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Ann C Noble - One of the best experts on this subject based on the ideXlab platform.
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Astringency and Bitterness of Flavonoid Phenols
2009Co-Authors: Ann C NobleAbstract:In beverages and fruits the lingering tactile sensation of Astringency,\nas well as the persistent taste of bitterness, are primarily elicited by\nflavonoid phenols. Chemically, relative Astringency of a compound is\ndefined by its effectiveness in precipitating protein. As the degree of\npolymerization of tannin increases, bitterness decreases, while\nAstringency increases. The astringent flavanol polymers or condensed\ntannins have a strong affinity for binding with proline rich proteins,\nsuch as those found in saliva. Sensorially Astringency is a drying or\nrough mouthfeel thought to result from decreased oral lubrication,\nfollowing binding of salivary proteins by tannins. This may explain the\nincrease in intensity of Astringency over several sips or wine or tea.\nAlso consistent with this hypothesis, subjects with low salivary flow\nrates perceive Astringency more intensely than high-flow individuals.
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Bitterness and Astringency of grape and wine polyphenols
Australian Journal of Grape and Wine Research, 2001Co-Authors: Franck Brossaud, Veronique Cheynier, Ann C NobleAbstract: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.
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effect of viscosity temperature and ph on Astringency in cranberry juice
Food Quality and Preference, 1999Co-Authors: H Peleg, Ann C NobleAbstract:Abstract This study explored the interactive effects of temperature, pH, viscosity and quinic acid in modifying Astringency of cranberry juice. A panel of 17 trained judges rated Astringency of nine samples, in duplicate, at 10 and 20 s after ingestion. Astringency intensity at both times showed the same trends, although the ratings were lower at 20 s. Addition of 1.5 g/l quinic acid lowered the pH to 2.59 and failed to produce a difference in Astringency from the base juice (pH 2.65) at 5°C and 25°C. Astringency of juice adjusted to pH 3 was significantly lower than either the base or quinic acid juices at both temperatures. Decreasing temperature caused an increase of about 2 cp in viscosity and lowered the perceived Astringency at all pH levels. Increasing the viscosity by 1.5 cp using CMC (carboxymethylcellulose, medium viscosity, Sigma Chemical) lowered the perceived Astringency for all pHs but the effect was only significant at 25°C. Thus, without varying the concentration of astringent compounds, Astringency intensity could be significantly modified by altering viscosity or pH. ©
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using repeated ingestion to determine the effect of sweetness viscosity and oiliness on temporal perception of soymilk Astringency
Food Quality and Preference, 1999Co-Authors: Sandrine Courregelongue, Pascal Schlich, Ann C NobleAbstract:Abstract Astringency is a persistent sensation which increases upon repeated ingestion. To evaluate the effect of viscosity, sucrose and oil on perception of Astringency during consumption of soymilk, a sequential sipping time–intensity (TI) procedure was utilized. For each soymilk, judges sipped the first of four ingestions and initiated the continuous recording of Astringency intensity. Each sip was expectorated at 10 s after ingestion, and sipped 10 s after expectoration of the previous stimulus. After the fourth sample, judges rated Astringency for 30 s. Traditional TI parameters, as well as rate of onset for each sip and increase in maximum intensity per sip were extracted from the TI curves. Maximum Astringency (IMAX) increased significantly with successive sips as did the Astringency at the time of sipping. Time to IMAX decreased from sip 1 to 3, but was longer for sip 4, which may be an artifact of the rapid test pace. Although addition of 60 g l −1 canola oil had no affect on Astringency, adding 40 g l −1 sucrose or increasing viscosity by 5 cp with CMC significantly lowered all Astringency parameters. The reduction in Astringency by CMC may result from restoration of salivary lubrication and in part by chelation or hydrogen bonding of CMC to the astringents reducing their ability to bind to salivary proteins. The reduction in Astringency produced by sucrose is more probably due to a cognitive process. ©
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bitterness and Astringency of flavan 3 ol monomers dimers and trimers
Journal of the Science of Food and Agriculture, 1999Co-Authors: Hanna Peleg, Pascal Schlich, Karine Gacon, Ann C NobleAbstract:Intensity of Astringency and bitterness of seven flavonoid compounds was evaluated by a time-intensity (TI) procedure. Eighteen trained judges rated intensity continuously from ingestion, through expectoration at 10 s until extinction of the sensation. The seven stimuli included two flavan-3-ol monomers, (+)-catechin and (−)-epicatechin, three dimers and two trimers synthesised from catechin or epicatechin by condensation with (+)-dihydroquercitin. As the degree of polymerisation increased, maximum bitterness intensity (Imax) and total duration (Ttot) decreased whereas Astringency Imax increased. The monomers were significantly higher in bitterness at Imax than the dimers, which were significantly higher than the trimers. Astringency Imax of the monomers was lower than the dimers or trimers, although no significant difference was found in Ttot among the polymer classes. The bond linking the monomeric units had an influence on both sensory properties. The catechin-catechin dimer linked by a 4→6 bond was more bitter than both catechin-(4→8)-catechin and catechin-(4→8)-epicatechin. Astringency was affected by both the specific linkage and the identity of the monomeric units with the dimer, catechin-(4→8)-catechin, being lower in Astringency than either catechin-(4→6)-catechin or catechin-(4→8)-epicatechin. © 1999 Society of Chemical Industry
Kunsong Chen - One of the best experts on this subject based on the ideXlab platform.
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dknac7 a novel high co2 hypoxia induced nac transcription factor regulates persimmon fruit de Astringency
PLOS ONE, 2018Co-Authors: Xinyue Shen, Miaomiao Wang, Donald Grierson, Wajeeha Jamil, Kunsong ChenAbstract:Artificial high-CO2 atmosphere (AHCA, 95% CO2 and 1% O2) has been widely applied as a postharvest de-Astringency treatment for persimmon fruit. AHCA increases expression of transcription factors, including ethylene response factors (DkERF), that target de-Astringency genes. Here, the promoter of DkERF9, a previously characterized AHCA-inducible and de-Astringency regulator, was utilized to screen a cDNA library by yeast one hybrid assay. A novel NAC transcription factor, named DkNAC7, was identified. Dual-luciferase assay indicated that DkNAC7 could not only trans-activate the promoter of DkERF9, but also activated the previously identified deAstringency-related gene DkPDC2. Real-time PCR analysis showed that DkNAC7 was up-regulated by AHCA treatment, in concert with the removal of Astringency from persimmon fruit and subcellular localization showed DkNAC7 was located in the nucleus. Thus, these results indicate that DkNAC7 is a putative transcriptional activator involved in regulating persimmon fruit deAstringency by trans-activition on both DkERF9 and DkPDC2, which encodes pyruvate decarboxylase.
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involvement of dktga1 transcription factor in anaerobic response leading to persimmon fruit postharvest de Astringency
PLOS ONE, 2016Co-Authors: Miaomiao Wang, Ziyuan Gong, Fang Fang, Xian Li, Donald Grierson, Kunsong ChenAbstract:Persimmon fruit are unique in accumulating proanthocyanidins (tannins) during development, which cause Astringency in mature fruit. In ‘Mopanshi’ persimmon, Astringency can be removed by treatment with 95% CO2, which increases the concentrations of ethanol and acetaldehyde by glycolysis, and precipitates the soluble tannin. A TGA transcription factor, DkTGA1, belonging to the bZIP super family, was isolated from an RNA-seq database and real-time quantitative PCR indicated that DkTGA1 was up-regulated by CO2 treatment, in concert with the removal of Astringency from persimmon fruit. Dual-luciferase assay revealed that DkTGA1 had a small (less than 2-fold), but significant effect on the promoters of de-Astringency-related genes DkADH1, DkPDC2 and DkPDC3, which encode enzymes catalyzing formation of acetaldehyde and ethanol. A combination of DkTGA1 and a second transcription factor, DkERF9, shown previously to be related to de-Astringency, showed additive effects on the activation of the DkPDC2 promoter. Yeast one-hybrid assay showed that DkERF9, but not DkTGA1, could bind to the DkPDC2 promoter. Thus, although DkTGA1 expression is positively associated with persimmon fruit de-Astringency, trans-activation analyses with DkPDC2 indicates it is likely to act by binding indirectly DkPDC2 promoter, might with helps of DkERF9.
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isolation and expression of nac genes during persimmon fruit postharvest Astringency removal
International Journal of Molecular Sciences, 2015Co-Authors: Miaomiao Wang, Fang Fang, Donald Grierson, Hongxun Wang, Kunsong ChenAbstract:NAC genes have been characterized in numerous plants, where they are involved in responses to biotic and abiotic stress, including low oxygen stress. High concentration of CO2 is one of the most effective treatments to remove Astringency of persimmon fruit owing to the action of the accumulated anoxia metabolite acetaldehyde. In model plants, NAC genes have been identified as being responsive to low oxygen. However, the possible relationship between NAC transcription factors and persimmon Astringency removal remains unexplored. In the present research, treatment with a high concentration of CO2 (95%) effectively removed Astringency of “Mopan” persimmon fruit by causing decreases in soluble tannin. Acetaldehyde content increased in response to CO2 treatment concomitantly with Astringency removal. Using RNA-seq and Rapid amplification of cDNA ends (RACE), six DkNAC genes were isolated and studied. Transcriptional analysis indicated DkNAC genes responded differentially to CO2 treatment; DkNAC1, DkNAC3, DkNAC5 and DkNAC6 were transiently up-regulated, DkNAC2 was abundantly expressed 3 days after treatment, while the DkNAC4 was suppressed during Astringency removal. It is proposed that DkNAC1/3/5/6 could be important candidates as regulators of persimmon Astringency removal and the roles of other member are also discussed.
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ethylene responsive transcription factors interact with promoters of adh and pdc involved in persimmon diospyros kaki fruit de Astringency
Journal of Experimental Botany, 2012Co-Authors: Donald Grierson, Ian B Ferguson, Kunsong ChenAbstract:The persimmon fruit is a particularly good model for studying fruit response to hypoxia, in particular, the hypoxia-response ERF (HRE) genes. An anaerobic environment reduces fruit Astringency by converting soluble condensed tannins (SCTs) into an insoluble form. Although the physiology of de-Astringency has been widely studied, its molecular control is poorly understood. Both CO2 and ethylene treatments efficiently removed the Astringency from ‘Mopan’ persimmon fruit, as indicated by a decrease in SCTs. Acetaldehyde, the putative agent for causing de-Astringency, accumulated during these treatments, as did activities of the key enzymes of acetaldehyde synthesis, alcohol dehydrogenase (ADH), and pyruvate decarboxylase (PDC). Eight DkADH and DkPDC genes were isolated, and three candidates for a role in de-Astringency, DkADH1, DkPDC1, and DkPDC2, were characterized by transcriptional analysis in different tissues. The significance of these specific isoforms was confirmed by principal component analysis. Transient expression in leaf tissue showed that DkPDC2 decreased SCTs. Interactions of six hypoxia-responsive ERF genes and target promoters were tested in transient assays. The results indicated that two hypoxia-responsive ERF genes, DkERF9 and DkERF10, were involved in separately regulating the DkPDC2 and DkADH1 promoters. It is proposed that a DkERF–DkADH/DkPDC cascade is involved in regulating persimmon de-Astringency.
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expression of ethylene response genes during persimmon fruit Astringency removal
Planta, 2012Co-Authors: Qian Xu, Ian B Ferguson, Kunsong ChenAbstract:Thirteen ethylene signaling related genes were isolated and studied during ripening of non-astringent ‘Yangfeng’ and astringent ‘Mopan’ persimmon fruit. Some of these genes were characterized as ethylene responsive. Treatments, including ethylene and CO2, had different effects on persimmon ripening, but overlapping roles in Astringency removal, such as increasing the reduction in levels of soluble tannins. DkERS1, DkETR2, and DkERF8, may participate in persimmon fruit ripening and softening. The expression patterns of DkETR2, DkERF4, and DkERF5 had significant correlations with decreases in soluble tannins in ‘Mopan’ persimmon fruit, suggesting that these genes might be key components in persimmon fruit Astringency removal and be the linkage between different treatments, while DkERF1 and DkERF6 may be specifically involved in CO2 induced Astringency removal. The possible roles of ethylene signaling genes in persimmon fruit Astringency removal are discussed.
Donald Grierson - One of the best experts on this subject based on the ideXlab platform.
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dknac7 a novel high co2 hypoxia induced nac transcription factor regulates persimmon fruit de Astringency
PLOS ONE, 2018Co-Authors: Xinyue Shen, Miaomiao Wang, Donald Grierson, Wajeeha Jamil, Kunsong ChenAbstract:Artificial high-CO2 atmosphere (AHCA, 95% CO2 and 1% O2) has been widely applied as a postharvest de-Astringency treatment for persimmon fruit. AHCA increases expression of transcription factors, including ethylene response factors (DkERF), that target de-Astringency genes. Here, the promoter of DkERF9, a previously characterized AHCA-inducible and de-Astringency regulator, was utilized to screen a cDNA library by yeast one hybrid assay. A novel NAC transcription factor, named DkNAC7, was identified. Dual-luciferase assay indicated that DkNAC7 could not only trans-activate the promoter of DkERF9, but also activated the previously identified deAstringency-related gene DkPDC2. Real-time PCR analysis showed that DkNAC7 was up-regulated by AHCA treatment, in concert with the removal of Astringency from persimmon fruit and subcellular localization showed DkNAC7 was located in the nucleus. Thus, these results indicate that DkNAC7 is a putative transcriptional activator involved in regulating persimmon fruit deAstringency by trans-activition on both DkERF9 and DkPDC2, which encodes pyruvate decarboxylase.
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involvement of dktga1 transcription factor in anaerobic response leading to persimmon fruit postharvest de Astringency
PLOS ONE, 2016Co-Authors: Miaomiao Wang, Ziyuan Gong, Fang Fang, Xian Li, Donald Grierson, Kunsong ChenAbstract:Persimmon fruit are unique in accumulating proanthocyanidins (tannins) during development, which cause Astringency in mature fruit. In ‘Mopanshi’ persimmon, Astringency can be removed by treatment with 95% CO2, which increases the concentrations of ethanol and acetaldehyde by glycolysis, and precipitates the soluble tannin. A TGA transcription factor, DkTGA1, belonging to the bZIP super family, was isolated from an RNA-seq database and real-time quantitative PCR indicated that DkTGA1 was up-regulated by CO2 treatment, in concert with the removal of Astringency from persimmon fruit. Dual-luciferase assay revealed that DkTGA1 had a small (less than 2-fold), but significant effect on the promoters of de-Astringency-related genes DkADH1, DkPDC2 and DkPDC3, which encode enzymes catalyzing formation of acetaldehyde and ethanol. A combination of DkTGA1 and a second transcription factor, DkERF9, shown previously to be related to de-Astringency, showed additive effects on the activation of the DkPDC2 promoter. Yeast one-hybrid assay showed that DkERF9, but not DkTGA1, could bind to the DkPDC2 promoter. Thus, although DkTGA1 expression is positively associated with persimmon fruit de-Astringency, trans-activation analyses with DkPDC2 indicates it is likely to act by binding indirectly DkPDC2 promoter, might with helps of DkERF9.
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isolation and expression of nac genes during persimmon fruit postharvest Astringency removal
International Journal of Molecular Sciences, 2015Co-Authors: Miaomiao Wang, Fang Fang, Donald Grierson, Hongxun Wang, Kunsong ChenAbstract:NAC genes have been characterized in numerous plants, where they are involved in responses to biotic and abiotic stress, including low oxygen stress. High concentration of CO2 is one of the most effective treatments to remove Astringency of persimmon fruit owing to the action of the accumulated anoxia metabolite acetaldehyde. In model plants, NAC genes have been identified as being responsive to low oxygen. However, the possible relationship between NAC transcription factors and persimmon Astringency removal remains unexplored. In the present research, treatment with a high concentration of CO2 (95%) effectively removed Astringency of “Mopan” persimmon fruit by causing decreases in soluble tannin. Acetaldehyde content increased in response to CO2 treatment concomitantly with Astringency removal. Using RNA-seq and Rapid amplification of cDNA ends (RACE), six DkNAC genes were isolated and studied. Transcriptional analysis indicated DkNAC genes responded differentially to CO2 treatment; DkNAC1, DkNAC3, DkNAC5 and DkNAC6 were transiently up-regulated, DkNAC2 was abundantly expressed 3 days after treatment, while the DkNAC4 was suppressed during Astringency removal. It is proposed that DkNAC1/3/5/6 could be important candidates as regulators of persimmon Astringency removal and the roles of other member are also discussed.
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ethylene responsive transcription factors interact with promoters of adh and pdc involved in persimmon diospyros kaki fruit de Astringency
Journal of Experimental Botany, 2012Co-Authors: Donald Grierson, Ian B Ferguson, Kunsong ChenAbstract:The persimmon fruit is a particularly good model for studying fruit response to hypoxia, in particular, the hypoxia-response ERF (HRE) genes. An anaerobic environment reduces fruit Astringency by converting soluble condensed tannins (SCTs) into an insoluble form. Although the physiology of de-Astringency has been widely studied, its molecular control is poorly understood. Both CO2 and ethylene treatments efficiently removed the Astringency from ‘Mopan’ persimmon fruit, as indicated by a decrease in SCTs. Acetaldehyde, the putative agent for causing de-Astringency, accumulated during these treatments, as did activities of the key enzymes of acetaldehyde synthesis, alcohol dehydrogenase (ADH), and pyruvate decarboxylase (PDC). Eight DkADH and DkPDC genes were isolated, and three candidates for a role in de-Astringency, DkADH1, DkPDC1, and DkPDC2, were characterized by transcriptional analysis in different tissues. The significance of these specific isoforms was confirmed by principal component analysis. Transient expression in leaf tissue showed that DkPDC2 decreased SCTs. Interactions of six hypoxia-responsive ERF genes and target promoters were tested in transient assays. The results indicated that two hypoxia-responsive ERF genes, DkERF9 and DkERF10, were involved in separately regulating the DkPDC2 and DkADH1 promoters. It is proposed that a DkERF–DkADH/DkPDC cascade is involved in regulating persimmon de-Astringency.
E.a. Foegeding - One of the best experts on this subject based on the ideXlab platform.
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Invited review: Astringency in whey protein beverages.
Journal of Dairy Science, 2020Co-Authors: B.g. Carter, E.a. Foegeding, Maryanne DrakeAbstract:ABSTRACT Astringency is the sensation of mouth drying and puckering, and it has also been described as a loss of lubrication in the mouth. Astringency is perceived as an increase in oral friction or roughness. Astringency caused by tannins and other polyphenols has been well documented and studied. Whey proteins are popular for their functional and nutritional quality, but they exhibit Astringency, particularly under acidic conditions popular in high acid (pH 3.4) whey protein beverages. Acids cause Astringency, but acidic protein beverages have higher Astringency than acid alone. Whey proteins are able to interact with salivary proteins, which removes the lubricating saliva layer of the mouth. Whey proteins can also interact directly with epithelial tissue. These various mechanisms of Astringency limit whey protein ingredient applications because Astringency is undesirable to consumers. A better understanding of the causes of whey protein Astringency will improve our ability to produce products that have high consumer liking and deliver excellent nutrition.
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roles of charge interactions on Astringency of whey proteins at low ph
Journal of Dairy Science, 2010Co-Authors: Bongkosh Vardhanabhuti, P J Luck, M A Drake, M A Kelly, E.a. FoegedingAbstract:Whey proteins are a major ingredient in sports drink and functional beverages. At low pH, whey proteins are astringent, which may be undesirable in some applications. Understanding the Astringency mechanism of whey proteins at low pH could lead to developing ways to minimize the Astringency. This study compared the Astringency of β-lactoglobulin (β-LG) at low pH with phosphate buffer controls having the same amount of phosphate and at similar pH. Results showed that β-LG samples were more astringent than phosphate buffers, indicating that Astringency was not caused by acid alone and that proteins contribute to Astringency. When comparing among various whey protein isolates (WPI) and lactoferrin at pH 3.5, 4.5, and 7.0, lactoferrin was astringent at pH 7.0 where no acid was added. In contrast, Astringency of all WPI decreased at pH 7.0. This can be explained by lactoferrin remaining positively charged at pH 7.0 and able to interact with negatively charged saliva proteins, whereas the negatively charged WPI would not interact. Charge interactions were further supported by β-LG or lactoferrin and salivary proteins precipitating when mixed at conditions where β-LG, lactoferrin, or saliva themselves did not precipitate. It can be concluded that interactions between positively charged whey proteins and salivary proteins play a role in Astringency of proteins at low pH.
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factors regulating Astringency of whey protein beverages
Journal of Dairy Science, 2008Co-Authors: Jason Beecher, M A Drake, P J Luck, E.a. FoegedingAbstract:Abstract A rapidly growing area of whey protein use is in beverages. There are 2 types of whey protein-containing beverages: those at neutral pH and those at low pH. Astringency is very pronounced at low pH. Astringency is thought to be caused by compounds in foods that bind with and precipitate salivary proteins; however, the mechanism of Astringency of whey proteins is not understood. The effect of viscosity and pH on the Astringency of a model beverage containing whey protein isolate was investigated. Trained sensory panelists (n = 8) evaluated the viscosity and pH effects on Astringency and basic tastes of whey protein beverages containing 6% wt/vol protein. Unlike what has been shown for alum and polyphenols, increasing viscosity (1.6 to 7.7 mPa·s) did not decrease the perception of Astringency. In contrast, the pH of the whey protein solution had a major effect on Astringency. A pH 6.8 whey protein beverage had a maximum Astringency intensity of 1.2 (15-point scale), whereas that of a pH 3.4 beverage was 8.8 (15-point scale). Astringency decreased between pH 3.4 and 2.6, coinciding with an increase in sourness. Decreases in Astringency corresponded to decreases in protein aggregation as observed by turbidity. We propose that Astringency is related to interactions between positively charged whey proteins and negatively charged saliva proteins. As the pH decreased between 3.4 and 2.6, the negative charge on the saliva proteins decreased, causing the interactions with whey proteins to decrease.
James A Kennedy - One of the best experts on this subject based on the ideXlab platform.
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wine and grape tannin interactions with salivary proteins and their impact on Astringency a review of current research
Molecules, 2011Co-Authors: Jacqui M. Mcrae, James A KennedyAbstract:Abstract: Astringency is an important characteristic of red wine quality. The sensation is generally thought to be produced by the interaction of wine tannins with salivary proteins and the subsequent aggregation and precipitation of protein-tannin complexes. The importance of wine Astringency for marketability has led to a wealth of research on the causes of Astringency and how tannins impact the quality of the sensation, particularly with respect to tannin structure. Ultimately, the understanding of how tannin structure impacts Astringency will allow the controlled manipulation of tannins via such methods as micro-oxygenation or fining to improve the quality of wines. Keywords: Astringency; condensed tannin; salivary proteins; wine 1. Introduction Tannins, including grape-derived condensed tannins (flavonoids) produce sensations of Astringency in food and drink and form the ‘structure’ or ‘body’ of red wine. The term Astringency refers to the drying and a puckering sensation in the mouth [1] and is a characteristic of red wine and its mouth-feel [2-5]. Wine tannin quality is dependent on the maximum intensity of the mouth feel, total duration and time taken to reach maximum intensity [6], as well as the extent of mouth drying and mouth roughness [1,7,8]. The spectrum of subtle differences in Astringency sensations was compiled as a ‘red wine
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Wine and grape tannin interactions with salivary proteins and their impact on Astringency: A review of current research
Molecules, 2011Co-Authors: Jacqui M. Mcrae, James A KennedyAbstract:Astringency is an important characteristic of red wine quality. The sensation is generally thought to be produced by the interaction of wine tannins with salivary proteins and the subsequent aggregation and precipitation of protein-tannin complexes. The importance of wine Astringency for marketability has led to a wealth of research on the causes of Astringency and how tannins impact the quality of the sensation, particularly with respect to tannin structure. Ultimately, the understanding of how tannin structure impacts Astringency will allow the controlled manipulation of tannins via such methods as micro-oxygenation or fining to improve the quality of wines.
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analysis of tannins in red wine using multiple methods correlation with perceived Astringency
American Journal of Enology and Viticulture, 2006Co-Authors: James A Kennedy, Jordan Ferrier, James F Harbertson, Catherine Peyrot Des GachonsAbstract:The purpose of this study was to assess the relationship between Astringency and tannin concentration in red wine using various analytical methods. Forty red wines were selected from a large commercial producer based on preliminary assessment of tannin variation and with selection intended to reflect potential variation in tannin amount. Tannin concentration was determined using previously published analytical methods, including absorption of light at 280 nm, reaction with 4-dimethylaminocinnamaldehyde, protein precipitation, phloroglucinolysis, and gel permeation chromatography. Results indicated that clear differences in tannin quantification existed in terms of the actual amount reported and in the relationship with perceived Astringency in red wine. The analytical methods having the strongest correlations with perceived Astringency were protein precipitation (r 2 = 0.82), phloroglucinolysis (r 2 = 0.73), and gel permeation chromatography (r 2 = 0.74). Given the equipment availability of most wineries, it was determined that protein precipitation was the most useful analytical method for Astringency assessment. Because the protein precipitation method is similar to the physiological response to astringents, it could become an important in vitro tool for understanding how tannin structure modification leads to modification in Astringency perception.
