ORIGINAL ARTICLE. Anthocyanins and Color Variables of Bulgarian Aged Red Wines

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1 JOURNAL OF FOOD COMPOSITION AND ANALYSIS (2002) 15, doi: /jfca Available online at on ORIGINAL ARTICLE Anthocyanins and Color Variables of Bulgarian Aged Red Wines Silvia Tsanova-Savova*, Stefan Dimovw, and Fany Ribarova*,1 *Department of Food Chemistry, National Center of Hygiene, Medical Ecology and Nutrition, 15 blvd. D. Nestorov, Sofia 1431, Bulgaria; and wnational Wine Research and Control Institute, 134 blvd. Tzar Boris III, Sofia 1618, Bulgaria Received September 10, 2001, and in revised form March 28, 2002 The main sensory parameter for the quality of red wines is their color. Twenty-one Bulgarian red wines from five different grape varieties were analyzed (Cabernet- Sauvignon, Merlot, Melnik, Mavrud and Gamza) in order to determine color variables and evaluate pigment matter. The results show highest proportion of red color in Cabernet-Sauvignon (da% = %), followed by Merlot, Mavrud, Melnik and Gamza (da% = %). Total anthocyanins reach maximal level for Cabernet-Sauvignon-1998 (274 mg/l) and minimal value for Melnik-1998 (22 mg/l), and correlate with da% value. The age index, polymeric anthocyanins/ monomeric anthocyanins, increases from 32.6% for Cabernet-Sauvignon-1998 to 87.5% for Gamza-1994 as the polymeric pigment forms have displaced the monomeric anthocyanins during aging process. r 2002 Elsevier Science Ltd. All rights reserved. Key Words: red wine; color variables; anthocyanins. INTRODUCTION Bulgarian diet reserves a special place for consumption of red wines. Aged red wines from local origin are the most popular. The first sensory parameter attracting consumers attention is the color of the wine, for it is considered a major feature for assessment of red wines quality. The phenolic compoundsfmainly anthocyanins and their polymeric products Fare responsible for the red color of wine. During maturation, aging and storage red wines change their sensory variables. For instance, the color of red wines loses its vividness and brightness. This change is mostly due to polymerization processes with the involvement of free monomeric anthocyanins (Glories, 1984a, b). After 1 year of storage free monomeric anthocyanins are half reduced in comparison with initial concentration, and in older aged wines they have almost faded away (Somers, 1971). The color density and hue are substantially dependent on ph and the presence of sulfur dioxide (Brouillard et al., 1978). The intensity of red color decreases with 1 To whom correspondence and reprint requests should be addressed. Tel: ; f.ribarova@nchmen.government.bg /02/ $35.00/0 r 2002 Elsevier Science Ltd. All rights reserved.

2 648 TSANOVA-SAVOVA ET AL. increasing ph value. Adding SO 2 to wine results in fast abolishment due to the formation of colorless anthocyanin sulfonate complex (von Elbe and Schwartz, 1996). The polymeric anthocyanins are generated in the processes of direct condensation and co-pigmentation (Asen et al., 1972; Santos-Buelga et al., 1995; Liao et al., 1992). Acetaldehyde, tannins and other phenolic compounds (e.g., catechins, proanthocyanidins) are involved in processes of condensation with anthocyanins, leading to the formation of polymeric forms (Timberlake and Bridle, 1976). These newly formed pigments are chemically more stable than the free monomeric forms, and they stabilize the wine color changing it to a more brick red hue (Mateus and de Freitas, 2001). The proportion of yellow color of aged wine is simultaneously enhanced with the increase of polymerization and oxidation degree. Another important factor that affects the color of wine is the self-association of anthocyanins, resulting in an overproportional increase of color intensity. A good knowledge of parameters characterizing the color spectrum of red wines helps the experts in assessing wine quality. The aim of this study is to assess color variables and anthocyanins composition in the most popular and widely consumed Bulgarian red wines. Sample MATERIALS AND METHODS Twenty-one Bulgarian red wines, popular on the Bulgarian market, were studied; they are listed in Table 1. The wines were 2 7 years aged. Some of the selected wines are available on the international market as well. Glories Color Variables Method A direct measurement of wine absorbance to 420, and 620 nm was carried out in a Specord UV/VIS Carl Zeiss Jena Spectrophotometer, with a 2 mm cell. The following variables were then calculated: color intensity (IC), wine color tint (T), proportion of red color (%Rd), proportion of blue color (%Bl), proportion of yellow color (%Ye), and proportion of red color produced by the flavylium cations of the free and bound anthocyanins (da%) (Glories, 1984a). Spectrophotometric Method of Somers and Evans The method was used for determination of the following parameters (Somers and Evans, 1977): degree of coloration of anthocyanins (a); degree of coloration of anthocyanins found after abolishing SO 2 effect upon wine color (a 0 ); total anthocyanins (mg/l); colored anthocyanins (mg/l); colorless anthocyanins (mg/l); total phenolics (mg/l) as equivalent gallic acid. For calculation, the equation proposed by Bakker was used: y = 29.5x+210, where y is the total phenolics in mg/l, and x is the total phenolics in absorbance units A HCl (Bakker et al., 1986). Features of Chemical Age Age index (i)fthe spectral ratio:polymeric/monomeric anthocyanins. Age index (i 0 )Fthe spectral ratio:polymeric/total anthocyanins. All parameters are calculated according to the formulas in methods cited above.

3 TABLE 1 Color variables of Bulgarian red wines. Method of Glories Wine no. Wine, region Vintage IC T %Ye %Rd %Bl da% year 1 Gamza, Lyaskovetz Gamza, Novo Selo Gamza, Suhindol, Reserve Gamza, Suhindol Gamza, Sofia, Cherpan region Mavrud, Asenovgrad Mavrud, Peroushtitsa Mavrud, Asenovgrad Mavrud, Peroushtitsa, Reserve Mavrud, Asenovgrad Melnik, Harsovo Melnik, Damianitza, Reserve 13 Melnik, Harsovo Melnik, Damianitza Melnik, Damianitza Merlot, Stambolovo, Reserve Merlot, Suhindol, Reserve Merlot, Targoviste, Reserve Cabernet-Sauvignon, Suhindol, Reserve Cabernet-Sauvignon, Svistov, Reserve Cabernet-Sauvignon, Targoviste, Reserve ANTHOCYANINS AND COLOR VARIABLES OF BULGARIAN RED WINES 649

4 650 TSANOVA-SAVOVA ET AL. RESULTS AND DISCUSSION The results for color variables of analyzed samples are presented in Table 1. Low color tint values, not exceeding T=0.6, are characteristic for young red wines (Glories, 1984a, b). The results of the studied wines show that the color tint values (T) are relatively high in almost all samples. Only wine no. 21 (Cabernet Sauvignon- Targoviste-1998) has a low color tint value (T = 0.6). The results presented in Table 1 evidence that sample no. 21 has also the lowest yellow color proportion (34.8%). All other wines have TX0.7, and the %Ye is equal to or greater than 39%. The optimal ratio between the components of red wine color is considered to be %Ye = 35%, %Rd = 55%, and %Bl = 10% (Glories, 1984b). In this aspect only Cabernet-Sauvignon wine no. 21 matches the set proportion. The difference between the proportion of the red %Rd and yellow %Ye is greater than 10% in three wine samples: nos. 18, 19, and 21. The yellow color proportion exceeds that of the red color in Gamza and Melnik wines (nos. 1, 2 and 14). These wines have strongly altered chromatic characteristics shifted to the yellow tones of the spectrum. Values of da% below 40% show that the color of the red wine is dark and atypical (Glories, 1984b). It can be seen that the parameter da% has the lowest values 34.4, 38 and 32.3%, respectively, for wine nos. 1, 2, and 14. As shown above, these wines have exactly the highest yellow color proportion. Gamza wines show da% values within the range %, followed by Melnik wines (da% = %), Mavrud (da% = %), Merlot (da% = %) and Cabernet- Sauvignon (da% = %). Cabernet Sauvignon wines nos. 19 and 21, Merlot no. 18 and Mavrud no. 8 have da% values equal to or greater than 50%Fan indicator that the wine has strongly expressed red color (Glories, 1984b). These results reveal that wines from the typical Bulgarian grape varieties Melnik and Gamza have less expressed red color. Mavrud wines with their chromatic characteristic are close to wines from internationally recognized grape varieties Cabernet-Sauvignon and Merlot. absorbance, a.e. CH 3 CHO wine SO 2 HCl wavenumber, cm -1 FIGURE 1. Spectra of wine no. 2 (Gamza-1995). A wine is an absorbance maximum of wine sample at nm. A SO 2 is an absorbance maximum of wine after addition of SO 2. A CH 3CHO is an absorbance maximum of wine after addition of acetaldehyde. A HCl is an absorbance maximum of wine sample diluted (1+100) in 1 m HCl.

5 ANTHOCYANINS AND COLOR VARIABLES OF BULGARIAN RED WINES 651 CH 3 CHO wine absorbance, a.u. SO A 2 HCl wavenumber, cm -1 FIGURE 2. Spectra of wine no. 21 (Cabernet-Sauvignon-1998). A wine is an absorbance maximum of wine sample at nm. A SO 2 is an absorbance maximum of wine after addition of SO 2. A CH 3 CHO is an absorbance maximum of wine after addition of acetaldehyde. A HCl is an absorbance maximum of wine sample diluted (1+100) in 1 m HCl. The effect of treatment of wines with sulfur dioxide and acetaldehyde can be observed in Figures 1 and 2. Wine nos. 2 and 21 were selected. These two wines show the most different spectra. The polymerization process in wine no. 2 (Gamza-1995) has advanced to a very high degree. The spectrum of native wine has an undefined absorbance maximum at nm, showing lack of free anthocyanins. Therefore, both the effects of sulfur dioxide and acetaldehyde are negligible (Fig. 1). When the spectrum of the native wine has a clearly defined maximum at nm, the abolishing effect of sulfur dioxide is very strong. After adding acetaldehyde to the sample the red color gets enhanced because of release of additional amount of free anthocyanins (Fig. 2). The results for total, monomeric, and polymeric anthocyanins, as well as the results for total phenolics are presented in Table 2. The polymerization processes in wine nos. 2 and 16 were extremely advanced, so it was not possible to calculate parameters a(%) and a 0 (%), and anthocyanins composition. The color of these wines was completely altered to yellow-brownish tone. The parameter a(%) represents the percentage of free colored anthocyanins that can be decolorized by sulfur dioxide (Somers and Evans, 1977). The results (Table 2) show that wine nos. 3, 4, and 14 have high a(%) values. At the same time, these samples reveal the lowest values of total anthocyanins, 42, 32 and 22 mg/l, respectively. The low amount of anthocyanins in the listed samples suggests the formation of insufficient amounts of colored polymeric forms between anthocyanins and tannins, which stabilize the pigmenting matter (Glories, 1984a). The small values of the difference between a 0 (%) and a(%) show that wines do not contain high amounts of free SO 2 (Somers and Evans, 1977). The difference a 0 % a% is minimal for wine no. 1FGamza, 1995 (0%) and maximal for wine no. 14FMelnik, 1998 (23%). It can be seen that this difference is higher in younger red wines.

6 652 TSANOVA-SAVOVA ET AL. TABLE 2 Degree of coloration, anthocyanins content, total phenolics, chemical age in 25 analyzed samples. Spectrophotometric method of Somers and Evans Wine no. a% a 0 % Total anthocyanins (mg/l) Colored anthocyanins (mg/l) Colorless anthocyanins (mg/l) Total phenolics (mg/l) i 0 % i% The smallest values of total anthocyanins are characteristic for Gamza (32 51 mg/l) and Melnik (22 88 mg/l) wines. The wines Mavrud, Merlot and Cabernet- Sauvignon have total anthocyanins exceeding 100 mg/l with the exception of wine no. 9 (98 mg/l). It is also seen that the values of colored anthocyanins are the lowest in Gamza (4 17 mg/l) and Melnik (8 16 mg/l) and comparatively higher in Mavrud (15 31 mg/l), Merlot (20 24 mg/l) and Cabernet-Sauvignon (18 46 mg/l) and correlate directly with da% levels. Gamza and Melnik wines, due to their low total and colored anthocyanins content, have weakly expressed red color while Cabernet- Sauvignon, Merlot and Mavrud, in conformity with their high anthocyanins content, have vivid red color. Our attention is drawn to the results for wines from the typical Bulgarian grapes of the Mavrud variety, which, by anthocyanins content, are equal to Cabernet-Sauvignon and Merlot wines. The data for total phenolic content show that almost all wines analyzed hold a high phenolic load levelfa requirement set for selecting wines for maturation (Somers, 1971). Relatively low phenolic content was obtained for Gamza wines, which shows that they are not quite appropriate for maturation. For young red wines the age indexes i% and i 0 % have low values (Somers and Evans, 1977). During aging and storage period, the age indexes levels tend to increase significantly. In this study, a maximal value for age index i% and i 0 % was reached for wine nos. 1 and 16, according to their distant vintage yearf1994. In Figure 3, the reverse relationship between index i% chemical age index of wine and da% is presented. It is clearly shown that da%fproportion of red color produced by the flavylium cations of free and bound anthocyaninsfdecreases, with progress of the polymerization process during aging and storage of wines.

7 ANTHOCYANINS AND COLOR VARIABLES OF BULGARIAN RED WINES da% i % % wine FIGURE 3. Reverse relationship between da% defined by method of Glories (1984a, b) and i% defined by method of Somers and Evans (1977). da%fproportion of red color produced by flavylium cations of the free and bound anthocyanins; i%fage index, spectral ratio: polymeric/monomeric anthocyanins. In the present study, the results for wine color and anthocyanins composition in typical Bulgarian red Gamza, Melnik, and Mavrud wines were compared with data for red wines, produced in Bulgaria from international grape varieties Cabernet- Sauvignon and Merlot. For Gamza and Melnik, a considerable alteration of wine color and pigment matter was observed, namely a significant increase of proportion of yellow color versus the proportion of red color. These wines were with relatively low content of different forms of anthocyanins and high proportion of the polymeric forms of pigment matter. Mavrud, Merlot and Cabernet-Sauvignon wines have characteristic, well-expressed red color. In these three wine brands, the content of different anthocyanins forms is similar, not depending on the vintage year and different maturation time. CONCLUSION The present study is a snapshot of chromatic characteristic of the most popular Bulgarian aged red wines. The results of this work show that the typical Bulgarian red Mavrud wine is very suitable for aging because of its high phenolic content and stable pigment matter. In this aspect, the quality of Mavrud wines are comparable with world famous wines produced from grape varieties Cabernet-Sauvignon and Merlot. REFERENCES Asen, S., Stewart R. N., and Norris K. H. (1972). Co-pigmentation of anthocyanins in plant tissues and its effect on color. Phytochemistry 11, Bakker, J., Bridel P., Timberlake, C. F., and Arnold, G. M. (1986). The colors, pigment and phenol contents of young port wines: effects of cultivar, season and site. Vitis 25,

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