Hach-Lange LZV936 - DR 6000 Brewery Analysis software Benutzerhandbuch
Seite 40
English 40
2.
Dilution
•
Dilute worts and beers 10 times with dist. H
2
O.
•
Dilute congress worts 5 times with dist. H
2
O.
3.
Empty value
a.
Displace 10 mL of the diluted sample with 5 mL 90 % acetic
acid, shake and proceed as for the main value.
4.
Main value
a.
Displace 10 mL of the diluted sample with 5 mL thiobarbituric
acid and shake.
b.
Place in a water bath of 70 °C for 70 min (158 °F) (avoid direct
sunlight, make sure that when positioning the reagent flasks
the temperature in the bath only temporarily sinks by 1–2 °).
c.
After elapse of the reaction time quickly cool down reagent
flasks to 20 °C (68 °F) (fast-flowing cold water or cold bath).
d.
Measure yellow coloration immediately in a 10 mm
rectangular cuvette at 448 nm against dist. H
2
O.
Results specifications
Thiobarbituric acid number (TAN), dimensionless number
Standard values
Light cast wort < 45
Light cold wort (after wort cooling) < 60
Literature
MEBAK brew-technical analysis methods, 4th edition 2002, Volume II, P.
35 et seq
Procedure for thiobarbituric acid number in beer/wort and
congress wort
1.
Prepare the zero solution, empty values and samples in
accordance with the work procedure.
2.
Select STORED PROGRAMS > SELECT BY NUMBER.
3.
Enter the number 2011 for the program "TAN C-wort". Confirm with
OK.
Enter the number 2012 for the program "TAN beer/wort". Confirm
with OK.
4.
Press START to start the program.
5.
Enter the zero solution (dist. H
2
O) and press ZERO.
Z1 is shown on the display.
6.
Insert the empty value cuvette (see sample preparation) and press
READ.
R1 is shown on the display.
7.
Insert the analysis cuvette with the prepared sample and press
READ.
The result is shown on the display.
Note: In order to analyze further samples, repeat the procedure
from step 6.
Iso-
and acids
Principle
Bitters are extracted with iso-octane from the acidified sample and
certain disruptive substances removed through washing of the extract
with acidic methanol. The concentration of iso-
acids and acids is
determined through measuring of the extinction in alkali methanol at
255 nm and 360 nm.
Application area
Beer, wort
Measurement range
0–60 mg/L