ISI 37-1e Determination of Colour of Adjunct Syrup.


1. Scope The method is applicable to liquid adjuncts.

 

 LT 26/08/1999
2. Principle Spectrophotometric determination of colour.

 
3. Reagents 3.1 Kieselguhr

 
4. Apparatus 4.1 Spectrophotometer with 10 mm cells and adjustable to 430 nm +/-0.5 nm

4.2 Membrane filter holder and filters with pore size 0.45 micron

 
5. Procedure Dilute one part of sample with nine parts of distilled water. Dilution factor (f). Dilution factor (f) = 10.
Filter the diluted sample through a membrane filter. Clarify if necessary by adding one gram of Kieselguhr to one litre diluted sample and prefilter before membrane filtration. Filtration and clarification can be omitted if haze of the diluted sample is negligible. Negligible ~ less than 1 EBC unit
Wavelenght is set at 430 nm. Fill 10 mm cell with distilled water and set absorbance to read 0.00. Rinse and fill cell with diluted sample (or filtered diluted sample) and read absorbance (A).

 
6. Calculation Colour in EBC units (express result to two significant figures)
= A*f*25 = A*10*25;

 

 Use factor 50 in stead of 25 if a 5 mm cell has been used
7. Notes CRA (Corn Refiners Association) method E-16 is an alternative spectrophotometric method at 450 nm. The CRA colour can be transformed into RBU (Reference Bottlers Units) and into Lovibond values.

 
8. Reference European Brewery Convention (EBC) method 6.9

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