Hach-Lange DR 5000 brewerie analysis, supplementary software LZV570 - Manual (Page 36)

36
Working procedures
4. Main value
a. Add 5 ml thiobarbituric acid to 10 ml diluted sample and
shake.
b. Place in a 70 °C water bath for 70 minutes (avoid direct
sunlight and ensure that, at most, the temperature in the
bath decreases only briefly by 1–2 °C when the test tubes
are introduced).
c. When the reaction time has elapsed, cool the test tubes
quickly to 20 °C (strongly flowing cold water or cooling
bath).
d. Measure the yellow colour immediately in 10 mm
rectangular cuvettes at 448 nm against H
2
O.
Results
Thiobarbituric acid number (TBN); dimensionless number
Standard values
Light finished wort < 45
Light cold wort (after wort cooling) < 60
Literature
MEBAK Brautechnische Analysenmethoden
4th Edition 2002 Volume II, pp 35ff
2.9.1 Procedure for measuring thiobarbituric acid number in beer and wort
1. Prepare samples and blank value solution as described in the
working procedure.
2. Select STORED PROGRAMS in the “Main Menu”. Select test
number 811 .
3. Insert zero value cuvette containing distilled water into the cell
compartment. Close the cell compartment. Touch ZERO .
4. Insert blank value cuvette (see sample preparation) into the cell
compartment. Close the cell compartment. Touch READ .
Display: E1.
5. Insert the sample cuvette containing the prepared sample into
the cell compartment. Close the cell compartment. Touch
READ . The result is displayed.