Patrick J. Williams

Novel monoterpene disaccharide glycosides of Vitis vinifera grapes and wines

Abstract β-Rutinosides (6-O-α- l -rhamnopyranosyl-β- d -glucopyranosides) and 6-O-α- l -arabinofuranosyl-β- d -glucopyranosides of geraniol, nerol and linalol have been isolated and characterized in Muscat of Alexandria grapes and wine. These monoterpene disaccharide glycosides, which are precursors of linalol oxidation state monoterpenes of the grape, are also present in another non-muscat Vitis vinifera var. Rhine Riesling.

Use of C18 reversed-phase liquid chromatography for the isolation of monoterpene glycosides and nor-isoprenoid precursors from grape juice and wines

Abstract Glycosidic derivatives of monoterpene flavourants of grapes and wines can be preparatively isolated by selective retention on a C 18 -bonded reversed-phase adsorbent. These components can thus be concentrated by a factor of 20,000 in a single chromatographic step. Class separation of monoterpene glycosides at different oxidation levels can also be achieved on the reversed-phase adsorbent. Teh process has also led to the discovery of precursors of 2-phenylethanol, benzyl alcohol, damascenone, vitispirane and 1,1,6-trimethyl-1,2-dihydronaphthalene. Additionally, many other related nor-isoprenoid compounds not previously known in grapes have been observed.

Glycosides of 2-phenylethanol and benzyl alcohol in Vitis vinifera grapes

Abstract β-Rutinosides and 6- O -α- l -arabinofuranosyl-β- d -glucopyranosides of 2-phenylethanol and benzyl alcohol have been found to co-occur with similar disaccharide glycosides of monoterpenes in Vitis vinifera vars. Muscat of Alexandria and Rhine Riesling. β- d -Glucopyranosides of these two alcohols were also identified in the fruit.

New linalool derivatives in muscat of alexandria grapes and wines

Abstract The CHCl 3 extract of Muscat of Alexandria grapes as well as extracts of wines made from these grapes were found to contain 3,7-dimethyloct-1-en-3,6,7-triol, 3,7-dimethyloct-1-en-3,7-diol, 3,7-dimethylocta-1,7-dien-3,6-diol and 3,7-dimethylocta-1,5-dien-3,7-diol.

Precursors of damascenone in fruit juices

Abstract The acid catalysed reactions of 6,7-megastigmadiene-3,5,9-triol and the β-D-glucosides of 5-megastigmen-7-yne-3,9-diol and 3-hydroxyl-β-damascone have been studied in relation to the formation of damascenone. The results show that hydrolysis of the allene triol could account for damascenone formation in the juices of grapes and other fruits.

Reducing haziness in white wine by overexpression of Saccharomyces cerevisiae genes YOL155c and YDR055w

Grape proteins aggregate in white wine to form haze. A novel method to prevent haze in wine is the use of haze protective factors (Hpfs), specific mannoproteins from Saccharomyces cerevisiae, which reduce the particle size of the aggregated proteins. Hpf1p was isolated from white wine and Hpf2p from a synthetic grape juice fermentation. Putative structural genes, YOL155c and YDR055w, for these proteins were identified from partial amino acid sequences of Hpf1p and Hpf2p, respectively. YOL155c also has a homologue, YIL169c, in S. cerevisiae. Comparison of the partial amino acid sequence of deglycosylated-Hpf2p with the deduced protein sequence of YDR055w, confirmed five of the 15 potential N-linked glycosylation sites in this sequence were occupied. Methylation analysis of the carbohydrate moieties of Hpf2p indicated that this protein contained both N- and O-linked mannose chains. Material from fermentation supernatant of deletion strains had significantly less activity than the wild type. Moreover, YOL155c and YIL169c overexpressing strains and a strain overexpressing 6xHis-tagged Hpf2p produced greater haze protective activity than the wild type strains. A storage trial demonstrated the short to midterm stability of 6xHis-tagged Hpf2p in wine.

3-oxo-α-ionol, vomifoliol and roseoside in Vitis vinifera fruit

Abstract 3-Oxo-β-ionol, vomifoliol and dehydrovomifoliol were identified for the first time in fruit from Vitis vinifera . The last named compound was mainly present free in the juice while the others existed predominantly as conjugates. In the case of vomifoliol, the conjugation was with glucose, i.e. as roseoside. Hydrolytic studies on 3-oxo-α-ionol and vomifoliol gave a range of compounds which have been recognized as fruit and plant products.

Gas chromatographic headspace analysis of Chardonnay and Semillon wines after thermal processing

ZusammenfassungFlüchtige Verbindungen der Weine Chardonnay und Semillon wurden mittels der dynamischen Kopfraum-Methode untersucht. Die flüchtigen Substanzen wurden selektiv mit einer Capillarsäule abgefangen und gaschromatographisch mit einer anderen Säule behandelt. Der Effekt einer Hitzebehandlung auf die Zusammensetzung der flüchtigen Verbindungen der Weine wurde untersucht. Durch Hydrolyse bei 45 °C wurden aus glykosidischen Vorstufen einige Norisoprenoid-Verbindung gebildet, die für das Aroma länger gelagerter Weine wichtig sind. Durch die Hitzebehandlung wurden die Anteile von 1,1,6-Trimethyl-1,2-dihydronaphtalen (TDN) und Vitispirane der Chardonnay- und Semillon-Weine erhöht. Zusätzlich wurden die flüchtigen Verbindungen solcher Referenzweine analysiert, denen die glykosidische Fraktion der Chardonnay- und Semillon-Traubensäfte zugesetzt worden war.AbstractVolatile compounds of Chardonnay and Semillon wines were analysed using a dynamic headspace method based on selective capillary column trapping and gas chromatography with another column. The effect of thermal treatment on the volatile composition of the wines was studied. Some grape derived norisoprenoid compounds, important to the aroma of aged wine, were formed at 45°C by hydrolysis from the glycosidic precursors. The heat treatment increased the proportion of 1,1,6-Trimethy1-1,2-dihydronaphthalene (TDN) and vitispirane in Chardonnay and Semillon wines. Headspace volatiles of model wines, to which the glycosidic fraction of Chardonnay and Semillon juices was added, were also analysed.

Lignan and phenylpropanoid glycerol glucosides in wine

Abstract Three glycoconjugates, 1-O-(β- D -glucopyranosyl)-2-[2-methoxy-4-(ω-hydroxypropyl)-phenoxy]-propan-3-ol, 1,2,3,4-tetrahydro-7-hydroxy-1-(4′-β-glucopyranosyl-3′-metho1xyphenyl)-6-methoxy-2,3-naphthalenedimethanol (isolariciresinol-β-4′-O-glucopyranoside) and, tentatively, 2,3-bis(4′-hydroxy-3′-methoxybenzyl)-butane-1,4-diol-β- D -glucoside (seco-isolariciresinol-β- D -glucoside) have been detected in Riesling wine by FAB-mass spectrometry/mass spectrometry and subsequently isolated and identified by spectral and chemical studies. The first of these compounds is a new shikimic acid metabolite of wine, and the latter two lignans represent a new category of wine phenols.

Free and bound 6,9-dihydroxymegastigm-7-en-3-one in Vitis vinifera grapes and wine

Abstract A-Hydroxy-4-(3-hydroxy-1-butenyl)-3,3,5-trimethylcyclohexanone (6,9-dihydroxymegastigm-7-en-3-one) was synthesized from vomifoliol and was identified for the first time as a common constituent of Vitis vinifera grapes in both free and conjugated forms, as well as a minor constituent of French and American oakwood extracts. The corresponding β- d -glucopyranoside was isolated from a Riesling wine.