Wine composition

The complexity of wine composition is a central reason for the vast variety of wines in the marketplace. In addition to water and ethanol, the major components, a variety of organic acids as well as metal ions from minerals in the skin of the grape are present. Initially, all of these substances remain dissolved in the bottled grape juice. As the fermentation process occurs, the increasing alcohol concentration in the wine alters the solubility of particular combinations of acid and metal ions. Unable to remain in solution, the insoluble substances settle as crystals. Since the process of red-wine making involves extended contact of the grape juice with the skins of the grapes (where the minerals are concentrated), wine crystals are more common in red wines than in white wines. 

Flores, J. H., Heatherbell, D. A., and McDaniel, M. R. (1990). Ultrafiltration of wine effect of ultrafiltration on White Riesling and Gewuerztraminer wine composition and stability. Am.. Enol. Vitic. 41, 207-214. 

Rudnitskaya, A., Schmidtke, b. M., Delgadillo, b, begin. A., and ScoUary, G. (2009b). Study of the influence of micro-oxygenation and oak chip maceration on wine composition using an electronic tongue and chemical analysis. Anal. Chim. Acta 642(1-2), 235-245. 

E Falque, E Fernandez. Effects of different skin contact times on Treixadura wine composition. Am J Enol Vitic 47(3) 309-312, 1996. 

Ough, C. S. (1992). Fermentation and wine composition. In "Winemaking Basics", (R. E. Gough, Ed.), pp. 92-145. Food Products Press. The Haworth Press, Inc. Publisher. 

Giudici, P., Zambonelli, C., Passarelli, P., and Castellari, L. (1995). Improvement of wine composition with cryotolerant Saccharomyces strains. Am. ]. Enol. Vitic. 46,143-147. 

In warmer vintages in the North Coast, grapes, especially riper grapes at 23°-24° Brix, may be low in titratable acidity. Desirable levels of acidity in white juice prior to fermentation range from 0.7 to 1.0 g/100 mL, depending on final wine composition and wine style desired. Tartaric acid is used most commonly for acidulation and often is added to juice prior to fermentation. Malic acid and citric acid also are used for acidulation. 

Effect of Yeast on Fermentation. North Coast enologists recognize the important effects yeast strains have on the management of the fermentation, its evenness and completion, and the wine composition. Rankine (23) reviewed the different effects of yeast strain on wine composition and noted especially the relationship of yeast strain to sulfur dioxide, hydrogen sulfide, and acetaldehyde production. 

Williams, J.T. Ough, C.S. Berg, H.W. White Wine Composition and Quality... 

Fermentation Rate, Wine Composition and Wine Quality, Am.J. Enol. Vitic. 1978, 29, 112-119. 

The biological aging process involves various changes in wine composition. Such changes are essentially the result of the metabolism of flor yeasts and, to a lesser extent, of other phenomena common to all types of aging processes including crystal precipitation, chemical reactions between wine components and extraction of substances from cask wood. 

Other reactions involving this aldehyde include the following (1) combination with sulphite ion, which substantially increases the proportion of bound sulphite in wine (2) formation of addition compounds with some polyphenols such as tannins and procyanidins, where it acts as a bridging molecule (Haslam and Lilley 1998) and (3) chemical oxidation to acetic acid, which only occurs to a small extent and has little influence on wine composition and quality. 

This chapter provides an updated overview of the current knowledge on the role played by enzymes in the process of transforming grapes into wine and on the possibility offered by new technologies to modify wine composition though a more effective control of enzymatic reactions. 

Wine composition Concentration from indigenous yeast fermentation wines relative to conventional wines... 

In addition to Saccharomyces cerevisiae, other species of the Saccharomyces sensu stricto group have recently become of interest to research and winemaking, in part because of their different capacities to modulate wine composition, and flavour... 

Howell et al. (2006) also carried out extensive metabolite profiling of the volatile metabolites produced in wines made by cofermentation with Saccharomyces strains. They found that cofermentation not only produced a metabolite profile different from wines made by monoculture fermentation, but that blends of the monoculture fermentation wine were also notably different. These various finding therefore strengthen the anecdotal observations of winemakers that cofermentation with two or more strains can potentially increase the flavour complexity of wines. These studies also suggest that cofermentation of yeasts with greater metabolic dissimilarity are likely to produce greater differences in the profile of volatile and non-volatile metabolites, as has been observed when mn-Saccharomyces yesists are cofermented with Saccharomyces (Sect. 8D.6.4). Additional studies are needed to understand better the complex metabolic interactions and to describe the major impacts on wine composition and flavour. 

Wine is a complex mixture consisting of indigenous components and those obtained by chemical and biochemical transformations by wine microorganisms and/or during wine aging. Wine composition varies widely and is influenced by the grape (variety, quality) and by the winemaking conditions. 

Morel-Salmi, C., Souquet, J. M., Bes, M., Cheynier, V. (2006). The effect of flash release treatment on phenolic extraction and wine composition. J. Agric. Food Chem.,54, 4270-4276. 

The above-mentioned metabolic activities of microorganisms should be taken into account when studying wine compositional alterations. In fact, the effect of... 

Brettanomyces can endure SO2 treatment in barrels (45). The yeast survives treatment in areas of limited SO2 contact around bung holes, in the oak, and in the yeast sediment (lees). Work by Swaffield Scott (61) showed yeast and bacteria could penetrate the porous cellular structure of oak barrels and establish active permanent sub-surface mixed cultures even after cleaning. Variations in wine composition (pH, anthocyanin concentration, nutrient content, and temperature) can affect SO2 treatment in wine (60,62). 

Th e complexity of wine composition has always challenged chemists and, as a result, there have been many meetings to discuss the chemistry and the related flavors. Scientific interest in these flavors has led to an increased understanding of wine chemistry, biochemistry, and sensory perception, and meetings of the American Chemical Society (ACS) have provided an important forum for sharing these discoveries from a presentation by Andre Tchelistcheff on malolactic fermentation at the 1949 ACS meeting in San Francisco to the most recent Wine Flavor Chemistry Symposium at the 1997 meeting in San Francisco, from which this volume is derived. 

Matrix Wine Composition Level DMS EtSH DES MTA DMDS ETA DEDS ME MTE MTP MTB BT HMT... 

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