Hach-Lange DR 5000 brewerie analysis, supplementary software LZV570 - Manual (Page 23)

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Working procedures
5. Loosely close test tube with glass stopper to prevent
evaporation losses.
6. Heat for exactly 16 min in boiling water in a water bath, then
cool for 20 min in a water bath at 20 °C.
7. Add 5 ml dilution solution.
8. Measure the absorbance within 30 min in a 10 mm rectangular
cuvette at 570 nm against a blank value solution treated in the
same way (H
2
O + colour reagent).
9. Correction for dark worts and beers (perform three times).
a. Introduce 2 ml of the diluted sample into a test tube.
b. Add 1 ml H
2
O instead of the colour reagent, then proceed
as described above.
c. Measure against H
2
O after adding 5 ml dilution solution
Results
The results are expressed in mg/l without decimal places.
Accuracy
r = 17
R = 28
Standard values
Finished wort (12%): 200–250 mg/l
Beer (12%): 100–120 mg/l
About 220–250 mg/l free amino-nitrogen should be present in the
original wort to ensure satisfactory primary and secondary
fermentation.
Interferences
The amino acids are present in very small amounts, so
contamination must be avoided at all costs. The carefully cleaned
test tubes should only be touched on the outside. Ground-glass
stoppers, etc., should be picked up with forceps.
Literature
MEBAK Brautechnische Analysenmethoden
4th Edition 2002 Volume II, pp 62ff
Remark
The working procedure described below specifies that the blank
value solutions, standard solution and sample should be measured
three times without correction when light beer and wort are
analysed.
In the case of dark beers, the working procedure specifies that the
blank value solution, standard solution, correction and sample
should be measured three times.