This method describes how to determine the total nitrogen in malt.
Malt intended for use in beer brewing or elsewhere in the food industry.
Determination of the percentage of nitrogen that has dissolved in the wort during the Congress mash method
Suitable for (Congress) mash
The Kolbach index is used to express the quantity of the nitrogenous substances found in malt, which go into solution under the conditions present during the Congress mash method. It is a measure of the degree of proteolytic modification of the malt and also provides an indication for the quantity of proteolytic enzymes contained in the malt. The Kolbach index is less conclusive than other methods due to its dependence on the total nitrogen content and the provenance of the barley. Therefore, it must always be considered together with the total nitrogen content.
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.
Determination of nitrogenous compounds in beer and wort (crude protein) detectable using Kjeldahl digestion
This method is suitable for wort and beer.
Nitrogen determination according to Kjeldahl is divided into the following steps:
Digestion of the sample (oxidation of proteins to H2O, CO2 and NH3), during which the NH3 is carried over in (NH4)2SO4 using H2SO4
Distillation (distillation of NH3 over into a boric acid solution)
Titration (determination of the amount of NH3 present in the receiver after distillation) [1]
Automatic determination of total nitrogen using catalytic combustion in wort and beer.
This method is suitable for wort and beer.
The sample is burned in an oxygen-rich atmosphere at approximately 1000 °C, producing nitrous oxides, which are catalytically reduced to elemental nitrogen. Other combustion products are eliminated by means of selective absorption.
The elemental nitrogen is measured with a thermal conductivity detector, which has been calibrated using a known nitrogen standard.
These automatic combustion devices require a carrier gas, e.g., helium or carbon dioxide.
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