Hach-Lange LZV936 - DR 6000 Brewery Analysis software - Handbuch (Seite 36)

English 36
8. Insert the correction cuvette (see sample preparation) and press
READ.
R7 is shown on the display.
Note: Proceed similarly with the correction cuvettes 2 and 3. R8 or
R9 will be shown on the display.
9. Insert the analysis cuvette with the prepared sample and press
READ.
R10 is shown on the display.
Note: Proceed similarly with the analysis cuvettes 2 and 3. R11 or
the result will be shown on the display.
The FAN result is shown in mg/L.
Note: In order to analyze further samples, repeat the procedure
from step 9.
Steam-volatile phenols
The degree of smoking of whiskey malts is determined through the
measurement of steam-volatile phenols. For beer production smoke
malts are required only in small quantities for smoked beers, a
Franconian specialty. Technical malfunctions during the drying process
can however cause the malts, which for normal beers are used for
processing, to demonstrate a smoky taste. The smoky taste can be
detected by customers in beers that should not have that taste.
Next to the organoleptic test, the spectrophotometric determination of
the steam-volatile phenols has proved the best method to establish
which malt delivery produces the undesirable smoke taste, and to what
extent this effects tank or bottled beers.
Principle
The phenol fraction extracted through steam is transformed with 4-
amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one (4-aminophenazone) in
the alkali environment and under the oxidation effect of potassium
hexacyanoferrate(III) into a pigment, which can be measured after
chloroform extraction spectrophotometrically.
Application areas
Malt, beer
Measurement range
0–20 mg/kg
Comments
Wheat beers cannot be analyzed using this method because, due to the
activity of the top-fermented yeast, they contain a high quantity of
steam-volatile phenols but no smoke flavor.
Accessories
• DLFU mill, mill gap 1 mm
• Steam distillation unit
• Separatory funnel, 1 L
• Spectrophotometer, 460 nm
• 40 mm rectangular cuvette OS
Reagents
• Chloroform, high purity
• Silicone anti-foam emulsion
• Phosphoric acid, concentrated (d=1.71)
• Copper sulfate, CuSO
4
x 5 H
2
O, 10 %
• Ammonium chloride, 5 %
• 4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one, 2 %: prepare
fresh daily
• Potassium hexacyanoferrate(III), K
3
[Fe(CN)
6
], 8 %: prepare fresh
daily