Astringent Sensation Research Articles

Definition of minimum maturity indices for harvesting of early-season sweet pomegranate (Punica granatum L.) fruit

SummaryThere are no defined maturity indices for harvesting early-season “sweet” pomegranate (Punica granatum L.) varieties, and this often results in the harvesting and marketing of inedible, immature fruit. We evaluated the changes in various maturity indices, and in sensory quality, during the ripening of two commercial, early-season “sweet” pomegranate varieties: ‘Acco’ and ‘Shani–Yonay’. The results showed that, during the last 5 weeks of fruit ripening, only slight changes occurred in peel and aril colour, and in the total soluble solids contents and titratable acidity of the juice. In contrast, during ripening, we observed gradual increases in fruit and aril fresh weights (FWs), and a decrease in hydrolysable tannin contents. Furthermore, these changes were accompanied by a gradual increase in fruit flavour preference, which mainly reflected a parallel decrease in the undesirable mouth-feel sensation of astringency. Finally, we found a high correlation (r 2 = 0.99) between the observed increases in fruit flavour and aril FW, and therefore suggest that an average mean aril FW of > 0.23 g may serve as a simple and reliable index of maturity for timing the commercial harvesting of these two early-season “sweet” pomegranate varieties.

Taste and Mouthfeel Properties of Red Wines Proanthocyanidins and Their Relation to the Chemical Composition

The aim of this work is to assess the relationship between the in-mouth sensory properties of proanthocyanidins (PAs) and its chemical composition. To achieve such a goal, the proanthocyanidin fraction from six different young commercial red wines was obtained by gel permeation chromatography. A sensory panel, selected on the basis of their PROP status and trained in taste and mouthfeel sensations, described both the wines and fractions. MALDI-TOF-MS and UPLC-MS were used to identify thoroughly the polyphenolic composition of each proanthocyanidin fraction. The results showed that the PAs fractions were exclusively described as astringent and persistent. The astringent subqualities studied (velvety and puckering/drying) were mainly related to the quantity of proanthocyanidins and the proportion of the extension flavanol units linked to proanthocyanidins. A significant negative correlation was found between both of the astringencies (velvety and puckering/drying). Furthermore, both subqualities appeared to contribute to the persistence. A significant correlation was observed between the astringency and the persistence data of the wines and fractions. Significant multiple linear regressions were found between the sensory astringency data and the chemical compounds analyzed. The concentration of proanthocyanidins present in young red wines is the major determinant of the differences perceived in the astringency. Additionally, the extension flavanol units linked to the proanthocyanidins seem to have a different impact on the astringent subqualities.

The flavor of pomegranate fruit: a review

Despite the increasing commercial importance of pomegranate, especially because of its recently discovered health-promoting benefits, relatively little is yet known regarding its sensory quality and flavor preferences, or about the biochemical constituents that determine its sensory characteristics. The perceived flavor of pomegranate fruit results from the combination of various taste, aroma and mouthfeel sensations. The taste is governed mainly by the presence of sugars (glucose and fructose) and organic acids (primarily citric and malic acids). The aroma evolves from the presence of dozens of volatiles, including alcohols, aldehydes, ketones, and terpenes, which provide a mixture of various 'green', 'woody', 'earthy', 'fruity', 'floral', 'sweet' and 'musty' notes. In addition, the sensory satisfaction during the eating of pomegranate arils is complemented by various mouthfeel sensations, including seed hardness and astringency sensations. In the present review we will describe the sensory quality and flavor preferences of pomegranate fruit, including the genetic diversity in flavor characteristics among distinct varieties. In addition, we will describe the dynamic changes that occur in fruit flavor during fruit ripening and postharvest storage.

The Joint Use of Electronic Nose and Electronic Tongue for the Evaluation of the Sensorial Properties of Green and Black Tea Infusions as Related to Their Chemical Composition

The objectives of the present study were to determine the effects of the brewing method on the amount of the major catechins, methylxanthines, total polyphenols and antioxidant capacity in green and black teas, and to correlate the chemical composition of tea infusions to their sensorial properties by the combined use of the electronic nose and tongue. For this purpose, tea infusions were prepared from 7 green teas and 6 black teas using different extraction times (3 - 5 and 10 min). The extraction of total polyphenols and catechins was increased by prolonging the infusion time from 3 - 5 to 10 min, while the caffeine amounts did not increase. The antioxidant activity of teas was well correlated with polyphenol content. Electronic tongue and electronic nose were able to discriminate green teas from black teas on the basis of their sensorial properties. Considering the taste, green teas were characterized by astringency and aftertaste-astringency and this sensation was increased by prolonging the infusion time; black teas were perceived as more bitter, sour, salty and the extraction time affected the astringent sensation. The aroma of green and black teas was discriminated by specific sensors and the increase of the extraction time produced more richly flavoured infusions. This work adds information about correlation between sensorial properties, antioxidant capacity and chemical composition of green and black teas.

Protein–polyphenol interaction on silica beads for astringency tests based on eye, photography or reflectance detection modes

Astringency is an organoleptic property of beverages and food products resulting mainly from the interaction of salivary proteins with dietary polyphenols. It is of great importance to consumers, but the only effective way of measuring it involves trained sensorial panellists, providing subjective and expensive responses. Concurrent chemical evaluations try to screen food astringency, by means of polyphenol and protein precipitation procedures, but these are far from the real human astringency sensation where not all polyphenol–protein interactions lead to the occurrence of precipitate. Here, a novel chemical approach that tries to mimic protein–polyphenol interactions in the mouth is presented to evaluate astringency. A protein, acting as a salivary protein, is attached to a solid support to which the polyphenol binds (just as happens when drinking wine), with subsequent colour alteration that is fully independent from the occurrence of precipitate. Employing this simple concept, Bovine Serum Albumin (BSA) was selected as the model salivary protein and used to cover the surface of silica beads. Tannic Acid (TA), employed as the model polyphenol, was allowed to interact with the BSA on the silica support and its adsorption to the protein was detected by reaction with Fe(III) and subsequent colour development. Quantitative data of TA in the samples were extracted by colorimetric or reflectance studies over the solid materials. The analysis was done by taking a regular picture with a digital camera, opening the image file in common software and extracting the colour coordinates from HSL (Hue, Saturation, Lightness) and RGB (Red, Green, Blue) colour model systems; linear ranges were observed from 10.6 to 106.0 μmol L−1. The latter was based on the Kubelka–Munk response, showing a linear gain with concentrations from 0.3 to 10.5 μmol L−1. In either of these two approaches, semi-quantitative estimation of TA was enabled by direct eye comparison. The correlation between the levels of adsorbed TA and the astringency of beverages was tested by using the assay to check the astringency of wines and comparing these to the response of sensorial panellists. Results of the two methods correlated well. The proposed sensor has significant potential as a robust tool for the quantitative/semi-quantitative evaluation of astringency in wine.

Opponency of astringent and fat sensations

In most cultures, people ingest a variety of astringent foods and beverages during meals, but the reasons for this practice are unclear. Many popular beliefs and heuristics, such as high tannin wines should be balanced with fatty foods, for example 'red wine with red meat', suggest that astringents such as pickles, sorbets, wines, and teas 'cleanse' the palate while eating. Oral astringents elicit 'dry, rough' sensations [1], in part, by breaking down mucinous lubricating proteins in saliva [2,3]. The introduction of oral lubricants, including fats, partially diminishes strong astringent sensations [4,5]. Thus, it appears that astringency and fattiness can oppose each other perceptually on an oral rheological spectrum. Most teas, wines, and 'palate cleansers', however, are only mildly astringent and an explanation of how they could oppose the fattiness of meals is lacking. Here, we demonstrate that weakly astringent stimuli can elicit strong sensations after repeated sampling. Astringency builds with exposures [6] to an asymptotic level determined by the structure and concentration of the compound. We also establish that multiple sips of a mild astringent solution, similar to a wine or tea, decrease oral fat sensations elicited by fatty food consumption when astringent and fatty stimuli alternate, mimicking the patterning that occurs during a real meal. Consequently, we reveal a principle underlying the international practice of 'palate cleansing'. Repeatedly alternating samples of astringent beverages with fatty foods yielded ratings of fattiness and astringency that were lower than if rinsing with water or if presented alone without alternation.

Interaction of different classes of salivary proteins with food tannins

Tannins are polyphenolic compounds commonly present in vegetables, fruits and derived products that interact with proteins, namely salivary proline-rich proteins (PRPs). This interaction forms (in)soluble aggregates that are supposed to be at the origin of the astringency sensation but that also influences tannins bioavailability. Therefore, this interaction was studied herein by HPLC and dynamic light scattering (DLS) using procyanidin trimer and PGG (pentagalloylglucose), to obtain information about the relative affinity of the interaction, solubility (both by HPLC) and size of the complexes formed (by DLS). The results show that mainly acidic PRPs (aPRPs) and statherin interact with both tannins, forming a significant quantity of complexes (either insoluble or soluble), while bPRPs (basic PRPs) interact poorly with procyanidin trimer and gPRPs (glycosylated PRPs) only complex with PGG. In general, PGG formed a high amount of insoluble complexes with salivary proteins while procyanidin trimer formed soluble complexes (except for statherin). For PGG, the maximum aggregation and complexes size (~200nm) correspond to the stoichiometric concentration (232μM). For procyanidin trimer, the concentrations used did not allow to reach the maximum of aggregation. These results highlight the influence and mechanisms that different tannins and salivary proteins could present in their interaction, and consequently in the development of the astringency sensation.

Influence of Stimulus Temperature on Orosensory Perception and Variation with Taste Phenotype

Recently, the phenomenon of thermal taste, where thermal tasters (TTs) perceive taste sensations from the application of thermal stimuli to the tongue, was described. Thermal taster status (TTS) appears to function as a marker of individual variation in orosensory perception, as TTs are more responsive to prototypical orosensory stimuli and flavor attributes in complex beverages than thermal non-tasters. The main objective of this study was to examine the influence of TTS on the relationship between stimulus temperature and orosensory perception. Propylthiouracil (PROP) responsiveness has long been used as an index of individual variation in oral sensation, as general orosensory responsiveness to a variety of stimuli associates with the ability and degree to which individuals perceive PROP's bitterness. PROP taster status (PTS), an expression of individuals' PROP responsiveness, was also examined. Perceptually equi-intense stimuli eliciting sweet, sour, bitter, and astringent sensations were presented at 5 °C and 35 °C and evaluated using time-intensity methodology. Unexpectedly, an apparent trend of TTs reporting higher maximum perceived intensities for all stimuli was not statistically significant, and an examination of individual subjects' data suggests further examination of the influence of TTS on orosensory stimuli is warranted. PROP bitterness and the perceived intensity of orosensory stimuli were not associated at either temperature; however, some differences between PTS groups were found. As previously reported, TTS and PTS interactions were not observed. Interestingly, temperature influenced the maximum intensity perceived from astringent, bitter, and sour stimuli, but not from the sweet stimulus.

Carbohydrates Inhibit Salivary Proteins Precipitation by Condensed Tannins

Condensed tannins are a group of polyphenols that are associated with the astringency sensation, as they readily interact and precipitate salivary proteins. As this interaction is affected by carbohydrates, the aim of this work was to study the effect of some carbohydrates used in the food industry [arabic gum (AG), pectin, and poligalacturonic acid (PGA)] on the salivary proteins/grape seed procyanidins interaction. This was assessed monitoring the salivary proteins that remain soluble in the presence of condensed tannins with the addition of carbohydrates (HPLC) and analysis of the respective precipitates (SDS-PAGE). The results show that pectin was the most efficient in inhibiting protein/tannin precipitation, followed by AG and PGA. The results suggest that pectin and PGA exert their effect by formation of a ternary complex protein/polyphenol/carbohydrate, while AG competes with proteins for tannin binding (competition mechanism). The results also point out that both hydrophilic and hydrophobic interactions are important for the carbohydrate effects.

Does flavor impact function? Potential consequences of polyphenol–protein interactions in delivery and bioactivity of flavan-3-ols from foods

Astringency is a component of the overall flavor experienced when consuming polyphenol rich foods and beverages such as tea, wine, cocoa and select fruits. Following consumption, the astringent sensation results from the well documented ability of polyphenols to bind to salivary proline rich proteins (PRP) and facilitate their precipitation in the oral cavity. In a similar fashion, polyphenols are also known to non-specifically bind food and other biological proteins. While much is known regarding the polyphenol–protein interactions leading to astringency, significantly less information is available regarding the impact of these polyphenol–protein interactions with food or other biological proteins on relevant physiological outcomes. This paper focuses on the interactions between flavan-3-ols, one of the most abundant dietary polyphenol forms, with proteins in food, salivary PRP and other physiological proteins. The physiological implications of these interactions in food and through the gut will be discussed in relation to manipulation of flavan-3-ol bioavailability, metabolism and biological activities including inhibition of digestive enzymes in the gut.

Application of the dual attribute time‐intensity (DATI) sensory method to the temporal measurement of bitterness and astringency in sorghum

SummaryBitterness and astringency are attributes generally cited as the cause of tannin sorghums being unpalatable. The objective here was to determine the effect of sorghums with varying tannin content on bitterness and astringency simultaneously using dual attribute time‐intensity (DATI). A trained panel assessed bitterness and astringency of bran infusions of tannin and tannin‐free sorghums. In both sorghum types, bitterness developed and reached maximum intensity faster (Tmax 22.5 s; P < 0.001) than astringency (27.9 s). The duration of the astringent sensation (Dtot 69.9 s) lasted longer than bitterness (66.3 s). Overall, the temporal parameters for bitterness distinguished infusions from tannin and tannin‐free sorghums slightly more clearly than those for astringency. The research established that, for sorghum, bitterness and astringency are related. The DATI method also revealed that panellists’ perceptions of the time course of bitterness and astringency differ.

Lubricating properties of human whole saliva as affected by β-lactoglobulin

The effect of β-lactoglobulin (β-LG) at pH 3.5 and 7.0 on lubricating property of saliva as related to astringency perception was investigated using tribology. Saliva was adsorbed onto surfaces of a rotating poly dimethylsiloxane (PDMS) ball and disc to form a film under conditions that mimic the rubbing contacts in the oral cavity ( Bongaerts, Rossetti, & Stokes, 2007) and the lubricity of saliva films upon exposure to astringent compounds was measured. While addition of non-astringent β-LG at pH 7.0 slowly increased friction of saliva film between tribopair surfaces, β-LG at pH 3.5 rapidly increased the friction coefficients of saliva, similar to other astringent compounds (epigallocatechin gallate and alum). This supports the hypothesis that astringency of β-LG arises from the loss of lubrication of saliva which is in agreement with the well-accepted astringency model of polyphenols. Increasing β-LG concentration at pH 3.5 (0.5–10% w/w) caused a rapid increase in friction coefficient; however, at the highest protein concentration, the friction coefficient, although higher than observed for water, was below the values observed for the lower protein concentrations. This suggests that static tribology testing is different from the dynamic in-mouth system such that a simple relationship between friction and sensory astringency cannot be found for all conditions.

EFFECT OF POLYPHENOL CONCENTRATIONS ON ASTRINGENCY PERCEPTION AND ITS CORRELATION WITH GELATIN INDEX OF RED WINE

ABSTRACT The aims of this work were to investigate the effect of polyphenol concentrations on astringency perception and gelatin index measurements in noncommercial red wines, as well as evaluate astringency evolution over time. Spearman coefficients showed a positive correlation between polyphenols at low concentration with gelatin index (P < 0.001), and astringency (P < 0.05). Gelatin index values and polyphenol concentrations were related by a power function at low polyphenol levels, but no correlation was shown when total polyphenol levels overcame 5.20 g/L. Similar relationships were found between perceived astringency/gelatin index, and astringency/polyphenol concentrations. It was evident that gelatin index was a better estimator of astringency when polyphenol levels were low, and astringency intensity did not increase when polyphenol concentrations were higher than 5.20 g/L. Time-intensity measurements of astringency showed that maximum intensity governed the evolution of sensation. PRACTICAL APPLICATIONS The findings from this research will aid winemakers to understand the availability of an in vitro assay to estimate the astringent sensation. This method's comparison and crossbreeding with sensory data will allow a better interpretation of what happens when wine is drunk.

Ability of a salivary intrinsically unstructured protein to bind different tannin targets revealed by mass spectrometry

Astringency is thought to result from the interaction between salivary proline-rich proteins (PRP) that belong to the intrinsically unstructured protein group (IUP), and tannins, which are phenolic compounds. IUPs have the ability to bind several and/or different targets. At the same time, tannins have different chemical features reported to contribute to the sensation of astringency. The ability of both electrospray ionization mass spectrometry and tandem mass spectrometry to investigate the noncovalent interaction occurring between a human salivary PRP, IB5, and a model tannin, epigallocatechin 3-O-gallate (EgCG), has been reported. Herein, we extend this method to study the effect of tannin chemical features on their interaction with IB5. We used five model tannins, epigallocatechin (EgC), epicatechin 3-O-gallate (ECG), epigallocatechin 3-O-gallate (EgCG), procyanidin dimer B2 and B2 3'-O-gallate, which cover the main tannin chemical features: presence of a gallate moiety (galloylation), the degree of polymerization, and the degree of B ring hydroxylation. We show the ability of IB5 to bind these tannins. We report differences in stoichiometries and in stability of the IB5•1 tannin complexes. These results demonstrate the main role of hydroxyl groups in these interactions and show the involvement of hydrogen bonds. Finally, these results are in line with sensory analysis, by Vidal et al. (J Sci Food Agric 83:564-573, 2003) pointing out that the chain length and the level of galloylation are the main factors affecting astringency perception.

Modelling texture perception by soft epithelial surfaces

This paper introduces a mechanistic approach to relate the sensations of touch by epithelial surfaces of for example skin, eye or mouth to the material properties of the substrate. The approach is to model the hydrodynamic and frictional forces exerted by the substrate onto the surfaces, which are deformable and compliant to these forces. Subsequently these forces are related to the neurological responses of the mechanoreceptors buried in these surfaces. The potential of the approach is illustrated for textural perception of food materials in the mouth. It leads to several concepts for textural perception in the mouth, some of which have been demonstrated previously and some of which are new. As a first example, the branching into high and low viscosity regimes for thickness perception found experimentally can be linked directly to the detection limit of the neural receptors. As a second example, by taking into account the intrinsic roughness and deformability of the papilla surface, estimates are obtained for the cross-over between the hydrodynamic friction regime, where the papilla tips are lubricated by a thin liquid film (smooth mouthfeel), and the boundary friction regime, where the papilla tips are in direct contact with the opposing surface of the palate (rough mouthfeel). This has implications for the role of viscosity on smoothness and astringency sensations. As a final example, the model suggests that the sensation of hard particles (grittiness) can be suppressed by increasing the viscosity of the medium, which is in agreement with experimental findings from sensory studies.

Contribution of the Temporal Dominance of Sensations (TDS) method to the sensory description of subtle differences in partially dealcoholized red wines

In this study, effect of partial alcohol reduction on the sensory modification of red wines was investigated. A Merlot and a Syrah wine were partially dealcoholized using reverse osmosis technique to span a range of three different alcohol contents (14–10%) by grape variety. Preliminary triangle tests indicated the existence of very slight differences between the dealcoholized wines of the study. Therefore, adapted descriptive methodologies had to be used. In a first step, wines were described with a comparative sensory profile by 16 trained panellists on 15 sensory attributes. Then, the same panellists profiled the wines with the TDS technique, which consists in identifying and rating sensations perceived as dominant repeatedly until the perception ends. Analysis of variance of the classical descriptive data confirmed the existence of subtle sensory differences among wines from a given grape variety with only three and five discriminated attributes for Merlot and Syrah, respectively. Analysis of TDS curves emphasized twice more discriminated attributes and pointed up temporal differences between wines that did not appear with the conventional sensory profile. Used together these methods appeared as promising as they resulted in complementary and complete descriptions of wines. Effect of dealcoholization was variable from one grape variety to another one. The constant effects of alcohol reduction, common to both Merlot and Syrah were the perception decrease of heat sensation, the substitution of heat sensation in attack by astringent (Merlot) or red fruits (Syrah) sensations, the decrease of bitter sensation after attack to the expense of fruity sensations, and the decrease of length in mouth. In case of Merlot, texture and astringency sensations were also affected by alcohol reduction whereas for Syrah, sweet sensation was affected. Wine is a complex product lying on a fragile balance and the least parameter modification induces variable effects according to the type of wines. Several kinds of interactions between ethanol and wine component must take place and make difficult the generalization of alcohol reduction effect on the sensory perception of wines.

Sensory Attributes of Complex Tasting Divalent Salts Are Mediated by TRPM5 and TRPV1 Channels

Complex tasting divalent salts (CTDS) are present in our daily diet, contributing to multiple poorly understood taste sensations. CTDS evoking metallic, bitter, salty, and astringent sensations include the divalent salts of iron, zinc, copper, and magnesium. To identify pathways involved with the complex perception of the above salts, taste preference tests (two bottles, brief access) were performed in wild-type (WT) mice and in mice lacking (1) the T1R3 receptor, (2) TRPV1, the capsaicin receptor, or (3) the TRPM5 channel, the latter being necessary for the perception of sweet, bitter, and umami tasting stimuli. At low concentrations, FeSO(4) and ZnSO(4) were perceived as pleasant stimuli by WT mice, and this effect was fully reversed in TRPM5 knock-out mice. In contrast, MgSO(4) and CuSO(4) were aversive to WT mice, but for MgSO(4) the aversion was abolished in TRPM5 knock-out animals, and for CuSO(4), aversion decreased in both TRPV1- and TRPM5-deficient animals. Behavioral tests revealed that the T1R3 subunit of the sweet and umami receptors is implicated in the hedonically positive perception of FeSO(4) and ZnSO(4). For high concentrations of CTDS, the omission of TRPV1 reduced aversion. Imaging studies on heterologously expressed TRPM5 and TRPV1 channels are consistent with the behavioral experiments. Together, these results rationalize the complexity of metallic taste by showing that at low concentrations, compounds such as FeSO(4) and ZnSO(4) stimulate the gustatory system through the hedonically positive T1R3-TRPM5 pathway, and at higher concentrations, their aversion is mediated, in part, by the activation of TRPV1.

Saliva Characteristics and Individual Sensitivity to Phenolic Astringent Stimuli

Astringency sensation is due to interactions between salivary proteins and phenols and is based on an increased-friction mechanism. Modifications to the profile of salivary proteins and their concentration could affect tannin/protein reactions and hence the intensity of perceived astringency. Salivary characteristics of 65 subjects were compared after abstention from phenol-containing food and immediately after ingestion of tannic acid. The effect of stimulation on saliva characteristics was expressed in terms of D value, computed as the arithmetic difference between values found in saliva samples from the 2 conditions. Based on D values, subjects were clustered in two groups. Cluster 1 (Cl1, 53 cases) was characterized by low D values thus indicating that the basal saliva condition was quickly restored in these subjects. Cluster 2 (Cl2) was composed of 12 subjects whose basal salivary condition was not quickly restored, particularly in terms of salivary protein concentration and profile and saliva haze-forming capacity. Sensory data showed that subjects capable of maintaining constant saliva characteristics were less sensitive to astringent stimuli than subjects in which the same stimulations induced significant saliva modifications. The results suggest that a large proportion of the population are able to maintain their salivary protein concentration and simultaneously intercept and inactivate dietary tannins.

Interaction of astringent grape seed procyanidins with oral epithelial cells

Mechanisms underlying astringency perception are not clearly understood. It has been suggested that oral epithelial cells play a role. A cell-based bioassay has been developed to define the interactions of astringent grape seed procyanidins with oral epithelial cells. Procyanidins are visualised and quantified after reaction with 4-(dimethylamino)cinnamaldehyde. This assay has demonstrated, conclusively, that astringent procyanidins bind to oral epithelial cells, and that the binding is concentration-, pH- and temperature-dependent, but is not affected by the presence of up to 13% ethanol. Furthermore, the presence of 13% ethanol did not alter in vivo astringency thresholds. However, a decrease in pH resulted in enhanced binding of grape seed procyanidins to oral epithelial cells, which supports our in vivo findings of decreased astringency recognition threshold at lower pH. These data indicate that the cells of the oral cavity may play a direct role in the astringent sensation.

Effects of Casein, Ovalbumin, and Dextran on the Astringency of Tea Polyphenols Determined by Quartz Crystal Microbalance with Dissipation

Tea polyphenols (TPPs) can bind with proteins and peptides through hydrophobic interaction and hydrogen bonding. Casein, ovalbumin, and dextran were used to investigate their influence on the interactions between TPP and gelatin and, therefore, to investigate their influence on TPP taste. Casein-g-dextran (CgD) and ovalbumin-g-dextran (OgD) grafting conjugates were prepared through the Maillard reaction. Dispersible CgD/OgD-TPP complexes formed in acidic pH solution even after a heating process. At the same weight ratio of protein to TPP, about 20-30% of TPP was bound to the proteins. TPP affinity for dextran is much lower. Gelatin, a model of the salivary proteins in buccal cavity, was immobilized on quartz crystal sensor surface through covalent bond. By use of a quartz crystal microbalance with dissipation, we found that the complexation of TPP with gelatin causes a dehydration and collapse of the gelatin layer on the sensor surface that is similar to the sensation of dryness and constriction on oral membranes caused by polyphenols. The complexation between TPP and casein/ovalbumin/dextran can decrease the interaction between TPP and gelatin by decreasing the free TPP molecules and shielding gelatin surface from TPP. Casein has stronger binding ability on the gelatin surface compared to ovalbumin and dextran, and therefore casein is more effective to decrease the sensation of astringency caused by TPP.