Astringency Sub-qualities Research Articles

PH dominates the temporal perception of astringency sub-qualities and saliva friction response – A study under iso-pH and iso-titratable acidity conditions in model wine

Astringency is a multidimensional perception comprising sensorily distinct sub-qualities. In wine production, attaining balanced astringency is critical to producing premium products. Although tannin has been viewed as the primary cause of wine astringency through colloidal interactions with salivary proteins and the modification of lubricating salivary film, how acids act in similar roles remains underexplored. This study aimed to address this gap by investigating the impact of acids (malic, lactic or tartaric acids) on the wine astringency profile under iso-pH and iso-titratable acidity (TA) conditions. Samples were sensorily evaluated with a progressive profiling method and tribologically tested to determine their impact on saliva lubrication. The results indicated that acids, independent of tannin, can elicit all astringency sub-qualities, and specifically that the pucker sub-quality is closely associated with low pH. pH had a more dominant impact on the temporal sensory scores than TA. At iso-TA, the score of all astringency sub-qualities was solely dependent on pH; at iso-pH, lowering TA increased the score of drying and roughness. The tribology results demonstrated that the rate of saliva friction increase was significantly correlated with pH but not TA. We propose that, during oral processing, pH dominates the process of saliva protein deformation, removal of lubricating pellicle, increased oral friction and astringency perception. However, high TA encourages saliva flow which neutralises oral pH and restores lubrication, counterbalancing the low pH’s contribution to astringency. Wine production processes could leverage this knowledge by implementing various acid-modification techniques to achieve the desired level of astringency quality of wines.

Relationship between salivary lubrication and temporal sensory profiles of wine mouthfeel and astringency sub-qualities

Wine mouthfeel plays an important role in sensory quality. Astringency, as an important aspect of mouthfeel, is composed of distinct sub-qualities associated with tannin-salivary colloidal interactions and loss of oral lubrication. Perception of wine mouthfeel is temporal – the sensory intensity of wine mouthfeel attributes changes over the oral process of evaluation. It remains unclear whether these changes in sensory are relevant to distinct physical processes. This study took sensory-instrumental and multivariate approaches to provide mechanistic insights into the wine mouthfeel during the temporal evaluation process. The sample set was created by doctoring ethanol, tannin, pH and mannoprotein in a Malbec. Wines were sensorily evaluated by a progressive profiling method and instrumentally tested using a soft-tribology protocol involving saliva. Results indicate that the scores of mouthfeel attributes are dependent on the interactive effect of matrix components. The decaying rate of the score for roughness after expectoration correlates with those for drying and pucker. The multivariate analyses indicate that tannin-protein interaction and high boundary friction in tribology are important in explaining the perception of all astringency sub-qualities. At the end of the evaluation, the boundary friction becomes less important in explaining the score of drying/roughness, while pH becomes less important in explaining the score of pucker. It is inferred that, after expectoration, saliva secretion recovers the oral lubrication; astringency sub-qualities are contributed less from the frictional mechanism but more from an alternative perceptive mechanism. The outcome could assist the wine industry in better managing the wine matrix to attain preferable mouthfeel characteristics.

Wine astringency: more than just tannin-protein interactions.

Red wines are characterized by their astringency, a very important sensory attribute that affects the perceived quality of wines. Three mechanisms have been proposed to explain astringency, and two theories describe how these mechanisms work in an integrated manner to produce tactile sensations such as drying, roughening, shrinking and puckering. The factors involved include not only tannins and salivary proteins, but also anthocyanins, grape polysaccharides and mannoproteins, as well as other wine matrix components that modulate their interactions. These multifactorial interactions could be responsible for different sensory responses and therefore need to be further studied. This review presents the latest advances in astringency perception and its possible origins, with special attention on the interactions of components, their impact on oral perception and the development of astringency sub-qualities. Future research efforts should concentrate on understanding the mechanisms involved as well as on the limiting factors related to the conformation and stability of the tannin-salivary protein complexes. © 2021 Society of Chemical Industry.

Tribology and QCM-D approaches provide mechanistic insights into red wine mouthfeel, astringency sub-qualities and the role of saliva

Wine mouthfeel and astringency play an important role in shaping the organoleptic quality and have been associated with tannin-salivary protein colloidal interactions. The mechanistic drivers of wine mouthfeel, especially those creating distinct astringency sub-qualities percepts, are yet to be fully realised due to the lack of appropriate measures. This study researched the friction behaviours of saliva-wine interactions, that allow inference of insights into the physicochemical origins of several important wine mouthfeel attributes. The red wine sample sets were created by doctoring various levels of ethanol, tannin, pH and mannoprotein on a Malbec. Samples were profiled sensorily and chemically. The friction behaviours of wine-saliva interaction and salivary viscoelasticity were investigated by soft-tribological protocols plus quartz crystal microbalance with dissipation. The sensory scores of mouthfeel attributes were modelled by physicochemical parameters using partial least squares regression. Results suggested that burning and resalivation are non-frictional-derived sensations driven by ethanol and acidity, respectively. Drying, grippy and rough are driven by tannin's adsorption on salivary film, which cause poor lubricity and a film strip-off thus exhibit as high boundary friction in tribology. Pucker is not directly driven by tannin but the weak viscoelasticity of salivary film, which is exhibited as the fast rate of friction increase in tribology. Smoothness is driven by less salivary protein precipitation, a highly viscoelastic salivary film, or the viscosity effects from mannoprotein. Fullness is driven by high viscosity by high ethanol. These models support the theory that wine mouthfeel attributes have dissimilar physicochemical origins that lead to distinct sensory experiences.

Differences in Astringency Subqualities Evaluated by Consumers and Trained Assessors on Sangiovese Wine Using Check-All-That-Apply (CATA).

The astringency of red wine represents an important factor of quality and liking evaluation by consumers, but it is sometimes associated to a negative feature. We studied the differences in astringency subqualities of Sangiovese wines between consumers and trained assessors. Wines belonging to three denominations (Chianti Classico, Toscana, Morellino di Scansano) and a Chianti Classico specification (Chianti Riserva), from three price ranges (low, medium, high) were evaluated. Regular wine consumers and trained panel assessed the wines applying the Check-All-That-Apply (CATA) questionnaire relative to six astringency attributes (silk, velvet, dry, aggressive, hard, mouthcoat). Differences between panels were more associated with the high-price wines, which were characterised by negative subqualities for consumers. Preference maps revealed that mouthcoat was the term mainly associated with consumers’ liking, while other subqualities as persistent, rich, and full-body, provided by the trained assessors, may represent the drivers of liking for Sangiovese wine. This study has demonstrated that a trained sensory panel provides highly valuable information regarding the mouthfeel characteristics of Sangiovese wines and the attributes driving consumer liking.

Sensory assessment of grape polyphenolic fractions: an insight into the effects of anthocyanins on in-mouth perceptions

Anthocyanins are extracted from grape skins during maceration and are responsible for the red colour of wine. Their contribution to in-mouth sensations is mainly related to their interactions with condensed tannins, which are largely responsible for wine astringency and mouthfeel-related features. Recently, the influence of several groups of polyphenols, together with other relevant non-phenolic wine constituents,was investigated in terms of their ability to modify the sensory perception of condensed tannins. The aim of this study was to investigate the influence of three acylation groups of anthocyanins (glucoside, acetylglucoside, and p-coumaroylglucoside) extracted from grape skins on in-mouth related features. An extract of total anthocyanins and their individual fractions were tasted using different sensory approaches (triangle test, check-all-that apply and descriptive analysis) and compared to polyphenols extracted from grape skins and seeds. The investigated sensations were overall astringency and astringency sub-qualities, which were divided into two groups: sensation during tasting (in-mouth, particulates) and sensation after expectoration (surface smoothness). Bitterness was also studied. Anthocyanin fractions were added to skin and seed extracts and tasted as mixtures to find out if anthocyanins modify in-mouth perception. Although the anthocyanin fractions showed a low sensory impact, total anthocyanins and the glucoside fraction were perceived at the concentration ranges found in wines (400 mg/L), and they were found to influence astringency intensity and soft astringency sub-qualities, such as “velvety” and “chalky”. The addition of glucoside anthocyanin (400 mg/L) to skin and seed extract (1000 mg/L) modified in-mouth perception; in particular, seed extract was perceived as being more astringent and was characterised by harsher astringency sub-qualities (surface smoothness and particulates). In contrast, the addition of glucoside anthocyanin to the skin extract led to lower surface smoothness, although the intensity of overall astringency was unchanged. These results confirm that the presence of anthocyanins can modify the perception of in-mouth sensations and interact to different extents with other polyphenols, thus leading to the modification of the intensity of astringency and its sub-qualities.

Exploring Olfactory-Oral Cross-Modal Interactions through Sensory and Chemical Characteristics of Italian Red Wines.

This work aimed at investigating red wine olfactory–oral cross-modal interactions, and at testing their impact on the correlations between sensory and chemical variables. Seventy-four Italian red whole wines (WWs) from 10 varieties, and corresponding deodorized wines (DWs), were evaluated by sensory descriptive assessment. Total phenols, proanthocyanidins, ethanol, reducing sugars, pH, titratable and volatile acidity were determined. PCA results highlighted different sensory features of the 10 wine types. ANOVAs (p < 0.05) showed that olfactory cues might play modulation effects on the perception of in-mouth sensations with 7 (harsh, unripe, dynamic, complex, surface smoothness, sweet, and bitter) out of 10 oral descriptors significantly affected by odours. Three weak but significant positive correlations (Pearson, p < 0.0001) were statistically found and supported in a cognitive dimension: spicy and complex; dehydrated fruits and drying; vegetal and unripe. In the absence of volatiles, correlation coefficients between sensory and chemical parameters mostly increased. Proanthocyanidins correlated well with drying and dynamic astringency, showing highest coefficients (r > 0.7) in absence of olfactory–oral interactions. Unripe astringency did not correlate with polyphenols supporting the idea that this sub-quality is a multisensory feeling greatly impacted by odorants. Results support the significance of cross-modal interactions during red wine tasting, confirming previous findings and adding new insights on astringency sub-qualities and their predictive parameters.

Effect of Different Enological Tannins on Oxygen Consumption, Phenolic Compounds, Color and Astringency Evolution of Aglianico Wine.

Background: In the wine industry, in addition to condensed tannins of grape origin, other commercial tannins are commonly used. However, the influence of oxygen uptake related to different tannin additions during the post fermentative phase in wine has not been completely investigated. In this study, we evaluated the influence of four different commercial tannins (namely, condensed tannins, gallotannins, ellagitannins and tea tannins) during four saturation cycles. Method: Wine samples were added with four different tannin classes (30 g/hL) as to have 5 different experimental samples: control, gallotannins (GT), condensed tannins (CT), ellagitannins (ET), and tea tannins (TT). The chemical composition of the four commercially available tannin mixtures was defined by means of NMR and high-resolution mass spectrometry. After the addition of tannins, each wine sample was oxidized by air over four cycles of saturation. During the experiment oxygen consumption rate (OCR), sulfur dioxide consumption, acetaldehyde production, phenolic compounds, chromatic characteristics, astringency measured by the reactivity towards saliva proteins and astringency subqualities were evaluated. Results: The experiment lasted 52 days. The addition of tannins influenced the oxygen consumption on the 1st day of the saturation cycles and, in the case of TT, a higher total consumption of oxygen was also detected. Acetaldehyde increased during the experiment while the native anthocyanins decreased throughout the oxidation process. Conclusion: Wines added with tannins featured improved color intensities with respect to the control; the addition of TT, GT and ET slightly promoted the formation of short polymeric pigments; the astringency, determined before and at the end of the experiment, decreased in all the samples, including the control wine, and mostly in the ET and GT samples.

Impact of 5-year bottle aging under controlled oxygen exposure on sulfur dioxide and phenolic composition of tannin-rich red wines

Aim: This study aims at understanding the impact of the initial phenolic composition on the evolution of red wines after long bottle aging.Materials and results: three different red wines rich in tannins, Aglianico, Casavecchia and Pallagrello, bottled with the same amount of total sulfur dioxide and different amounts of free sulfur dioxide, were analysed after 5 years of bottle aging under controlled exposure to oxygen passing through the closure. Acetaldehyde and monomeric anthocyanins were determined by HPLC, the chromatic characteristics and the main phenolic classes by spectrophotometry, the saliva precipitation index (SPI) by CHIP electrophoresis, and the astringency subqualities by sensory analysis. The results confirmed that during aging there is an increase in polymerisation reactions. A higher amount of acetaldehyde was detected in wines which were bottled with a lower content of free SO2 and were less rich in anthocyanins and tannins; a significant closure effect was observed for these wines. Regarding the influence of closure on tannins, significant slight differences in vanilline reactive flavans and SPI content were observed for Pallagrello wines only, which were characterised by higher values for tannins at bottling. Astringency subqualities differed with closures for each wine.Conclusion: this study indicates that the amount of initial free and combined sulfur dioxide, as well as that of anthocyanins and tannins, are key factors in driving polymerisation reactions and the aging of red wines. After five years of bottle aging the influence of closure could still be observed.Significance of the study: this study provides new insights into the parameters that need to be evaluated before bottling in order to avoid the wrong evolution of red wines after long bottle aging.

Oral interactions between a green tea flavanol extract and red wine anthocyanin extract using a new cell-based model: insights on the effect of different oral epithelia

Phenolic compounds (PC) are linked to astringency sensation. Astringency studies typically use simple models, with pure PC and/or proteins, far from what is likely to occur in the oral cavity. Different oral models have been developed here, comprising different oral epithelia (buccal mucosa (TR146) and tongue (HSC-3)) and other main oral constituents (human saliva and mucosal pellicle). These models, were used to study the interaction with two PC extracts, one rich in flavanols (a green tea extract) and one rich in anthocyanins (a red wine extract). It was observed that within a family of PC, the PC seem to have a similar binding to both TR146 and HSC-3 cell lines. When the oral constituents occur altogether, flavanols showed a higher interaction, driven by the salivary proteins. Conversely, anthocyanins showed a lower interaction when the oral constituents occur altogether, having a higher interaction only with oral cells. Epigallocatechin gallate, epicatechin gallate, epigallocatechin-3-O(3-O-methyl) gallate were the flavanols with the highest interaction. For the studied anthocyanins (delphinidin-3-glucoside, peonidin-3-glucoside, petunidin-3-glucoside and malvidin-3-glucoside), there was not a marked difference on their interaction ability. Overall, the results support that the different oral constituents can have a different function at different phases of food (PC) intake. These differences can be related to the perception of different astringency sub-qualities.

Astringency subqualities and sensory perception of Tuscan Sangiovese wines

Aim: The Sangiovese grape cultivar is at the basis of the most well-known Italian wines produced in the Tuscany region. However, little is known about the sensory characteristics of Tuscan Sangiovese wines, and the diversity in astringency subqualities has never been investigated. In this study we evaluated the sensory perception of 16 commercial Sangiovese wines belonging to four categories of denomination (Chianti DOCG, CH; Chianti Classico DOCG, CC; Morellino di Scansano DOCG, MS; Toscana IGT, TS), and again after 20 months of bottle aging.Methods and results: A sensory evaluation was made, consisting of the astringency subqualities, taste, odor, and aroma profiles of wines. In addition, chemical analyses were carried out for the base parameters, polyphenols and some volatile compounds. Astringency subqualities varied depending on the percentage of Sangiovese in wines (from 80 % to 100 %). Blended Sangiovese wines were characterized by positive mouthfeel sensations. According to these, the drivers of liking the wines were associated with soft, mouthcoat, and rich subqualities. The Tuscan Sangiovese denominations were differentiated by volatile active compounds, whereas after about two years of bottle aging the astringency subqualities better achieved this task. Moreover, aging also influenced the evolution of wines: CC and CH wines positively evolved, revealing a complex odor profile; MS lost the fruity character; and TS was less involved in sensory modification.&#x0D; Conclusions: For the first time, a detailed evaluation of the astringency subqualities of commercial Sangiovese wines was undertaken. Sangiovese subqualities differed according to the percentage of Sangiovese and denomination. Tuscan denominations were distinguished by peculiar sensory characteristics. In addition, bottle aging significantly influenced the evolution of the sensory perception of Sangiovese wine. In particular, mono-varietal Sangiovese wine needed a long period of aging to soften the astringency characteristics.Significance and impact of the study: Sangiovese wine represents - with its denominations and styles - the best-known and high-quality Italian wine in the world, and its popularity is increasing worldwide. Tuscan Sangiovese wines are often a blend with other red varieties of the region, and these can vary according to the production regulations. This study aimed to improve the knowledge of the sensory characteristics of Sangiovese wines belonging to different denominations and made with different percentages of this grape cultivar. In particular, the astringency subqualities are fundamental to fully appreciating the quality of the red wine during tasting.

Effect of marc pressing and geographical area on Sangiovese wine quality

Sangiovese is one of the most widespread grape cultivar in Italy. Owing to Sangiovese's ability to take on characteristics of region, climate and those imparted by the winemaker, wines made from this grape vary widely in colour and flavour. In this study, we evaluated the effect of marc pressing on polyphenolic and sensory quality of Sangiovese wines from different areas of Tuscany. 100% Sangiovese grapes were elaborated according to the same protocol obtaining 8 free-run and press wines. Polyphenolic analyses comprised: colour parameters, pigmented polymers, anthocyanins, tannins, flavans, phenolic compounds (HPLC-MS), phloroglucinolysis. Sensory analysis (astringency intensity and subqualities, taste, odor, aroma) was carried out by a trained jury. The effect of marc pressing depended on native phenolic compounds and on geographical area. Furthermore, wines from the same area showed a high variability. In general, press wines showed less colour, pigmented polymers, flavonols, and more flavan-3-ols. Pressing showed an influence on sensory characteristics related to astringency subqualities and aroma. Free-run wines were perceived as more acid, less adhesive, hard, aggressive, and characterized by soft tannins and full aroma than press wines. Indeed, the aroma of Sangiovese free-run wines had an important pool of odorants able to produce fruity and balsamic notes.

Aging of Aglianico and Sangiovese wine on mannoproteins: Effect on astringency and colour

During the last years different commercial preparations based on yeast derivatives have been used in order to replace traditional ageing on lees. Three commercial mannoproteins (MP; MF; MS) were tested in Aglianico and Sangiovese red wine during one year of aging to evaluate the influence on astringency characteristics (astringency intensity and 16 subqualities), colour parameters (CIE L*a*b* coordinates, total anthocyanins, pigmented polymers) and reactive phenolic compounds (BSA-reactive tannins, saliva-reactive tannins, vanillin reactive flavans) after 3, 6 and 12 months. The taste, odor and aroma profiles completed the sensory evaluation of one-year aged wines. The effect of commercial mannoproteins on studied parameters depended on wine variety and aging period. As regard wine colour evolution, the formation of pigmented polymers was promoted from the 6th month in Aglianico by MS and MF, and in Sangiovese by all mannoproteins. Regarding wine sensory evaluation, MP reduced the astringency of Aglianico and enhanced the positive subqualities, while all mannoproteins favored spicy and balsamic notes revelation. In Sangiovese, green tannins and herbaceous notes decreased at the same time as floral notes, satin tannins and wine body augmented. Finally, the use of commercial mannoproteins improved some sensory characteristics of red wines related to positive astringency subqualities and aroma persistence.

Dose–response functions and methodological insights for sensory tests with astringent stimuli

AbstractSensations such as bitterness and astringency can limit the acceptance of many purportedly healthy foods. The purpose of this study was to investigate dose–response relationships of various astringent and bitter stimuli in a beverage, and to simultaneously gain additional methodological insight for the effects of wording, repeated tasting, and beverage matrix on these sensations. Untrained participants were presented with samples of a “flavored beverage” or water containing various concentrations of four stimuli (alum, malic acid, tannic acid, and quinine) and were asked to rate intensities of tastes (bitterness, sourness, and sweetness) and astringency subqualities (roughing, drying, and constricting or puckering) using a generalized visual analog scale. Using constricting in place of puckering had no effect on ratings. The effects of repeated tasting and beverage matrix on astringency perception were stimulus‐dependent. This study informs future investigations to understand the psychophysics of tastes and astringency.Practical applicationsThis study provides stimulus‐ and quality‐specific data to improve astringency research. Furthermore, dose–response functions will aid researchers when selecting appropriate concentrations of astringent stimuli. We also provide recommendations for a variety of testing contexts, such as beverage matrix and the number of samples, to optimize the design of astringency studies, especially for naïve participants. This study further demonstrates how affective responses influence evaluation of astringent samples among untrained participants.

Relationship between astringency and phenolic composition of commercial Uruguayan Tannat wines: Application of boosted regression trees

Phenolic compounds play a major role in the intensity and characteristics of wine astringency. However, studies involving commercial wine samples are still scarce. The aim of the present work was to study the relationship between astringency and phenolic composition of commercial Uruguayan Tannat wines using boosted regression trees (BRT), a novel predictive method. Forty commercial Tannat wines were evaluated by a trained sensory panel (9 members), who assessed their total astringency intensity using time-intensity (TI) and described their astringency sub-qualities using a check-all-that-apply (CATA) question composed of sixteen terms. The polyphenolic profiles of the wines were determined by HPLC-MS and conventional oenological parameters were also obtained. Fifty BRT models with different partitions of the data in training and test sets were built for astringency maximum intensity (Imax) and for the frequency of use of the 16 astringency sub-qualities considered in the CATA question. As predictor variables, 84 phenolic compounds and oenological parameters were considered for all BRT models. Both strong and weak predictive models were obtained for each response variable. Predictive accuracy was much higher for astringency intensity than for the frequency of mention of astringency sub-qualities. Still, the BRT models allowed to point out to some compositional variables most likely involved in wine astringency perception. Total tannin concentration (chemically determined) was the most relevant explanatory variable for sensory astringency, while flavan-3-ols were the individual phenolic compounds with the highest contribution to astringency, particularly some dimers, trimers and the sum of non-galloylated tetramers. However, the effect of these predictors differed according to the astringency sub-quality considered as response. As expected, non-linear relationships between phenolic compounds and astringency were found. These results contribute to the understanding of the influence of phenolic composition on wine astringency and stress the potential of BRT models for identifying the compounds responsible for this complex sensory characteristic.

Astringency evaluation of Tannat wines: Comparison of assessments from trained assessors and experts

AbstractAstringency is one of the differential characteristics of Tannat wine, the emblematic wine of the Uruguayan wine‐making industry. The aim of this study was twofold: First, to compare wine astringency characterization of experts and trained assessors, and second, to identify which astringency characteristics influence experts' perception of astringency quality. Six commercial Uruguayan Tannat wines were evaluated in triplicate by a trained assessors panel (n = 9). Assessors rated the global astringency intensity using a time‐intensity task, and described astringency subqualities using a check‐all‐that‐apply (CATA) question composed of 16 terms. Samples were also assessed by 30 experts who rated astringency intensity and quality using 9‐point structured scales. In addition, experts described astringency subqualities of samples and of their ideal high‐quality Tannat wine using a CATA question. Significant differences among samples were found in astringency intensity for both panels and expert's perceived quality. Agreement between trained assessors and experts in astringency intensity evaluations was observed, but differences in their description of astringency subqualities were found. Astringency quality as perceived by experts was not related only to astringency global intensity; astringency subqualities complex and velvety were the main drivers of astringency quality, while puckery, sand paper, and irritant significantly lowered quality scores.Practical applicationsWine astringency characterization is a very complex task that should ideally be performed by a group of trained assessors following standardized protocols. However, most wineries still rely on the judgment of wine experts for decision‐making. Results from the present work suggest that although trained assessors and experts evaluated wine astringency similarly, their description of astringency subqualities strongly differed.

Effect of enological tannin addition on astringency subqualities and phenolic content of red wines

AbstractFour Italian red wine varieties (Sangiovese, Montepulciano, Barbera, Nero d'Avola) were used to investigate the effect of enological tannins on astringency characteristics and phenolic content of red wines. Wines were treated with three tannins of different origins (G = grape, E= oak, and P = exotic wood) at two concentrations (10, 20 g/hl) and aged for 1 year. Wines were evaluated for astringency and for 16 subqualities using check‐all‐that‐apply questions. In addition, polymeric pigments, tannins, flavans, total anthocyanins, and color parameters were analyzed. Enological tannin promoted color stability by pigmented polymers formation. Astringency intensity was not enhanced, even better an improvement of mouthfeel sensations was achieved with wood‐derived tannins. Multivariate analysis revealed a great influence of the variety on astringency and phenolic characteristics of wines. Therefore, the initial phenolic composition of wine seems to be the main driver of the evolution of wine during aging.Practical applicationsTannin addition is an enological practice widely widespread because of many economical benefits. The use of enological tannins during aging can contribute to color stabilization and to an improvement of astringency subqualities of wines. Training on astringency subqualities with touch standards coupled with the check‐all‐that‐apply questions can provide an interesting way to reveal the different aspects of red wine astringency. Despite high astringency and high phenolic content, a wine may present desirable subqualities which can improve wine experience. Finally, a tailored use of enological tannins depends on wine variety.

Sensory characterization of the astringency of commercial Uruguayan Tannat wines

Astringency is one of the most important characteristics that define the quality of red wine, and is of particular relevance for Tannat, Uruguayan emblematic red wine variety. Astringency is a time-dependant and complex sensory characteristic, related to several sensations, or sub-qualities, that can be simultaneously perceived. The aim of the present study was to obtain a sensory characterization of the astringency of commercial Uruguayan Tannat wines. Forty samples with different characteristics in terms of vintage, price segment and aging in oak barrels were assessed by a panel of 9 trained assessors. Total astringency intensity was evaluated using time-intensity (TI), while astringency sub-qualities were described using a check-all-that-apply (CATA) question composed of sixteen terms. TI and the CATA question provided different information on the astringency of Tannat wines. Regarding global astringency, samples mainly differed in intensity-related parameters rather than in the development of astringency over time, although the variability was moderate. A wide range of sub-qualities, from silky and velvety to harsh and aggressive were used to describe the astringency of the evaluated wines. Four groups of samples with different astringency characteristics were identified, but this sorting was not related to vintage, price segment or aging in oak barrels. Further research is necessary to better understand how astringency characteristics are influenced by production variables, and to understand their relationship to consumers' and experts' perceived quality of Tannat wines.

Oenological perspective of red wine astringency

&lt;p&gt;&lt;strong&gt;Abstract&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Red wine is a complex matrix and its organoleptic characteristics are affected by a high complexity of wine compounds, namely polyphenols. One of the most important sensations and also a quality attribute of red wine is astringency. Along the years the major mechanism proposed to astringency perception is the interaction and precipitation of salivary proteins (in particular proline-rich proteins) by red wine polyphenols, namely tannins. Furthermore, it is also known that this interaction is affected by other red wine compounds such as carbohydrates.&lt;/p&gt;&lt;p&gt;The polyphenolic composition of red wine could be modified by modulation of the several oenological steps. Hence, the modulation of oenological steps could allow modulation of astringency and/or astringency sub-qualities. Crucial oenological steps include ripening, maceration and fermentation stabilization (fining), filtration and aging. Along this review, the influence of these oenological processes in wine polyphenolic composition is systematically revised converging in how it affects astringency from an oenological perspective.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;

Sensory evaluation of bitterness and astringency sub-qualities of wine phenolic compounds: synergistic effect and modulation by aromas

Mouthfeel characteristics of wine phenolic compounds (catechin, epicatechin, coumaric acid, caffeic acid, protocatechuic acid and gallic acid) were evaluated by sensory analysis using a Labeled Magnitude Scale for rating the intensity of the perceived sensations. Synergisms on bitterness and on astringent sub-qualities were detected when the phenolic compounds were tested as mixtures in comparison to individual compounds, maintaining the total amount of stimulus constant in all tasted samples. Principal component analysis was applied to observe trends in the data and to indicate relationships between phenolic substances and sensory attributes. It allowed us to easily visualize the synergistic effect discussed above. To our knowledge, this is the first time that astringency synergism between phenolic compounds has been described. This research also shows that wine aromas may modulate the perception of the astringency. In this study, the addition of volatile compounds increased the intensity of the astringent perception of the flavanol solutions and also its persistence.