Hach-Lange DR 5000 brewerie analysis, supplementary software LZV570 - Manual (Page 35)

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Working procedures
2.9 Thiobarbituric acid number (TAN)
The thiobarbituric acid number is a sum parameter for the thermal
effects on malt and wort. It is a parameter that, apart from
5-hydroxymethylfurfural (HMF), covers a large number of products
of the Maillard reaction and other organic compounds.
Principle
The test sample reacts with a solution of thiobarbituric acid and
acetic acid and the resulting yellow colour is measured with the
help of a spectrophotometer.
Fields of application
Beer, wort, congress wort or malt extract
Measuring range
0–100
Accessories
• Water bath (70 °C)
• Brown test tubes with ground-glass stoppers (20 ml or 25 ml)
• Spectrophotometer (448 nm)
• 10 mm rectangular cuvettes (OS grade)
Reagents
• Acetic acid (90%):
Dilute 225 g 100% acetic acid (glacial acetic acid) with H
2
O to
250 g.
• Thiobarbituric acid (0.02 mol/l):
Dissolve 0.288 g 2-thiobarbituric acid (M = 144.15 g/mol) in a
100 ml measuring flask with 90% acetic acid by heating in a
water bath. Cool to 20 °C then make up to the mark with 90%
acetic acid. Prepare freshly each day.
• Kieselguhr
Sample preparation
Note: The analysis procedure is empirical and should therefore be adhered
to exactly.
1. Clarify turbid test solutions by filtration over kieselguhr.
2. Dilution
• Dilute worts and beers 10-fold with H
2
O
• Dilute congress worts 5-fold with H
2
O
3. Blank value
a. Add 5 ml 90% acetic acid to 10 ml diluted sample, shake
and proceed as for the main value.