Comparison of methods for the analysis of smoke related phenols and their conjugates in grapes and wine

Background and Aims: Australian grape growers and winemakers have typically relied on guaiacol and 4‐methylguaiacol measurements to determine smoke exposure of grapes following bushfires or prescribed burns. However, the guaiacol and 4‐methylguaiacol content of grapes does not always correlate with the extent of taint in resultant wines. This study compared several methods for the analysis of smoke related phenols and their conjugates in grapes and wine, to determine their capacity as diagnostic assays for smoke exposure. Methods and Results: Smoke‐affected grapes were sourced from commercial vineyards exposed to bushfire smoke and from experimental field trials involving the application of smoke to grapevines, and small‐scale wines were made from a number of these samples. Several analytical methods were applied to grapes and wine to determine the concentration of smoke related phenols and their conjugates. Strong correlations were observed between the glycoconjugate content of smoke‐affected grapes and the concentration of guaiacol and 4‐methylguaiacol released following acid hydrolysis of juice. Conclusions: Where smoke‐affected grapes contain low or non‐detectable levels of guaiacol and 4‐methylguaiacol, analytical methods that quantify their glycoconjugate forms (either directly or indirectly) provide a better indication of the extent of smoke exposure. Significance of the Study: This is the first study to compare different methods for assessing smoke exposure in grapes and wine, through analysis of free and bound guaiacol and 4‐methylguaiacol. These methods will allow grape growers and winemakers to more reliably assess smoke exposure of grapes, enabling better informed decisions to be made with regards to harvesting and processing smoke‐affected grapes.     

Characterisation and evolution of grape polyphenol profiles of Vitis vinifera L. cv. Tannat during ripening and vinification

Background and Aims: Changes in different polyphenol families during grape ripening and vinification were determined in Tannat grapes. This was done to establish a polyphenol profile for Tannat grapes during ripening and for young wines. Methods and Results: We demonstrated, by high‐performance liquid chromatography with diode array detection and mass spectrometry (HPLC‐DAD‐MS) analysis, that the content of flavan‐3‐ols in Tannat seeds was higher than that reported for a large number of other grape varieties analysed. Forty per cent of the total flavan‐3‐ols in seeds were galloylated compounds, whereas the flavan‐3‐ol profile in skins was characterised by the absence of galloylated forms. Prodelphinidins in skins ranged between 30 and 35% with very low values for epigallocatechin. Epicatechin gallate was not detected in Tannat wine and galloylated forms represented a low percentage of total flavan‐3‐ols. Tannat grapes had very high concentrations of anthocyanins in skins with levels increasing during ripening. Eleven phenolic acids were identified in Tannat grape skins and wines, but only gallic and protocatechuic acids were found in the seeds. Conclusions: Tannat wines were shown to have one of the highest levels of phenolic compounds reported for vinifera grape varieties. The profiles for different polyphenol families present in Tannat grapes (skins and seeds) and wines were determined. Significance of the Study: The results presented will help to better understand the phenolic winemaking potential of this variety and its functional properties within food chemistry.     

Determination of phenolic compounds of grape skins during ripening by NIR spectroscopy

The potential of near infrared spectroscopy (NIRS) to determine the content of phenolic compounds in red grapes has been evaluated. The near infrared spectra of intact grapes and grape skins throughout maturity were recorded using a fibre-optic probe and a transport quartz cup, respectively. Reference values of phenolic compounds were obtained by HPLC-DAD-MS. Modified Partial Least Squares (MPLS) regression was used to develop the quantitative models for flavanols, flavonols, phenolic acids, anthocyanins and total phenolic compounds. The procedure reported here seems to have an excellent potential for fast and reasonable cost analysis. The results of this work show that the models developed using NIRS technology together with chemometric tools allow the quantification of total phenolic compounds and the families of main phenolic compounds in grape skins throughout maturation. The validation of these models showed the best results for the determination of flavonols (differences between HPLC and NIRS of 7.8% using grapes and 10.7% using grape skins) in the external validation procedure. Good results in the external validation were also obtained for the determination of total phenolic compounds (differences of 11.7% using grapes and 14.7% using grape skins). The best results were generally obtained recording the spectra directly in intact grapes.     

近红外光谱分析技术在花生原产地溯源中的应用

采用近红外光谱结合化学计量学方法对不同省份来源的花生样品进行溯源研究。首先花生近红外光谱通过标准正态变换加去趋势化预处理降噪、主成分分析降维和小波转换降噪降维两种处理,然后结合线性判别分析、贝叶斯判别分析和k最近邻分析3种判别模型对不同省份来源地花生进行判别。通过分析最优判别组合结果表明,小波转换结合k最近邻分析对花生产地分类效果最好,原始正确分类率为100.0%;交叉验证正确分类率为55.9%。初步实现了花生产地判别,但模型的性能仍有待提高。     

新疆葡萄中3种生物活性物质的含量分析

为开发利用新疆葡萄,分析了新疆葡萄中生物活性物质的构成及其含量。采用超声法和回流法分别提取葡萄皮、籽中的齐墩果酸、白藜芦醇和原花青素,用高效液相色谱法和比色法分别测定葡萄皮、籽中齐墩果酸、白藜芦醇和原花青素的含量。葡萄中齐墩果酸主要存在于葡萄皮中,含量可高达1%左右,符合工业化提取要求;地产葡萄品种的齐墩果酸含量相对高于欧洲引进品种;齐墩果酸含量比较:人工发酵葡萄皮>自然发酵葡萄皮>新鲜葡萄皮。葡萄皮白藜芦醇的含量高于葡萄籽;欧洲引进葡萄品种白藜芦醇含量相对高于地产葡萄;白藜芦醇含量比较:人工发酵葡萄皮>自然发酵葡萄皮>新鲜葡萄皮>陈旧葡萄皮。葡萄籽原花青素含量高于葡萄皮;地产与欧洲引进葡萄品种的原花青素含量比较接近;原花青素含量比较:新鲜葡萄籽>自然发酵葡萄籽>人工发酵葡萄籽。由结果可以看出新疆葡萄富含齐墩果酸、白藜芦醇及原花青素等多种具有营养保健功能的生物活性物质。     

Comparison of analytical methods for the determination of condensed tannins in grape skin

Background and Aims: Condensed tannins extracted from grapes are an important organoleptic component of wine. Assessing tannin level in grapes requires an effective analytical method. This study compared the efficacy of three analytical methods. Methods and Results: Condensed tannin levels were measured in 38 grape skin samples by protein and methylcellulose precipitation and by high‐performance liquid chromatography (HPLC)‐phloroglucinolysis. Total phenolics were determined by absorbance at 280 nm. Tannin levels by protein and methylcellulose precipitation were of similar magnitude, while levels determined by HPLC‐phloroglucinolysis were generally higher. No correlation was found between the level of phenolics and tannins by any of the methods employed. Neither was there a correlation between tannin levels determined by HPLC‐phloroglucinolysis and by precipitation, although previously a strong correlation had been reported between protein precipitation and HPLC‐phloroglucinolysis in wine. Conclusions: The ratio of tannin to non‐tannin phenolics is highly variable between cultivars. Each analytical method measures a different fraction of the tannin extracted from grape skin. Significance of the Study: The disparity between analytical methods requires that method selection reflect the decision‐making that will utilise the information produced. For example, protein precipitation of tannins by bovine serum albumin (BSA) has been correlated with perceived astringency; consequently this may be the best indicator of potential mouthfeel.     

Plant protection product residues in red grapes and Teran PTP wine

Between 2011 and 2013, a total of 73 grape and 82 wine samples from winegrowing district Kras (Karst) were analysed for plant protection product (PPP) residues. The samples were analysed for the presence of 215 different active compounds using two multiresidual analytical methods: gas chromatography coupled with mass spectrometry and liquid chromatography coupled with tandem mass spectrometry. Residues were found in 91.8% of all grape samples and in 67.1% of all wine samples. In all grape samples, residues were below maximum residue levels (MRLs) and 58.9% of all grape samples contained active substances at a level of less then 10% of the MRL. Nearly 33% of all Teran PTP wines did not contain PPP residues at all. Residues diminish during processing of grapes to wine, so their content in wine was low. Therefore, it could be concluded that grapes and wine in the winegrowing district Kras are safe for consumers.     

Discrimination of seasonality in cheeses by near-infrared technology

BACKGROUND: Owing to the importance of the season of collection of milk for cheese quality, a study was made of the usefulness of near‐infrared spectroscopy (NIRS) for discriminating the seasonal origin (winter or summer) of milk and quantifying the fat content of cheeses, since fat is one of the components most affected by the season of collection of milk for the elaboration of cheeses. RESULTS: In the internal validation, 96% of samples from winter milk and 97% of samples from summer milk were correctly classified, while in the external validation the prediction rate of samples correctly classified was 92%. Moreover, quantitative models allowed the determination of fat in winter, summer and winter + summer cheeses. CONCLUSION: Rapid prediction of the fat content of cheeses and the seasonal origin (winter or summer) of milk was achieved using NIRS without previous destruction or treatment of samples. Copyright © 2011 Society of Chemical Industry     

Profiles of Phenolic Acids and Flavan‐3‐ols for Select Chinese Red Wines: A Comparison and Differentiation According to Geographic Origin and Grape Variety

The profiles of phenolic acids and flavan‐3‐ols for the selected Chinese red wines and the potential of using phenolic acids and flavan‐3‐ols to differentiate the geographic origin and grape variety of wines from China are investigated in this study. Significant differences and markers could be found according to the geographical origin and grape variety. Through a canonical discriminant analysis a good differentiation was developed according to the geographic origin or grape variety, and the accuracy of the discriminant model was 88.9% and 100%, respectively. According to the phenolic acid and flavan‐3‐ols profiles of the wine samples and good differentiation in the region and the variety discriminant analysis, minimal fraudulent claims were noted for the Chinese red wines investigated.     

Yeasts isolated from three varieties of grapes cultivated in different locations of the Dolenjska vine-growing region, Slovenia

The number and diversity of yeasts on grape berry surfaces are influenced by several factors, such as grape variety, degree of grape maturity at harvest, climatological conditions, geographic location, physical damage of grapes, the intensity of pest management etc. Cvicek is a typical Slovene wine, which has obtained a special protection under the Slovene Wine Law for its geographical origin. This blended red wine is produced from different grape varieties (Vitis vinifera L.), mostly from red grapes of Zametovka and Modra frankinja and from white grapes of Kraljevina. The aim of this study was to evaluate the impact of geographical locations in the Dolenjska vine-growing region and to obtain precise information about the influence of different grape varieties on the composition of yeast community on grape berries. The restriction fragment length polymorphism of PCR-amplified fragments from the rDNA gene cluster (PCR RFLP of rDNA) has been used for the differentiation of yeast species. The standard identification procedure has been performed on representative strains that shared identical RFLP profiles. The number of yeasts and yeast species isolated varied according to different grape varieties, Zametovka, Modra frankinja and Kraljevina (V. vinifera L.) and according to different sampling location. On the surface of grape berries 13 different yeast species have been identified. Saccharomyces cerevisiae has not been found.     

On-Vine Monitoring of Grape Ripening Using Near-Infrared Spectroscopy

This study evaluated the ability of near-infrared (NIR) spectroscopy to characterise the behaviour of white and red grapes during on-vine ripening, as a function of grape position in the bunch (high, middle and low) and bunch orientation (north, south, east and west) and to distinguish between different ripening stages with a view to optimising harvesting times depending on the grape variety and the type of wine to be made. A total of 24 bunches of two wine-grape varieties (cv. Pedro Ximénez and cv. Cabernet Sauvignon) were labelled and analysed directly on the vine using a commercially available handheld micro-electro-mechanical system spectrophotometer (1,600?C2,400?nm). Principal component analysis was performed to study relationships between the various configurations (grape position and bunch orientation), ripening stages and spectral data. Results for the white-grape variety showed that grapes high on the bunch behaved differently during ripening from those in central or low positions and that east-facing bunches behaved differently from the rest. For both varieties, analysis of bunch spectral characteristics enabled three stages of ripening to be distinguished: early, middle and late. Subsequently, the ability of NIR technology to classify wine grapes as a function of reducing-sugar content, with a view to optimising harvest timing, was evaluated by partial least squares discriminant analysis: 88?% of white grapes and 88?% of red grapes were correctly classified while over 79?% of samples were correctly assigned to representative groups. These results confirmed that NIR technology in the spectral range 1,600?C2,400?nm is an appropriate technique for on-vine monitoring of the ripening process, enabling selective harvesting depending on the type of wine to be made.     

Assessment of grey mould (Botrytis cinerea) impact on phenolic and sensory quality of Bordeaux grapes,musts and wines for two consecutive vintages

Background and Aims: The impact of grey mould (Botrytis cinerea (B. cinerea)) was quantified on chemical, phenolic and sensory qualities of grapes, derived musts and wines. Methods and Results: Analyses were carried out by using naturally or artificially infected grape berries at ripeness or overripeness. In grape seeds, chemical analyses revealed no major differences between healthy and rotten grapes. In grape skins of Botrytis‐affected berries, concentrations of all the phenolic compounds (anthocyanins and proanthocyanidin monomers, dimers and trimer) decreased drastically. Mean degree of polymerization of the proanthocyanidin polymeric fraction was also affected in skins. Chemical analyses of musts and wines made with different percentages of rotten berries showed a moderate impact of the pathogen on their phenolic composition. Nevertheless, sensory analyses underlined a loss of wine sensory quality perceptible from a threshold as low as 5% of Botrytis‐affected grapes onwards. Conclusion: Phenolic variations and the associated negative impact in grapes, derived musts and wines may be related to oxidation phenomena from B. cinerea. The main effects of severity/age of grey mould and the level of berry maturity are also discussed. Significance of the Study: B. cinerea drastically affects the phenolic and organoleptic properties of grape skins and derived wines. Therefore, prophylactic actions early in the vineyard, evaluation of the sanitary status of the harvested grapes and berry sorting are primordial even under low disease pressure.     

Comparison and Chemometric Analysis of the Phenolic Compounds and Organic Acids Composition of Chinese Wines

Characteristics of 106 wines from 5 major grape varieties and 3 typical geographic regions in China were investigated by means of profiling of organic acids and phenolic compounds analysis. An ultra‐performance liquid chromatography method was developed and thus, large number of samples could be determined in a quick and reliable way. The results showed that different origins and varieties were characteristic of various profiles of organic acid and phenolic compounds. In order to investigate possible correlation between organic acids and phenolic compounds content and grape variety and/or geographical origin, analysis of variance and linear discriminant analysis (LDA) were conducted. A satisfactory LDA result for red wines according to geographic origin was obtained, in which the correct classification was 100% and the leave‐one‐out validation accuracy was 90%. The corresponding results of white wines were 91% and 86%, respectively. When LDA was processed, according to grape varieties, the proportionality of successfully classified wines was 96%, while the leave‐one‐out validation accuracy was 94%. The organic acids and phenolic compounds profiles were useful in the classification of Chinese wines according to grape variety and geographic origin.     

Suitability of elemental fingerprinting for assessing the geographic origin of pumpkin (Cucurbita pepo var. styriaca) seed oil

An analytical method was developed and validated for the classification of the geographical origin of pumpkin seeds and oil from Austria, China and Russia. The distribution of element traces in pumpkin seed and pumpkin seed oils in relation to the geographical origin of soils of several agricultural farms in Austria was studied in detail. Samples from several geographic origins were taken from parts of the pumpkin, pumpkin flesh, seeds, the oil extracted from the seeds and the oil-extraction cake as well as the topsoil on which the plants were grown. Plants from different geographical origin show variations of the elemental patterns that are significantly large, reproducible over the years and ripeness period and show no significant influence of oil production procedure, to allow to a discrimination of geographical origin. A successful differentiation of oils from different regions in Austria, China and Russia classified with multivariate data analysis is demonstrated.     

Non‐galloylated and galloylated proanthocyanidin oligomers in grape seeds from Vitus vinifera L. cv. Graciano,Tempranillo and Cabernet Sauvignon

Non‐galloylated and galloylated flavan‐3‐ol composition in seeds from Vitis vinifera L. var. Graciano, Tempranillo and Cabernet Sauvignon grapes harvested in 2000, 2001 and 2002 at the same geographical area were determined using normal‐phase HPLC coupled with electrospray ionization mass spectrometry (LC/ESI‐MS) detection. Non‐galloylated and monogalloylated flavan‐3‐ols up to octamers, and di‐, and trigalloylated flavan‐3‐ols up to heptamers were identified in all grape seeds. Comparisons of the flavan‐3‐ol composition in three grape varieties harvested in three different years indicate that levels of non‐galloylated flavan‐3‐ols decrease as the degree of polymerization increased, whereas the monogalloylated dimers were present in the highest levels in all varieties and vintages. The levels of other monogalloylated flavan‐3‐ols varied in different vintages. Tempranillo contained the lowest levels of non‐galloylated and monogalloylated flavan‐3‐ols, whereas Graciano contained the highest levels, with the exception of non‐galloylated flavan‐3‐ols in vintage 2001, and non‐galloylated monomers in vintages 2000 and 2002. Grape seeds from vintage 2000 contained the highest levels of both non‐galloylated and galloylated structures. Statistical analyses indicate that the distribution of the flavan‐3‐ols is primarily determined by genetic factors and is also strongly influenced by climate conditions. Copyright © 2006 Society of Chemical Industry     

基于数字图像及随机最小二乘的红提串果粒尺寸检测分级方法

红提尺寸是衡量其品质的重要指标,为了实现整串红提的尺寸分级,本研究提出了一种基于机器视觉的尺 寸分级方法。通过双通道相机同时采集红提的红-绿-蓝（Red-Green-Blue,RGB）图像和近红外（near infrared,NIR） 图像,利用归一化超绿法去除RGB图像中干扰的绿色果梗信息,同时利用形态学重构的亮度局部极大值的方法对 NIR图像中的红提果粒进行识别和定位。采用梯度分割法有效地截取果粒轮廓并去除边缘轮廓中的干扰弧段,再利 用随机最小二乘椭圆检测的方法提取果粒尺寸,并对整串红提分级。采用该方法对42 串红提进行尺寸检测分级, 正确分级38 串,分级正确率为90.48%。实验结果表明：该方法分级正确率高,能够为葡萄市场分级提供技术支持。     

A Review of the Authentication of Wine Origin by Molecular Markers

Viniculture is one of the oldest agricultural activities of humans. The selection of grape varieties is of primary concern for factors such as wine quality and is dependent on the grapevine variety employed. Under today's conditions, and the sanctions imposed by world markets in the competitive wine sector, wine producers have been compelled to use different analysis methods in order to prove quality. However, some of these methodologies can be very time‐consuming. Recently, highly polymorphic molecular markers have been applied to the characterisation and differentiation of grapes in must and wine. With DNA profiles, the determination of origin and the use of this information on the label can act as a powerful quality control tool in the wine sector. In this review, the advantages of molecular markers and the applications of the markers in determining the origin in must and wine, are discussed with the aim of bringing together the limited number of studies (studies conducted with DNA markers) related to the determination of the grape variety in must and wine.     

Plant protection product residues in white grapes and wines of “Malvasia Istriana” produced in Istria

Monitorting of plant protection product residues was performed in 12 grape and 66 wine samples of “Malvasia Istriana” variety, produced in Istria winegrowing region of Croatia and Slovenia. The samples were analysed for the presence of 169 different active compounds using two multiresidual analytical methods: gas chromatography coupled with mass spectrometry and liquid chromatography coupled with tandem mass spectrometry. Residues were found in 58.3% of all the inspected grape samples and in 28.8% of all the inspected wine samples. Beside that contents of residues in grapes were below 10% of maximum residue level values and they should not represent any risk for “Malvasia Istriana” grape or wine consumers.     

Varietal and geographic classification of French red wines in terms of pigments and flavonoid compounds

Thirty-four French red wines originating from six different grape varieties and three different production areas were analysed in duplicate for 15 anthocyanins, ten flavonoids and three colour parameters, F-statistics, principal component analysis and stepwise discriminant analysis were used to identify and to explain differences among samples. Clear difference between wines made from different varieties were mainly related to anthocyanin 3-acylglucosides. Malvidin and peonidin 3-acetylglucosides were found in increasing concentrations in wines made respectively from Grenache, Carignan, Cinsault, Merlot, Carbernet Sauvignon and Cabernet Franc grapes; the concentrations of peonidin and malvidin 3-p-coumarylglucosides were higher in the Cinsault wines studied. Cabernet Sauvignon and Merlot wines made near Bordeaux had a less intense colour and a higher malvidin 3-glucoside content than wines from the same varieties produced near Narbonne. Wines made from Merlot, Cabernet Sauvignon and Cabernet Franc grapes contained more catechin, epicatechin and myricetin when produced in the south than in the north (Narbonne, Bordeaux, Angers). Of the samples analysed, 96%, and all of the nine extra wines, were correctly classified according to the variety of the grapes using four anthocyanins and catechin selected by step wise discriminant analyses.     

红外表面加热结合冷冻处理对葡萄自动脱皮效果的影响

为了实现对冷冻葡萄的快速、高效脱皮,采用冻前红外表面加热处理和冻后红外表面加热处理2种方式,探索不同时间红外表面加热预处理结合冷冻手段对葡萄自动脱皮效果的影响。结果表明,冻前红外表面加热处理5 min以上能够使葡萄果皮出现明显的开裂现象,自动脱皮效果明显,然而过长时间的红外处理也会导致葡萄硬度、颜色等指标的下降。冻后短时红外处理能够更好保持葡萄的品质,1 min的红外表面加热能够保证葡萄在未解冻的前提下出现裂口,从而使得后续可以采用各种手段使葡萄实现自动脱皮。