometry

The 4-mercapto-4-methylpentan-2-one (4MMP) is a key aroma compound in wines, especially in Sauvignon Blanc ones. Its accurate quantification is quite difficult due to its traces levels and its reactivity in wine conferred by the thiol function. In this paper, we proposed a new method for its quantification in wine without any sample preparation, based on automated derivatization procedure by methoximation and SIDA–SPME–GC–MS/MS analysis. The derivatization procedure was adapted from a previously published method in order to decrease the amount of reagents and the volume of wine (only 3 mL are required). The use of SPME and the detection conditions have also been optimized to reach the best sensitivity as possible. The method was then validated according to the International Organization of Vine and Wine recommendations and exhibited excellent performances. Indeed, this method allowed us to quantify the 4MMP in wine at traces levels (LOD = 0.19 ng L⁻¹) with reproducible results (RSD < 15%) and a very good accuracy (recovery = 102%).     

Development of a sensitive non-targeted method for characterizing the wine volatile profile using headspace solid-phase microextraction comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry

Future understanding of differences in the composition and sensory attributes of wines require improved analytical methods which allow the monitoring of a large number of volatiles including those present at low concentrations. This study presents the optimization and application of a headspace solid-phase microextraction (HS-SPME) method for analysis of wine volatiles by comprehensive two-dimensional gas chromatography (GC×GC) time-of-flight mass spectrometry (TOFMS). This study demonstrates an important advancement in wine volatile analysis as the method allows for the simultaneous analysis of a significantly larger number of compounds found in the wine headspace compared to other current single dimensional GC-MS methodologies. The methodology allowed for the simultaneous analysis of over 350 different tentatively identified volatile and semi-volatile compounds found in the wine headspace. These included potent aroma compound classes such as monoterpenes, norisoprenoids, sesquiterpenes, and alkyl-methoxypyrazines which have been documented to contribute to wine aroma. It is intended that wine aroma research and wine sensory research will utilize this non-targeted method to assess compositional differences in the wine volatile profile.