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The influence of botanical species (Quercus and Castanea sativa) and geographical origin (Portugalthree different sites, France and North America) on the qualitative and quantitative content of some extractable low molecular weight phenolic compounds was assessed by HPLC. Chestnut wood had the highest total content of low molecular weight phenolic compounds, followed by the Portuguese oaks and the French oaks, whereas the American oak had the lowest content of these compounds. The contents of phenolic acids, phenolic aldehydes, scopoletin and umbelliferone were significantly different among the studied woods. Both the botanical species and the geographical origin affect the content of low molecular weight organic compounds of woods used in Portuguese cooperage. The results also show that the botanical species seem to be more important than the geographical origin to explain the difference in the wood phenolic composition. So, the separation of trees according to their origin is of considerable interest for coopers and winemakers to choose wisely the woods for the ageing of brandies. KeywordsPortuguese oak French oak American oak Chestnut Phenolic compounds HPLC Brought to you by | University of Arizona Authenticated Download Date | 6/5/15 8:01 PM

The effect of addition of grape seed tannins on the phenolic composition, chromatic characteristics, and antioxidant activity of red wine was studied. Two highly pure commercial grape seed tannins (GSE100 and GSE300) were selected, and their phenolic compositions were determined. Two types of red wines were made with Castelão/Tinta Miúda (3/2, w/w) grapevine varieties by fermentation on skin using two different maceration times, which correspond to the wines rich and poor in polyphenols, respectively. Each of these wines was used for experimentation with the addition of GSE100 and GSE300 before and immediately after alcoholic fermentation. Phenolic composition, chromatic characteristics, and antioxidant activity of the finished red wines were analyzed by HPLC-DAD, CIElab 76 convention, and DPPH radical test, respectively. The results showed that the addition of grape seed tannins had obvious effects of increasing color intensity and antioxidant activity only in the wines poor in polyphenols. Although GSE300 contained much higher amounts of di- and trimer procyanidins and a lower amount of polymeric proanthocyanidins, it provided effects of increasing the color intensity and antioxidant activity of the wines poor in polyphenols similar to those of GSE100. Furthermore, GSE100 released more gallic acid to wines than GSE300, although no gallic acid was detected in GSE100. Tannins added after alcoholic fermentation had a better effect on phenolic composition of red wine than tannins added before alcoholic fermentation.

Monomer and polymer flavan-3-ols and anthocyanins are the two major groups of phenolic compounds in red wine and one of the most important reactions during red wine ageing is the condensation reaction, either direct or indirect, between these two classes of compounds. In this work, the reaction of (+)-catechin, (-)-epicatechin and dimer procyanidin B2 with malvidin 3-glucoside, in the presence of acetaldehyde, was carried out in wine model solutions at pH 1.7 and 3.2. Identification of the reaction products was carried out by high-performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS) and MS(n) analysis. Various reaction products were detected. The structures of three condensation products - malvidin-3-glucoside-ethyl-(epi)catechin-1''-hydroxyethyl, malvidin-3-glucoside-ethyl-dimer-vinyl and malvidin-3-glucoside-ethyl-dimer-1''-hydroxyethyl - were identified in a model solution for the first time. Moreover, in the reaction solution containing dimer B2 at pH 3.2, monomer epicatechin, trimer and tetramer procyanidins were also detected indicating that, under these conditions, dimer procyanidins can either be hydrolyzed to monomers or polymerized to higher oligomer or polymers.