The procedure determines nitrogen and proteins in organic material. With the Kjeldahl process, the boiling point of sulfuric acid of 337 degrees Celsius is increased with the aid of catalysts. About 380 degrees is the optimum digestion temperature for organic material in sulfuric acid. The protein content is determined by multiplying the analytically determined nitrogen content with factor 6.25, for wheat, and flour with factor 5.7. With the Kjeldahl process, the nitrogen content is determined in 4 stages.

Fibers are an important element of human nutrition and are directly connected with the natural components of foodstuff. Basically, the term refers to a group of fundamental food components that enter the stomach and small intestines undigested and reach the colon nearly unaltered. Fibers are comprised of indigestible plant parts and consist mainly of various types of starch-free polysaccharides (NSP) and lignin.

Crude fiber is the portion of feed, which remains after treatment with acids, alkalies and solvents as indigestible constituent. The main component of crude fiber is cellulose.