Hach-Lange DR 5000 brewerie analysis, supplementary software LZV570 - Manual (Page 9)

9
Section 2 Working procedures
2.1 Bitter units (EBC method)
Principle
The bitter substances, mainly iso-a-acids, are extracted from the
acidified sample with iso-octane and the concentration in the
extract is determined with a spectrophotometer.
Fields of application
Beer, worts
Measuring range
10–40 BU (beer)
20–60 BU (wort)
Accessories
• Centrifuge tubes with solvent-tight stoppers (35 ml)
• Glass beads
• Shaker
• Centrifuge (3000 rpm)
• Spectrophotometer (275 nm)
• 10 mm rectangular cuvette (QS grade)
Reagents
• Hydrochloric acid, 6N
• Iso-octane (2,2,4-trimethylpentane), spectroscopically pure
(absorbance measured in 10 mm rectangular cuvette (QS
grade) at 275 nm against H
2
O < 0.010) (for example Uvasol)
Sample preparation
1. Clarify wort and cloudy beer by centrifuging at 3000 rpm for
15 min (do not filter sample).
2. Expel carbon dioxide from sample without losing any foam.
3. Bring the sample to 20 °C and pipette 10 ml (5 ml wort + 5 ml
dist. H
2
O) into a centrifuge tube.
4. Add 0.5 ml 6N hydrochloric acid, 20 ml iso-octane and 3 glass
beads.
5. Close centrifuge tube and shake mechanically for 15 min at
20 °C.
6. Centrifuge for 3 min at 3000 rpm.
7. Measure the absorbance of the iso-octane extract in a 10 mm
rectangular cuvette at 275 nm against iso-octane of the same
quality (blank value).