Determination of low-molecular weight nitrogenous compounds in wort and beer (< 2600 Da) by means of molybdate precipitation
This method is suitable for wort and beer.
Determination of low-molecular weight nitrogenous compounds in wort and beer (< 2600 Da) after precipitating the high and middle-molecular weight nitrogenous compounds with molybdate
The nitrogen content in the filtrate is determined using Kjeldahl or Dumas.
Precipitation with phosphomolybdic acid provides information regarding the medium molecular weight nitrogenous substances present in samples of wort and beer. Nitrogenous substances with a molecular weight greater than 2600 Da are precipitated [1]. However, a quantitative elimination of all nitrogenous substances of an equivalent molecular weight does not occur, which indicates specificity toward certain nitrogenous substances.
Nitrogenous substances of a medium molecular weight can be calculated as the difference between the nitrogenous substances precipitated with molybdic acid and those precipitated with magnesium sulfate [2, 3].
The reagent phosphomolybdic acid itself is not necessary for the analysis; a solution of sodium molybdate is sufficient. Through the addition of sulfuric acid, enough phosphoric acid is released from the phosphates present in wort and beer to form phosphomolybdic acid.
The method describes how to determine the phosphate content of water photometrically with a cuvette test.
Phosphate ions form a yellow color in the presence of the molybdovanadate reagent. The color is determined using a photometer.
Water intended for use as an ingredient in the production of beer (brewing liquor) or other foods
In an acidic solution, in the presence of ammonium molybdate, dissolved silicic acid or silicates produce silicomolybdic acid which exhibits a yellow color. After the addition of a reducing agent, a blue color emerges which is proportional to the quantity of the silicic acid present in a certain concentration range.