Commission Regulation (EEC) No 000/90 (repealed)Show full title

40. CHROMATIC PROPERTIES U.K.

1. WINES AND MUSTS U.K.

1.1. Definitions U.K.

The chromatic properties of a wine are defined as its luminosity and its chromaticity.

The luminosity is represented by the transmittance and it varies inversely with the colour intensity of the wine.

The chromaticity is represented by the dominant wavelength (which characterizes the tint) an the purity of the colour.

By convention, and for reasons of convenience, the chromatic properties of red and rosé wines are given as the colour intensity and the tint, in keeping with a procedure adopted as the usual method.

1.2. Principle of the methods U.K.

1.2.1. Reference method U.K.

This is a spectrophotometric method which makes it possible to determine the tristimulus values and three chromaticity coordinates necessary for the specification of the colour as laid down by the International Commission on Illumination (CIE).

1.2.2. Usual method (applicable to red and rosé wines) U.K.

This is a spectrophotometric method by which the chromatic properties are expressed by convention as follows:

The colour intensity is given by the sum of the absorbences at wavelengths af 420, 520 and 620 nm for radiation traversing a 1 cm optical path in the sample.

The tint is expressed by the ratio of the absorbences at 420 nm and 520 nm.

1.3. Reference method U.K.

1.3.1. Apparatus U.K.

1.3.1.1. Spectrophotometer enabling measurements to be made between 300 and 700 nm. U.K.

1.3.1.2. Glass cells in pairs, with optical paths, b, equal to 0,1, 0,2, 0,5, 1,2 and 4 cm. U.K.

1.3.2. Procedure U.K.

1.3.2.1. Preparation of the sample U.K.

Cloudy wine must be clarified by centrifugation. The bulk of the carbon dioxide in young and sparkling wines must be removed by shaking under vacuum.

1.3.2.2. Measurements U.K.

The optical path, b, in the glass cell should be so chosen that the measured absorbence lies between 0,3 and 0,7.

The following guidance is given for the appropriate choice of the optical path: use cells of 2 (or 4) cm optical path for white wines, with 1 cm for rosé wines and with 0,1 cm (or 0,2 cm) for red wines.

The spectrophotometric measurements should be made using distilled water, in a cell with the same optical path, b, as reference liquid to establish the zero of the absorbence scale at wavelengths 445, 495, 550 and 625 nm.

The four corresponding absorbences for the wine should then be measured to three decimal places for the optical path, b. Let these be A ₄₄₅, A ₄₉₅, A ₅₅₀, A ₆₂₅.

1.3.3. Calculations U.K.

Together with Table I, use these values of the absorbences for the optical path, b cm to obtain the corresponding transmittances (T%). Let these be T ₄₄₅, T ₄₉₅, T ₅₅₀ and T ₆₂₅.

• Calculate the tristimulus values X, Y and Z expressed as decimal fractions from the following expressions:

  X = 0,42 T ₆₂₅ + 0,35 T ₅₅₀ + 0,21 T ₄₄₅

  Y = 0,20 T ₆₂₅ + 0,63 T ₅₅₀ + 0,17 T ₄₉₅

  Z = 0,24 T ₄₉₅ + 0,94 T ₄₄₅

• Calculate the chromaticity coordinates x and y from:

1.3.4. Expression of results U.K.

1.3.4.1. The relative luminosity is given by the value of Y expressed as a percentage. (For complete darkness, Y = 0 %; for colourless liquids, Y = 100 %.) U.K.

1.3.4.2. The chromaticity is expressed by the dominant wavelength and the purity. U.K.

The determination of these two quantities makes use of the chromaticity diagram bounded by the spectral locus as given in Figure 1. The point O plotted in this diagram represents the white light source used and has the coordinates of a standard source, C, x_o = 0,3101 and y_o = 0,3163, representing daylight of average brightness.

• Dominant wavelength

  Plot the point C with coordinates x, y on the chromaticity diagram.

  If C is outside the triangle AOB, draw the straight line joining O to C and extend it to cut the spectral locus at the point S, which corresponds to the dominant wavelength.

  If C is inside the triangle AOB, draw the straight line from C to O and extend it to intersect the spectral locus at a point corresponding to the wavelength of the colour complementary to that of the wine. This wavelength is denoted by its value followed by the letter C.

• Purity

  If the point C is outside the triangle AOB, the purity is given as a percentage by the ratio:

  

  If the point C is inside the triangle AOB, the purity is given as a percentage by the ratio:

  

  (1)

  where P is the point where the straight line OC cuts the line of purples (line AB).

  Purity is also given directly by chromaticity diagrams from the known values of x and y (Figures 2, 3, 4, 5 and 6).

1.3.4.3. Results U.K.

The colour of a wine is completely defined by its luminosity, its chromaticity (expressed by the dominant wavelength) and its purity.

These should be indicated in the analysis report with the value of the optical path in which the measurements were made.

F1 1.4. Usual method U.K.

F1 1.4.1. Apparatus U.K.

F1 1.4.1.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . U.K.

F1 1.4.1.2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . U.K.

F1 1.4.2. Preliminary preparation of the sample U.K.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

F1 1.4.3. Procedure U.K.

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F1 1.4.4. Expression of results U.K.

F1 1.4.4.1. Calculations U.K.

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Textual Amendments

F1 Deleted by Commission Regulation (EC) No 1622/2000 of 24 July 2000 laying down certain detailed rules for implementing Regulation (EC) No 1493/1999 on the common organisation of the market in wine and establishing a Community code of oenological practices and processes.

TABLE 1 Transformation of absorbences to transmittances (T%) U.K.

Method of use U.K.

Find the first decimal figure of the absorbence in the first vertical column, and call its row R. Find the second decimal figure of the absorbence in the top horizontal row and call its column C. Read the figure in the box at the intersection of the row R and the column C. To calculate the transmittance, divide this figure by 10 if the absorbence is less than 1, by 100 if it lies between 1 and 2, and by 1 000 if it lies between 2 and 3.

Note: U.K.

The figure in the top right-hand corner of each box enables the third decimal figure of the absorbence to be taken into account by interpolation. U.K.

	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		832		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		8		7		8
4	398		389		380		371		363		355		347		339		331		324
		7		7		7		7		6		7		6		6		6		6
5	316		309		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		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: U.K.

Absorbence	0,47	1,47	2,47	3,47
T %	33,9	3,4	0,3	0

Transmittances T % are to be expressed to the nearest 0,1 %.

2. RECTIFIED CONCENTRATED MUSTS U.K.

2.1. Principle of the method U.K.

The absorbence of the rectified concentrated must is measured at 425 nm through a thickness of 1 cm after dilution to bring the sugar concentration to 25 % (m/m) (25° Brix).

2.2. Apparatus U.K.

2.2.1. Spectrophotometer enabling measurements to be made between 300 and 700 nm. U.K.

2.2.2. Glass cells with optical paths of 1 cm. U.K.

2.2.3. Membrane filter of pore diameter 0,45 µm. U.K.

2.3. Procedure U.K.

2.3.1. Preparation of the sample U.K.

Use the solution with a sugar concentration of 25 % (m/m) (25° Brix) prepared as described in the chapter ‘pH’, section 4.1.2. Filter is through a membrane filter of pore diameter 0,45 µm.

2.3.2. Determination of absorbence U.K.

Zero the absorbence scale at a wavelength of 425 nm using a cell with an optical path of 1 cm containing distilled water.

Measure the absorbence A at the same wavelength of the solution containing 25 % sugar (25° Brix) prepared as in 2.3.1 and placed in a cell with an optical path of 1 cm.

2.4. Expression of results U.K.

The absorbence at 425 nm of the rectified concentrated must in a solution with 25 % sugar (25° Brix) is quoted to two decimal places.

(1)

This distance must be given in a direction going from O to C.