Hach-Lange DR 5000 brewerie analysis, supplementary software LZV570 - Manual (Page 43)

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Working procedures
5. Pipette 10 ml of the mixed distillate into each of two 50 ml
Erlenmeyer flasks (main value solution, blank value solution).
6. Blank value solution
• Add 2.5 ml 4N hydrochloric acid.
7. Main value solution
• Add 0.5 ml 1,2-phenylenediamine solution, mix and allow
to stand in a dark place for 30 min.
• Then add 2 ml 4N hydrochloric acid.
8. Within 20 min, measure the absorbance of the main value
solution against the blank value solution at 335 nm in 20 mm
rectangular cuvettes.
Results
The result is expressed in mg/kg to two decimal places.
Accuracy
SD = ± 0.01
Required value
For light “Vollbier” (beer with a high original gravity) < 0.15 mg/kg.
Remarks
If series of analyses are carried out, the apparatus need not be
cleaned or rinsed between the individual determinations but can be
refilled immediately with beer after it has automatically emptied.
After a series of distillations the adhering residues should be
removed with sodium hydroxide solution or some other suitable
cleaning agent.
Any acetohydroxy acids that are present in beer after the filling
stage are oxidised to diketones in the presence of O
2
. Before the
actual analysis the beer sample can be thermostated at 70 °C for
1.5 hours for the purpose of analysing the total diketone content.
Literature
MEBAK Brautechnische Analysenmethoden
4th Edition 2002 Volume II, pp 134ff