Grapes aroma compounds

GRAPE AROMA COMPOUNDS TERPENES, C13-NORISOPRENOIDS, BENZENE COMPOUNDS, AND 3-ALKYL-2-METHOXYPYRAZINES... 

The analytical conditions commonly used for analysis of grape aroma compounds are reported in the Table 4.1. Figure 4.9 reports the mass spectra of the principal terpenols and norisoprenoids identified in grapes not reported in the main libraries commercially available. 

TABLE 4.1. Common GC/MS Conditions Used for Analysis of Grape Aroma Compounds... 

Pectinases and (3-glucanases are the only enzymes allowed in wine-making by European legislation. They are used as clarification and filtration agents and also to release aroma compounds that are mostly present in grape as nonvolatile glycosidic precursors. Pectolytic enzymes are also reported to increase extraction of phenolic compounds and wine color... 

Lund, C. M., Nicolau, L., Gardner, R. C., and Kilmartin, P. A. (2009). Effect of polyphenols on the perception of key aroma compounds from Sauvignon Blanc wine. Aust.. Grape Wine Res. 15,18-26. 

Table 11.2 Summary of most important aroma compounds in wine, excluding off-flavours, and the impact of grapes and microorganisms (modified according to [11])... 

For the color, tannin, and aroma compounds to be transferred from the skins to the fermenting wine it is necessary to mix the floating skins with the wine. This punching down the cap should be done about every 6-8 hrs with a wooden or stainless steel plunger. The less color in the grapes, the more frequently the juice and skins should be punched so there be maximum color extraction. 

While most of the studies carried out to date have focused on the evolution of the primary compounds, such as the sugar and acid components, little data exist for the other quality characteristics, and in particular, for aroma. However, most of these studies have been conducted on the aromatic varieties. For instance, some experimental studies conducted on different aromatic cultivars under different conditions mainly reported the evolution of terpene compounds during the dehydration process. Accordingly, it has been showed that after the grape harvest, activation or inhibition of the metabolism involved in the biosynthesis of the aroma compounds is strictly dependent on the grape dehydration technique. 

Most of the studies on Botrytis-specific aroma compounds have investigated the aroma composition of wines (Table 6.7). Only a few have focused on what occurs in the grape. On synthetic media, the main odorous compounds produced by B. cinerea are aromatic aldehydes (benzaldehyde, phenylacetaldehyde), and furfural (Kikuchi et al., 1983). Sarrazin et al. (2007a) confirmed the higher concentration of phenylacetaldehyde in noble-rotted grapes. 

The aroma of botrytized wines has been studied more extensively than that of the grapes. Mashuda et ah (1984) identified the lactone sotolon (4,5-dimethyl-3-hydroxy-2,(5)-furanone) as a principal compound in a botrytized aroma. Sotolon is also a key aroma compound in flor wines, for example, vin jaune, sherry (Dubois et ah, 1976 Martin and Etievant, 1991 Moreno et ah, 2005). However, Sponholz and Hiihn (1993) found no correlation between the degree of Botrytis infection and sotolon... 

Miklosy, E., Kalmar, Z., and Kerenyi, Z. (2004). Identification of some characteristic aroma compounds in noble rotted grape berries and aszu wines from Tokaj by GC-MS. Acta Aliment. Hung. 3,215-226. 

Sarrazin, E., Dubourdieu, D., and Darriet, P. (2007a). Characterization of key-aroma compounds of botrytized wines, influence of grape botrytization. Food Chem. 103, 536-545. 

Rapp, A. and Versini, G. (1991). Influence of nitrogen compounds in grapes on aroma compounds of wine. In proceedings of the international symposium on nitrogen in grapes and wine. Am. Soc. Enol. Vitic. 323,156-164. 

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