anthocyanins and color variables of bulgarian

7/31/2019 Anthocyanins and Color Variables of Bulgarian

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increasing pH value. Adding SO2 to wine results in fast abolishment due to theformation of colorless anthocyaninsulfonate complex (von Elbe and Schwartz,1996). The polymeric anthocyanins are generated in the processes of directcondensation 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 withanthocyanins, leading to the formation of polymeric forms (Timberlake and Bridle,1976). These newly formed pigments are chemically more stable than the freemonomeric forms, and they stabilize the wine color changing it to a more brick redhue (Mateus and de Freitas, 2001). The proportion of yellow color of aged wine issimultaneously enhanced with the increase of polymerization and oxidation degree.Another important factor that affects the color of wine is the self-association ofanthocyanins, resulting in an overproportional increase of color intensity.

A good knowledge of parameters characterizing the color spectrum of red wineshelps the experts in assessing wine quality. The aim of this study is to assess colorvariables and anthocyanins composition in the most popular and widely consumedBulgarian red wines.

MATERIALS AND METHODS

Sample

Twenty-one Bulgarian red wines, popular on the Bulgarian market, were studied;they are listed in Table 1. The wines were 27 years aged. Some of the selected winesare available on the international market as well.

Glories Color Variables Method

A direct measurement of wine absorbance to 420, 520 and 620 nm was carried out ina Specord UV/VIS Carl Zeiss Jena Spectrophotometer, with a 2 mm cell. Thefollowing variables were then calculated: color intensity (IC), wine color tint (T),proportion of red color (%Rd), proportion of blue color (%Bl), proportion ofyellow color (%Ye), and proportion of red color produced by the flavylium cationsof 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 andEvans, 1977): degree of coloration of anthocyanins (a); degree of coloration ofanthocyanins found after abolishing SO2 effect upon wine color (a

0); total antho-cyanins (mg/L); colored anthocyanins (mg/L); colorless anthocyanins (mg/L); totalphenolics (mg/L) as equivalent gallic acid. For calculation, the equation proposed byBakker was used: y = 29.5x+210, where y is the total phenolics in mg/L, and x is thetotal phenolics in absorbance units AHCl280 4

(Bakker et al., 1986).

Features of Chemical Age

Age index (i)Fthe spectral ratio:polymeric/monomeric anthocyanins.

Age index (i0

)F

the spectral ratio:polymeric/total anthocyanins.

All parameters are calculated according to the formulas in methods cited above.

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TABLE 1

Color variables of Bulgarian red wines. Method of Glories

Wine no. Wine, region Vintageyear

IC T %Ye

1 Gamza, Lyaskovetz 1994 3.7 1.1 50.02 Gamza, Novo Selo 1995 6.1 1.0 45.53 Gamza, Suhindol, Reserve 1998 5.3 0.8 39.6 4 Gamza, Suhindol 1999 5.9 0.9 41.55 Gamza, Sofia, Cherpan region 1999 4.7 0.9 41.9 6 Mavrud, Asenovgrad 1994 6.9 0.9 42.37 Mavrud, Peroushtitsa 1995 5.8 0.9 43.18 Mavrud, Asenovgrad 1996 5.8 0.9 43.1

9 Mavrud, Peroushtitsa, Reserve 1996 5.8 0.9 43.1 10 Mavrud, Asenovgrad 1997 6.0 0.9 41.711 Melnik, Harsovo 1995 4.3 1.0 45.312 Melnik, Damianitza,

Reserve1996 4.5 0.9 43.3

13 Melnik, Harsovo 1997 4.4 0.4 42.514 Melnik, Damianitza 1998 3.7 1.1 47.915 Melnik, Damianitza 1999 4.2 1.0 41.016 Merlot, Stambolovo, Reserve 1994 6.5 1.0 45.0 17 Merlot, Suhindol, Reserve 1996 4.4 0.9 41.4 18 Merlot, Targoviste, Reserve 1998 4.9 0.7 39.0 19 Cabernet-Sauvignon, Suhindol, Reserve 1996 4.7 0.8 40.0 20 Cabernet-Sauvignon, Svistov, Reserve 1996 5.0 0.9 43.4 21 Cabernet-Sauvignon, Targoviste, Reserve 1998 6.9 0.6 34.8


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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 1evidence that sample no. 21 has also the lowest yellow color proportion (34.8%). Allother 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 onlyCabernet-Sauvignon wine no. 21 matches the set proportion. The difference betweenthe proportion of the red %Rd and yellow %Ye is greater than 10% in three winesamples: nos. 18, 19, and 21. The yellow color proportion exceeds that of the redcolor in Gamza and Melnik wines (nos. 1, 2 and 14). These wines have stronglyaltered 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 andatypical (Glories, 1984b). It can be seen that the parameter dA% has the lowestvalues 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 showdA% values within the range 34.448.1%, followed by Melnik wines (dA% = 32.345%), Mavrud (dA% = 40.650%), Merlot (dA% = 41.755.8%) and Cabernet-Sauvignon (dA% = 46.959.2%). Cabernet Sauvignon wines nos. 19 and 21, Merlotno. 18 and Mavrud no. 8 have dA% values equal to or greater than 50%Fanindicator that the wine has strongly expressed red color (Glories, 1984b). Theseresults reveal that wines from the typical Bulgarian grape varieties Melnik andGamza have less expressed red color. Mavrud wines with their chromatic

characteristic are close to wines from internationally recognized grape varietiesCabernet-Sauvignon and Merlot.

26 24 22 20 18 16

A520

HCl

A520

SO2

A520

A520

CH3CHO

wavenumber, cm-1

absorbance,a.e.

wine

FIGURE 1. Spectra of wine no. 2 (Gamza-1995). Awine520 is an absorbance maximum of wine sample at 520

nm. ASO2520 is an absorbance maximum of wine after addition of SO2. ACH3CHO

520 is an absorbance maximumof wine after addition of acetaldehyde. AHCl520 is an absorbance maximum of wine sample diluted (1+100) in1mHCl.



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The effect of treatment of wines with sulfur dioxide and acetaldehyde can beobserved in Figures 1 and 2. Wine nos. 2 and 21 were selected. These two wines showthe 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 undefinedabsorbance maximum at 520 nm, showing lack of free anthocyanins. Therefore, boththe effects of sulfur dioxide and acetaldehyde are negligible (Fig. 1). When thespectrum of the native wine has a clearly defined maximum at 520 nm, the abolishingeffect of sulfur dioxide is very strong. After adding acetaldehyde to the sample thered 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 theresults for total phenolics are presented in Table 2.

The polymerization processes in wine nos. 2 and 16 were extremely advanced, so itwas not possible to calculate parameters a(%) and a0(%), and anthocyanins

composition. The color of these wines was completely altered to yellow-brownishtone.

The parameter a(%) represents the percentage of free colored anthocyanins thatcan 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, thesesamples reveal the lowest values of total anthocyanins, 42, 32 and 22 mg/L,respectively. The low amount of anthocyanins in the listed samples suggests theformation of insufficient amounts of colored polymeric forms between anthocyaninsand tannins, which stabilize the pigmenting matter (Glories, 1984a).

The small values of the difference between a0(%) and a(%) show that wines do notcontain high amounts of free SO2 (Somers and Evans, 1977). The difference

a

0

%a% is minimal for wine no. 1F

Gamza, 1995 (0%) and maximal for wine no.14FMelnik, 1998 (23%). It can be seen that this difference is higher in younger redwines.

SO2

CH3CHO

26 24 22 20 18 16

A520

HCl

A520

wine

A520

A520

wavenumber, cm-1

absorbance,a.u.

FIGURE 2. Spectra of wine no. 21 (Cabernet-Sauvignon-1998). Awine520 is an absorbance maximum ofwine sample at 520 nm. A

SO2520 is an absorbance maximum of wine after addition of SO2. A

CH3CHO

520 is anabsorbance maximum of wine after addition of acetaldehyde. AHCl520 is an absorbance maximum of winesample diluted (1+100) in 1mHCl.

ANTHOCYANINS AND COLOR VARIABLES OF BULGARIAN RED WINES 651


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The smallest values of total anthocyanins are characteristic for Gamza (3251mg/L) and Melnik (2288 mg/L) wines. The wines Mavrud, Merlot and Cabernet-Sauvignon have total anthocyanins exceeding 100 mg/L with the exception of wineno. 9 (98 mg/L). It is also seen that the values of colored anthocyanins are the lowestin Gamza (417 mg/L) and Melnik (816 mg/L) and comparatively higher in Mavrud(1531 mg/L), Merlot (2024 mg/L) and Cabernet-Sauvignon (1846 mg/L) andcorrelate directly with dA% levels. Gamza and Melnik wines, due to their low totaland 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 equalto Cabernet-Sauvignon and Merlot wines.

The data for total phenolic content show that almost all wines analyzed hold ahigh 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 i0% have low values (Somers andEvans, 1977). During aging and storage period, the age indexes levels tend toincrease significantly. In this study, a maximal value for age index i% and i0% wasreached 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%F

proportion of red colorproduced by the flavylium cations of free and bound anthocyaninsFdecreases, withprogress of the polymerization process during aging and storage of wines.

TABLE 2

Degree of coloration, anthocyanins content, total phenolics, chemical age in 25 analyzed samples.Spectrophotometric method of Somers and Evans

Wineno.a

%a0

% Totalanthocyanins(mg/L)

Coloredanthocyanins(mg/L)

Colorlessanthocyanins(mg/L)

Totalphenolics(mg/L)

i

0

% i%

1 11.9 11.9 33.6 4 29.6 921 35 87.52 1463 55.7 86.53 40.5 50.0 42 17 25 1224.8 34.7 62.54 50.0 65.6 32 16 16 1404.8 40.6 66.15 29.4 35.3 51 15 36 1404.8 29.7 62.56 21.4 25.7 140 31 109 1702.7 18.3 50.77 17.0 30.0 100 17 83 1732.2 14.9 55.28 13.8 26.5 188.8 26 162.8 1640.8 13.2 39.09 15.2 32.7 98 15 83 1879.7 23.5 54.3

10 11.8 16.5 170 28 142 1850.2 13.5 51.711 18.9 24.3 76 16 60 1372.3 23.0 60.912 13.6 20.5 88 12 76 1611.3 22.5 64.013 17.9 28.2 78 14 64 1640.8 21.5 54.214 36.4 59.1 22 8 14 1640.8 38.0 63.915 27.0 39.2 40.8 11 29.8 15552.3 29.7 60.016 1879.4 53.2 74.117 15.2 24.2 132 20 112 1578.8 14 42.918 13.6 21.6 176 24 152 1669.8 12.6 42.419 12.8 25.7 156 20 136 1699.8 13.9 41.220 16.1 26.8 112 18 94 1820.7 18.5 50.021 16.8 24.8 274 46 228 1699.7 9.3 32.6



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In the present study, the results for wine color and anthocyanins composition intypical Bulgarian red Gamza, Melnik, and Mavrud wines were compared with datafor red wines, produced in Bulgaria from international grape varieties Cabernet-Sauvignon and Merlot. For Gamza and Melnik, a considerable alteration of winecolor and pigment matter was observed, namely a significant increase of proportionof yellow color versus the proportion of red color. These wines were with relativelylow content of different forms of anthocyanins and high proportion of the polymericforms of pigment matter. Mavrud, Merlot and Cabernet-Sauvignon wines havecharacteristic, well-expressed red color. In these three wine brands, the content ofdifferent anthocyanins forms is similar, not depending on the vintage year anddifferent maturation time.

CONCLUSION

The present study is a snapshot of chromatic characteristic of the most popularBulgarian aged red wines. The results of this work show that the typical Bulgarian redMavrud wine is very suitable for aging because of its high phenolic content and stablepigment matter. In this aspect, the quality of Mavrud wines are comparable withworld 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, 11391144.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, 4052.

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

winek

%

dA%

i%

FIGURE 3. Reverse relationship between dA% defined by method of Glories (1984a, b) and i% definedby method ofSomers and Evans (1977). dA%Fproportion of red color produced by flavylium cations ofthe free and bound anthocyanins; i%Fage index, spectral ratio: polymeric/monomeric anthocyanins.

ANTHOCYANINS AND COLOR VARIABLES OF BULGARIAN RED WINES 653


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Brouillard, R., Delaporte, B., and Dubois, J.-E. (1978). Chemistry of anthocyanin pigments. 3. Relaxationamplitudes in pH jump experiments. J. Am. Chem. Soc. 100, 62026205.

Glories, Y. (1984a). La couleur des vins rouges. Mesure, origine et interpre tation. Partie I. Connaiss. VigneVin. 18, 195217.

Glories, Y. (1984b). La couleur des vins rouges. Mesure, origine et interpre tation. Partie II. Connaiss.

Vigne Vin. 18, 253271.Liao, H., Cai, Y., and Haslam, E. (1992). Polyphenols interactions. Anthocyanins: copigmentation and

color changes in red wines. J. Sci. Food Agric. 59, 299305.

Mateus, N. and De Freitas, V. (2001). Evolution and stability of anthocyanin-derived pigments duringport wine aging. J. Agric. Food Chem. 49, 52175222.

Santos-Buelga, C., Bravo-Haro, S., and Rivas-Gonzalo, J. C. (1995). Interactions between catechin andmalvidin-3-monoglucoside in model solutions. Z. Lebensm. Unters. Forsch. 1, 269274.

Somers, T. C. (1971). The polymeric nature of wine pigments. Phytochemistry 10, 21752186.

Somers, T. C. and Evans, M. E. (1979). Grape pigment phenomena: interpretation of major losses duringvinification. J. Sci. Food. Agric. 30, 623633.

Somers, T. C. and Evans, M. E. (1977). Spectral evaluation of young red wine, anthocyanin equilibrium,total phenolic, free and molecular SO2. J. Sci. Food. Agric. 28, 279287.

Timberlake, C. F. and Bridle, P. (1976) Interpretations between anthocyanins, phenolic compounds andacetaldehyde and their significance in red wines. Am. J. Enol. Vitic. 27, 105.

von Elbe, J. H. and Schwartz, S. J. (1996). In Colorants in Food Chemistry (R. Owen and E. Fennema,Eds.), pp. 685691. Marcel Dekker, Inc., New York, Basel, Hong Kong.


anthocyanins and color variables of bulgarian

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