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Nitrogen determination according to Kjeldahl is divided into the following steps:

1. Digestion of the sample (oxidation of proteins to H₂O, CO₂ and NH₃), during which the NH₃ is carried over in (NH₄)₂SO₄ using H₂SO₄

2. Distillation (distillation of NH₃ over into a boric acid solution)

3. Titration (determination of the amount of NH₃ present in the receiver after distillation) [1]

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.

Determination of FAN content by photometrically measuring the color intensity of Ruhemann's purple from the ninhydrin reaction.

The ninhydrin reaction is the best known of the color reactions in amino acid chemistry [1]. Ninhydrin is an oxidant and brings about the oxidative decarboxylation of amino acids, producing CO₂, NH₃ and the formation of an aldehyde. The aldehyde produced in this reaction possesses one less carbon atom than the original amino acid that served as the reactant. Reduced ninhydrin then reacts with non-reduced ninhydrin and the NH3 that was liberated to generate a blue pigment (all amino acids except for proline) or in the case of proline, a yellow pigment. Fructose also takes part in the color reaction as a reducing compound. Potassium iodide present in the solution used for dilution preserves the ninhydrin in an oxidized state and thus inhibits undesirable secondary reactions. The solution to be analyzed is heated together with ninhydrin at a pH of 6.7 and the resulting color is measured at 570 nm [3].

This method quantifies amino acids, ammonia and also the terminal α-amino groups of the peptides and proteins. Proline is also measured in part at the wavelength employed in this method.

The method is non-specific for α-amino nitrogen, because γ-amino butyric acid found in wort also generates a color reaction in the presence of ninhydrin. 

Yeast (16 g/100 ml) is added to (boiled) wort or beer in an Erlenmeyer flask and allowed to ferment completely in approx. 7 h under constant agitation. The limit of attenuation is calculated from the difference between the extract content prior to (original gravity) and after fermentation. [1, 2, 3]

Yeast is added to (boiled) wort or beer in an Erlenmeyer flask and allowed to ferment completely under constant agitation. The limit of attenuation is calculated from the difference between the extract content prior to (original gravity) and after fermentation. [1, 2]

The degree of turbidity present in a beer sample can be compared to a clear beer of the same brand and style to which EBC formazin standard solution has been added to produce haze in the beer. The degree of turbidity can be determined through visual comparison of the two beers.