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Wine color measures

The wine color, measured at pH 3.6 in the absence of SO2, ranged from 5.5 to 12.3 AU with a mean of 8.24 and a coefficient of variation of 22%. This variation is quite large given that it is for wines of the same cultivar, season and appellation and the effects of SO2 and pH on wine color have been removed. [Pg.43]

Table III. Calibration statistics for all wine color measures. Table III. Calibration statistics for all wine color measures.
The method used to measure the amount of the copigment complex in a red wine, and the other measures, is referred to as the copigmentation assay. This method measures the absorbance of a sample altered by dilution together with those resulting from additions of acetaldehyde or sulfur dioxide (7, 8). The procedure differs from previous methods in that all readings are made at a standardized pH (3.6) and at 12% ethanol and makes no assumptions about the extinction coefficients, ionization or the color shifts. It also subtracts the color due to copigmentation from wine color in order to make the anthocyanin estimate. [Pg.38]

The range of the color due to copigmentation was from 1.8 to 5.7 with a mean of 3.3 and a coefficient of variation of 28%. This variation is the highest of all the color measures, considerably more variation than the anthocyanin content and this must be due to the variation between the wines in their cofactor content. This wide variation within wines of a single cultivar and region would have been underestimated if the traditional measures of color had been used. [Pg.43]

Color was determined by the method of Somers and Evans (10). All absolbance measurements were conducted using a Beckman (Irvine, CA) DU-6 spectrophotometer. Absorbance of the wine was measured at 420 and 520 nm with a 1 mm length path cuvette. Thirty yl of 20% sodium metabisulfite solution were added to another 2 ml of wine. Samples were mixed by inversion and allowed to stand at 20°C for 45 min and absorbance measured at 520 nm. One hundred yl of wine were added to 10 ml of 1 M HC1, mixed and held at 10°C for 3 hr and absorbance measured at 520 nm. All absorbance values were adjusted to a 10 mm length path and corrected for dilution. Color expressions were calculated as follows ... [Pg.338]

Probably as a resnlt of the colloidal statns of the coloring matter, there is no direct proportionality between absorption and dilution. Conseqnently, spectrophotometric measurements mnst be made on a 1 mm optical path, using nndilnted wine. These measnrements are used to calculate the values used to describe wine color (Glories, 1984). [Pg.178]

The yellow color of wine is measured at 420 nm, althongh the spectrum has no maximum for this value. The respective participation of the two preceding fractions in this color is around 50% for dry white wine, but changes a great deal when the wine is oxidized, either by chemical or enzymatic means (laccase). The phenolic fraction is then responsible for most of the color. [Pg.200]

Table 8.19. Yellow color measurements as well as 3-mercapto-hexanol (3MH) and sotolon content of wines after three years in bottle... Table 8.19. Yellow color measurements as well as 3-mercapto-hexanol (3MH) and sotolon content of wines after three years in bottle...
Several important measures of wine quality ean be evaluated by mathematical combination of absorbance values at multiple wavelengths (Bain). Wine color intensity, a measure of how dark the wine is, is ealeulated from the sum of the absorbanees at 420, 520, and 620 nm. The wine hue is a measure of the appearance of the wine and is ealeulated from the ratio of absorbance at 420 nm to absorbance at 520 nm. The Thermo Fisher Seientifie software on the Evolution Array UV/VIS spee-trophotometer ean ealeulate the intensity, hue, and the CIE L a b values, as well as the eolor dif-ferenee values (the delta values) eompared to a standard. Red wines exhibit an absorbanee between 400 and 650 nm, eentered at about 500 nm, due to the presence of anthocyanin. No such peak appears in the spectra of white wines. The CIE eolor measurements are earried out in transmittance mode. Table 5.12 shows results for the color and color difference measurements. [Pg.417]

The measurement of optic density, absorbance, is widely used to determine wine color (Volume 2, Section 6.4.5) and total phenolic compounds concentration (Volume 2, Section 6.4.1). In these works, the optic density is noted as OD, OD 420 (yellow), OD 520 (red), OD 620 (blue) or OD 280 (absorption in ultraviolet spectrum) to indicate the optic density at the indicated wavelengths. [Pg.502]

Colorimetric measurements have been applied to various analyses of red wines and model wine solutions. °° ° ° Accurate definitions of the wines have been achieved by the L (lightness) and a (redness) values, while the representation of AL against AC revealed the color differences between various wines. ° The color stability of wine and model wine solutions toward storage time and bleaching by sulfur dioxide has been extensively studied by Bakker et while the color stability of a range of anthocyanin-containing... [Pg.115]


See other pages where Wine color measures is mentioned: [Pg.2261]    [Pg.2261]    [Pg.110]    [Pg.302]    [Pg.156]    [Pg.164]    [Pg.165]    [Pg.167]    [Pg.171]    [Pg.1231]    [Pg.539]    [Pg.137]    [Pg.35]    [Pg.36]    [Pg.40]    [Pg.47]    [Pg.53]    [Pg.55]    [Pg.58]    [Pg.179]    [Pg.223]    [Pg.339]    [Pg.413]    [Pg.267]    [Pg.437]    [Pg.290]    [Pg.170]   
See also in sourсe #XX -- [ Pg.64 , Pg.65 ]




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