ISI 37-1e Determination of Colour of Adjunct Syrup.
| 1. Scope |
The method is applicable to liquid adjuncts.
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LT 26/08/1999 |
| 2. Principle |
Spectrophotometric determination of colour.
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| 3. Reagents |
3.1 Kieselguhr
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| 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
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| 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 | |
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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).
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| 6. Calculation |
Colour in EBC units (express result to two significant figures) = A*f*25 = A*10*25;
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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.
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| 8. Reference | European Brewery Convention (EBC) method 6.9 |
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