Hach-Lange DR 5000 brewerie analysis, supplementary software LZV570 - Manual (Page 16)

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Working procedures
2. After the carbon dioxide has been expelled, pipette 10 ml beer
into a test tube with a glass stopper, then tilt the tube slightly
and add 0.25 ml 0.005M DPI solution.
3. Close the test tube immediately and invert it twice to mix the
contents, starting the stopwatch after the first inversion.
4. Immediately fill a 10 mm rectangular cuvette with the mixture.
60 sec after adding the reagent, measure the absorbance at
520 nm against a blank value solution (decarbonated beer
without added reagent).
Results
The results are expressed as the proportion of the DPI-amount
(in %) that was reduced by 10 ml beer in 60 sec.
Accuracy
V
cr
= ± 1%
Standard values
> 60 very good
50–60 good
45–50 satisfactory
< 45 poor
Literature
MEBAK Brautechnische Analysenmethoden
4th Edition 2002 Volume II, pp 104ff
2.3.1 Procedure for measuring reducing power
1. Prepare samples as described in the working procedure.
2. Select STORED PROGRAMS in the “Main Menu”. Select test
number 804 .
3. Insert blank value cuvette (see sample preparation) into the cell
compartment. Close the cell compartment. Touch ZERO .
4. Insert the sample cuvette containing the prepared sample into
the cell compartment and close the cell compartment. After 60
sec touch
READ . The result is displayed.