Chromatic properties (Type-IV)
OIV-MA-F1-08 Chromatic properties
Type IV method
- 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)
- 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.
- 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.
3.2. Determination of absorbance
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.
- 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