Applicable for all (laboratory) worts
Medium and high molecular weight proteins are precipitated by phosphomolybdic acid. The nitrogen is determined in the filtrate. Therefore, the results express the amount of low molecular weight proteins.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
Ammonium ions react at a pH of approx. 12.6 with hypochlorite ions and salicylate ions in the presence of sodium nitroprusside, which serves to catalyze the reaction, to form a green color (indophenol blue).
The nitrogen/raw protein content of malting barley intended for the production of malt for use in brewing must be determined in advance.
The determination of nitrogen content according to Kjeldahl is divided into the following steps:
a. Digestion of the sample (oxidation of substances H2O, CO2, NH3)
b. Distillation (distillation of NH3 over into a boric acid solution)
c. Titration (determination of the amount of NH3 present in the receiver after distillation)
a. Digestion → 2 NH3 + H2SO4 → (NH4)2SO4
b. (NH4)2SO4 + 2 NaOH → Na2SO4 + 2 NH3 + 2 H2O
3 NH3 + H3BO3 → (NH4)3BO3
c. 2 (NH4)3BO3 + 3 H2SO4 → 3 (NH4)2SO4 + 2 H3BO3
This method describes how to determine the total nitrogen in malt.
Malt intended for use in beer brewing or elsewhere in the food industry.
Suitable for Congress mash
Wort is produced according to the Congress mash method (fine grind), and then the nitrogen content of the wort is determined.
Suitable for Congress mash
The amount of soluble nitrogenous substances in Congress wort is determined using spectrophotometry at wavelengths of 215 and 225 nm.