Color Characterization of Bordeaux Red Wines Produced without Added Sulfites

Nowadays, the development of naturalness as a concept is illustrated in the oenological field by the development of wine produced with lower inputs, sometimes even without any addition of SO₂ throughout the winemaking process, up to the bottling stage. Despite the increase in the offer of these wines, they remain poorly explored in the literature and require characterization. This study was developed to evaluate the color of Bordeaux red wines without SO₂ addition using colorimetric and polymeric pigments analysis. From a batch of commercial Bordeaux red wines with and without SO₂ addition, and experimental wines produced from homogenous grapes according to different winemaking processes, colorimetric analyses (CIELab and color intensity (CI)) revealed a large difference in wine color depending on the presence or absence of SO₂. Indeed, wines without SO₂ were significantly darker and presented with a deeper purplish color. According to these observations, polymeric pigments were quantified using UPLC-DAD/ESI QTof, and a higher concentration of polymeric pigments bound by the ethylidene bridge was observed in wines without SO_2. This correlated with differences observed for CIELab and CI. Finally, a comparison with polymeric tannins bound by ethylidene bridge was made and revealed that no differences were observed between wines with and without added SO₂. This underlines the affinity difference between tannins and anthocyanins to react with acetaldehyde to form ethylidene bridges.

Oxyresveratrol and Gnetol Glucuronide Metabolites: Chemical Production, Structural Identification, Metabolism by Human and Rat Liver Fractions, and In Vitro Anti-inflammatory Properties

Stilbene metabolites are attracting great interest because many of them exhibit similar or even stronger biological effects than their parent compounds. Furthermore, the metabolized forms are predominant in biological fluids; therefore, their study is highly relevant. After hemisynthesis production, isolation, and structural elucidation, three glucuronide metabolites for oxyresveratrol (ORV) were formed: trans-ORV-4'-O-glucuronide, trans-ORV-3-O-glucuronide, and trans-ORV-2'-O-glucuronide. In addition, two glucuronide metabolites were obtained for gnetol (GN): trans-GN-2'-O-glucuronide and trans-GN-3-O-glucuronide. When the metabolism of ORV and GN is studied in vitro by human and rat hepatic enzymes, four of the five hemisynthesized compounds were identified and quantified. Human enzymes glucuronidated preferably at the C-2' position, whereas rat enzymes do so at the C-3 position. In view of these kinetic findings, rat enzymes have a stronger metabolic capacity than human enzymes. Finally, ORV, GN, and their glucuronide metabolites (mainly at the C-3 position) decreased nitric oxide, reactive oxygen species, interleukin 1β, and tumor necrosis factor α production in lipopolysaccharide-stimulated macrophages.

High-Performance Liquid Chromatography-Hydrogen/Deuterium Exchange-High-Resolution Mass Spectrometry Partial Identification of a Series of Tetra- and Pentameric Cyclic Procyanidins and Prodelphinidins in Wine Extracts

A solid-phase extraction method was applied for the identification of a series of unconventional crown (macrocyclic) B-type proanthocyanidin tetramers (m/z 1169.2557, 1185.2507, 1201.2456, and 1217.2405) and pentamers (m/z 1457.3191, 1473.3140, 1489.3090, 1505.3039, and 1521.2988) containing (epi)catechins only (procyanidins) or (epi)catechins and (epi)gallocatechins (prodelphinidins). These compounds were identified in red wine by high-performance liquid chromatography-high-resolution mass spectrometry coupled with online hydrogen/deuterium exchange (HDX) after purification with a C18 solid-phase extraction phase from the original wine sample. The number and type of monomer units present in each procyanidin and prodelphinidin are discussed on the basis of the experimental measured masses, their retention time distribution among observed isomers, tandem mass spectrometry fragmentations, and the HDX-induced shift of the theoretical monoisotopic mass. The elution in reverse-phase high-performance liquid chromatography shifted to lower retention times when the ratio of (epi)gallocatechin units in these molecules increased with respect to the content of (epi)catechin units, as a consequence of the increase of polarity.

Recent advances of the OIV working group on oenological tannins in the study of the functionalities of oenological tannins

This communication actualizes the status of the research of the OIV working group on oenological tannins with the purpose of deepening the knowledge of the mechanisms and functionalities of oenological tannins in winemaking. The obtained results confirm that oenological tannins really exert an effect as copigments and that they really protect the wine color against the negative effect of the enzyme laccase present in grapes affected by the infection of Botrytis cinerea.

New insight about the functionality of oenological tannins; Main results of the working group on oenological tannins

This communication synthetize all the results obtained by the OIV working group on oenological tannins to the current date. The obtained results confirm that oenological tannins really exert a protection effect against grape juice and wine oxidation because they have antioxidant activity, they consume directly oxygen and they exert an inhibitory effect on the laccase activity. Moreover, oenological tannins also exert a copigmentation effect which can improve and protect de color of red wines.

Adaptation of two groups of Oenococcus oeni strains to red and white wines: the role of acidity and phenolic compounds

AIMS

Oenococcus oeni is the lactic acid bacteria species which is the most adapted to wine. Recently, two groups of strains that form two genetic lineages were described in red and white Burgundy wines. The aim of this study was to analyse the phenotypes of these strains in order to determine how they have adapted specifically to either red or white wine.

METHODS AND RESULTS

Four strains from each group were tested in grape must and in wines to evaluate their tolerance to pH and to phenolic compound content. White wine strains proved to be the most tolerant to low pH, both in grape must and in wine, whereas they were inhibited by the presence of grape tannins in wine. Red wine strains were more sensitive to acidity, but very resistant to phenolic compounds.

CONCLUSIONS

The results suggest that pH and phenolic compounds drive strain selection at several stages of wine production.

SIGNIFICANCE AND IMPACT OF THE STUDY

Although it is well known that O. oeni is well adapted to wine, this study shows that strains of some genetic lineages within this species have evolved to adapt better than others to specific types of wines.

Structures of polymeric pigments in red wine and their derived quantification markers revealed by high-resolution quadrupole time-of-flight mass spectrometry

RATIONALE

The quantification of polymeric pigment families in red wine through their derived quantification markers released during phloroglucinolysis will allow the understanding of their formation kinetics and evolutions during aging which has not been achieved until now and is in urgent need. The identification of these quantification markers was achieved by high-resolution mass spectrometry (HRMS) in this study.

METHODS

HRMS was used to clarify the fragmentation patterns in positive mode of polymeric pigments and identify their derived quantification markers released during phloroglucinolysis.

RESULTS

With HRMS, identification of (epi)catechin-malvidin-3-O-glucoside adducts was simplified to MS/MS, and the fragmentation pattern of malvidin-3-O-glucoside-(epi)catechin adducts was clearly demonstrated. The attribution of four detected ions at m/z 1071.2765 in red wine to the trimeric structure of (epi)catechin-[malvidin-3-O-glucoside-A type linkage-(epi)catechin] and [malvidin-3-O-glucoside-A type linkage-(epi)catechin]-(epi)catechin was achieved for the first time by MS/MS and evidence given by phloroglucinolysis. Moreover, four kinds of derived quantification markers released from polymeric pigments during phloroglucinolysis were also identified.

CONCLUSIONS

The fragmentation pathways of polymeric pigments in red wine and their derived quantification markers released during acidic chemical depolymerisation were clarified which will allow their quantification in red wine.

Kinetics of browning, phenolics, and 5-hydroxymethylfurfural in commercial sparkling wines

We analyzed the degree of browning (absorbance at 420 nm), the phenolics, and the 5-hydroxymethylfurfural (5-HMF) content in six sparkling wines series kept at three temperatures (4, 16, and 20 °C) for over 2 years. Caffeic acid, trans-coutaric acid, p-coumaric acid, and 5-HMF were the compounds with the greatest correlation with browning and time. 5-HMF was the only compound that evolved linearly at all temperatures. We propose that 5-HMF is a better time-temperature marker than the A₄₂₀ parameter or phenolics, because it shows higher linearity with time at all temperatures, is more sensitive to temperature changes, and has lower variability. The kinetics of 5-HMF was studied showing a zero-order behavior. We propose mathematical models that wineries can use to predict the browning shelf life of their sparkling wines as a function of the storage time and temperature.

Scalping of light volatile sulfur compounds by wine closures

Closures have an important influence on wine quality during aging in a bottle. Closures have a direct impact on oxygen exposure and on volatiles scavenging in wine. Model wine solution soaking assays of several types of closures (i.e., natural and technical cork stoppers, synthetic closures, screw caps) with two important wine volatile sulfur compounds led to a considerable reduction in their levels. After 25 days, cork closures and synthetic closures, to a lesser extent, have significantly scavenged hydrogen sulfide and dimethyl sulfide. These compounds have a determinant impact on wine aging bouquet, being largely responsible for "reduced off-flavors". Hydrogen sulfide levels are often not well correlated with the exposure of wine to oxygen or with the permeability of the closure. Its preferential sorption by some types of closures may explain that behavior. Scalping phenomenon should be taken into account when studying wine post-bottling development.

Insights into lignin primary structure and deconstruction from Arabidopsis thaliana COMT (caffeic acid O-methyl transferase) mutant Atomt1

The Arabidopsis mutant Atomt1 lignin differs from native lignin in wild type plants, in terms of sinapyl (S) alcohol-derived substructures in fiber cell walls being substituted by 5-hydroxyconiferyl alcohol (5OHG)-derived moieties. During programmed lignin assembly, these engender formation of benzodioxane substructures due to intramolecular cyclization of their quinone methides that are transiently formed following 8-O-4' radical-radical coupling. Thioacidolytic cleavage of the 8-O-4' inter-unit linkages in the Atomt1 mutant, relative to the wild type, indicated that cleavable sinapyl (S) and coniferyl (G) alcohol-derived monomeric moieties were stoichiometrically reduced by a circa 2 : 1 ratio. Additionally, lignin degradative analysis resulted in release of a 5OHG-5OHG-G trimer from the Atomt1 mutant, which then underwent further cleavage. Significantly, the trimeric moiety released provides new insight into lignin primary structure: during polymer assembly, the first 5OHG moiety is linked via a C8-O-X inter-unit linkage, whereas subsequent addition of monomers apparently involves sequential addition of 5OHG and G moieties to the growing chain in a 2 : 1 overall stoichiometry. This quantification data thus provides further insight into how inter-unit linkage frequencies in native lignins are apparently conserved (or near conserved) during assembly in both instances, as well as providing additional impetus to resolve how the overall question of lignin macromolecular assembly is controlled in terms of both type of monomer addition and primary sequence.

Probing native lignin macromolecular configuration in Arabidopsis thaliana in specific cell wall types: further insights into limited substrate degeneracy and assembly of the lignins of ref8, fah 1-2 and C4H::F5H lines

The interest in renewable, plant-derived, bioenergy/biofuels has resulted in a renaissance of plant cell-wall/lignin research. Herein, effects of modulating lignin monomeric compositions in a single plant species, Arabidopsis, are described. The earliest stage of putative "AcBr/Klason lignin" deposition was apparently unaffected by modulating p-coumarate 3-hydroxylase or ferulate 5-hydroxylase activities. This finding helps account for the inability of many other studies to fully suppress the reported putative levels of lignin deposition through monolignol biosynthesis manipulation, and also underscores limitations in frequently used lignin analytical protocols. The overall putative lignin content was greatly reduced (circa 62%) in a plant line harboring an H-(p-hydroxyphenyl) enriched lignin phenotype. This slightly increased H-monomer deposition level apparently occurred in cell-wall domains normally harboring guaiacyl (G) and/or syringyl (S) lignin moieties. For G- and S-enriched lignin phenotypes, the overall lignification process appeared analogous to wild type, with only xylem fiber and interfascicular fiber cells forming the S-enriched lignins. Laser microscope dissection of vascular bundles and interfascicular fibers, followed by pyrolysis GC/MS, supported these findings. Some cell types, presumably metaxylem and possibly protoxylem, also afforded small amounts of benzodioxane (sub)structures due to limited substrate degeneracy (i.e. utilizing 5-hydroxyconiferyl alcohol rather than sinapyl alcohol). For all plant lines studied, the 8-O-4' inter-unit frequency of cleavable H, G and/or S monomers was essentially invariant of monomeric composition for a given (putative) lignin content. These data again underscore the need for determination of lignin primary structures and identification of all proteins/enzymes involved in control of lignin polymer assembly/macromolecular configuration.

Plant cell walls are enfeebled when attempting to preserve native lignin configuration with poly-p-hydroxycinnamaldehydes: evolutionary implications

The lignin deficient double mutant of cinnamyl alcohol dehydrogenase (CAD, cad-4, cad-5 or cad-c, cad-d) in Arabidopsis thaliana [Sibout, R., Eudes, A., Mouille, G., Pollet, B., Lapierre, C., Jouanin, L., Séguin, A., 2005. Cinnamyl alcohol dehydrogenase-C and -D are the primary genes involved in lignin biosynthesis in the floral stem of Arabidopsis. Plant Cell 17, 2059-2076], was comprehensively examined for effects on disruption of native lignin macromolecular configuration; the two genes encode the catalytically most active CAD's for monolignol/lignin formation [Kim, S.-J., Kim, M.-R., Bedgar, D.L., Moinuddin, S.G.A., Cardenas, C.L., Davin, L.B., Kang, C., Lewis, N.G., 2004. Functional reclassification of the putative cinnamyl alcohol dehydrogenase multigene family in Arabidopsis. Proc. Natl. Acad. Sci., USA 101, 1455-1460]. The inflorescence stems of the double mutant presented a prostrate phenotype with dynamic modulus properties greatly reduced relative to that of the wild type (WT) line due to severe reductions in macromolecular lignin content. Interestingly, initially the overall pattern of phenolic deposition in the mutant was apparently very similar to WT, indicative of comparable assembly processes attempting to be duplicated. However, shortly into the stage involving (monomer cleavable) 8-O-4' linkage formation, deposition was aborted. At this final stage, the double mutant had retained a very limited ability to biosynthesize monolignols as evidenced by cleavage and release of ca. 4% of the monolignol-derived moieties relative to the lignin of the WT line. In addition, while small amounts of cleavable p-hydroxycinnamaldehyde-derived moieties were released, the overall frequency of (monomer cleavable) 8-O-4' inter-unit linkages closely approximated that of WT for the equivalent level of lignin deposition, in spite of the differences in monomer composition. Additionally, 8-5' linked inter-unit structures were clearly evident, albeit as fully aromatized phenylcoumaran-like substructures. The data are interpreted as a small amount of p-hydroxycinnamaldehydes being utilized in highly restricted attempts to preserve native lignin configuration, i.e. through very limited monomer degeneracy during template polymerization which would otherwise afford lignins proper in the cell wall from their precursor monolignols. The defects introduced (e.g. in the vascular integrity) provide important insight as to why p-hydroxycinnamaldehydes never evolved as lignin precursors in the 350,000 or so extant vascular plant species. It is yet unknown at present, however, as to what levels of lignin reduction can be attained in order to maintain the requisite properties for successful agronomic/forestry cultivation. Nor is it known to what extent, if any, such deleterious modulations potentially compromise plant defenses. Finally, prior to investigating lignin primary structure proper, it is essential to initially define the fundamental characteristics of the biopolymer(s) being formed, such as inter-unit frequency and lignin content, in order to design approaches to determine overall sequences of linkages.

Reaction tissue formation and stem tensile modulus properties in wild-type and p-coumarate-3-hydroxylase downregulated lines of alfalfa, Medicago sativa (Fabaceae)

To our knowledge, xylary reaction tissue has never been reported in a forage crop species. Here we report the discovery of reaction tissue in a transgenic line of Medicago sativa (pC3H, for the gene for p-coumarate-3-hydroxylase) with reduced lignin content and in the wild-type (WT) line. Based on microscopy and biomechanical testing of internodal alfalfa branch sections, the transgenic (pC3H-I) line, relative to the WT (1) apparently formed more reaction tissue containing gelatinous fibers with adjacent thick-walled fibers (presumed to be "intermediate" tissue) more rapidly, (2) had more xylem tissue, and (3) had comparable tensile dynamic modulus properties. These findings thus establish the (limited) ability of this perennial angiosperm to form (inducible) reaction tissue in a manner somewhat analogous to that of woody arborescent angiosperms. The potential of effectuating reductions in lignin amounts in (woody) angiosperms with increased formation of reaction (tension wood) tissue is discussed because reaction tissues are often viewed as a deleterious trait in processing for many agronomic/industrial applications, especially with the current interest in biofuels.

The Arabidopsis cinnamoyl CoA reductase irx4 mutant has a delayed but coherent (normal) program of lignification

Previous studies have indicated that the Arabidopsis thalianairregular xylem 4 (irx4) mutant is severely lignin-deficient, forming abnormal lignin from aberrant monomers. Studies of lignin structure in dwarfed cinnamoyl CoA reductase (CCR)-downregulated tobacco were also previously reported to incorporate feruloyl tyramine derivatives. The lignin in the Arabidopsis irx4 mutant was re-investigated at 6 weeks and at maturation (9 weeks). Application of (1)H, (13)C, 2D Heteronuclear Multiple Quantum Coherence and 2D Heteronuclear Multiple Bond Coherence spectroscopic analyses to the lignin-enriched isolates from both Arabidopsis wild-type (Ler) and the CCR-irx4 mutant at both developmental stages revealed that only typical guaiacyl/syringyl lignins were formed. For the irx4 mutant, the syringyl content at 6 weeks growth was lower, in accordance with a delayed but coherent program of lignification. At maturation, however, the syringyl/guaiacyl ratio of the irx4 mutant approached that of wild-type. There was no evidence for feruloyl tyramines, or homologues thereof, accumulating as a chemical signature in lignins resulting from CCR mutation. Nor were there any noticeable increases in other phenolic components, such as hydroxycinnamic acids. These findings were further confirmed by application of thioacidolysis, alkaline nitrobenzene oxidation and acetyl bromide analyses. Moreover, in the case of CCR downregulation in tobacco, there were no NMR spectroscopic correlations that demonstrated feruloyl tyramines being incorporated into the lignin biopolymers. This study thus found no evidence that abnormal lignin formation occurs when CCR activity is modulated.