Volatile and glycosidically bound composition of Loureiro and Alvarinho wines

Composition of Loureiro and Alvarinho wines from the Vinhos Verdes region, respecting free volatile compounds as well as glycosidically bound aroma precursors, was exhaustively determined by GC-MS after adsorption on XAD-2 resin. On the whole, were identified and quantified 120 volatile compounds in the free fraction and 77 glycosidically bound compounds, belonging to C6-compounds, alcohols, fatty acids ethyl esters, esters of organic acids, acetates, monoterpenic alcohols, monoterpenic oxides and diols, C13-norisoprenoids, volatile phenols, volatile fatty acids and carbonyl compounds. Globally, the wines of the two cultivars present similar composition on volatiles. However, respecting varietal compounds, Loureiro wines are richer than Alvarinho ones with regard to C6-compounds and monoterpenic compounds, occurring the opposite for volatile phenols. It was also demonstrate that wines of both varieties may benefit the aroma reserve, present as glycoconjugates, as it is susceptible of being technologically explored. Linalool, Ho-trienol, α-terpineol, contributing with fruity and floral notes, and β-damascenone mostly for Alvarinho, confering tropical fruit notes, are the varietal compounds which may particularly influence the aroma of these wines. Respecting fermentative compounds, Alvarinho is also particularly rich in fatty acids ethyl esters related to lipid metabolism and acetates of fusel alcohols, which can provide it a fruity character; Loureiro contains higher levels of esters of organic acids and 2-phenylethanol, conferring fruity and floral notes. Sensory analysis agree with chemical analyses showing a pronounced tree and tropical fruit character for Alvarinho wines while Loureiro wines present more intense citrus fruit notes.Centre of Biological Engineering of Universidade do Minho; Estação Vitivinícola Amândio Galhano (EVAG); Solar de Serrade; EVAG; Comissão de Viticultura da Região dos Vinhos Verdes

Changes in the concentration of volatile oak compounds and esters in red wine stored for 18 months in re-used French oak barrels

Studies were made of changes in concentration of oak-wood-derived volatiles and the evolution of esters in red wine during storage in twice-used French oak barrels. Wine samples were taken after 8, 10, 12, 15, and 18 months maturation in the barrels. Results showed that most of the volatile compounds extracted from the wood (furanic compounds, volatile phenols, lactones) reached maximum concentration between 10 and 12 months of barrel storage. After 18 months of maturation many of the compounds showed concentrations similar to those found after 10 to 12 months. However, the concentrations of furfural, 5-methyl furfural, furfuryl alcohol, coniferaldehyde, acetovanillone and phenol in wines aged for 18 months were lower than those reached after 10 to 12 months. The concentration of the ethylphenols increased right up to 18 months of ageing, which can only have a negative impact on the quality of the wine. There were few modifications in the concentration of esters, except for ethyl lactate which reached peak concentration after 12 months maturation and decreased thereafter

Multiple glucosyltransferase activities in the grapevine Vitis vinifera L

© 2008 Australian Society of Viticulture and Oenology Published online at www.interscience.wiley.comThe conjugation by glycosyltransferases of sugars to primary and secondary metabolites is widespread among plants and almost certainly a prerequisite for the accumulation of secondary metabolites at high levels. In the case of the grapevine, Vitis vinifera, modulating the levels of specific secondary berry metabolites is a desirable outcome for the development of wines with particular style characteristics. This can be achieved only by a thorough understanding of the processes underlying glucoside formation and accumulation during berry development. Using protein extracts prepared from leaves and berries of Vitis vinifera cvs, we show here that glucosyltransferase activities can be detected against a wide range of substrates. Among the substrates glucosylated were several classes of phenylpropanoids, including flavonols, anthocyanidins, flavanones, flavones, isoflavones, and a stilbene. Additionally, simple phenols and monoterpenes were glucosylated. Total soluble leaf proteins subjected to ion-exchange chromatography separated into fractions with differing glucosyltransferase activities. This provided strong evidence for the existence both of multiple distinct enzyme activities, and multiple isozymes catalysing identical reactions. Polyclonal antiserum raised to a V. vinifera UDP-glucose:anthocyanidin glucosyltransferase was used to demonstrate the existence of multiple glucosyltransferases in berries and leaves of the grapevine cvs Muscat of Alexandria and Shiraz, thereby confirming data obtained previously through biochemical analyses of recombinant glucosyltransferase