Hach-Lange LZV936 - DR 6000 Brewery Analysis software - Handbuch (Seite 27)

English 27
Work procedures
Bitter units (EBC method)
Principle
Bitter substances, mainly iso-  acids, are extracted with iso-octane from
the acidified sample and the concentration in the extract is determined
spectrophotometrically.
Application area
Beer, worts
Measurement range
10–40 bitter units (beer)
20–60 bitter units (wort)
Accessories
• Centrifuge glasses with solvent-proof seals, 35 mL
• Glass beads
• Shaking machine
• Centrifuge, 3000 rpm
• Spectrophotometer, 275 nm
• 10 mm rectangular cuvette QS
Reagents
• Hydrochloric acid, 6N
• Iso-octane (2,2,4-trimethylpentane), spectroscopic pure (extinction
measured in 10 mm rectangular cuvette QS at 275 nm against dist.
H
2
O <0.010) (e.g. Uvasol)
Sample preparation
1. Separate wort and cloudy beer through centrifuging at 3000 rpm
for 15 min (do not filter sample)
2. Remove carbon dioxide from the beer without removing any foam.
3. Pipette 10 mL (or 5 mL wort + 5 mL dist. H
2
O) of the sample
maintained at 20 °C (68 °F) into a centrifuge glass.
4. Add 0.5 mL 6N hydrochloric acid, 20 mL iso-octane and
three glass beads.
5. Seal the centrifuge glass and leave to shake mechanically for
15 min at 20 °C (68 °F).
6. Centrifuge for 3 min at 3000 rpm.
7. Measure the extinction of the iso-octane extract in 10 mm
rectangular cuvette at 275 nm against iso-octane of the same
quality (blank value).
Results specifications
Bitter units (BU) without decimals
Accuracy
r = -0.36 + 0.05 m
R = 0.72 + 0.14 m
Standard values
Beer: 10–40 BU, depending on nature, sort, type and origin
Wort: 20–60 BU, depending on beer and bitters yield
Literature
MEBAK brew-technical analysis methods
4th edition 2002, Volume II, P. 114 et seq