Analysis of red wine phenolics: Comparison of HPLC and spectrophotometric methods

A recently developed ion-pair normal phase HPLC method which allows a precise chromatographic evaluation of the whole class of high-molecular-mass phenolics of wine was used in order to check the performance of spectrophotometric methods. Thirty-two monovarietal red wines (vintages 1993 and 1998) were analysed for total high-molecular-mass phenolics, proanthocyanidins with 2-4 units, and proanthocyanidins formed by 5 or more units, by means of the normal phase HPLC method. In addition the following spectrophotometric assays were performed: total phenols by Folin-Ciocalteu, Bate-Smith transformation of proanthocyanidins into cyanidin and catechins and proanthocyanidins reactive to vanillin.

Role of the variety and some environmental factors on grape stilbenes

V. vinifera L. 'Barbera', 'Croatina', 'Malvasia di Candia aromatica', growing in the Piacenza viticultural area (North-West Italy) at four elevations (150, 240, 320, 420 m a.s.l.), were tested at harvest for grape stilbene (trans-resveratrol, trans-piceid, cis-piceid) synthesis over three years (2000-2002). Meteorological data were recorded, as well as vine production and fruit quality parameters. The most significant findings were:trans-piceid was the most abundantly produced stilbene compound (103 μg·kg-1 berry FW), while trans-resveratrol was the least produced (57 μg·kg-1 berry FW);'Barbera' and 'Croatina' had similar trans-resveratrol berry levels (71 μg·kg-1 berry FW and 76 μg·kg-1 berry FW respectively), higher than 'Malvasia di Candia aromatica' (24 μg·kg-1 berry FW);'Barbera' had the highest trans-piceid and cis-piceid concentrations (235 and 136 μg·kg-1 berry FW, respectively) while 'Malvasia di Candia aromatica' had the lowest levels (13 and 1 μg·kg-1 berry FW, respectively);stilbenes increased with elevation up to 320 m, while decreasing at the highest altitude;the vintage year only significantly affected the cis-piceid berry concentration which was positively related to the relative humidity at the end of ripening, and negatively related to degree-days at the end of ripening.

Selective use of wine yeast strains having different volatile phenols production

Among Saccharomyces cerevisiae wine yeasts, we found a high frequency of strains having the ability to decarboxylate 4-hydroxycinnamic acid and 3-methoxy-4-hydroxy-cinnamic acid. From Gewurztraminer juices fermented by S. cerevisiae wine strains with and without such character, we obtained wines with considerably different levels of volatile phenols and some interesting evidences of the likely precursors of 4-vinylguaiacol and 4-vinylphenol. The identification of yeast strains by electrophoretic karyotyping gave us the possibility of evaluating the effective contribution of the yeast in the organoleptic characteristic of Traminer wines associated with the concentration of such volatile phenols

Methyl salicylate glycosides in some Italian varietal wines

Glycosides are ubiquitous plant secondary metabolites consisting of a non-sugar component called an aglycone, attached to one or more sugars. One of the most interesting aglycones in grapes and wine is methyl salicylate (MeSA), an organic ester naturally produced by many plants, particularly wintergreens. To date, nine different MeSA glycosides from plants have been reported, mainly spread over the genera Gaultheria, Camellia, Polygala, Filipendula, and Passiflora. From a sensorial point of view, MeSA has a balsamic-sweet odor, known as Wintergreen. MeSA was found in Vitis riparia grapes, in Vitis vinifera sp. and in the Frontenac interspecific hybrid. We found that the MeSA glycosides content in Verdicchio wines and in some genetically related varieties (Trebbiano di Soave and Trebbiano di Lugana) was very high. In order to understand which glycosides were present in wine, the methanolic extract of Verdicchio wine was injected into a UPLC-Q-TOF-HDMS and compared to the extracts of different plants rich in such glycosides. Using pure standards, we confirmed the existence of two glycosides in wine: MeSA 2-O-β-d-glucoside and MeSA 2-O-β-d-xylopyranosyl (1-6) β-d-glucopyranoside (gaultherin). For the first time, we also tentatively identified other diglycosides in wine: MeSA 2-O-α-l-arabinopyranosyl (1-6)-β-d-glucopyranoside (violutoside) and MeSA 2-O-β-d-apiofuranosyl (1-6)-β-d-glucopyranoside (canthoside A), MeSA 2-O-β-d-glucopyranosyl (1-6)-O-β-d-glucopyranoside (gentiobioside) and MeSA 2-O-α-l-rhamnopyranosyl (1-6)-β-d-glucopyranoside (rutinoside). Some of these glycosides have been isolated from Gaultheria procumbens leaves by preparative liquid chromatography and structurally annotated by 1H- and 13C-NMR analysis. Two of the peaks isolated from Gaultheria procumbens leaves, namely MeSA sambubioside and MeSA sophoroside, were herein observed for the first time. Six MeSA glycosides were quantified in 64 Italian white wines, highlighting the peculiar content and pattern in Verdicchio wines and related cultivars. The total concentration in bound and free MeSA in Verdicchio wines varied in the range of 456–9796 μg/L and 5.5–143 μg/L, respectively, while in the other wines the bound and free MeSA was below 363 μg/L and 12 μg/L, respectively. As this compound’s olfactory threshold is between 50 and 100 μg/L, our data support the hypothesis that methyl salicylate can contribute to the balsamic scent, especially in old Verdicchio wine