Grapes amino acids

Higher alcohols are formed by yeast, either directly from sugars or from grape amino acids by the Ehrlich reaction (Figure 2.5). This reaction... 

Amino acids are the most prevalent form of total nitrogen by weight in grape juice and wine. Indeed, the total free amino acid concentration varies from 1 to 4 g/1, depending on the year. In ripe grapes, amino acids generally represent 30-40% of total nitrogen. 

Fig. 11.4 Sequence comparison of Arabidopsis geranyllinalool synthase with other Arabidopsis TPS and putative or characterized linalool and geranyllinalool synthases from Clarkia, Medicago, poplar and grape. A neighbor-joining tree generated from an amino acid sequence alignment (QustalX) of 13 TPS proteins is shown. Numbers are bootstrap values higher than 800 out of 1,000 replicates. TPS proteins belong to different families as indicated by letters. V. vinifera putative GES, Acc. 002268557 P. trichocarpa putative GES, Acc. 002305640...

The next step of the biotechnical sequence, yeast fermentation, is of the utmost importance to the chemistry of winemaking as well as to the formation of flavor substances. We have investigated this previously using 14C-tagged compounds (16). Amino acids, for example, enter the yeast fermentation with a quasi biochemical valence with regard to the formation of metabolic side products like alcohols and esters. In that respect, the composition of the fermentation substrate, the grape must, is highly important to the formation of aroma substances by yeasts. 

An extensive review of analytical methods used in determining amino acids in grapes and wine was reported by Ough and Bustos (92). This paper also includes a comprehensive review of the amino acid composition of musts and wine. In addition, Amerine (21), Amerine and Joslyn (2), and Amerine et al. (3) reviewed amino acids in grapes and wine. 

The literature indicates that most studies pertaining to amino acids have been devoted to grape varieties of the species V. vinifera. In general, investigations have shown that grape varieties of the species V. vinifera and V. labrusca are qualitatively similar in amino acid composition. However, the concentrations of amino acids vary over a wide range, and the varietal effect is significant (83, 93, 94, 95, 96, 97, 98, 99, 100). 

Changes in amino acid composition in grapes are influenced by maturity, season, location, and environmental conditions as reported by several workers (8, 84, 96,101,103, 104, 105). 

P Martin, C Polo, MD Cabezudo, MV Dabrio. Dansyl amino acids behavior on a Radial-Pak C18 column. Derivatization of grape wine musts, wines, and wine vinegars. J Liq Chromatogr 7 539-558, 1984. 

Dominguez et al. [71] L-Amino acids D-Amino acids Grapes r,-Amino acid oxidase or D-amino acid oxidase and peroxidase/entrapped in electrode composite matrix by physical inclusion Graphite-Teflon-ferrocene composite electrode/OV vs. Ag/AgCl Ferrocene... 

In addition to heterocycles in grape juice, there are also many acyclic precursors that are converted by fermentation, aging, and other modifications into heterocycles for example, hydroxyl carboxylic acids, polyphenols, and amino acids. 

B. cinerea utilizes a significant part of the grape s assimilable nitrogen content, including ammonium and amino acids. In some studies, a significant decrease (by 30-80%) in the total amino acid content has been reported in Botrytis-affected grapes, compared to the healthy grapes (Dittrich and Sponholz, 1975 Dittrich et ah, 1975 Rapp and Reuther, 1971). 

All amino acids, except proline, may be used by Saccharomyces cerevisiae in grape juice fermentation. Amino acids can be directly used to synthesize proteins. However, the amino acid composition of the grape juice is not necessarily similar to the needs of the cell. For that reason, yeasts must use the remaining amino acids to synthesize those which it lacks (Hensche and Jiranek 1993 Ribereau-Gayon et al. 2000b). In this case, ammonia is incorporated into other amino acids whereas the carbon skeleton is metabolized by the cell. 

Finally, the relationship between the amino acid composition of grapes and the final aromatic composition of wine has been recently described (Hernandez-Orte et al. 2002, 2006). Therefore, it is possible that in the near future grape juice will be complemented with specific mixtures of amino acids in order to improve the aromatic quality of wine. 

Hemandez-Orte, P., Cacho, J., Ferreira, V. (2002) Relationship between varietal amino acid profile of grapes and wine aromatic composition. Experiments with model solutions and chemo-metric study, J. Agric. Food Chem., 50, 2891-2899. 

Around 20 free amino acids were detected in grape musts, representing on average 28-39% of the total nitrogen, depending on whether these corresponded to musts of white or red wine grapes, respectively (Rapp and Versini 1991). The amino acid... 

In a study by Dizy and Polo (1996), the majority amino acids in grape must of the Malvar variety were glutamine, arginine, proline and y-aminobutyric acid (GABA). The authors found that the concentration of proline rose during fermentation, while... 

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