Possible Role of High-Molecular-Weight Salivary Proteins in Astringency Development.

Since the initial findings that food tannin/salivary protein interaction and subsequent precipitation is the main cause of the astringency development, numerous studies have concentrated on the supramolecular characterization of these bindings. Most of these works have focused on the low-molecular-weight salivary proteins, in particular proline-rich proteins, hardly considering the involvement of the high-molecular-weight salivary proteins (HMWSPs). Herein, different techniques such as fluorescence quenching, Isothermal Titration Calorimetry and HPLC-MS-DAD were employed to determine the occurrence of molecular interactions between three HMWSPs, namely, mucin, α-amylase and albumin, and a complex extract of tannins composed mainly of flavan-3-ols. The obtained results prove the capability of the three HMWSPs to effectively interact with the flavan-3-ol extract, involving different forces and action mechanisms. Flavan-3-ols are capable of interacting with mucins by a mechanism that includes the formation of stable ground-state complexes that led to approximately 90% flavan-3-ol precipitation, while for albumin and α-amylase, the interaction model of a "sphere of action" was established, which represented only 20% flavan-3-ol precipitation. These data highlight the relevance of including HMWSPs in astringency analyses, paying special heed to the role of mucins in the interaction and subsequent precipitation of dietary tannins.

Phenolic composition and sensory dynamic profile of chocolate samples enriched with red wine and blueberry powders.

Cabernet Sauvignon (CS) and a combination of Cabernet Sauvignon with blueberry extract (CS + B), were spray dried (using maltodextrin DE10, 13.5% w/w as a carrier) to obtain two types of phenolic-rich powders. The addition of blueberry to CS increased phenolic compounds content by 16%. Eight chocolate formulations were obtained by modifying concentrations of cocoa solids, cocoa butter, and sugar. Six of the samples were added with 10% w/w of phenolic-rich powder, while two of them remained as powder-free controls. The anthocyanin and flavan-3-ol profiles of chocolates were determined by HPLC-DAD-MS and HPLC-MS, respectively. In addition, the sensory dynamic profile of samples was assessed by Temporal Dominance of Sensations with a consumer panel. Results showed that the addition of phenolic-rich powders produced a significant increase in the anthocyanin composition obtaining the highest anthocyanin content in the white chocolate added with CS + B powder. On the other hand, adding 10% of CS powder to dark chocolate (55% cocoa pellets) did not result in a significant increase in phenolic compounds. The addition of phenolic-rich powders to chocolates influenced visual color, texture, and taste, leading to new products with distinctive characteristics and increasing the possibility of using phenolic-rich powders as innovative and healthy ingredients.

Supramolecular Study of the Interactions between Malvidin-3-O-Glucoside and Wine Phenolic Compounds: Influence on Color.

Supramolecular study of the interactions between the major wine anthocyanin, malvidin-3-O-glucoside (Mv3G) and different wine phenolic compounds (quercetin 3-O-ß-glucopyranoside (QG), caffeic acid, (-)-epicatechin, (+)-catechin, and gallic acid) has been performed at two different molar ratios (1:1 and 1:2) in acidic medium where flavylium cation predominates (pH ≤ 2). Color variations have been evaluated by differential colorimetry using CIELAB color space. These studies have been complemented with isothermal titration calorimetry assays and molecular dynamics simulations. The color of Mv3G flavylium cation is modified by the interaction with QG toward more bluish and intense colors. Interaction constants between the anthocyanin and the different phenolic compounds were obtained, ranging from 9.72 × 108 M-1 for QG to 1.50 × 102 M-1 for catechin. Hydrophobic interactions and H-bonds are the main driving forces in the pigment/copigment aggregation, except for the interactions where caffeic acid is involved, in which hydrophobic interactions acquire greater preponderance.

Role of Anthocyanins in the Interaction between Salivary Mucins and Wine Astringent Compounds.

Wine astringency is a very complex sensation whose complete mechanism has not been entirely described. Not only salivary proline-rich proteins (PRPs) are involved in its development; salivary mucins can also play an important role. On the other hand, it has been described that anthocyanins can interact with PRPs, but there is no information about their potential role on the interactions with mucins. In this work, the molecular interactions between salivary mucins (M) and different wine phenolic compounds, such as catechin (C), epicatechin (E) and quercetin 3-ß-glucopyranoside (QG), as well as the effect of the anthocyanin malvidin 3-O-glucoside (Mv) on the interactions with mucins, were assessed by isothermal titration calorimetry (ITC). Results showed that the interaction between anthocyanin and mucins is stronger than that of both flavanols analyzed, since the affinity constant values were 10 times higher for anthocyanin than for catechin, the only flavanol showing interaction in binary assay. Moreover, at the concentration at which polyphenols are usually found in wine, flavonols seem not to be involved in the interactions with mucins. These results showed, for the first time, the importance of wine anthocyanins in the mechanisms of astringency involving high-molecular-weight salivary proteins like mucins.

In search for flavonoid and colorimetric varietal markers of Vitis vinifera L. cv Rufete wines.

The better adaptation of autochthonous grape varieties to environmental changes is increasing the interest on them. Previous studies on Vitis vinifera L. cv Rufete, the flagship of DOP "Sierra de Salamanca", demonstrated its phenolic potential to produce quality wines. The present study aims at discovering flavonoid (HPLC-DAD-MSn) and colorimetric (CIELAB) varietal markers in commercial Rufete wines (RW) that could be employed to discriminate them from those made with other varieties or mixtures. Compared to Tempranillo wines (TW), RW showed lower phenolic contents, with lower proportions of anthocyanins and flavonols but greater of flavanols. Principal Component Analysis applied to flavonoid and chromatic variables allowed varietal separation of the samples along PC2, which was mostly driven by %total prodelphinidins, %oligomeric procyanidins and C ab * (greater in TW) and by %monomeric procyanindins and L* (greater in RW) and, additionally, by the proportions of A-type vitisins, acetaldehyde-related pigments, quercetin 3-O-glucuronide and Quercetin/Myricetin ratio (all greater in RW). The results of the present study show that the typicity of Rufete grapes is quite preserved in the wines made with up to 95% of Rufete and 5% of Tempranillo grapes or wines and independently of the enological practices of the different wineries.

Effect of the addition of soluble polysaccharides from red and white grape skins on the polyphenolic composition and sensory properties of Tempranillo red wines.

Soluble polysaccharides from white (PSW) and red (PSR) grape skins were obtained to be evaluated as potential modulators of the unbalanced astringency of a Tempranillo red wine. The modulation of astringency was evaluated by a sensory panel and it seemed to be related to the changes in the polyphenolic profile. Isothermal Titration Calorimetry (ITC) studies, employed to characterize flavan-3-ol-polysaccharide interactions, showed that PSR decreased noticeably wine astringency causing a great flavan-3-ol loss (ca. 40 %), since they interacted more spontaneously with the flavan-3-ols (ca. ΔGtotal = -2.14 × 104 cal/mol) than PSW (ca. ΔGtotal = -1.32 × 104 cal/mol). The strength of these interactions seems to be related to the polysaccharide molecular size and to the presence of arabinogalactans in the structure. On the contrary, PSW showed no relevant effects on wine astringency. Furthermore, potential variations of color were also assessed and no deleterious effect was observed after the addition of any polysaccharide.

Role of Oak Ellagitannins in the Synthesis of Vitisin A and in the Degradation of Malvidin 3-O-Glucoside: An Approach in Wine-Like Model Systems.

Recent studies highlight the influence that oak ellagitannins can have on wine astringency and color. Direct reactions between flavanols or anthocyanins with vescalagin have been reported to occur, but participation of these compounds in the formation of other types of derivatives has only been suggested but not demonstrated. This study aims at evaluating, in wine-like model systems, the possible different roles of the main oak ellagitannins, castalagin and vescalagin, alone or combined, in the synthesis of vitisin A and in the degradation of malvidin 3-O-glucoside. In the presence of pyruvic acid, the anthocyanin disappeared mainly as a result of the synthesis of vitisin A, whereas in its absence, degradation reactions prevailed. In general, ellagitannins increased the synthesis of vitisin A, decreased the total content of degradation products, and changed the degradation profile, with differences observed between castalagin and vescalagin. The results of the study revealed that the fate of malvidin 3-O-glucoside is conditioned by the presence of ellagitannins.

Phenolic Profiles and Biological Activities of Extracts from Edible Wild Fruits Ehretia tinifolia and Sideroxylon lanuginosum.

Ehretia tinifolia Linnaeus (Boraginacea) and Sideroxylon lanuginosum Michaux (Sapotaceae) are wild fruits consumed in North America and are appreciated for their pleasant flavor and sweet taste. However, details regarding their composition and biological properties in the available literature are scarce. This study reports the phenolic composition, antioxidant, antiproliferative activities, and digestive enzymatic inhibition of amberlite-retained methanolic extracts from both fruits. Results revealed that these wild fruit extracts are rich in antioxidants. S. lanuginosum had lower phenolic but higher flavonoid contents (21.4 ± 1.5 mg GAE/100 g FW and 6.42 ± 0.9 mg CE/100 g FW) than E. tinifolia (64.7 ± 2.6 mg GAE/100 g FW and 5.1 ± 0.4 mg CE/100 g FW). HPLC-DAD-MS/MS analysis showed rosmarinic acid as a major polyphenol in E. tinifolia and quercetin glucoside in S. lanuginosum. Polyphenols content in E. tinifolia was related to a significant free radical scavenging ability: DPPH (EC50 = 0.32 ± 0.03 mg/mL), TEAC (4134 ± 9.7 µM TE/g dry extract), and hemolysis inhibition (IC50 = 58.55 ± 2.4 µg/mL). Both extracts were capable of inhibiting α-glucosidase, partially inhibiting α-amylase, and showed no inhibition against lipase, while showing antiproliferative activity against HeLa, HT-29 and MCF-7 cancer cell lines. Our study revealed that these wild fruit extracts are rich in health-beneficial phytochemicals and hold significant potential for elaborating functional foods.

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.

Bacterial Fertilizers Based on Rhizobium laguerreae and Bacillus halotolerans Enhance Cichorium endivia L. Phenolic Compound and Mineral Contents and Plant Development.

Today there is an urgent need to find new ways to satisfy the current and growing food demand and to maintain crop protection and food safety. One of the most promising changes is the replacement of chemical fertilizers with biofertilizers, which include plant root-associated beneficial bacteria. This work describes and shows the use of B. halotolerans SCCPVE07 and R. laguerreae PEPV40 strains as efficient biofertilizers for escarole crops, horticultural species that are widely cultivated. An in silico genome study was performed where coding genes related to plant growth promoting (PGP) mechanisms or different enzymes implicated in the metabolism of phenolic compounds were identified. An efficient bacterial root colonization process was also analyzed through fluorescence microscopy. SCCPVE07 and PEPV40 promote plant development under normal conditions and saline stress. Moreover, inoculated escarole plants showed not only an increase in potassium, iron and magnesium content but also a significant improvement in protocatechuic acid, caffeic acid or kaempferol 3-O-glucuronide plant content. Our results show for the first time the beneficial effects in plant development and the food quality of escarole crops and highlight a potential and hopeful change in the current agricultural system even under saline stress, one of the major non-biological stresses.

Rhizobium laguerreae Improves Productivity and Phenolic Compound Content of Lettuce (Lactuca sativa L.) under Saline Stress Conditions.

Lettuce (Lactuca sativa L.) is a widely consumed horticultural species. Its significance lies in a high polyphenolic compound content, including phenolic acids and flavonols. In this work, we have probed the ability of Rhizobium laguerreae HUTR05 to promote lettuce growth, under in vitro and greenhouse conditions (both non-saline and saline conditions). This strain has shown several in vitro plant growth promotion mechanisms, as well as capacity to colonize lettuce seedlings roots. We have analyzed the effect of the rhizobacterium inoculation on mineral and bioactive compounds in lettuce, under greenhouse conditions, and found a rise in the content of certain phenolic acids and flavonoids, such as derivatives of caffeoyl acid and quercetin. The genome analysis of the strain has shown the presence of genes related to plant growth-promoting rhizobacteria (PGPR) mechanisms, defense from saline stress, and phenolic compound metabolism (such as naringenin-chalcone synthase or phenylalanine aminotransferase).

Agricultural and Food Waste: Analysis, Characterization and Extraction of Bioactive Compounds and Their Possible Utilization.

The characterization and reutilization of agricultural and food waste is an important strategy to ensure the sustainable development of the agricultural and food industries. As a result, the environmental impact of these industries can be reduced, thus contributing to the fight against environmental problems, mainly to those related to a potential mitigation of climatic change. This Special Issue includes five papers that reported important findings from research activities related to the reutilization of by-products from food processing industries, which help to increase the knowledge in this field.

Blending strategies for wine color modification â : Color improvement by blending wines of different phenolic profiles testified under extreme oxygen exposures.

Limited oxygenation and over-oxidation experiments were designed to compare the phenolic and chromatic characters of base wines Cabernet Franc (CF), Cabernet Sauvignon (CS), and their counterparts that blended with modifier wines Marselan (MA) and Petit Verdot (PV). In both limited oxygenation and over-oxidation conditions, all blend wines generally contained higher C*ab, a* and Red%, and lower hab, b* and Yellow% than their base wine counterparts, because MA contributed flavonols (copigments) and anthocyanins, and PV contributed flavanols (anthocyanin derived pigments precursors). Chromatic changes that can be perceived by human eye (ΔE*ab) in CF based blend wines were more obvious than that of CS based blend wines, which indicate that base wine with lower phenolic concentrations and weak phenolic profiles (CF) might be more prone to be chromatically modified than base wine with higher phenolic concentrations and distinct phenolic profiles (CS). Chemical influences of different blending strategies on anthocyanin derivatives' formations were depending on phenolic profiles of the modifier wines and base wines, and also on the oxygen exposure. The results suggest that the chromatic improvement of base wines could be realized by blending modifier wines under different oxygen exposures.

Cell Wall Mannoproteins from Yeast Affect Salivary Protein-Flavanol Interactions through Different Molecular Mechanisms.

It is known that interactions between wine flavanols and salivary proline-rich proteins (PRPs) are one of the main factors responsible for wine astringency. The addition of commercial yeast mannoproteins (MPs) to wines has been pointed to as a possible tool to modulate the excessive astringency due to a lack of phenolic maturity at harvest time that might occur as a consequence of global climate change. The aim of this work was to study by isothermal titration calorimetry and molecular dynamics simulation the molecular mechanisms by which mannoproteins could modulate astringency elicited by tannins and if it can be influenced by mannoprotein composition. Results obtained indicate that the MPs assayed had an important impact on astringency through the formation of ternary aggregates with different solubilities or by preventing the flavanol-PRP interaction by a competitive mechanism, although in a different strength, depending on the size and the compositional characteristic of the mannoprotein.

Increase in phenolic compounds of Coriandrum sativum L. after the application of a Bacillus halotolerans biofertilizer.

BACKGROUND: There is an urgent need for a new sustainable way of satisfying the increasing demand for food worldwide. One of the main challenges is replacing chemical fertilizers with biofertilizers, which include plant root-associated beneficial microorganisms. The present study reports, for the first time, the effects of SCCPVE07 bacterial strain with respect to improving not only plant development, but also the nutritional content and bioactive compounds content of Coriandrum sativum L., one of the most economically important crops, even for plant growth under salinity stress. RESULTS: Innoculated coriander plants (C. sativum L.) showed an increase in potassium, carbon, calcium and iron content. A significant improvement in phenolic compounds contents was also observed. The contents of 5-O-caffeoylquinic acid, cinnamic acid, 4-methoxy-cinnamic acid hexoside, K-3-O rutinoside, Q-3-O-rutinoside, Q-3-O-glucoside and Q-3-O-glucuronide were significantly enhanced. Moreover, an efficient bacterial root colonization and a noted growth promotion were demonstrated. Bacterial genome was sequenced and analysed. Gene coding related to Plant growth promotion (PGP) mechanisms and proteins involved in plant defence from salinity or in the metabolism of phenolic compounds, such as quercetin 2,3-dioxygenase and phenolic acid decarboxylase, were identified. CONCLUSION: The results obtained in the present study show, for the first time, the beneficial effects of the inoculation of a bacterial Bacillus halotolerans biofertilizer on coriander crops with respect to increasing the content in bioactive compounds and plant development. © 2020 Society of Chemical Industry.

Inhibition Mechanisms of Wine Polysaccharides on Salivary Protein Precipitation.

In this work, high-performance liquid chromatography, fluorescence quenching, nephelometry, and sodium dodecyl sulfate polyacrylamide gel electrophoresis were used to study the effect of polysaccharides naturally present in wine [rhamnogalacturonan II (RG II) and arabinogalactan proteins (AGPs)] on the interaction between salivary proteins (SP) together present in saliva and tannins (punicalagin (PNG) and procyanidin B2). In general, the RG II fraction was more efficient to inhibit SP precipitation by tannins, especially for acidic proline-rich proteins (aPRPs) and statherin/P-B peptide, than AGPs. The RG II fraction can act mainly by a competition mechanism in which polysaccharides compete by tannin binding. However, in the presence of Na+ ions in solution, no RG II effect was observed on SP-tannin interactions. On the other hand, dependent upon the saliva sample as well as the tannin studied, AGPs can act by both mechanisms, competition and ternary (formation of a ternary complex with SP-tannin aggregates enhancing their solubility).

Interaction between Ellagitannins and Salivary Proline-Rich Proteins.

The first contact of tannins with the human body occurs in the mouth, where some of these tannins are known to interact with salivary proteins, in particular with proline-rich proteins (PRPs). These interactions are important at a sensory level, especially for astringency development, but could also affect the biological activities of the tannins. This study gathers information on the relative affinity of the interaction, complex stoichiometry, and tannin molecular epitopes of binding for the interactions between the families of PRPs (bPRPs, gPRPs, and aPRPs) and three representative ellagitannins (castalagin, vescalagin, and punicalagin). These interactions were studied by saturation-tranfer difference NMR and microcalorimetry. The effect of the PRP-ellagitannin interaction on their antioxidant ability was also assessed by ferric reduction antioxidant power (FRAP) assays. The results support a significant interaction between the studied tannins and PRPs with binding affinities in the micromolar range. Punicalagin was always the ellagitannin with higher affinity. aPRPs were the salivary PRPs with higher affinity. Moreover, it was observed that when ellagitannins are present in low concentrations (5-50 µM), as occurs in food, the antioxidant ability of these tannins when complexed with salivary PRPs could be significantly impaired.

Effect of the presence of different oak ellagitannins in their own disappearance under oxidative or inert atmosphere.

The disappearance of the C-glycosidic ellagitannins over time can occur even in absence of oxygen and their disappearance rate seems to be affected by the presence of other ellagitannins in the media. The objective of this work was to study the influence of the presence of other ellagitannins and/or oxygen on the individual evolution of the main oak ellagitannins in simple model systems in order to understand their behaviours in more complex media, such as wine. In all the studied conditions, vescalagin disappeared faster than castalagin, highlighting its greater reactivity. Oxygen increased the individual disappearance rate, as also occurred when more than one type of ellagitannin was present, above all if the additional ellagitannin(s) contained the same conformation in C1 as vescalagin. Experimental data were fitted to a kinetic model considering both the oxygen-dependent and oxygen-independent reactions, making possible the comparison between individual compounds in different scenarios.

Effect of malvidin-3-glucoside and epicatechin interaction on their ability to interact with salivary proline-rich proteins.

At red wine pH, malvidin-3-glucoside (mv-3-glc), the major anthocyanin of red wine, is expected to be present mainly in its non-colored hemiketal form. However, due to copigmentation with flavanols (e.g. epicatechin), the stabilization of the colored forms of mv-3-glc occurs. Some flavanols have been linked to astringency, due to their ability to interact/precipitate salivary proteins, namely proline-rich proteins (PRPs). So, a major question is if this copigmentation interaction could affect the ability of flavanols to interact with SP. To answer this, the effect of the interaction between mv-3-glc and epicatechin with basic and acidic PRPs, was investigated by saturation-tranfer difference (STD)-NMR and isothermal titration calorimetry (ITC). The most relevant result was that epicatechin:mv-3-glc mixture presents a synergic effect toward the interaction with both PRPs when compared to individual polyphenols. Furthermore, was observed that epicatechin interaction was driven by hydrophobic and hydrophilic interactions while mv-3-glc interaction was driven by electrostatic interactions.

Human Bitter Taste Receptors Are Activated by Different Classes of Polyphenols.

Polyphenols may contribute directly to plant-based foodstuffs flavor, in particular to astringency and bitterness. In this work, the bitterness of a small library of polyphenols from different classes [procyanidin dimers type B, ellagitannins (punicalagin, castalagin, and vescalagin) and phenolic acid ethyl esters (protocatechuic, ferulic, and vanillic acid ethyl esters] was studied by a cell-based assay. The bitter taste receptors (TAS2Rs) activated by these polyphenols and the half-maximum effective concentrations (EC50) of each agonist-TAS2Rs pair were determined. Computational methodologies were used to understand the polyphenol molecular region responsible for receptor activation and to get insights into the type of bonds established in the agonist-TAS2Rs pairs. The results show the combinatorial pattern of TAS2Rs activation. TAS2R5 seems to be the only receptor exhibiting a bias toward the activation by condensed tannins, while TAS2R7 seems more tuned for hydrolyzable (ellagi)tannins. Additionally, at the concentrations usually found for these compounds in foodstuffs, they can actively contribute to bitter taste, especially ellagitannins.