Among the elements that make up the structure of foods, those containing nitrogen are called protein. Protein is derived from the Greek word meaning of primary importance. Proteins are of primary importance in human nutrition. The proteins in the body of living things have very different properties. There are different proteins in different organs in the same organism. Proteins are compounds with large molecules that come together with the building blocks of amino acids. Uncountable proteins are synthesized in nature with different combinations of 22 amino acids. In nature, only plants can form proteins from inorganic substances. Plants add nitrogenous compounds from the soil to carbohydrates during photosynthesis and form amino acids, ie proteins. In this way, nitrogen enters the food chain.

Nitrogen gas is present in the air up to 80 percent. However, the atoms of nitrogen molecules in the air are very tightly bonded to each other and do not react easily. Therefore, this gas must somehow be transformed into the form that can be used by living things and must be returned to the air in a cycle so that it is not consumed by living things. Plants cannot absorb nitrogen in this way. Nitrogen needs to be transformed into plants that can be used by plants, but must return to air in a cycle before it is consumed. Bacteria do this largely.

The amount of nitrogen present in the protein is 16 percent. Therefore, the amount of protein in foods is calculated over nitrogen. The percent 22 of the human body is proteins, ie proteins are the most found substance in the body after water.

With the Kjeldahl method, all nitrogen-containing compounds that are not in protein form can be detected as proteins. This method is called crude protein determination. This method, which is mostly used in chemical analysis of feeds, calculates the actual protein and the amount of nitrogen-containing substances such as ammonia, aminoacids and nitrates using a constant multiplier of the amount of nitrogen.

Protein and crude protein determination studies are carried out in authorized laboratories. In these studies, standards and analysis methods published in our country and in foreign countries are complied with.