Characterisation and classification of Spanish Verdejo young white wines by volatile and sensory analysis with chemometric tools

BACKGROUND: Nowadays, Verdejo young wine is exported to many countries all over the world, so it is considered one of the most important Spanish white young wines. In spite of its commercial and historical repercussions, little information is available about the aromatic profile of Spanish Verdejo young wine. The aim of our study was to give further information about this aspect, focusing our research on the characterisation and classification of Verdejo young wine. RESULTS: Aroma of the Verdejo, Sauvignon blanc and barrel‐fermented and barrel‐aged Verdejo wines—all from the D.O. Rueda, Spain—was evaluated using gas chromatographic and sensory analyses. A good relationship was found between the chemical composition and some of the sensory attributes of the wines. The wine samples were correctly classified according to their grape variety and oenological practice showing a 100% of correct classification using chemical or sensory data. CONCLUSIONS: Characterisation and differentiation of Spanish Verdejo wines was achieved, for the first time, showing different groups of Verdejo wines with similar volatile composition and sensory profiles. Copyright © 2009 Society of Chemical Industry     

Phenolic compounds in a Spanish red wine aged in barrels made of Spanish,French and American oak wood

A red Rioja wine was aged in barrels made of Spanish oak wood for 21 months. The evolutions of colour percentage intensity, families of phenolic compounds and low molecular weight phenolic compounds were studied in these wines and compared with those of the same wine aged in barrels made of French and American oak. The analysis of chromatic parameters and total anthocyanins indicates that the wines aged in Spanish and French oak wood barrels have similar chromatic characteristics, but are significantly different to those of wines aged in barrels made of American oak wood, indicating a different degree of modification of the colour. The ageing process also had an important influence on the low molecular weight polyphenols composition of wine. The evolution of these components allowed the production of wines with different characteristics, in relation to the type of wood used in barrel making process. On the other hand, Spanish oak wood can be considered suitable for barrel production for quality wines, since a wine aged in barrels made of Spanish oak wood showed similar and intermediate characteristics to those of the same wine aged in French and American oak woods.     

Thiol precursors in Catarratto Bianco Comune and Grillo grapes and effect of clarification conditions on the release of varietal thiols in wine

Background and Aims

Varietal thiols characterise the typical aroma of several white wines, such as Sauvignon Blanc. Their presence and sensory perception were suggested in two Sicilian grape cultivars, Catarratto Bianco Comune (CBC) and Grillo, though it has not been analytically proven.

Methods and Results

Varietal thiol precursors and free varietal thiols were assessed in CBC and Grillo grapes, musts and wines by ultra‐performance liquid chromatography/electrospray ionisation high‐resolution MS. The isobaric compounds including S‐3‐(hexanal)‐glutathione and S‐3‐(4‐mercapto‐4‐methylpentan‐2‐one)‐glutathione (GSH‐4MMP) were distinguished by comparing their accurate masses and high‐resolution‐MS/MS spectra with those of their synthetic standards. S‐3‐(Hexanal)‐glutathione, S‐3‐(hexan‐1‐ol)‐glutathione and S‐3‐(hexan‐1‐ol)‐cysteine were found in grape, must and wine, whereas GSH‐4MMP and its hydrolysed forms were not found. Their concentration decreased during winemaking, mostly after grape pressing. We compared the effect of clarification conditions based on the exposure of must to either air or CO₂ on the concentration of thiol precursors and free thiols in wine; however, negligible differences were observed. The concentration of free thiols in the wines was found to be in the range 400–1100 ng/L and they were unaffected by the two clarification conditions tested.

Conclusions

The isobaric S‐3‐(hexanal)‐glutathione and GSH‐4MMP were clearly distinguished for the first time by ultra‐performance liquid chromatography/high‐resolution MS through their retention times and MS spectra. These varietal thiols were revealed in CBC and Grillo wines for the first time. The air‐free and air‐exposed clarification treatments had little effect on the concentration of the varietal thiols.

Significance of the Study

This study highlights the major impact of the varietal thiols (mainly 3‐mercapto‐hexan‐1‐ol and its acetate form) on the sensory properties of CBC and Grillo wines.     

Evolution of esters in aged Chardonnay wines obtained with different vinification methods

BACKGROUND: During wine ageing on lees yeast lysis takes place and some enzymes from the yeast cells, such as esterases, may be released. These enzymes might determine ester synthesis and could be also involved in their breakdown. In this study, the evolution of esters in Chardonnay wine fermented in stainless steel tanks and aged in bottles (conventional vinification) was compared with the evolution of esters in the same wine fermented and aged in barrel on lees. In this way, it was hoped to determine the influence of distinct methods of vinification on the evolution of esters in Chardonnay wine. RESULTS: The concentration of acetate esters of higher alcohols decreased in all the wines independently of the vinification method. However, the ethyl esters of fatty acids decreased in wine aged in barrel and increased in wine aged in bottle, so it would seem that these compounds interact with the lees present in the barrels and/or with the wood of the barrel. The ethyl esters of organic acids increased during ageing both in barrel and bottle. CONCLUSION: The ageing of Chardonnay wine in barrel on lees did not favour the formation of esters compared to the same wine aged in bottle. Copyright © 2009 Society of Chemical Industry     

Impact of chemical profile on sensory evaluation of tropical red wines

This study evaluated the correlation between the chemical composition of red wines and the sensory perception of the products. The visual, gustatory and flavour attributes of eight samples of tropical red wines were characterised by semi-trained panellists using the check-all-that-apply methodology. Titratable and volatile acidity, pH, contents of ethanol, total polyphenols and anthocyanins, and the chromatic parameters of the red wine samples were determined. The analysis of the correlations between visual attributes and sensory perception indicated that the evaluation of the wine colour attributes can predict other sensory characteristics related to aromas and flavours. This enabled the wine tasters to distinguish subtle variations in the visual attributes of the product. The results of this study indicated that panellists who underwent short-term training can sensorially perceive the influence of physicochemical variables on wine quality. Additionally, the correlation analysis enabled the identification of production adjustments and the understanding of the consumer perception of a complex product.     

Exclusion of sunlight from Shiraz grapes alters wine colour, tannin and sensory properties

The aim of this study was to determine how changes in grape composition brought about by artificial shading (sunlight exclusion) influence wine properties including colour, flavonoid composition and sensory attributes. Prior to flowering, bunches of Shiraz grapes were enclosed in boxes designed to eliminate light without altering bunch temperature and humidity. This artificial bunch shading had little effect on berry ripening and accumulation of sugar but at harvest the shaded bunches had smaller berries and higher seed weight, juice pH and titratable acidity. The amount of anthocyanins in the fruit was not changed significantly but anthocyanin composition in the shaded berries was shifted towards dioxygenated anthocyanins (the glucosides of cyanidin and peonidin derivatives). Shaded fruit had increased seed tannins and decreased skin tannins but the largest relative change in flavonoids was a marked decrease in flavonols in the shaded fruit, similar to previous studies. Wines made from shaded fruit had lower wine colour density, total phenolics, anthocyanins and tannins when the wine was bottled and after ageing for up to three years. Analysis of potential flavour compounds following acid hydrolysis indicated that the wines made from shaded fruit had decreased levels of glycosides of β-damascenone and 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN). Sensory analysis of the wines indicated no significant difference in aroma attributes but the wines made from shaded fruit were rated lower for astringency, fruit flavour and flavour persistence in-mouth sensory attributes. The results indicate that extreme shading of Shiraz fruit can decrease wine colour, anthocyanins and tannins as well as altering sensory attributes.     

Multivariate statistical analysis for the classification of oak-aged wines based on their chromatic characteristics

The objective of this study was to characterise oak-aged wines according to the ageing conditions by measuring colour and phenolic compounds, and to study the correlations between the studied variables to understand the relationship among them, and help to clarify some of the mechanisms involved in the modification of colour during wine ageing. The results show that the colour of aged wines can be mainly attributed to polymeric compounds and not to monomeric anthocyanins; the cluster analysis showed that the samples could be mainly separated as regards the age of the barrel. The discriminant analysis achieved a good sample separation regarding oak origin and barrel age.     

Investigation on the role played by fermentation esters in the aroma of young Spanish wines by multivariate analysis

The role played by ethyl esters of fatty acids and by acetates of higher alcohols on the aroma of young wines from neutral grape varieties has been investigated. The statistical methods used have been stepwise linear regression and principal components analysis. Very significant conclusions have been reached. The role played by these compounds depends on the type of wine. In white wines their main role is in the perception of tree fruit and tropical fruit notes. It has been demonstrated that the former notes are linked to ethyl esters, while the latter are linked mainly to acetates of higher alcohols. In rose wines the intensity of tree fruit aroma was correlated with ester content, however no clear conclusion was reached about the role of various compounds on the perception of quality. Finally, in red wines these compounds do not determine the intensity of fruit aromas, and they only play a modulating role on aroma quality. This indicates that red grape varieties must have other aroma compounds which are responsible for the fruity characteristics of wines.     

添加葡萄籽单宁对橡木桶陈酿‘赤霞珠’和‘马瑟兰’干红葡萄酒香气的影响

采用气相色谱-质谱联用法和感官分析排序法,研究橡木桶陈酿前添加葡萄籽单宁（200 mg/L）对陈酿12 个月后‘赤霞珠’和‘马瑟兰’干红葡萄酒香气组分和感官特征的影响。结果表明：添加葡萄籽单宁对2 个品种葡萄酒香气的影响各异。葡萄籽单宁添加促进了橡木桶陈酿期间‘赤霞珠’葡萄酒中香草酸、香草醛、香草酸乙酯、糠醛、乙酰呋喃和糠醇等橡木来源香气物质的浸出,而抑制‘马瑟兰’干红葡萄酒中糠醛、乙酰呋喃、糠醇、5-甲基糠醛和5-羟甲基糠醛等橡木来源香气物质的浸出。添加葡萄籽单宁后,‘赤霞珠’葡萄酒的生青味和浆果香降低,烘烤味增强,‘马瑟兰’葡萄酒的生青味和花香略有增强,对陈酿型干红葡萄酒的生产具有重要指导作用。     

FLAVOR AND AROMA ATTRIBUTES OF RIESLING WINES PRODUCED BY FREEZE CONCENTRATION AND MICROWAVE VACUUM DEHYDRATION

This article describes the production of sweet dessert wines produced using late‐harvest freeze concentration, wine produced from fresh grapes frozen using refrigeration and wine produced from grapes partially dried using microwave vacuum dehydration. The objective was to compare the aroma and flavor attributes of the wines to determine the effect of each method of juice concentration. The replicated wine samples were evaluated by 12 experienced judges, and the wines were analyzed using solid‐phase microextraction. The microextraction detected 28 compounds; however, levels of concentration of these compounds were below published aroma thresholds. Although all the wines were judged as acceptable sweet dessert wines, the judges detected significant differences. The wine made from the dehydrated grapes exhibited lower fresh fruit aroma, higher fusel oils and oxidation, and flavor notes including citrus/grapefruit and acidity were lower.     

不同工艺对‘关口’葡萄干白葡萄酒品质的影响

目的:采用不同酿造工艺技术对‘关口’葡萄进行干白葡萄酒的酿造,揭示不同果皮浸渍工艺对‘关口’葡萄干白葡萄酒的影响,以期最大程度地发挥‘关口’葡萄的深加工可能性。方法:分别对‘关口’葡萄进行发酵前的果皮浸渍(fermentation before skin contact,FbSC)、带皮发酵(fermentation on skins,FoS),以澄清汁发酵作对照处理,测定各处理所得葡萄酒的基本理化指标、酚类物质、香气成分,并进行感官评价。结果:与对照组相比,采用FbSC和FoS工艺所得葡萄酒的pH值均增加,可滴定酸质量浓度均降低;对于采用FoS工艺所得的葡萄酒,其总酚、总黄酮、总黄烷醇、单体酚的质量浓度显著高于采用FbSC工艺所得的葡萄酒和对照组的葡萄酒(P0.05),香气成分总质量浓度则显著低于FbSC组和对照组(P0.05);与对照组相比,采用FbSC和FoS工艺所得葡萄酒的香气成分中的酸类和酯类物质质量浓度显著降低(P0.05),醇类和萜烯类物质质量浓度显著增大(P0.05)。另外,经过FbSC与FoS处理后,‘关口’葡萄干白葡萄酒的香气由以果香等香气为主转化为以果干、蜂蜜及成熟水果类香气为主;并且在澄清度、颜色、香气质量、口感纯正度、口感浓度、口感持久性、口感质量、整体平衡性等方面也均优于对照组。结论:果皮浸渍处理一定程度上提高了‘关口’葡萄干白葡萄酒的品质。     

Impact of exogenous tannin additions on wine chemistry and wine sensory character

Tannins are an important part of wine quality and are frequently added during winemaking. Tannin additives and their impact on wine are poorly documented. This work sought to characterize a range of enological tannins and their contribution to wine quality. Enological tannins were analysed for protein precipitable tannins and iron reactive phenolics. One tannin product was added to a Merlot wine during barrel ageing, at a range of concentrations from 60 to 300 mg/l. Condensed and hydrolysable tannins were added to Cabernet Sauvignon wine post-pressing at a recommended and excessive rate. Wines were analysed for anthocyanin, small and large polymeric pigment, precipitable tannin, iron reactive phenolics and sensory character. Enological tannins contained 12-48% tannin and recommended additions had little impact on wine tannin. High tannin additions were readily measured in the wines and were discriminated in sensory analysis with lower intensities of most parameters except brown colour, bitterness and earthy character. Recommended addition rates are too low to impact the measured tannin concentration of Merlot and Cabernet Sauvignon wines from Washington (USA). High enological tannin additions had a measureable impact on final wine had a negative impact on sensory character. Tannins are added to wines for a range of reasons and represent one of many input costs in an industry increasingly seeking efficiencies in response to global economic circumstances, over-supply and an ongoing price point squeeze. This research suggests many tannin additions may be unjustified and have limited or negative impacts on quality.     

Effects of mechanical thinning on fruit and wine composition and sensory attributes of Grenache and Tempranillo varieties (Vitis vinifera L.)

Background and Aims: Cost-effective yield control is required by the wine industry in order to reduce the existing worldwide wine surplus and to improve grape quality. The object of this study was to evaluate the chemical and sensory effects on the resulting wines of mechanical cluster thinning performed at different intensities on Grenache, and at different timings (pea size and veraison) on Tempranillo. Methods and Results: The experiments were conducted with a machine harvester in 2007 on two commercial vertical shoot-positioned vineyards in Spain's Rioja region. In both varieties, mechanical thinning was effective in yield reduction and resulted in more ripened fruit, and wines with higher alcohol and pH values, more intense colour and increased phenolic content. Regardless of the thinning intensity, sensory changes were less noticeable in Grenache than in Tempranillo wines. Of the latter, those from vines thinned during veraison were less aromatic and sour, but had increased astringency. Conclusions: Yield management through mechanical thinning induced changes to the chemical composition of fruit and wines as well as to the wines' aroma, taste and mouthfeel. The extent of the sensory implications seems to depend on several factors such as the variety and timing of thinning application. Significance of the Study: This is one of the first studies addressing the effects of mechanical thinning on the sensory properties of the resulting wine and has implications for viticultural management practices.     

Criteria to discriminate between wines aged in oak barrels and macerated with oak fragments

Wine aging in barrels is carried out to increase stability and achieve more complex aromas. In the last few years, however, the practice of macerating wine with small fragments of toasted oak (chips) has become increasingly common. This conveys similar tastes, aromas, and wooden notes to the wine as those obtained with traditional barrel aging, but much faster and at a fraction of the cost. Without proper regulation, this could lead to fraud if wine macerated with chips is offered as barrel aged wine.In the present study, 75 volatile compounds have been determined by applying gas chromatography–mass spectrometry (MS) and flame ionization detection (FID). It has been found that compounds directly related to the wood have greater discriminative power for telling apart wines aged in barrels from those macerated with oak fragments, but no single compound permits flawless classification. Therefore, we have studied the effect of the addition of oak fragments of different origins, different oak types, different formats and subjected to different toasting processes on a set of 231 samples from 6 Spanish Denominations of Origin wines (DOs), and compared them to those same wines aged in oak barrels. In light of the results, we have developed a set of criteria which allows distinguishing with high degree of accuracy between wines which have been aged in barrels and those macerated with oak fragments. The application of these criteria to different wines allows correct classification in over 90% of cases.