Appendix 3: Calculation of Free Amino Nitrogen Contents of Wort and Malt

Calculation of nitrogen contents of worts of different gravities.

1 Measure the free ammo nitrogen level in the Institute of Brewing malt wort.
2 Ascertain from tables (reference 1 below) the appropriate concentration of soluble extract in gm per 100 ml at 20° C for the Institute of Brewing wort and for the defined wort.
3 Calculation:
If A = free amino nitrogen (mgs per litre) in Institute of Brewing wort
C1 = soluble extract in gms per 100 ml at 20° C for Institute of Brewing wort
C2 =soluble extract in gms per 100 ml at 20° C for the defined wort

then

Free amino nitrogen (mgs per litre) at the defined gravity

Notes
• The calculation can be simplified by taking C1 and C2 = excess gravity of the Institute of Brewing wort and defined wort respectively.
• The same equation can be used to calculate total soluble nitrogen in wort.

Calculation of free amino nitrogen content as dry basis in malt

A x 0·5065 = mgs free amino nitrogen in 50 gms malt as is

or

mgs free amino nitrogen in gms malt dry basis

where M = moisture content %

% free amino nitrogen in dry malt

Calculation of free amino nitrogen in total soluble nitrogen

% free amino nitrogen in total soluble nitrogen

where T = total soluble nitrogen in malt, dry basis.

Note
The factor 0·5065 has been derived assuming that the volume of spent grains in a 515 mls mash is 8·5 mls. Currently, when calculating total soluble nitrogen the volume of spent grain is taken to be 15 mls. The error involved is not considered to be significant. This anomoly has been brought to the attention of The Institute of Brewing Analysis Committee.

Reference
Goldiner, F., Klemann, H., and Kampf, W. Rohrzucker, Alcohol, Stammewurke and Korrektionstafel, 1966 Institute for Garungsgewerbe, Seestrasse 13, D-l, Berlin N65, Germany.