Kjeldhal method

Pork fat contains more unsaturated fatty acids than beef and its linoleic acid content is double that in beef. Heat produced volatiles in red meat fats are listed in Table IV. The presence of pyrazines in the volatiles of beef fat is due to the presence of nitrogenous compounds in the fat amounting to 0.1-0.2%N, (Kjeldhal method). These compounds might be proteins, peptides, amino acids, and amine moities in polar lipids. Such compounds... 

The determination of nitrogen by the Kjeldhal method includes a preliminary distillation of the sample. Protein content can be estimated using these methods as can the determination of ammoniacal and total nitrogen in various samples including fertilizers. 

Figure 20.27 (a) FTIR spectra of acrylonitrile butadiene rubber (film casting) (b) Correlation graph of acrylonitrile content from Kjeldhal method and FTIR. Reproduced with permission fron Ref [108] 2007, Elsevier. 

At several occasions the soil in which the grass was cultivated was fertilised with large amounts of nitrates (ca. 180 kg ha ) up to one month before the harvest. As a consequence, the nitrate content of the material is high (approx. 3 g kg ) which is the reason for the difference between results of Kjeldhal-N and total-N determinations. The Kjeldahl method does not reduce nitrates at low temperatures, so the results of the total-N determinations are therefore significantly higher. For this reason, it was decided to certify both the total-N content and the Kjeldahl-N content as the latter is of great importance for the practical use of the material (Kjeldahl-N can in principle be bio-converted in the living body into protein). 

Determination of nitrogen in coal sample (Kjeldhal Gunning method)... 

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