OIV-MA-F1-08 Chromatic properties

Type IV method

 

1. Principle of the method

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

2. Apparatus

 

2.1.   Spectrophotometer enabling measurements to be made between 300  and 700 nm.

2.2.   Glass cells with optical paths of 1 cm.

2.3.   Membrane filter of pore diameter 0.45 μm.

3. Procedure

3.1.   Preparation of the sample

Use the solution with a sugar concentration of 25 % (m/m) (25° Brix) prepared as described in the chapter 'pH', section 4.1. Filter through a membrane filter of pore diameter 0.45 μm.

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

Measure the absorbance A at the same wavelength of the solution containing 25 % sugar (25° Brix) prepared as in 3.1 and placed in a cell with an optical path of 1 cm.

4. Expression of results

 

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

Repeatability (r)

• r =  0.01 AU at 25°Brix