This method describes how the protein content in malting barley is determined. Protein plays an essential role in the production of beer. Barley with a high protein content is more difficult to malt and leads to greater malting losses. Barley with a low amount of protein is preferable, especially for beers light in color. As the protein content of barley increases, its extract content decreases.As the protein content of barley increases, its extract content decreases. This method is also suitable for malting wheat.
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