The winemaking process

At the beginning of the winemaking process, the yeasts start to metabolize the sugars and other nutrients present in the grape juice. The yeasts use all these nutrients to obtain energy and increase tlieir population (Boulton et al. 1996 Ribereau-Gayon... 

The authors, invited by M.C. Polo and M.V. Moreno-Arribas to write this book, are recognized in their own field for their research and ability to transfer scientific results from the laboratory to the winemaking process and storage cellar, and here provide updates on the most recent advances in the field. 

Monoterpenes, norisoprenoids - some C13 megastigmane compounds -some benzenoid compounds called shikimates because of their origin from shikimic acid, and some polyfunctional sulphured compounds, are the most important grape-derived aroma compounds. In the winemaking process, these molecules are transferred to the wine both as free and bound forms. 

MHA). This method can be applied in routine analysis in the winemaking process, in both monitoring and quality control. (Fedrizzi et al., 2007a 2007b). Due to the very low sensory threshold in wines of... 

The method of sample preparation for grape proteins analysis should be chosen according to the aim of the study. If grape proteins have to be studied in relation to wine characteristics and technology, it is convenient to start from the so-called free run juice , a material representative of the must, in which the proteins are supposed to be involved in the winemaking process and wine quality. The free run juice is obtained by... 

Almeida, C.M.R. and Vasconcelos, M.T.S.D. (2004) Does the winemaking process influence the wine 87Sr/86Sr A case study. Food Chemistry, 85, 7-12. 

Castineira Gomez, M.M., Brandt, R., Jakubowski, N. and Andersson, J.T. (2004a) Changes of the metal composition in German white wines through the winemaking process. A study of 63 elements by Inductively Coupled Plasma - Mass Spectrometry. J. Agric. Food Chem., 52, 2953-2961. 

This chapter summarizes current information regarding the bacteria important during the winemaking process including AcetobacterIGluconobacter, Lactobacillus, Oenococcus, and Pediococcus, as well as the impact these microorganisms have on wine quality and public health concerns. Furthermore, the interactions that occur between these microorganisms and S. cerevisiae and their influences on wine quality are discussed. 

Bauza, T., Blaise, A., Teissedre, P.L., Mestres, J.P., Daumas, F., and Cabanis, J.C. 1995. Changes in biogenic amines content in musts and wines during the winemaking process. Sci. Aliments 15, 559-570. 

The main volatiles in wines are the higher aliphatic alcohols, ethyl esters, and acetates formed from yeasts during fermentation. Acetates are very important flavors characterized by fruity notes, C4-Ci0 fatty acid ethyl esters manly confer fruity scents to the wine. Other wine aroma compounds are C6 alcohols, such as 1-hexanol and cis- and trans-3-hexen-l-ol, 2-phenylethanol, and 2-phenylethyl acetate. Contents of these compounds in wine are linked to the winemaking processes used fermentation temperature, yeast strain type, nitrogen level in must available for yeasts during fermentation, clarification of wine (Rapp and Versini, 1991). Much literature on the wine aroma compounds was reported in reviews by Schreier (1979) and Rapp (1988). 

Volatile acidity in wine is considered to be a highly important physicochemical parameter, to be monitored by analysis throughout the winemaking process. Although it is an integral part of total acidity, volatile acidity is clearly considered separately, even if it only represents a small fraction in quantitative terms. 

Table 1.9. Changes in the buffer capacity of must from different pressings of Chardonnay grapes at various stages in the winemaking process. (Buffer capacity is expressed in meq/1). (Dartiguenave, 1998)...

Table 1.9 shows the changes in buffer capacity in successive pressings of a single batch of Chardonnay grapes from the 1995 and 1996 vintages, at the main stages in the winemaking process. 

As they are highly reactive, flavanol molecules condense together. Unlike anthocyanins and flavo-nols, they do not have glycosylated forms. However, they may be bonded to polysaccharides in grapes and extracted as complexes in the winemaking process. 

In many European wine growing areas where large quantities of tannins are extracted during the winemaking process, the wines are turbid, unrefined, and aggressive, requiring several years aging to clarify and acquire finesse. This is the only case in which precipitation of polymerized tannins makes the wine softer. 

Changes in coloring matter the (mauve) complexes with ethyl cross-bonds develop into orange pyrano-vinyl procyanidins. The reaction kinetics are disturbed by the presence of polysaccharides and, are apparently temperature dependent. This explains the difference between great wines that remain truly red for many years and more modest wines that rapidly take on a more yellow hue, as well as those that are saturated with oxygen during the winemaking process. 

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