Olga Laureano

Comparative study of the phenolic composition of seeds and skins from Carménère and Cabernet Sauvignon grape varieties (Vitis vinifera L.) during ripening.

The phenolic composition of skins and seeds from Vitis vinifera L. cv. Carménère and Cabernet Sauvignon grapes during ripening was evaluated by high-performance liquid chromatography-diode array detection and spectrophotometric analysis. As compared to Cabernet Sauvignon grape skins, Carménère grape skins presented higher contents of total anthocyanins, monomeric flavan-3-ols, and total flavonoids, a higher mean degree of polymerization, a higher percentage of galloylation, a higher average molecular weight of the flavanol fraction, and a higher color intensity. As compared to Cabernet Sauvignon grape seeds, Carménère grape seeds presented a lower content of monomeric flavan-3-ols, a higher mean degree of polymerization, a higher percentage of galloylation, a higher average molecular weight of the flavanol fraction, a lower content of (+)-catechin, and higher contents of (-)-epicatechin, epicatechin-3-O-gallate, gallic acid, and dimeric procyanidins esterified with gallic acid. Altogether, we conclude that Carménère grapes present a differential composition and evolution of phenolic compounds when compared to Cabernet Sauvignon grapes.

Interactions of Oligomeric Procyanidins in Model Wine Solutions Containing Malvidin‐3‐Glucoside and Acetaldehyde

Interactions of grape seed flavanols, dimeric, galloylated dimeric and trimeric procyanidins with malvidin-3-glucoside and acetaldehyde were studied in wine-like model solutions. Malvidin-3-glucoside and oligomeric procyanidins reacted very slowly, with eventual formation of yellow xanthylium salts. The concentrations of malvidin-3-glucoside and oligomeric procyanidins decreased faster in the presence of acetaldehyde and the colour augmentation with shift towards violet was attributed to the formation of new coloured compounds, detectable by HPLC and linked at different positions by CH 3 CH bridges. The rate of loss of procyanidins in the presence of malvidin-3-glucoside and acetaldehyde varied according to the complexity of the components. Monomeric (+)-catechin and (-)-epicatechin reacted more slowly than dimer procyanidins B 1 , B 2 and B 3 while trimer C 1 (epicatechin 4β → 8 epicatechin 4β → 8 epicatechin) presented the highest degradative reaction rate.

Volatile composition analysis by solid-phase microextraction applied to oak wood used in cooperage (Quercus pyrenaica and Quercus petraea) : effect of botanical species and toasting process

The purpose of this study was to investigate the sorption of selected volatile substances from oak wood-chip samples (Quercus pyrenaica Willd. and Quercus petraea L.) subjected to different toasting levels, namely, without toasting, with medium toasting, and with strong toasting, through the use of solid-phase microextraction (SPME). The main volatile compounds identified as a function of the toasting level and botanical species were furfural, hexanal, α-pinene, d-limonene, decanal, vitispirane, ethyl hexanoate, cis-3-methyl-γ-octalactone (“oak lactone” or “whisky lactone”), α-terpineol, p-xylene, and nonanal. Considering the data obtained from the toasted woods (medium and strong intensity) in comparison with those of nontoasted woods, it can be pointed out that the average peak area and the number of compounds identified in the gas chromatogram decreased during the toasting process. In general, regarding the compounds analyzed, quantitative differences were found between the two oak wood species under study. High values of volatile compounds were found in Quercus pyrenaica oak wood chips. In addition, for the number of compounds identified in oak wood extracts and directly extracted from solid oak wood chips by SPME, it is concluded that the best extraction process for volatile compounds from oak wood is the use of oak wood-chip liquid extracts.

Effect of Saccharomyces strains on the quality of red wines aged on lees

Ageing on lees involves ageing the wine in contact with yeast cells after fermentation. If combined with the addition of oak chips, it can soften the wood flavour and increase the aromatic complexity of wine. The aim of the present work is to optimise both ageing techniques through selection of an adequate Saccharomyces cerevisiae strain. The study lasted 6 months and content of polysaccharides, anthocyanins, proanthocyanidins, volatile compounds, colour parameters and sensory analysis, were periodically evaluated. Among the strains tested, G37 showed the highest release of polysaccharides (24.4±5.5 mg l(-1)). Vanillin, syringaldehyde and furfuryl alcohol increased with ageing time in 7VA2 treatment. The wine aged with CTPL14 strain presented fewer monomeric and oligomeric proanthocyanidins (12.4±0.6 and 83.4±8.3 mg l(-1), respectively), and showed the lowest astringency and bitterness sensations. Results show an improvement in the sensory profile of the red wine aged with a combination of these two techniques.

Relationship Between Biogenic Amines and Free Amino Acid Contents of Wines and Musts from Alentejo (Portugal)

The concentration of biogenic amines and free amino acids was studied in 102 Portuguese wines and 18 musts from Alentejo demarcated (D.O.C.) regions. Most wines were commercial, except for 38 monovarietals obtained by micro vinification. Musts from the varieties used to produce the latter wines were also studied. Both biogenic amines and free amino acids were analyzed by HPLC using fluorescence detection for their o-phthalaldehyde/fluorenylmethyl chloroformate (OPA/FMOC) derivatives. The most significant amines (average 10.8 mg/L for histamine+tyramine in red, and 7.4 mg/L for white wines) were found to be present at low levels and, although no important relationship between each individual biogenic amine could be obtained, the total amine content depends significantly on the assimilable amino acid content in wine.

Ellagitannins from Portuguese oak wood (Quercus pyrenaica Willd.) used in cooperage: influence of geographical origin, coarseness of the grain and toasting level

Abstract The ellagitannins and ellagic acid from extracts of Portuguese oak wood chips (Quercus pyrenaica) used in cooperage from different origins (Gerês and Guarda forests) were analysed by HPLC. The results were compared with the ellagitannin content of wood chips obtained from American (Q. alba) and French (Q. petraea) oak. The influence of heat treatment and the coarseness of the grain on ellagitannins and ellagic acid were also studied. Five ellagitannins (vescalagin, castalagin, roburin D, roburin E and grandinin) and ellagic acid were quantified. Vescalagin and castalagin were the most abundant individual ellagitannins in all of the oak wood chips studied. Portuguese oak wood had the highest content of ellagitannins and ellagic acid, followed by the French and American oaks. The geographical origin of Portuguese oak and the coarseness of the grain of French oak affected the content of ellagitannins and ellagic acid. In general, the ellagitannin content decreased with the toasting process, while the ellagic acid content increased. The toasting process had the highest impact on ellagitannin composition in comparison to the other variables studied.

Vitis vinifera secondary metabolism as affected by sulfate depletion: diagnosis through phenylpropanoid pathway genes and metabolites

Grapevine (Vitis vinifera L.) is rich in phenylpropanoid compounds, namely flavonoids and stilbenes which, present in most tissues, are described as antioxidants and known to accumulate in response to biotic and abiotic stress. Grapevine is then a choice model for studying the interplay between the phenylpropanoid pathway and nutrient deficiency. Here we report the response to sulfur deficiency (-S) of flavonoids and stilbenes biosynthetic pathways in chlorophyll tissues (plantlets) and cell culture. Anthocyanins and trans-resveratrol accumulated in plantlets and trans-resveratrol glucoside in cell cultures in response to sulfur deficiency, while a significant decrease in chlorophyll was observed in -S plantlets. The up-regulation of chalcone synthase gene and the downstream flavonoid biosynthesis genes dihydroflavonol reductase and anthocyanidin synthase matched the accumulation of anthocyanins in -S V. vinifera plantlets. The mRNA level of stilbene synthase gene(s) was correlated tightly with the increase in trans-resveratrol and trans-resveratrol glucoside levels, respectively in -S plantlets and cell cultures. As a whole, the present study unveil that V. vinifera under sulfur deficiency allocates resources to the phenylpropanoid pathway, probably consecutive to inhibition of protein synthesis, which can be advantageous to resist against oxidative stress symptoms evoked by -S conditions.

Effect of Winery Yeast Lees on Touriga Nacional Red Wine Color and Tannin Evolution

Red wine aging on lees is a winemaking practice used to achieve more rounded and less astringent wines. In two different trials, external yeast lees were added to a red wine and their effects on wine color and tannin evolution during aging were studied. Results indicated that the addition of yeast lees did not affect color stabilization during the studied period. Color compounds and condensed tannins were rapidly adsorbed to the yeast lees at the beginning of the experiment. There was a retarding effect on proanthocyanidin polymerization reaction by the addition of yeast lees, leading to the maintenance of low and medium molecular weight tannins in solution. Two different interactions were observed: first, proanthocyanidin adsorption by the yeast lees, primarily ones with the highest polymerization degree, and second, the retarding of proanthocyanidin polymerization, likely by the mannoproteins released by yeast lees. The age of the yeast lees was a factor in mannoprotein release and its effect in wine.

Extraction of Some Ellagic Tannins and Ellagic Acid from Oak: Wood Chips (Quercus pyrenaica L.) in Model Wine Solutions: Effect of Time, pH, Temperature and Alcoholic Content

The subject of the present work is the study of the influence of pH, temperature, alcoholic content and time on the extraction of some individual ellagic tannins (castalagin, vescalagin, grandinin, roburin D and E) and ellagic acid from oak wood chips (Quercus pyrenaica L.) within model wine solutions. The determination of these compounds by reversed-phase high-performance liquid chromatography (HPLC), after 104 extraction days, enabled us to establish the qualitative and quantitative evolution of each component and the effect of each extraction condition on individual and total ellagic tannins from oak wood chips. Vescalagin and castalagin were the most abundant individual ellagic tannins measured under all extraction conditions. Individual ellagic tannins and ellagic acid increased during the first weeks of extraction, followed by a decrease. Under the extraction conditions examined, temperature was the main factor influencing ellagic tannins and elagic acid evolution. The results suggest that a decrease/degradation of these compounds is less noticeable at low temperatures (12oC). After 104 extraction days the ellagic tannins content in a model wine solution at 12oC was higher than the content of ellagic tannins in solutions at 20oC. On the other hand, the effects of alcoholic content and pH of model wine solutions on the extraction and evolution of the analysed compounds (except for castalagin and vescalagin) seemed to be less important than temperature.

Evaluation of Portuguese and Spanish Quercus pyrenaica and Castanea sativa species used in cooperage as natural source of phenolic compounds

A study on the phenolic composition of Portuguese and Spanish Castanea sativa and Quercus pyrenaica woods used in cooperage has been carried out with the aim of looking for an extra value for the wood residues generated in cooperage industries. Results showed that both species are an important source of valuable phenolic compounds, although differences in the phenolic content were found. Chestnut samples showed the highest concentration of total phenolic compounds, being especially rich in vescalagin, gallic acid, vanillic aldehyde and syringaldehyde. The geographical origin was another parameter to take into account. Portuguese chestnut samples showed higher amounts of phenolic compounds than the Spanish samples, with vescalagin, gallic acid, vanillic acid and syringaldehyde being the most important features. As a consequence, the residues generated in the cooperage industry from chestnut and Q. pyrenaica heartwood seem to be an important source of valuable phenolic compounds, particularly those from Portuguese chestnuts.