Astringent Sensation Research Articles

Integrated Transcriptomic and Proteomic Analysis Identifies Novel Regulatory Genes Associated with Plant Growth Regulator-Induced Astringency in Grape Berries.

Astringency influences the sensory characteristics and flavor quality of table grapes. We tested the astringency sensory attributes of berries and investigated the concentration of flavan-3-ols/proanthocyanidins (PAs) in skins after the application of the plant growth regulators CPPU and GA3 to the flowers and young berries of the "Summer Black" grape. Our results showed that CPPU and GA3 applications increase sensory astringency perception scores and flavan-3-ol/proanthocyanidin concentrations. Using integrated transcriptomic and proteomic analysis, differentially expressed transcripts and proteins associated with growth regulator treatment were identified, including those for flavonoid biosynthesis that contribute to the changes in sensory astringency levels. Transient overexpression of candidate astringency-related regulatory genes in grape leaves revealed that VvWRKY71, in combination with VvMYBPA1 and VvMYC1, could promote the biosynthesis of proanthocyanidins, while overexpression of VvNAC83 reduced the accumulation of proanthocyanidins. However, in transient promoter studies in Nicotiana benthamiana, VvWRKY71 repressed the promoter of VvMYBPA2, while VvNAC83 had no significant effect on the promoter activity of four PA-related genes, and VvMYBPA1 was shown to activate its own promoter. This study provides new insights into the molecular mechanisms of sensory astringency formation induced by plant growth regulators in grape berries.

Sensory description of beverages of intervarietal hybrids of Conilon and Robusta: Natural and fermented coffees

AbstractThis study describes the sensory profile of beverages of Coffea canephora hybrids (clones BRS 2314 and BRS 2357) in natural (N) and fermented (F) versions. Flash Profile and Temporal Dominance of Sensations were performed; physicochemical characteristics were evaluated. Increase in total titratable acidity and reduction in pH was observed with fermentation. BRS 2314 beverages had higher contents of 5‐caffeoylquinic acid and caffeine. Natural coffees were described as having brown/coffee color, coffee aroma and flavor, roasted aroma and flavor, sweet aroma, and sour taste, and presenting dominance of coffee and tobacco flavors, and bitter and sour tastes. Fermented coffees were described as full‐bodied and having non‐characteristic, fermented and herbal aromas, astringent sensation, bitter taste and bitter aftertaste, and residual flavors, with the dominance of chocolate, fermented and roasted flavors, and bitter taste. BRS 2357 beverages were characterized by bitter taste and bitter aftertaste. BRS 2314N beverage presented attributes considered positive for quality.Practical ApplicationsThe results are relevant for the coffee production chain and consumers. Intervarietal hybrids of Conilon and Robusta are grown in an area characterized by family farming and with great prospects for sustainable production (in the Rondônia/BR state, Western Amazon) and are developed to express the best characteristics of both botanical varieties, as the high potential of Robusta coffees for fine cup beverages. The hybrid clones were successfully evaluated by experts, but the results do not necessarily correspond to the consumers' insights into coffee brew quality. In addition, fermentation allows to produce beverages with different nuances. The joint use of quick methodologies for static (Flash Profile) and temporal (Temporal Dominance of Sensations) sensory descriptions provided a closer representation of the consumers' perception of those products. This information brings new market perspectives for high‐yield Coffea canephora coffees that are now going through a moment of breaking paradigms regarding quality.

Paper chromatography approach for the assessment of interaction between red wine and whole saliva

In-mouth interaction of red wine compounds with salivary proteins is a primary event allegedly responsible for eliciting the mouth-feel sensation of astringency. Those interactions have been currently associated with precipitation of salivary protein/polyphenol complexes. However, such single physicochemical evidence for interaction does not account for the complexity of astringency. This study aimed to develop a paper chromatography method to assess interactions between red wine and the salivary protein fraction using stepwise series of red wine/saliva binary mixtures from 100% wine to 100% saliva (“Alpha and Omega series”). Aliquots of each one of the mixtures were spotted on a cellulose membrane to scrutinize independently the distribution areas of wine components (naturally pink-colored) and salivary protein (stained blue in Coomassie Brilliant R-250). This double target detection revealed interactions between saliva and red wine components along most of the quantitative Alpha and Omega series, a point of equivalence corresponding to maximum interactivity for both complex reactants and a non-diffusible sub-fraction of saliva displaying the highest interactivity. The results indicate a novel way to assess quantitatively physicochemical interactions between red wines and human saliva but also provide new lights to approach the identification of molecular salivary structures involved in triggering astringency.

Brewing with Unmalted and Malted Sorghum: Influence on Beer Quality

One of the earliest biotechnological processes is brewing, which uses conventional raw materials like barley malt and, to a lesser extent, wheat malt. Today, adjuncts are used in the brewing of 85–90% of the world’s beer, with significant regional differences. The results of this study’s brewing were compared to those of beer made only from malted barley. Malted and unmalted sorghum were suggested for use in this study’s brewing. In order to improve the technical mashing operation and raise output yield, commercial enzymes were introduced. The following physicochemical analyses of the finished beer were carried out in accordance with regulatory requirements: original extract (% m/m), apparent extract (% m/m), alcohol content (% v/v, % m/m), density (g/cm3), turbidity (EBC), pH, color (EBC), bitterness value (IBU), oxygen content (mg/L), carbon dioxide content (g/L). A nine-point hedonic scale was used to conduct the sensory evaluation of the beer samples. Sorghum was easily included into the technological process to create a finished product that, in many ways, resembled traditional beer, making sorghum appropriate for typical beer drinkers. The laboratory brewing formula that produced the highest-quality results of all the tested variants included 60% sorghum malt and 40% unmalted sorghum: original extract 11.26% m/m, apparent extract 4.59% m/m, alcohol content 4.12% v/v, turbidity 0.74 EBC, CO2 content 5.10 g/L. The resulting sorghum beer typically has low alcohol content, a complex, aromatic, slightly sour flavor, a mild bitter or astringent sensation, and less stable foam.

Processing of Sweet, Astringent and Pungent Oral Stimuli in the Human Brain

Taste and oral somatosensation are intimately related to each other from peripheral receptors to the central nervous system. Oral astringent sensation is thought to contain both gustatory and somatosensory components. In the present study, we compared the cerebral response to an astringent stimulus (tannin), with the response to one typical taste stimulus (sweet – sucrose) and one typical somatosensory stimulus (pungent – capsaicin) using functional magnetic resonance imaging (fMRI) of 24 healthy subjects. Three distributed brain sub-regions responded significantly different to the three types of oral stimulations: lobule IX of the cerebellar hemisphere, right dorsolateral superior frontal gyrus, and left middle temporal gyrus. This suggests that these regions play a major role in the discrimination of astringency, taste, and pungency.

Combining sensory panels with Analytic Hierarchy Process (AHP) to assess nectarine and peach quality

The aim of this study is to combine the Analytic Hierarchy Process (AHP) with sensory analysis for assessing the quality of stone fruits, such as peaches and nectarines. To this end, a multicriteria model based on the AHP is proposed, which could be used in any process of evaluation or selection of these fruits. It is compared with the Quantitative Descriptive Analysis (QDA) performed by trained panellists. The AHP results showed that gustatory phase was the most important attribute in both the positive (54%) and negative (80%) models. In the next level of attributes, the most important were sweetness and juiciness (63.1% of the weight for nectarines and 55.1% for peaches), while for rejection the most important attributes were the bitter, sour or astringent sensation of the gustatory phase (around 25% each attribute). The prioritisation obtained for the samples of fruits was the same as the QDA. AHP also provided the tasting profile of every panellist. With the AHP, time and costs are saved and accuracy of the results is improved. In the case of stone fruits, where variability is high throughout the season, the combination of QDA and AHP can help the food industry by matching consumer’s expectations better and faster.

Pollen quality and sensory attributes of Algerian jujube (Ziziphus lotus (L.) Lam.) honeys

Honey bees and beekeeping activity are of huge importance for the crop production and biodiversity conservation as well as for the economic impact due to ecosystem services. In the south of Algeria, the jujube blooming is an essential forage source for honey bees. The aim of this study was to determine the melissopalynological and sensory characteristics of Algerian jujube honey. Nineteen samples of jujube honey collected in south Algeria over the period from 2016 to 2018 were analyzed. The unifloral designation attributed to the honey was confirmed by a pollen analysis following the established standard methods. Sensory analysis is carried out testing the color, the odor and aromas. The results showed that Ziziphus lotus pollen was predominant in all samples, and in terms of sensory analysis, color ranged from amber yellow to light brown; the determined scent classes were warm, floral and woody with medium intensity; the aroma was represented by medium intensity with the warm caramelized, floral fruity and woody classes. Sweet flavor is perceived at medium intensity, acidic flavor is weak, astringent sensation is average and the piquant note is perceived with a low intensity. This work proves to be important for improving the knowledge in typical honeys.

Exploring The Relative Astringency of Tea Catechins and Distinct Astringent Sensation of Catechins and Flavonol Glycosides via an In Vitro Assay Composed of Artificial Oil Bodies.

Artificial oil bodies covered by a recombinant surface protein, caleosin fused with histatin 3 (a major human salivary peptide), were employed to explore the relative astringency of eight tea catechins. The results showed that gallate-type catechins were more astringent than non-gallate-type catechins, with an astringency order of epicatechin gallate > epigallocatechin gallate > gallocatechin gallate > catechin gallate > epigallocatechin > epicatechin > gallocatechin > catechin. As expected, the extension of brewing time led to an increase in catechin content in the tea infusion, thus elevating tea astringency. Detailed analysis showed that the enhanced proportion of gallate-type catechins was significantly higher than that of non-gallate-type catechins, indicating that tea astringency was elevated exponentially, rather than proportionally, when brewing time was extended. Rough surfaces were observed on artificial oil bodies when they were complexed with epigallocatechin gallate (a catechin), while a smooth surface was observed on those complexed with rutin (a flavonol glycoside) under an atomic force microscope and a scanning electron microscope. The results indicate that catechins and flavonol glycosides induce the sensation of rough (puckering) and smooth (velvety) astringency in tea, respectively.

REDUCE THE SULPHUR DIOXIDE CONTENT OF WINE BY BIOLOGICAL PROCESS IN RELATION TO THE CONTENT OF POLYPHENOLIC SUBSTANCES

In recent years, many papers have paid attention to the bioactive compounds, particularly to the antioxidant activity of polyphenolic compounds in food and beverages, due to their positive effect on human body. Therefore, the phenolic compounds and their antioxidant capacity become an important quality parameter, especially in niche markets concerned with health benefits. 
 Wine is an excellent source of various classes of polyphenols. The phenolic compounds are responsible for the sensory characteristics, particularly colour, astringency, bitterness, and aroma, too. Another very important ingredient in the wine is added the sulphur dioxide, which has the role to protect these reductive components of wines.
 Sulphur dioxide has the effects of antioxidant, antimicrobial and preservative that is mutually merging. However, it is possible to increase the stability of the complex of biologically active substances (BAS), as holders of natural antioxidant capacity. The present contribution brings opportunities rather than full elimination, but a substantial reduction of the content of sulphur dioxide, which protects the wine during the entire technological process of manufacture and treatment. The dosage of sulphur dioxide can be reduced in its values from 15 to 40% of the total health of the authorized maximum sulphur dioxide content of wine.

Sensory and Nutraceutical Properties of Infusions Prepared with Grape Pomace and Edible-Coated Dried–Minced Grapes

Grapes and grape/wine byproducts such as non-fermented/semi-fermented or fermented grapes, skins, and seeds are a rich source of polyphenols, known to have nutraceutical properties. Grape byproducts present a great potential for the development of new beverages, such as infusions and tisanes. This work aimed to study the effects of different drying temperatures on the sensory and chemical properties of fermented grape pomace infusions, and to evaluate the same sensory and chemical characteristics on infusions of dried–minced grapes coated with different organic matrices. At the end of the work, it was possible to conclude that the presence of some coating agents results in changes in the sensory characteristics of the infusions, also altering the recorded antioxidant activity. However, all matrices seemed suitable for coating, and none showed negative characteristics in the infusions. Furthermore, of the three infusions (50, 60, and 70 °C), the one prepared with dehydrated grape pomace at 70 °C was the one with the highest pH value, highest °Brix value, and significantly greater concentration of phenolic compounds. In the sensory analysis, the constant presence of a bitter taste and astringent sensation stood out, which are not positive aspects from a sensory point of view. However, the addition of natural flavors—especially honey—made the infusion more sensorially pleasant. Overall, grape pomace dehydrated at 70 °C made it possible to obtain a product with phenolic compounds and antioxidant capacity that is more promising to integrate into human food, particularly via the preparation of infusions. Furthermore, the consumer may, if they so choose, add honey or another agent as a natural flavoring, making the final infusion more pleasant from a sensory point of view.

DkmiR397 Regulates Proanthocyanidin Biosynthesis via Negative Modulating DkLAC2 in Chinese PCNA Persimmon.

Persimmon fruits accumulate a large amount of proanthocyanidins (PAs), which makes an astringent sensation. Proanthocyanidins (PAs) are the polymers of flavan-3-ols stored in plant vacuoles under laccase activation. A laccase gene, DkLAC2, is putatively involved in PAs biosynthesis and regulated by microRNA (DkmiR397) in persimmon. However, the polymerization of PAs in association with miRNA397 still needs to be explored in persimmon. Here, we identified pre-DkmiR397 and its target gene DkLAC2 in ‘Eshi 1’ persimmon. Histochemical staining with GUS and dual luciferase assay both confirmed DkmiR397-DkLAC2 binding after co-transformation in tobacco leaves. Diverse expression patterns of DkLAC2 and DkmiR397 were exhibited during persimmon fruit development stages. Moreover, a contrasting expression pattern was also observed after the combined DkLAC2-miR397 transformation in persimmon leaves, suggesting that DkmiR397 might be a negative regulator of DkLAC2. Similarly, the transient transformation of DkmiR397 in persimmon fruit discs in vitro also reduced PA accumulation by repressing DkLAC2, whereas the up-regulation of DkLAC2 increased the accumulation of PAs by short tandem target mimic STTM-miR397. A similar expression pattern was observed when overexpressing of DkLAC2 in Arabidopsis wild type (WT) and overexpression of DkLAC2, DkmiR397 in persimmon leaf callus. Our results revealed that the role of DkmiR397 repressed the expression of DkLAC2 concerning PA biosynthesis, providing a potential target for the manipulation of PAs metabolism in persimmon.

Comparison of different maceration and non-maceration treatments for enhancement of phenolic composition, colour intensity, and taste attributes of Malvazija istarska (Vitis vinifera L.) white wines

To investigate the effect of several vinification techniques aimed to enhance wine phenolic profile and sensory quality, maceration treatments of different duration and temperature (pre-fermentative cold one day maceration at 10 °C, seven days maceration at 16 °C, and prolonged post-fermentative 21 day maceration at 16 °C) and non-maceration treatments including tannin addition and late harvest grapes vinification were performed and compared to a standard white grape processing treatment. Produced wines were subjected to the analysis of phenols by high-performance liquid chromatography, colour intensity, and quantitative descriptive and hedonic sensory analysis. The increase in individual phenolic compound concentrations was mostly pronounced in maceration treatment wines, for both phenolic acids and flavan-3-ols, as well as for the sum of phenolic compound concentrations determined by high-performance liquid chromatography that tripled in relation to that determined in control treatment wine. Pre-fermentative cold maceration led to a moderate increase in phenolic compounds content without accentuating bitterness and astringency sensations. Wine phenolic composition and colour intensity were mostly affected by the prolonged post-fermentative 21 day maceration. Vinification of late harvest grapes produced a wine graded with the highest positive score for taste. The obtained distinct wine styles resulting from the application of the investigated practices may lead to a further diversification of white wine market.

Characterization of wine astringency contributed by acetaldehyde-mediated condensation between flavan-3-ols and grape skin/seeds polyphenol

Since the grape skin and seed contain different phenolic substances, the proportion of the skin and seed will affect the wine mouthfeel during the wine making process. During the wine ageing, the interaction between flavanols with anthocyanins is an important reaction and considered linked to astringency. Hence, a major question is whether changing the skin-seed ratio will affect the polymerization of phenolic substances in wine, thus affecting the astringency of wine. To answer this, astringency of wine was studied by changing the content of grape skins and seeds by SDS-PAGE, fluorescence quenching and sensory taste. Besides, acetaldehyde-mediated condensation reaction between different flavan-3-ols and malvidin-3-glucoside were studied in model solution. The result showed that grape skins and seeds contribute differently to astringency sensation, mainly because of the difference in the type and content of flavanols and anthocyanins contained in them. In addition, acetaldehyde-induced flavan-3-ols: anthocyanin mixture presents a strong effect toward the interaction with BSA when compared to other phenolic combinations. Furthermore, it was observed that the protein-binding ability of the polyphenols in red wine has a strong correlation with the wine astringency intensity.

Effects of brewing conditions and coffee species on the physicochemical characteristics, preference and dynamics of sensory attributes perception in cold brews

The study aimed to assess the dominant sensory attributes and preference for cold brews prepared with different coffee species under different brewing conditions. Four beverages were brewed using Arabica and Robusta coffees with either a coarser coffee grind and extraction at 5 °C or a finer grind and extraction at 15 °C. Coffee flavor and bitter taste were dominant sensory attributes of all beverages, regardless of material and preparation. While there were no differences in preference, the composition and dominant sensory attributes differed among the cold brews. The use of different coffee species had a greater impact on the composition and the perception of the attributes of the cold brews than brewing conditions. Sourness and coffee flavor were more dominant in Arabica cold brews, which had higher trigonelline content and acidity, but bitter taste dominance was further reported. Meanwhile, bitterness and astringent sensation were more dominant in Robusta cold brews, with higher caffeine and total chlorogenic acid content; however, a high coffee flavor dominance was also observed.

DkMYB14 is a bifunctional transcription factor that regulates the accumulation of proanthocyanidin in persimmon fruit

SUMMARYProanthocyanidins (PAs) are phenolic secondary metabolites that contribute to the protection of plant and human health. Persimmon (Diospyros kaki Thunb.) can accumulate abundant PAs in fruit, which cause a strong sensation of astringency. Proanthocyanidins can be classified into soluble and insoluble PAs; the former cause astringency but the latter do not. Soluble PAs can be converted into insoluble PAs upon interacting with acetaldehydes. We demonstrate here that DkMYB14, which regulates the accumulation of PA in persimmon fruit flesh, is a bifunctional transcription factor that acts as a repressor in PA biosynthesis but becomes an activator when involved in acetaldehyde biosynthesis. Interestingly, both functions contribute to the elimination of astringency by decreasing PA biosynthesis and promoting its insolubilization. We show that the amino acid Gly39 in the R2 domain and the ethylene response factor‐associated amphiphilic repression‐like motif in the C‐terminal of DkMYB14 are essential for the regulation of both PA and acetaldehyde synthesis. The repressive function of DkMYB14 was lost after the mutation of either motif, and all activities of DkMYB14 were eliminated following the mutation of both motifs. Our results demonstrate that DkMYB14 functions as both a transcriptional activator and a repressor, directly repressing biosynthesis of PA and promoting its insolubilization, resulting in non‐astringency in persimmon.

A Review of Tannin Determination Methods Using Spectrophotometric Detection in Red Wines and Their Ability to Predict Astringency

Astringency is an important sensory attribute that influences red wine quality. The astringent sensation inside the mouth is caused by a group of molecules called tannins. These molecules can be quantified and analysed by several numbers of methods, such as the Bate Smith method, Adams Harbertson assay, and methylcellulose precipitation method. All these methods are colourimetric, however they differ on the principle on which they are based and, as well as on the tannin pool they are able to measure. In the literature, it is possible to find a wide range of concentrations of tannins for the main red wines varieties, which have been evaluated by the methods herein reviewed. For instance, higher tannin concentrations are obtained using the Bate Smith method (2.08-3.48 g/L tannin) compared with the Adams Harbertson assay (0.58-0.14 g/L tannin), which exhibit the lowest results. However, studies that directly compare results obtained with these methods are scarce. The aim of this work is to compare tannin concentrations in red wines and along with how sensory astringency correlates with tannin concentration measured by these three methods.

Effect of different yeast mannoproteins on the interaction between wine flavanols and salivary proteins

Unbalanced wine astringency, caused by a gap between phenolic and technological grape maturities, is one of the consequences of the global climate change in the vitiviniculture. To resolve it, potential strategies are being currently used, like the addition of commercial yeast mannoproteins (MPs) to wines. In this work, the main interactions responsible for the wine astringent sensation, namely, interactions between human salivary proteins and wine flavanols have been studied by Dynamic Light Scattering (DLS) and liquid chromatography coupled to DAD and MS detectors (HPLC–DAD–MS), in presence or absence of two MPs with different saccharide/protein ratio. The results indicate that there are differences on the substrate specificity for each mannoprotein and that its action mechanism could change not only depending on the mannoprotein composition but also on the flavanol structure. MPs with elevated carbohydrate content could act thought the stabilization of soluble aggregates with human salivary proteins and flavanols, mainly non-galloylated flavanol oligomers, whereas MPs with higher protein percentage mostly could precipitate flavanols (mainly non-galloylated ones with low degree of polymerization) which partially prevents the formation of insoluble flavanol–salivary protein aggregates.

Perspectives on Astringency Sensation: An Alternative Hypothesis on the Molecular Origin of Astringency

Flavor is one of the main drivers of food consumption and acceptability. It is associated with pleasure feels during eating. Flavor is a multimodal perception corresponding to the functional integration of information from the chemical senses: olfaction, gustation, and nasal and oral somatosensory inputs. As a result, astringency, as a sensation mediated by the trigeminal nerves, influences food flavor. Despite the importance of astringency in food consumer acceptance, the exact chemosensory mechanism of its detection and the nature of the receptors activated remain unknown. Herein, after reviewing the current hypotheses on the molecular origin of astringency, we proposed a ground-breaking hypothesis on the molecular mechanisms underpinning this sensation as a perspective for future research.

Multivariate correlation of the astringency sensory perception with the phenolic profiling of cashew apple genotypes

Astringency has limited the acceptability of cashew apples and its products, despite their high nutritive value and antioxidant activity. The identification of phenolic compounds that correlate with astringency was measured directly using a sensory panel and multivariate correlation analysis of sensory descriptors for astringency and its sub-qualities with the phenolic profiling from 9 different clones of cashew apple. A trained sensory panel rated sweet taste, acid taste, astringency, harshness in mouth and throat irritation, and the phenolic compounds were identified using an ultra-performance liquid chromatography-high resolution mass spectrometry system. The exploratory and regression multivariate analyses highlighted a positive correlation of anacardic acids, mainly 15:1, with the sensation of astringency and its sub-qualities (harshness in mouth and irritation in the throat), which associate them as probable chemical markers of astringency in cashew apples. The results may be useful for breeders to concomitantly obtain cashew apples with high concentrations of bioactive compounds and pleasant taste.

Influence of oral movement, particle size, and zeta potential on astringency of whey protein

AbstractAstringency is an important characteristic in whey protein products that leads to lower consumer liking, improvements in astringency may improve consumer acceptance of high protein products. The contributions of oral movement, particle size, and zeta potential on the perception of whey protein astringency were investigated. Trained panelists documented the astringency of 10% (w/w) whey protein isolate (WPI, >90% protein) solutions at pH 3.4 or 7.0 with or without oral movements. In a second experiment, 67 commercial WPI and whey protein concentrate 80% protein (WPC80) were evaluated for particle size and zeta potential at neutral pH, and of these, 21 were selected for further evaluation of astringency. Acidification of WPI increased astringency, but astringency was also documented in a neutral pH range (pH 6.0–7.0). Oral movements increased the perception of astringency (p < 0.05), suggesting that part of the astringent sensation was due to the interaction of whey proteins with receptors on oral tissues and oral movement further increasing astringency perception, possibly by friction of delubricated oral surfaces. Commercial WPI and WPC80 varied widely in particle size, zeta potential, and astringency. Astringency of WPI solutions were correlated with zeta potential (p < 0.05, r = −.81). WPC80 were astringent, but astringency of WPC 80 was not correlated with particle size or zeta potential (p > 0.05, r = .14, .40). These results provide information on the mechanism of whey protein astringency perception, which may facilitate the development of whey protein products with decreased astringency.Practical ApplicationsAstringency of whey proteins is complex and a result of multiple mechanisms. This study established that oral movements and zeta potential are linked to the astringency of whey protein. These results further explain the mechanisms of astringency and may help to identify possible methodologies to reduce astringency in whey protein ingredient applications.