Chromatic Characteristics (Type-IV)
OIV-MA-AS2-07B Chromatic characteristics
Type IV method
- Definitions
The "chromatic characteristics" of a wine are its luminosity and chromaticity. Luminosity depends on transmittance and varies inversely with the intensity of color of the wine. Chromaticity depends on dominant wavelength (distinguishing the shade) and purity.
Conventionally, and for the sake of convenience, the chromatic characteristics of red and rosé wines are described by the intensity of color and shade, in keeping with the procedure adopted as the working method.
- Principle of the methods
(applicable to red and rosé wines)
A spectrophotometric method whereby chromatic characteristics are expressed conventionally, as given below:
- The intensity of color is given by the sum of absorbencies (or optical densities) using a 1 cm optical path and radiations of wavelengths 420, 520 and 620 nm.
- The shade is expressed as the ratio of absorbance at 420 nm to absorbance at 520 nm.
- Method
3.1. Apparatus
3.1.1. Spectrophotometer enabling measurements to be made between 300 and 700 nm.
3.1.2. Glass cells (matched pairs) with optical path b equal to 0.1, 0.2, 0.5, 1 and 2 cm.
3.2. Preparation of the sample
If the wine is cloudy, clarify it by centrifugation; young or sparkling wines must have the bulk of their carbon dioxide removed by agitation under vacuum.
3.3. Method
The optical path b of the glass cell used must be chosen so that the measured absorbance A, falls between 0.3 and 0.7.
Take the spectrophotometric measurements using distilled water as the reference liquid, in a cell of the same optical path b, in order to set the zero on the absorbance scale of the apparatus at the wavelengths of 420, 520 and 620 nm.
Using the appropriate optical path b, read off the absorbencies at each of these three wavelengths for the wine.
3.4. Calculations
Calculate the absorbencies for a 1 cm optical path for the three wavelengths by dividing the absorbencies found (
, 
and 
) by b, in cm.
3.5. Expression of Results
The color intensity I is conventionally given by:
and is expressed to three decimal places.
The shade N is conventionally given by:
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and is expressed to three decimal places.
Table 1
Converting absorbance into transmittance (T%)
Method: find the first decimal figure of the absorbance value in the left‑hand column (0-9) and the second decimal figure in the top row (0-9).
Take the figure at the intersection of column and row: to find the transmittance, divide the figure by 10 if absorbance is less than 1, by 100 if between 1 and 2 and by 1000 if between 2 and 3.
Note: The figure in the top right hand corner of each box enables the third decimal figure of the absorbance to be determined by interpolation.
|
0 |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
|
|
23 |
22 |
22 |
21 |
21 |
20 |
20 |
19 |
19 |
19 |
|
|
0 |
1000 |
977 |
955 |
933 |
912 |
891 |
871 |
851 |
932 |
813 |
|
18 |
18 |
17 |
17 |
16 |
16 |
16 |
15 |
15 |
15 |
|
|
1 |
794 |
776 |
759 |
741 |
724 |
708 |
692 |
676 |
661 |
646 |
|
14 |
14 |
14 |
14 |
13 |
13 |
13 |
12 |
12 |
12 |
|
|
2 |
631 |
617 |
603 |
589 |
575 |
562 |
549 |
537 |
525 |
513 |
|
11 |
11 |
11 |
11 |
10 |
9 |
9 |
10 |
10 |
9 |
|
|
3 |
501 |
490 |
479 |
468 |
457 |
447 |
436 |
427 |
417 |
407 |
|
9 |
9 |
9 |
8 |
8 |
8 |
8 |
7 |
8 |
||
|
4 |
398 |
389 |
380 |
371 |
363 |
355 |
347 |
339 |
331 |
324 |
|
7 |
7 |
7 |
6 |
7 |
6 |
6 |
6 |
6 |
||
|
5 |
316 |
309 71 |
302 |
295 |
288 |
282 |
275 |
269 |
263 |
257 |
|
6 |
5 |
6 |
5 |
5 |
5 |
5 |
5 |
5 |
5 |
|
|
6 |
251 |
245 |
240 |
234 |
229 |
224 |
219 |
214 |
209 |
204 |
|
4 |
5 |
4 |
4 |
4 |
4 |
4 |
4 |
4 |
||
|
7 |
199 |
195 |
190 |
186 |
182 |
178 |
174 |
170 |
166 |
162 |
|
3 |
4 |
3 |
4 |
4 |
3 |
3 |
3 |
3 |
3 |
|
|
8 |
158 |
155 |
151 |
148 |
144 |
141 |
138 |
135 |
132 |
129 |
|
3 |
3 |
3 |
2 |
3 |
2 |
3 |
2 |
3 |
2 |
|
|
9 |
126 |
123 |
120 |
117 |
115 |
112 |
110 |
107 |
105 |
102 |
Example:
|
Absorbance |
0.47 |
1.47 |
2.47 |
3.47 |
|
T% |
33.9% |
3.4% |
0.3% |
0% |
Transmittance (T%) is expressed to the nearest 0.1%.
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Figure 1: Chromaticity diagram, showing the locus of all colors of the spectrum |
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Figure 2: Chromaticity diagram for pure red wines and brick red wines |
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Figure 3: Chromaticity diagram for pure red wines and brick red wine |
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Figure 4:Chromaticity diagram for pure red wines and purple wines |
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Figure 5:Chromaticity diagram for pure red wines and purple red wines |
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Figure 6: Chromaticity diagram for brick red wines and purple red wines |
Bibliography:
- BOUTARIC A., FERRE L., ROY M., Ann. Fals. Fraudes, 1937, 30, 196.
- SUDRAUD P., Ann. Technol. Agric., 1958, no 2, 203.
- MARECA CORTES J., Atti Acc. Vite Vino, 1964, 16.
- GLORIES Y., Conn. vigne et Vin, 1984, 18, no 3, 195.