The following nitrogenous substances are found in wort and beer:
Amino acids, peptides, proteins, nucleic acids and their derivates, ammonium salts, nitrates, heterocyclic compounds as well as aliphatic and aromatic amines. In practical applications, amino acids, peptides, proteins and ammonium salts are of particular interest. The amino acids and ammonium salts are the most important sources of nitrogen for the yeast. They shape to a large extent which fermentation by-products are created through yeast metabolism and at which concentrations. The medium and high molecular weight proteinaceous compounds (peptides, proteins) are especially significant for the colloidal stability (shelf life), mouthfeel and for foam stability. For this reason, it is necessary to measure not only the total amount of protein but also the relative amounts of each of the proteinaceous compounds in wort and beer.
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.