Hach-Lange LZV936 - DR 6000 Brewery Analysis software - Handbuch (Seite 28)

English 28
Procedure for bitter units
1. Prepare the blank value and the samples according to the work
procedure.
2. Select STORED PROGRAMS > SELECT BY NUMBER.
3. Enter the number 2001 for the program "Beer bitter units". Confirm
with OK.
Enter the number 2003 for the program "Wort bitter units". Confirm
with OK.
4. Press START to start the program.
5. Enter the blank value (see sample preparation) and press ZERO.
6. Insert the analysis cuvette with the prepared iso-octane and press
READ.
The result is shown on the display.
Note: In order to analyze further samples, repeat the procedure
from step 6.
Total polyphenols (EBC method)
Principle
Polyphenols react with iron(III) ions in alkali solution under formation of
colored iron complexes; the ensuing brownish coloring is measured
spectrophotometrically.
Application area
Beer, worts
Measurement range
0–800 mg/L
Accessories
• Centrifuge
• Spectrophotometer, 600 nm
• 10 mm rectangular cuvette OS
Reagents
• Carboxymethylcellulose-ethylenediaminetetraacetic acid solution
(CMC-EDTA-Na):
a. Weigh out 10 g CMC (low-viscosity) and 2 g EDTA-Na
2
b. Dissolve the substances by stirring in approximately 500 mL
H
2
0, after complete dissolution fill with H
2
0 to 1 L, if necessary,
clear through centrifuging.
• Ammonium iron(III) citrate, 3.5%:
a. Dissolve3.5 g ammonium iron(III) citrate, green (16 % Fe) in
H
2
0 to 100 mL; the solution must be completely clear and can
be stored for approximately 1 week
b. Ammonia, diluted: dilute
1 part concentrated ammonia (d = 0.91) with 2 parts H
2
0
Sample preparation
1. Remove carbon dioxide from the beer by shaking.
2. Clear the cloudy wort or beers through centrifuging.
3. Measure out 10 mL sample + 8 mL CMC-EDTA solution into a
25 mL volumetric flask and mix thoroughly.
4. Add 0.5 mL iron(III) solution and mix thoroughly.
5. Add 0.5 mL diluted ammonia solution and mix thoroughly.
6. Fill with H
2
0 to 25 mL and mix thoroughly.
7. Measure the extinction after 10 min in a 10 mm rectangular
cuvette at 600 nm against a blank value.
8. Production of the blank value
a. Measure out 10 mL of sample (remove carbon dioxide in the
beer with shaking, remove cloudiness of wort or beer with
centrifuging) into a 25 mL volumetric flask.
b. Add 8 mL CMC-EDTA solution and mix thoroughly.
c. Add 0.5 mL diluted ammonia solution and mix thoroughly.
d. Fill with H
2
0 to 25 mL and mix thoroughly.
Note: Mix the solution thoroughly after the addition of each individual
reagent..