Characterizing the astringency of red wine: a case study

Red table wines of quality are characterized by pleasing and complex mouth-feel sensations, the most important of these being astringency. While a comprehensive set of terms has been developed over time to describe the flavor of red wines, an appropriate vocabulary describing the astringent sensations produced by these wines is not well defined. This paper presents a structured vocabulary derived by a panel of experienced wine tasters that can be used to describe the astringent sub-qualities of red wines. Multidimensional scaling of sorting data showed that an experienced panel and a group of skilled red wine-makers had similar interpretations of the relationships among the astringency terms. A tasting panel was successfully trained to identify and consistently rate the intensity of the astringent sub-qualities encountered in a set of one year old Shiraz wines. A novel approach of using finger touch standards to represent the astringent sensations experienced in the mouth was utilized.     

红葡萄酒涩感研究进展

涩感是影响红葡萄酒感官质量及内在品质的关键因素。文章参考国内外研究结果,对比分析了红葡萄酒中的涩感物质、涩感产生机理、涩感强度及质量的影响因素、涩感的评价方法,为改善红葡萄酒质量提供参考。红葡萄酒中的涩感物质包括缩合单宁、水解单宁以及有机酸,涩感是由涩感物质和口腔作用引起的一种干燥的、粗糙的、褶皱的,收敛性的触觉,涩感的强度及质量主要取决于单宁的浓度、聚合度、结构特点,此外还受葡萄品种、产区、酿酒方式影响,涩感的评价方法主要有感官评价、化学分析这2大类,这2种方法往往结合使用以获取最佳分析结果。此外,合理选择葡萄原料及酿造方式也是提升红葡萄酒质量的有效方法。     

New insight in characterization of red wine astringency using soft tribology method

The variation of friction coefficient (μ) of model wine and model saliva mixtures with entrainment speed (V_R) on simulated oral surfaces was evaluated by oral tribology. Combined with techniques of dynamic light scattering (DLS), atomic force microscopy (AFM), rheometer, and quartz crystal microbalance with dissipation monitoring (QCM-D), the correlation between characteristics of the model wine and model saliva mixtures (particle size and morphology, suspension viscosity, adsorption film thickness, and viscoelasticity) and the oral lubrication loss was established. The results showed that the higher the concentration of tannin in the model wine, the larger the size of the complexes with the model saliva, and the higher the thickness, viscoelasticity, and roughness of the adsorption film formed, which resulted in the increase of friction coefficient in the boundary lubrication regime. Different from previous results, it is found that the maximum value of the friction coefficient (μ_max) in the boundary regime has the best positive correlation with the astringency perception intensity of the model wine accordingly.     

Cabernet sauvignon red wine astringency quality control by tannin characterization and polymerization during storage

Cabernet Sauvignon wine grape variety is an emblematic cultivar of Bordeaux winegrowing region. Twenty-three vintages of Cabernet Sauvignon wines from chateau Mouton Rothschild were studied using chemical and sensory analysis. Total phenolic compounds, total anthocyanins, total tannins, hue, CI (colour intensity), titratable acidity, ethanol level and pH were evaluated. Percentage of galloylation (%G), of prodelphinidins (%P) as well as mean degree of polymerization (mDP) were also determined. Sensory analysis concerning astringency intensity using a 0–7 point scale was performed in parallel. Correlations between bottle wine ageing and mDP and astringency were obtained. Increasing age gave lower scores in astringency intensity (R ² = 0.598, p = 0.000) and inferior mDP values (R ² = 0.851, p = 0.000). In addition, we evidenced that mDP is an analytical parameter for estimating astringency (R ² = 0.556, p = 0.000) in red CS (Cabernet Sauvignon) wine from Pauillac denomination.     

Insights on the chemical basis of the astringency of Spanish red wines

The main goal of the present study is to provide an insight on the role played by non-volatile molecules on the different in-mouth attributes, particularly astringency. For achieving such goal, the main in-mouth sensory attributes of 34 oaked Spanish red wines were measured by a trained panel. The wine content in 30 sensory-active molecules was analysed by different HPLC based methodologies together with classical enological parameters and two proanthocyanidin indexes. Fourteen compounds (aconitic acids, polymeric proanthocyanidins, caftaric, caffeic and coutaric acids and seven quercetins) were found to be at concentrations above reported taste thresholds and to have a reasonably high range of occurrence. Two highly statistically significant models for astringency were built with those compounds. Even if the models could not be fully validated by sensory addition experiments, the research has demonstrated that wine astringency is driven by polymeric proanthocyanidins and by certain phenolic acids, the rate trans/cis-aconitic acid and flavonol profiles. The research has highlighted the existence of extremely complex interactions between non-volatile compounds on the in-mouth sensory perception. Particularly remarkable is the lack of additivity and potential antagonism found between the pairs cis/trans-aconitic acids, between aconitic and caffeic acids and between quercetin-3-O-galactoside and quercetin-3-O-glucoside. Also remarkable was the sweetness × astringent interaction and the matrix-dependence of the sensory responses elicited by flavonols. These results suggest the need for new paradigms and experimental procedures for fully decoding the real sensory relevance of individual non-volatile compounds in the overall wine flavour.     

Comparison of procedures for reducing astringency carry-over effects in evaluation of red wines

The intensity of astringency of red wine increases when a single wine is sipped repeatedly or during evaluation of several red wines in one session. The effectiveness of different rinses in reducing or preventing the build-up of astringency was evaluated using time-intensity (TI) methodology. Trained subjects continuously rated the intensity of an astringent red wine using a sip and spit protocol. Ten s after the wine was sipped, it was expectorated. Ten s later, a rinse was sipped, which was spat out after another 10 s. Judges rated until astringency was no longer perceived. Between wine-rinse combinations, subjects rinsed twice with de-ionised water for 20 s. Intensity ratings at maximum intensity and at 5 s intervals were extracted from the TI curves and subjected to analysis of variance. Pectin (1 g/L) reduced astringency more effectively than water, polyvinylpyrrolidone (PVP) (4 g/L), gelatin (6 g/L), or ovalbumin (4 g/L) (Experiment 1). Low (1g/L) and high (5 g/L) concentrations of pectin and a high (1 g/L) concentration of carboxymethylcellulose (CMC) decreased astringency significantly more than rinses of Polycose, (5 and 40 g/L), CMC (0.01 g/L) or water (Experiment 2). In a third Experiment, unsalted crackers were shown to be more effective in decreasing astringency than water, although the pectin (5 g/L) rinse was superior to crackers and water. For the inter-stimulus rinse protocol to be most effective, it was found to be important to remove the residuals from each 'rinse' by extensive water rinses before tasting the next wine.     

Influence of grape composition and winemaking on the anthocyanin composition of red wines of Tannat

The anthocyanin composition of Tannat red wines obtained with four winemaking techniques was evaluated in different years. The wines were elaborated with traditional maceration (TM), cold pre‐fermentative maceration, delayed extraction of anthocyanins and extended maceration. Two vinifications were carried out for each technique, employing 70 kg of grapes in each one. The anthocyanin composition of wines was analysed by high‐performance liquid chromatography–diode array detection. The results confirm the fundamental role of the grape composition on the anthocyanin composition of the wines. The winemaking had an important effect on the total concentration of anthocyanins and also may modify the anthocyanic profile of wines. The wines obtained with TM had higher or similar content of anthocyanins than those elaborated with the other techniques. Canonical discriminant analysis of data showed that vintage has a greater effect on anthocyanin concentration than winemaking techniques.     

Red wine astringency: a review

The chemical and physical basis for red wine astringency is reviewed. Models describing the physiological foundation of astringency are presented and compared. The phenolic and other red wine components that evoke astringency are described, together with their sensory properties and the factors that affect their perception. The paper also presents a detailed account of the chemical properties of saliva and the possible modes of interaction between these and red wine phenolics that lead to the necessary physical changes in saliva required to elicit astringency. Reasons for differences in astringency perception across oral sites and amongst individual tasters are also discussed. It is concluded that whilst great advances have been made in the field of red wine phenolic chemistry in recent years, a better understanding of the effect of wine polyphenol-salivary protein interaction on the rheological properties of saliva is required in order to gain a comprehensive understanding of red wine astringency.     

The antioxidant activity of Californian red wines does not correlate with wine age

A range of physico‐chemical properties of 21 Californian red wines from 1 to 28 years old were correlated with wine age. The level of monomeric phenolics and low molecular‐weight phenolic oligomers decreased with age, while the level of high molecular‐weight phenolics increased. On the other hand, total phenols given by the Folin–Ciocalteau method, antioxidant capacity determined using a controlled chain reaction of methyl linoleate and the intensity of the anodic peak determined by cyclic voltammetry (CV) did not show any significant correlation with wine age. Total phenols and the shapes of CV traces were more dependent on the grape variety and the particular viticultural and wine‐making practices rather than on wine age. At the same time, young and aged wines showed a pronounced difference in the shape of [O₂] traces recorded during the oxidation of methyl linoleate in a micellar solution inhibited by wine addition. Possible reasons why the antioxidant activity of red wines does not correlate with wine age are discussed. Copyright © 2006 Society of Chemical Industry     

Anthocyanin profile of young red wines of Tannat,Syrah and Merlot made using maceration enzymes and cold soak

Anthocyanins are the main pigments of young red wines. The aim of this work was to evaluate the anthocyanin composition of red wines produced by alternative procedures of winemaking and different grape varieties. For this purpose, wines of Tannat, Syrah and Merlot were made by traditional maceration (TM), addition of maceration enzymes (ENZ) and cold soak (CS). Syrah wines had the highest proportions of malvidin (86.0 ± 1.0) and peonidin (5.5 ± 0.4), while Tannat wines had the highest of delphinidin (6.9 ± 0.8), petunidin (13.2 ± 0.6) and nonacylated glucosides (73.6 ± 0.6). Cold soak increased the anthocyanins contents in Tannat and Merlot wines. In turn, maceration enzymes affect the anthocyanin profile and the stability of the colour of wines. Discriminant analysis of data showed significant separation of the wines of each variety as the anthocyanin profile showed the varietal fingerprint, despite the different winemaking procedures.     

Intensity of taste and astringency sensations elicited by red wines is associated with sensitivity to PROP (6-n-propylthiouracil)

The relationship between sensitivity to 6-n-propylthiouracil (PROP) and taste and astringency perception elicited by red wines was examined. Twenty-five subjects were classified into three PROP sensitivity groups (non-tasters, tasters and super-tasters) based on their bitterness ratings of a 0.32 mM PROP solution as measured on a Labeled Magnitude Scale (LMS). In a completely randomized block design, subjects used the LMS to rate the bitterness, astringency and acidity intensities of three commercial red wines. Contrary to the findings of previous studies with wine, bitterness, astringency and acidity intensities were all correlated with individual PROP taster status. PROP non-tasters gave significantly lower intensity ratings for the bitterness, astringency and acidity of the red wines than did PROP tasters and super-tasters. Individual differences among taster groups may be related to preference and consumption behavior of consumers of wine and other alcoholic beverages.     

Bitterness and astringency of grape and wine polyphenols

Extracts containing anthocyanins (ACN), and skin tannins (SKIN) and seed tannins (SEED) were prepared from Vitis vinifera cv. Cabernet Franc grapes grown in the Loire Valley, and characterised. Phenolic fractions from Cabernet Franc wines made from three Loire Valley locations were also isolated and characterised. Bitterness and astringency of ACN, SEED and SKIN as well as the wine extracts were evaluated by time intensity procedures in citric acid solution and in a base white wine. SEED and SKIN were equally astringent when tasted at the same concentration in spite of differences in tannin composition. The lower molecular weight (MW) of SEED was equal in astringency to larger MW SKIN which had a lower percentage of galloylation. The SEED fraction was slightly more bitter than the SKIN fraction in the citric acid solution, although no difference could be detected between samples in base white wine. Astringency of ACN alone was much lower than either SKIN or SEED. Addition of ACN to either tannin fraction produced very small sensory effects in citric acid. In wine, addition of ACN to either SEED or SKIN increased astringency significantly over either fraction alone, but had no effect on bitterness. The wine fractions differed only in astringency, which was correlated with tannin units as determined by thiolysis.     

Sensory assessment and chemical measurement of astringency of Greek wines: Correlations with analytical polyphenolic composition

The purpose of this study was to measure the astringency of selected Greek red wines and to assess the relationship between sensory and chemical data. Nine red wines produced by three native Greek grape varieties (agiorgitiko, xinomavro and mavrodafni) were used and their astringency and bitterness was assessed by a trained panel. In addition, their astringency was estimated chemically employing the ovalbumin precipitation method. Their polyphenolic composition was also determined by High Performance Liquid Chromatography (HPLC). The sensory data showed that mandilaria was the most astringent variety whereas agiorgitiko was the least. Statistical analysis of the results indicated that the chemical data obtained for astringency significantly correlated with the sensory determinations. In addition, significant correlations were obtained between the sensory data and the wine polyphenolic composition.     

Comparison of analytical methods for measuring proanthocyanidins in wines and their relationship with perceived astringency

The concentration of proanthocyanidins from twenty red wines from cv. Cabernet Sauvignon, five rosé wines from cv. Cabernet Sauvignon and five white wines from cv. Sauvignon Blanc was quantified using four analytical methodologies, and their relationship with the perceived astringency was investigated. Proanthocyanidin concentrations were determined by a methylcellulose precipitation assay, a protein precipitation assay and two colourimetric methods (Bate‐Smith and vanillin assay). The four methodologies showed high repeatability but differed widely in proanthocyanidin concentrations. The methylcellulose and protein precipitation assays could not quantify proanthocyanidins in rosé and white wines. The protein precipitation assay gave the lowest concentration of proanthocyanidins in all of the red wines. The methylcellulose precipitation assay (r = 0.7725; r² = 0.59) and the protein precipitation assay (r = 0.6828; r² = 0.47) showed a strong correlation with the perceived astringency compared with the colourimetric methods. The strong correlation of the methylcellulose precipitation method with the perceived astringency could be a useful tool to estimate red wine astringency.