Taste-guided isolation of sweet-tasting compounds from grape seeds, structural elucidation and identification in wines

Untargeted metabolomics analyses to identify a new sweet compound released during post-fermentation maceration of wine

The sensory quality of a wine is mainly based on its aroma and flavor. Sweetness contributes in the gustatory balance of red wines. The investigation of compounds involved in this flavor was based on empirical observations, such as the increase in wine sweetness during yeast autolysis, concomitant to post-fermentation maceration in red winemaking. An untargeted metabolomics approach using UHPLC-HRMS has been developed to discover a new sweet molecule released during this stage. Among several markers highlighted, one compound was selected to be isolated by various separative techniques. It was unambiguously identified by NMR as N6-succinyladenosine and is reported for the first time in wine at an average concentration of 3.16 mg/L in 85 red wines. Furthermore, sensory analysis has highlighted its sweetness. In addition to discovering a new sweet compound in wine, this study proposes new tools for studying taste-active compounds in natural matrices.

Identification of Two New Taste-Active Compounds in Oak Wood: Structural Elucidation of Potential β-Methyl-γ-octalactone Precursors and Quantification in Spirits

Barrel aging is a crucial stage that influences the taste of wines and spirits, particularly increasing their sweetness and bitterness. This increase is caused by nonvolatile compounds released from oak wood. To search for such molecules, we performed a taste-guided inductive fractionation protocol using several analytical techniques. By using HRMS and NMR, two new galloylated derivatives were elucidated. Their enzymatic hydrolysis revealed the formation of β-methyl-γ-octalactone, indicating that they are potential precursors. The taste properties of these isomers revealed a sweet and bitter taste for P-WL-1 and P-WL-2, respectively. An LC-HRMS quantification method was performed to evaluate the influence of aging parameters such as botanical origin and toasting process on their concentrations. Several spirits were also analyzed to confirm their presence in this matrix. These results improve the understanding of the molecular markers responsible for the taste of beverages.

Exploring UPLC-QTOF-MS-based targeted and untargeted approaches for understanding wine mouthfeel: A sensometabolomic approach

This study aimed to establish relationships between wine composition and in-mouth sensory properties using a sensometabolomic approach. Forty-two red wines were sensorially assessed and chemically characterised using UPLC-QTOF-MS for targeted and untargeted analyses. Suitable partial least squares regression models were obtained for "dry", "sour", "oily", "prickly", and "unctuous". "Dry" was positively contributed by flavan-3-ols, anthocyanin derivatives (AntD), valine, gallic acid and its ethyl ester, and peptides, and negatively by sulfonated flavan-3-ols, anthocyanin-ethyl-flavan-3-ols, tartaric acid, flavonols (FOL), hydroxycinnamic acids (HA), protocatechuic ethyl ester, and proline. The "sour" model included molecules involved in "dry" and "bitter", ostensibly as a result of cognitive interactions. Derivatives of FOLs, epicatechin gallate, and N-acetyl-glucosamine phosphate contributed positively to "oily", as did vanillic acid, HAs, pyranoanthocyanins, and malvidin-flavan-3-ol derivatives for "prickly", and sugars, glutathione disulfide, AntD, FOL, and one HA for "unctuous". The presented approach offers an interesting tool for deciphering the sensory-active compounds involved in mouthfeel perception.

Identifying Umami Peptides Specific to the T1R1/T1R3 Receptor via Phage Display

Umami peptides are small molecular weight oligopeptides that play a role in umami taste attributes. However, the identification of umami peptides is easily limited by environmental conditions, and the abundant source and high chromatographic separation efficiency remain difficult. Herein, we report a robust strategy based on a phage random linear heptapeptide library that targets the T1R1-Venus flytrap domain (T1R1-VFT). Two candidate peptides (MTLERPW and MNLHLSF) were readily identified with high affinity for T1R1-VFT binding (KD of MW-7 and MF-7 were 790 and 630 nM, respectively). The two peptides exhibited umami taste and significantly enhanced the umami intensity when added to the monosodium glutamate solution. Overall, this strategy shows that umami peptides could be developed via phage display technology for the first time. The phage display platform has a promising application to discover other taste peptides with affinity for taste receptors of interest and has more room for improvement in the future.

Sensory-guided isolation and identification of new sweet-tasting dammarane-type saponins from Jiaogulan (Gynostemma pentaphyllum) herbal tea

The purpose of this study was to elucidate the chemical basis for the sweet property produced by Gynostemma pentaphyllum and find new natural high-potency (HP) sweeteners. Sixteen new compounds (gypenosides YN 1-16) were obtained by sensory-guided isolation and identification, in which fifteen of them were sweet-tasting constituents with sweetness intensities 10-100 times higher than that of sucrose evaluated by human sensory panel test. Their structures were established by 1D and 2D nuclear magnetic resonance spectra, mass spectroscopy, infrared spectroscopy, UV-visible spectroscopy, and chemical method. Gypenoside YN 4 was the sweetest compound with a concentration of 15.504 ± 1.343 mg/kg, while gypenoside YN 12 has the highest concentration (1397.674 ± 12.948 mg/kg), as shown by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Structure-activity relationship analysis implied that the compounds' sweetness intensity was associated with side-chain substitutions at C-20 or the number of glucosyl groups at C-3. These new plant-derived natural products may be potential natural sweeteners.

Comprehensive metabolomics analysis of key taste components in different varieties of table grapes

Grapes are one of the world's largest fruit crops, which are rich in nutrients and taste. Summer Black, Gui Fei, Kyoho Grape, Giant Rose, Shine Muscat, and Rosario Bianco are the six most popular table grapes in Wuxi city, Jiangsu province. Owing to the lack of comprehensive investigations of metabolites in table grapes, the metabolic causes of differences in their taste are unknown. In this study, metabolites of six table grapes were profiled using ultra-high-performance liquid chromatography-Q-Exactive Orbitrap tandem mass spectrometry combined with a multivariate analysis. Orthogonal partial least squares discriminant analysis clearly discriminated among the metabolites of these varieties. Metabolic pathway analysis revealed that carbohydrate and amino acid metabolisms was highly conserved among these varieties. Our results suggest that the taste differences in the six table grape varieties can be explained by variations in composition and abundance of carbohydrates, organic acids, amino acids, and polyphenols. This study provides comprehensive insights into the underlying metabolic causes of taste variation in table grapes. This article is protected by copyright. All rights reserved.

Isolation of a new taste-active brandy tannin A: Structural elucidation, quantitation and sensory assessment

Enjoying a glass of spirits can be one of the delights of life. While it is well known that their taste improves during barrel aging, the molecular explanations of this phenomenon remain largely unknown. The present work aimed at searching for taste-active compounds formed in spirits during aging. An untargeted metabolomic approach using HRMS was applied on "eau-de-vie" of cognac. A fractionation protocol was then performed on brandies to isolate a targeted compound. By using HRMS and NMR, its structure was elucidated for the first time. This new ellagitannin, called brandy tannin A, considerably increased the sweetness of spirits at 2 mg/L. After development of an LC-HRMS quantitation method, it was assayed in various spirits and was detected mainly in cognacs up to 7 mg/L. These findings demonstrate the sensory contribution of this compound and more generally the relevance of combining metabolomics and separative techniques to purify new taste-active compounds.

Untargeted LC-HRMS profiling followed by targeted fractionation to discover new taste-active compounds in spirits

Taste is a key driver of food and beverage acceptability due to its role in consumers' pleasure. The great interest that natural food and beverages now arouse lies notably in the complexity of their taste, which in turn is related to a wide range of taste-active compounds. Going beyond the classic divide between targeted and untargeted strategies, an integrative methodology to spirits was applied. Untargeted profiling of several cognac spirits was implemented by LC-HRMS to identify compounds of interest among hundreds of ions. A targeted fractionation protocol was then developed. By using HRMS and NMR, dihydrodehydrodiconiferyl alcohol was identified and described for the first time in spirits and oak wood. It was characterized as sweet at 2 mg/L in two matrices and was quantified in spirits up to 4 mg/L. These findings demonstrated how this methodology is relevant and effective to discover new taste-active compounds.

Understanding sweetness of dry wines: First evidence of astilbin isomers in red wines and quantitation in a one-century range of vintages

Astilbin (2R, 3R) was recently reported to contribute to wine sweetness. As its aglycon contains two stereogenic centers, three other stereoisomers may be present: neoisoastilbin (2S, 3R), isoastilbin (2R, 3S), and neoastilbin (2S, 3S). This work aimed at assaying their presence for the first time in wines as well as their taste properties. The isomers were synthesized from astilbin and purified by semi-preparative HPLC. With the four stereoisomers, a sweet taste was perceived whose intensity varied with the configuration. Their content was assayed by developing a UHPLC-Q-Exactive method. The method was applied to screen astilbin and isomers in various wines, especially in different vintages from the same estate. While young wines contained higher concentrations of astilbin than the old ones, the concentrations of the other isomers, mainly neoastilbin, were higher in the old wines, suggesting their formation over time.

NMR spectroscopy in wine authentication: An official control perspective

Wine authentication is vital in identifying malpractice and fraud, and various physical and chemical analytical techniques have been employed for this purpose. Besides wet chemistry, these include chromatography, isotopic ratio mass spectrometry, optical spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy, which have been applied in recent years in combination with chemometric approaches. For many years, ² H NMR spectroscopy was the method of choice and achieved official recognition in the detection of sugar addition to grape products. Recently, ¹ H NMR spectroscopy, a simpler and faster method (in terms of sample preparation), has gathered more and more attention in wine analysis, even if it still lacks official recognition. This technique makes targeted quantitative determination of wine ingredients and nontargeted detection of the metabolomic fingerprint of a wine sample possible. This review summarizes the possibilities and limitations of ¹ H NMR spectroscopy in analytical wine authentication, by reviewing its applications as reported in the literature. Examples of commercial and open-source solutions combining NMR spectroscopy and chemometrics are also examined herein, together with its opportunities of becoming an official method.

Isolation of Taste-Active Triterpenoids from Quercus robur: Sensory Assessment and Identification in Wines and Spirit

Six new triterpenoids (1-6), two known genins (7 and 8), and five known functionalized triterpenoids (9-13) were isolated from a Quercus robur heartwood extract. The purification protocol was guided by LC-HRMS by searching for structural analogues of bartogenic acid on the basis of their putative empirical formula. The structures of the new compounds were unequivocally elucidated using HRESIMS and 1D/2D NMR experiments. Sensory analyses were performed in water and in a non-oaked white wine on the pure compounds 1-13 at 5 mg/L. All molecules were perceived as bitter in water and wine, but they were mostly reported as modifying the wine taste balance. Using LC-HRMS, compounds 1-13 were observed in oaked red wine and cognac and were semiquantified in oak wood extracts. The influence of two cooperage parameters, oak species and toasting process, on compounds 1-13 content was studied. All compounds were found in quantities significantly higher in pedunculate than in sessile oak wood. Toasting is a key step in barrel manufacture and modulates the concentration of the discussed compounds. Significantly higher quantities were observed in untoasted wood compared to medium or highly toasted wood. These findings provide new insights into the molecular origin of taste changes due to oak aging.