9. Spectrometric determination
of the colour of beer
PRINCIPLE
The absorbance of beer is
measured at a wavelength of
430 nm. The colour in EBC (European
Brewery Convention) units is
obtained by multiplying the
absorbance by a factor.
EQUIPMENT
- SpektraTM
spectrophotometer,
- micropipette,
- blisters,
- membrane filters, pore
size 0.45 mm,
- membrane filter holder.
REAGENTS
PROCEDURE
Filter the beer sample through
a membrane filter. Dilute the
sample, e.g., 10x (only dark
beer), so that the transmittance
at 430 nm falls within the measuring
range.
Pipette 400 mL
of deionising-water/blank-solution
into the hollow of a blister.
Use the blue LED at its maximum
intensity and set the transmittance
for the blank to 100. Then pipette
400 mL
of the beer sample into the
next hollow of a blister and
read the transmittance. Calculate
the absorbance and evaluate
the colour of the beer sample.
CALCULATION
Colour (EBC units) = A x f
x 4 x 25 = A x f x 100
A = absorbance of
the sample
f = dilution
factor
A = - log T
T = transmittance
of the sample
EXPRESSION OF RESULTS
Beer regulations determine
that for all types of beer:
- Light beer up to 30
EBC units,
- dark beer higher than
30 EBC units.
Developed and prepared
by: Avrelija GOJKOVIČ KUMPERGER,
Živilska šola Maribor
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