This method describes how the extract content of adjuncts is determined.
After gelatinization of the starch in the adjunct, the starch is liquefied and converted through the addition of malt. Subsequently, the extract content is determined according to the procedure given in the method for malt analysis.
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]
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
The nitrogen/raw protein content of barley intended for the production of brewing malt must be determined in advance.
The sample is combusted in a pure oxygen atmosphere at approx. 1000 °C. The resulting mix of gases comes into contact with a CuO/Pt catalyst and is thereby completely oxidized and subsequently freed of all by-products which could potentially interfere with analysis.
After the nitrogen oxides formed in the combustion process are reduced upon contact with tungsten, all nitrogen compounds in the sample are reduced to elemental nitrogen (N2). The elemental nitrogen is then detected by means of a thermal conductivity detector (TCD), the signal of which is quantitatively evaluated by a dedicated integrator.