Wine Bitterness Research Articles

Extraction and structural analysis of mannoproteins from different species of yeast: Bitter suppression and the potential mechanisms for wine

To rich the research for mannoproteins (MPs) suppressive effect on the bitterness of wine, this study distinguished bitterness into initial bitterness and bitter aftertaste. By utilizing the thermal alkali extraction method, MPs were extracted from three different yeast species: Saccharomyces cerevisiae (CECA), Lachancea thermotolerans (A38), and Torulaspora delbrueckii (2082). Their basic structures, addition concentrations, and correlation with bitter suppression ability were characterized. CECA exhibited stronger initial bitterness suppression ability, may attributed to its more branches and lack of a triple-helix structure. 2082 showed greater bitter aftertaste suppression and might due to smaller particle aggregation, fewer branches, and triple-helix structure. Additionally, it was noteworthy that due to the unique structure of 2082, it may bound more monomer and oligomeric proanthocyanidins (MOPC) on MPs surface, reducing its initial bitterness suppression ability. Concerning concentration, the increase in polysaccharide chain polymerization hindered further interaction with MOPC, leading to a decrease in its initial bitterness suppression ability. Bitter aftertaste exhibited different behaviors. As the concentration of CECA increased, there was an increase in oral adhesion instead.

Migration of Tannins and Pectic Polysaccharides from Natural Cork Stoppers to the Hydroalcoholic Solution.

Ellagitannins, condensed tannins, and pectic-derived polysaccharides were removed from natural cork stoppers using hydroalcoholic solution. Two main populations of migrated compounds were determined; the major one with molecular weight (MW) between 0.2 and 1 kDa and the second with 2.1 kDa and polydispersity of 1.3. Two residual populations mainly composed of condensed tannins were also observed between 2.5 and 4.5 kDa and higher than 15 kDa. Simple, C-glycosidic, complex, and oligomeric ellagitannins were identified by high-performance liquid chromatography-diode array detection/electrospray ionization-mass spectrometry (HPLC-DAD/ESI-MS). Ellagitannins linked to condensed tannins and some pectic-derived polysaccharides were also tentatively identified by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF-MS). This preliminary work opens an opportunity for the cork stoppers industry due to the relevance of this type of compounds on the astringency and bitterness of wines.

Sensory variability associated with anthocyanic and tannic fractions isolated from red wines

Tannins and anthocyanins are important modulators of the intrinsic quality of red wines, playing a major role in consumer preference and appreciation. Tannins are chiefly responsible for the astringency in wines although their role in eliciting different astringent subqualities is still relatively unknown. On the other hand, the sensory contribution of anthocyanic fractions is even less clear. The main aim of the present study was to assess whether anthocyanic fractions from red wine elicit specific mouthfeel and taste attributes that differ from their tannin counterparts, and to evaluate the contribution of anthocyanic and tannic fractions to taste and mouthfeel of red wines. Isolation of tannin (Ftannin) and anthocyanin (Fantho) fractions from 20 wines involved reversed-phase semipreparative liquid chromatography followed by solid phase extraction. The 40 derived fractions subsequently underwent sensory characterisation using a labelled sorting task and a rate-K attributes method. Bitterness and dryness were the salient attributes differing among the sensory spaces of both Fantho and Ftannin. Likewise, other independent and non-correlated mouthfeel dimensions differed for both Fantho (“grainy” and mouthcoating”) and Ftannin (“gummy”). A significant linear model predicting wine dryness from the “dry” intensity of Fantho and Ftannin was obtained, with tannic fractions presenting a higher contribution than anthocyanic fractions. These results not only confirmed that tannins have a major implication in red wine dryness but also unequivocally demonstrated a relevant implication of certain anthocyanins in this attribute. In contrast, bitterness of the original wines could not be directly related to the bitterness perceived in any of the two groups of fractions. The addition of an extremely bitter anthocyanic fraction to wines only increased bitterness in certain wines, suggesting that bitterness in wines may result from perceptual interactions and that some wines contain strong bitterness suppressors.

Natural extracts from grape seed and stem by-products in combination with colloidal silver as alternative preservatives to SO2 for white wines: Effects on chemical composition and sensorial properties.

The search for alternative additives to sulfur dioxide, with antioxidant and antimicrobial activity, in the production of wines is one of the current objectives of the enological industry. In the present study, aqueous extracts obtained from winery byproducts (grape seeds and stems), alone or in combination with colloidal silver complex, have been used in white vinification. The antimicrobial effect of the extracts was similar to that of sulfur dioxide, being more effective on lactic and acetic bacteria in those wines to which colloidal silver was added. The effect on the color, the phenolic compounds and the volatile fraction of the wines was evaluated, as well as their sensory profile. The use of both extracts modified the color of the wines, increasing the chromatic parameters a* and b*, indicating a browning tendency, although no other signs of oxidation were found. Wines with seed extracts contained higher amounts of flavan-3-ols, and a significant increase in some volatile compounds such as fatty acid ethyl esters and benzene compounds, which were identified in the extracts. From a sensorial point of view, the wines with stem extracts were the most similar to those elaborated with SO2, detecting a certain bitterness in wines with seed extracts.

Effect of flavonols on wine astringency and their interaction with human saliva

The addition of external phenolic compounds to wines in order to improve their sensory quality is an established winemaking practice. This study was aimed at evaluating the effect of the addition of quercetin 3-O-glucoside on the astringency and bitterness of wines. Sensory results showed that the addition of this flavonol to wines results in an increase in astringency and bitterness.Additionally, flavonol-human salivary protein interactions were studied using fluorescence spectroscopy, dynamic light scattering and molecular dynamic simulations (MD).The apparent Stern-Volmer (KsvApp) and the apparent bimolecular quenching constants (kqApp) were calculated from fluorescence spectra. The KsvApp was 12620±390M−1, and the apparent biomolecular constant was 3.94×1012M−1s−1, which suggests that a complex was formed between the human salivary proteins and quercetin 3-O-glucoside.MD simulations showed that the quercetin 3-O-glucoside molecules have the ability to bind to the IB937 model peptide.

Development of a quantitation method to assay both lyoniresinol enantiomers in wines, spirits, and oak wood by liquid chromatography-high resolution mass spectrometry.

Wine taste balance evolves during oak aging by the release of volatile and non-volatile compounds from wood. Among them, an enantiomer of lyoniresinol, (+)-lyoniresinol, has been shown to exhibit bitterness. To evaluate the impact of (+)-lyoniresinol on wine taste, a two-step quantitation method was developed and validated. First, (±)-lyoniresinol was assayed in wines, spirits, and oak wood macerates by C-18 liquid chromatography-high resolution mass spectrometry (LC-HRMS). Then, the lyoniresinol enantiomeric ratio was determined by chiral LC-HRMS in order to calculate the (+)-lyoniresinol content. In red and white wines, the average concentrations of (+)-lyoniresinol were 1.9 and 0.8mg/L, respectively. The enantiomer proportions were not affected by bottle aging, and lyoniresinol appeared to remain stable over time. The sensory study of (+)-lyoniresinol established its perception threshold at 0.46mg/L in wine. All the commercial wines quantitated were above this perception threshold, demonstrating its impact on wine taste by an increase in bitterness. In spirits, (+)-lyoniresinol ranged from 2.0 to 10.0mg/L and was found to be released continuously during oak aging. Finally, neither botanical origin nor toasting was found to significantly affect the (+)-lyoniresinol content of oak wood. Graphical abstract From oak wood to wine: evaluation of the influence of (+)-lyoniresinol on the bitterness of wines and spirits.

Evaluation of bitterness in white wine applying descriptive analysis, time-intensity analysis, and temporal dominance of sensations analysis

Bitterness in wine, especially in white wine, is a complex and sensitive topic as it is a persistent sensation with negative connotation by consumers. However, the molecular base for bitter taste in white wines is still widely unknown yet. At the same time studies dealing with bitterness have to cope with the temporal dynamics of bitter perception. The most common method to describe bitter taste is the static measurement amongst other attributes during a descriptive analysis. A less frequently applied method, the time-intensity analysis, evaluates the temporal gustatory changes focusing on bitterness alone. The most recently developed multidimensional approach of the temporal dominance of sensations method reveals the temporal dominance of bitter taste in relation to other attributes. In order to compare the results comprised with these different sensory methodologies, 13 commercial white wines were evaluated by the same panel. To facilitate a statistical comparison, parameters were extracted from bitterness curves obtained from time-intensity and temporal dominance of sensations analysis and were compared to bitter intensity as well as bitter persistency based on descriptive analysis. Analysis of variance differentiated significantly the wines regarding all measured bitterness parameters obtained from the three sensory techniques. Comparing the information of all sensory parameters by multiple factor analysis and correlation, each technique provided additional valuable information regarding the complex bitter perception in white wine.

Characterization of taste-active fractions in red wine combining HPLC fractionation, sensory analysis and ultra performance liquid chromatography coupled with mass spectrometry detection

Five Tempranillo wines exhibiting marked differences in taste and/or astringency were selected for the study. In each wine the non-volatile extract was obtained by freeze-drying and further liquid extraction in order to eliminate remaining volatile compounds. This extract was fractionated by semipreparative C18-reverse phase-high performance liquid chromatography (C18-RP-HPLC) into nine fractions which were freeze-dried, reconstituted with water and sensory assessed for taste attributes and astringency by a specifically trained sensory panel. Results have shown that wine bitterness and astringency cannot be easily related to the bitter and astringent character of the HPLC fractions, what can be due to the existence of perceptual and physicochemical interactions. While the bitter character of the bitterest fractions may be attributed to some flavonols (myricetin, quercetin and their glycosides) the development of a sensitive UPLC–MS method to quantify astringent compounds present in wines has made it possible to demonstrate that proanthocyanidins monomers, dimers, trimers and tetramers, both galloylated or non-galloylated are not relevant compounds for the perceived astringency of the fractions, while cis-aconitic acid, and secondarily vainillic, and syringic acids and ethyl syringate, are the most important molecules driving astringency in two of the fractions (F5 and F6). The identity of the chemicals responsible for the astringency of the third fraction could be assigned to some proanthocyanidins (higher than the tetramer) capable to precipitate with ovalbumin.

Acrolein in Wine: Importance of 3-Hydroxypropionaldehyde and Derivatives in Production and Detection

Certain lactic acid bacteria strains belonging to the genus Lactobacillus have been implicated in the accumulation of 3-hydroxypropionaldehyde (3-HPA) during anaerobic glycerol fermentation. In aqueous solution 3-HPA undergoes reversible dimerization and hydration, resulting in an equilibrium state between different derivatives. Wine quality may be compromised by the presence of 3-HPA due to the potential for spontaneous conversion into acrolein under winemaking conditions. Acrolein is highly toxic and has been implicated in the development of bitterness in wine. Interconversion between 3-HPA derivatives and acrolein is a complex and highly dynamic process driven by hydration and dehydration reactions. Acrolein is furthermore highly reactive and its steady-state concentration in complex systems very low. As a result, analytical detection and quantification in solution is problematic. This paper reviews the biochemical and environmental conditions leading to accumulation of its precursor, 3-HPA. Recent advances in analytical detection are summarized, and the roles played by natural chemical derivatives are highlighted.

Updated Knowledge About the Presence of Phenolic Compounds in Wine

Phenolic compounds are partly responsible for the color, astringency, and bitterness of wine, as well as for numerous physiological properties associated with wine consumption. Mass spectrometry has allowed for great progress in the identification and characterization of wine polyphenols. The aim of the present article is to summarize the numerous advances recently achieved in this field. The main type of phenolic compounds found in wine, including hydroxybenzoic and hydroxycinnamic acids, stilbenes, flavones, flavonols, flavanonols, flavanols, and anthocyanins, are firstly described. Chemical reactions and mechanisms involving phenolic compounds during winemaking are also extensively discussed, including enzymatic and chemical oxidation reactions, direct and acetaldehyde-mediated anthocyanin-tannin condensation reactions, acetaldehyde-mediated and glyoxylic acid-mediated tannin-tannin condensation reactions and, C-4/C-5 anthocyanin cycloaddition reactions with 4-vinylphenols, vinylflavanols and pyruvic acid, among others, leading to the formation of pyranoanthocyanins. Useful mass spectral data of well-known and novel phenolic compounds recently identified in wine, and details related to their fragmentation pathway according to different ionization techniques, are given.

Bitterness in wine

Bitterness in wine is elicited primarily by flavonoid phenols, which are bitter and astringent, and by ethanol. Monomeric flavonoid phenols are primarily bitter but as the molecular weight increases upon polymerization, astringency increases more rapidly than bitterness. The chiral difference between the two wine flavan-3-ol monomers produces a significant difference in temporal perception of bitterness: (−)-epicatechin is significantly more bitter and had significantly longer duration of bitterness than (+)-catechin. Ethanol enhances bitterness intensity and duration, whereas varying wine pH has little or no effect on perceived bitterness. Whereas PROP status had no signficant effect on temporal perception of bitterness or astringency, subjects with low salivary flow rates took longer to reach maximum bitterness and astringency intensity and reported longer persistence of both attributes than high-flow subjects.

The Effect of Ethanol, Catechin Concentration, and pH on Sourness and Bitterness of Wine

Eighteen wines, varying in ethanol (8%, 11%, 14% v/v), pH (2.9, 3.2, 3.8), and (+) catechin (100 and 1500 mg/ L) were prepared using a dealcoholized white wine concentrate. In a completely randomized design, sourness and bitterness intensities were rated by 20 subjects. Bitterness intensity was increased by the largest magnitude by raising ethanol concentration, whereas lowering the pH produced the biggest increase in sourness. Increasing ethanol from 8 to 11% v/v or 11 to 14% v/v produced 51% or 41% increases in bitterness, whereas addition of 1400 mg catechin raised bitterness only 28%. as pH was raised from 2.9 to 3.2, bitterness was also significantly enhanced, but a further increase from pH 3.2 to pH 3.8 had no significant impact. Sourness decreased with increasing pH and ethanol had no effect on sourness except at pH 3.2, where the increase in ethanol from 8% to 14% diminished sourness significantly. Catechin addition, while increasing bitterness, did not affect sourness.

Metabolism of Pathogenic Clostridia in Complex Carbohydrate-Rich Culture Media.

One of the characteristics of the pathogenic and many of the non-pathogenic clostridia is their marked ability to digest and further metabolize proteins and protein derivatives during growth in the usual culture media. Ammonia, volatile acids, CO2, and H2 are produced during the anaerobic breakdown of proteins and amino acids. Carbohydrates are the source of most of the energy in carbohydrate-rich media, and large quantities may be consumed, due to the formation of neutral compounds, CO2 and H2. Dextrose yields ethyl alcohol and formic (CO2 and H2), acetic, butyric, and lactic acids. In the later stages of the fermentation the commercially important clostridia may yield very large quantities of acetone, and iso-propyl and butyl alcohols. The same products may be obtained from lactic and pyruvic acids. Acetic acid may be converted into acetone and butyl alcohol. The presence of acetone and the higher alcohols in cultures of pathogenic clostridia has not been reported. Acrolein is found in cultures of Cl. perfringens (welchii) in glycerol broth. The presence of acrolein in fruit juices and the bitterness of wine have been attributed to the growth of this organism. Acetone may be reduced to iso-propyl alcohol; aldehydes and acids are reduced to alcohols; and acetaldehyde may yield acetylmethyl carbinol. The clostridia thus appear to be versatile in their abilities to carry out chemical reactions with a wide variety of substances. A comparative quantitative study of the metabolism of the pathogenic clostridia under identical conditions of growth has never been made, nor have the principal products of metabolism in the usual liquid media with added dextrose been determined. In the present paper, data from 5 species of pathogenic clostridia are presented.