Chemistry of Wine Flavor - ACS Publications - American Chemical

Chapter 4

Comparison of Different White Wine Varieties in Odor Profiles by Instrumental Analysis and Sensory Studies

Downloaded by UNIV OF SYDNEY on August 29, 2013 | http://pubs.acs.org Publication Date: December 28, 1998 | doi: 10.1021/bk-1998-0714.ch004

H. Guth Deutsche Forschungsanstalt für Lebensmittelchemie, Lichtenbergstrasse 4, 85748 Garching, Germany

Two different white wine varieties (Gewürztraminer and Scheurebe), which differ in their odor profiles, were investigated by gas chromatographyolfactometry (GC-O). Aroma extract dilution analysis (AEDA) and static headspace analysis-olfactometry (SHA-O) yielded 41 and 45 odor-active compounds for Scheurebe and Gewürztraminer wines, respectively. An unknown compound with coconut-like and woody odor qualities, which has not yet been detected in wine or a food, was identified as (3S,3aS,7aR)3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one (wine lactone). Quantitation and calculation of odor activity values of potent odorants showed, that differences in odor profiles of both varieties were mainly caused by cis-rose oxide in Gewürztraminer and 4-mercapto-4-methylpentan-2-one in Scheurebe. Reconstruction of the flavor and quantitation of potent odorants in the different stages of wine making of Gewürztraminer will be discussed.

Up to now more than 680 volatile compounds have been identified in different white wine varieties (/) but little is known about the actual contribution to the overall flavor. This paper summarizes the screening experiments of the most odor active compounds in Gewurztraminer and Scheurebe wines by aroma extract dilution analysis (AEDA) and static headspace analysis-olfactometry (SHA-O), followed by quantitation and calculation of odor activity values (OAV's). Reconstruction of the flavor of both varieties and sensory studies will be discussed. Furthermore the influence of various ethanol concentrations on the overall flavor profile of Gewurztraminer wine was examined. Investigations about changes during the different stages of wine making of Gewurztraminer (after pressing of grapes, after yeast fermentation, after malolactic fermentation and after maturing in high-grade steel tank) will be reported. The influence of barrel aging on the overall flavor of Gewikztraminer wine will be the subject of later sections of the present paper.

© 1999 American Chemical Society In Chemistry of Wine Flavor; Waterhouse, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.

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Gas chromatography-olfactometry (GC-O) The odorants, which contribute significantly to the flavor of a food, can be localized in the capillary gas chromatogram of the volatile fraction by gas chromatographyolfactometry (GC-O) (2, 3). Various methods were developed to determine the odoractivity of the eluting compounds. Using Charm-analysis Chrisholm et al. (4), Schlich and Moio (5) and Moio et al. (6) evaluated B-damascenone, 3-methylbutyl acetate, 2phenylethanol, vanillin, butan-2,3-dione, guaiacol, 4-vinylguaiacol, ethyl cinnamate, linalool and various ethylesters, as the most potent odorants of Chardonnay and White Riesling wines. By application of the Osme technique, Miranda-Lopez et al. (7) investigated the volatile fractions of different vintages of the variety Pinot noir. High Osme values were found for 3-methylbutanol, 2-phenylethanol, 2-phenylethyl acetate, hexanoic acid, y-nonalactone and 3-(methylthio)-l-propanol. Berger (8) identified (E)6-damascenone and phenylethanol as key odorants of Chardonnay-Semillon wines, as these compounds showed the highest flavor dilution (FD)- factors in aroma extract dilution analysis (AEDA). Recently, A E D A and SHA-O yielded 41 and 45 odor active compounds for Scheurebe and Gewurztraminer wines, respectively (9). Ethyl 2-methylbutyrate, ethyl isobutyrate, 2-phenylethanol, 3-methylbutanol, 3-hydroxy-4,5-dimethyl-2(5H)furanone, 3-ethylphenol and one unknown compound, named wine lactone, showed high flavor dilution (FD)- factors (Table I) in Gewurztraminer and Scheurebe wines. 4Mercapto-4-methylpentan-2-one belongs to the most potent odorants only in the variety Scheurebe whereas cis-rose oxide was perceived only in Gewurztraminer (Table I). 4-Mercapto-4-methylpentan-2-one was identified for the first time in Sauvignon blanc wines (10). The unknown compound with coconut, woody and sweet odor quality, which has not yet been detected in wine or a food, was identified as 3a,4,5,7atetrahydro-3,6-dimethylbenzofuran-2(3H)-one (wine lactone) (77). Because of the three asymmetric centers in the molecule there exist eight different stereoisomers. To identify the stereochemistry of wine lactone syntheses for the enantiomers were developed. On the basis of enantioselective gas chromatography the stereochemistry of wine lactone was in agreement with the 3S,3aS,7aR-enantiomer (12); for this stereoisomer a low odor threshold was determined (0.00002 ng/L air):

O (3S,3aS,7aR)- 3a,4,5,7a-Tetrahydro-3,6-dimethylbenzofuran-2(3H)-one

In Chemistry of Wine Flavor; Waterhouse, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1998.

41 Table I. Results of Aroma Extract Dilution Analysis of Gewurztraminer and Scheurebe FD-Factor


Compound

Wine lactone Ethyl isobutyrate Ethyl 2-methylbutyrate 3-Methylbutanol 2-Phenylethanol 3-Ethylphenol 3-Hydroxy-4,5-dimethyl-2(5H)-furanone Ethyl 3-methylbutyrate Ethyl butyrate 2-Methylpropanol Ethyl hexanoate cis-Rose oxide 4-Mercapto-4-methylpentan-2-one Ethyl octanoate Acetic acid Linalool Butyric acid 2-/3-Methylbutyric acid 5 -Ethy 1-4-hy droxy-2-methy 1-3 (2H)-furanone Ethyl trans-cinnamate

Scheurebe

1000 100 100 100 100 100 100 10 10 10 10 10) of Potent Odorants of Scheurebe and Gewurztraminer Wines Concentration (jug/L)


Odorant

Scheurebe

4-Mercapto-4-methylpentan-2-one Ethyl octanoate Ethyl hexanoate 3-Methylbutyl acetate Ethyl isobutyrate (E)-B-Damascenone Linalool cis-Rose oxide Wine lactone Ethyl butyrate

0.40 270 280 1450 480 0.98 307 3.0 0.10 184

(667) (135) (56) (48) (32) (20) (20) (15) (10) (9)

Gewurztraminer 1 was in complete agreement with that of the original Gewurztraminer wine. The latter result indicates that 29 odorants are necessary to simulate the overall flavor of Gewurztraminer wine. Reduction of ethanol content. The significance of ethanol for the overall flavor of alcoholic beverages was already mentioned by Williams and Rosser (23) and Rothe and Schroder (24). Sensory investigations of dealcoholized Sauvignon blanc, Chardonnay Semillon and Muskat Ottonel wines were performed by Fischer et al. (25). The authors established that the dealcoholization process reduced the fruity attributes and the mouthfeeling of wines. With regard to the aroma and taste of ethanol reduced wines the influence of ethanol concentrations was investigated. To take into account the taste components for the sensory evaluation these compounds were analyzed. The determination of taste components was performed according to the general procedures described in (26). The results are combined in Table IV. The ethanol content of model C (Table IQ) to which the taste compounds, detailed in Table IV, were added, was reduced stepwise and the resulting mixtures were compared with that of the original model with 100 g ethanol/L (experiment 1, Table V). The reduction of ethanol concentration to 90 g/L (experiment 2) was not noticed by the sensory panel. A further reduction to 80 g/L and 70 g/L (experiment 3) led to a weak change in the overall flavor and taste. The assessors described the mixture with more fruity and flowery odor qualities and an increasing acidic character. A reduction to 60 g/L and 50 g/L (experiment 4) led to a significant difference to the original model. The model was characterized with strong fruity and flowery notes. The mouthfeeling was diminished and a further increase of the acidic character was observed. Experiment 5 (30 g/L) and experiment 6 ( 1 0 - 0 g/L) resulted in a drastically change of the overall flavor and taste and the samples differed strongly from the original model (experiment 1). The sensory panel described the mixtures with strong fruity, flowery, acidic and adstringent aroma notes. These results indicate that ethanol reduction changes not only the flavor profile but also the taste profile. Changes of Flavor Compounds during Wine Making of Gewurztraminer Investigations during the different stages of wine making of Gewurztrarniner wine (after pressing of grapes, after yeast fermentation, after malolactic fermentation and after maturing in high-grade steel tank) yielded a strong increase of the most potent odorants ethyl isobutyrate, ethyl butyrate, ethyl hexanoate, ethyl octanoate, 3-methylbutyl acetate, cis-rose oxide and (E)-B-damascenone during yeast fermentation (Figure 1 and 2). After malolactic fermentation only negligible changes were recognized. During further ripening (4 months) in high-grade steel tanks an increase in concentration of wine lactone, linalool and cis-rose oxide (Figure 2), and a decrease of the amount of (E)-Bdamascenone (Figure 2), 3-methylbutyl acetate, ethyl butyrate, ethyl hexanoate and ethyl octanoate (Figure 1) was observed. In various publications (27, 28) the decrease of ethyl butyrate, ethyl isobutyrate, ethyl hexanoate, ethyl octanoate and 3-methylbutyl acetate during wine maturing was mentioned. The authors supposed that during aging of wines a hydrolysis of the esters occurs. The release of glycosidic bound terpene compounds, e.g. linalool, by hydrolysis and/or enzymatic reactions during wine making was reported by Williams et al. (29), Ayran et al. (30) and Gunata et al. (57).



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Figure 1. Concentrations of ethyl butyrate, ethyl hexanoate, ethyl octanoate, ethyl isobutyrate and 3-methylbutyl acetate in different stages of wine making; 1 = after pressing of grapes, 2 = after yeast fermentation, 3 = after malolactic fermentation, 4 = after matoing in high-grade steel tanks.



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Figure 2. Concentrations of cis-rose oxide, linalool, (E)-B-damascenone and wine lactone in different stages of wine making; 1 = after pressing of grapes, 2 = after yeast fermentation, 3 = after malolactic fermentation, 4 = after maturing in high-grade steel tanks.

American Chemical Society Library 1155 16th St. N. W.

In Chemistry of Wine Waterhouse, A., et al.; Washington, D.Flavor; C. 20036 ACS Symposium Series; American Chemical Society: Washington, DC, 1998.

48 Table IV.

Concentrations and taste values (> 0.1) of compounds in Gewurz traminer and Scheurebe wines

Compound

Concentration (mg/L) Gewurztraminer

Scheurebe


Group 1: acidic, adstringent Acetic acid Tartaric acid Citric acid Malic acid Lactic acid Succinic acid Oxalic acid y-Aminobutyric acid

280 1575 875 377 1680 590 100 21

(2.3) (7.9) (2.5) (5.0) (1.2) (12.6) (2.0) (53)

255 1260 594 4790 980 480

Chemistry of Wine Flavor - ACS Publications - American Chemical

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