Define Quantitative or Analytical Method for Estimation of Nitrogen and Protein?

You may recall reading earlier that proteins contain nitrogen along with carbon, hydrogen and some other substances. Nitrogen (N) in food not only comes from amino acids in protein but also exists in additional forms that may or may not be used as a part of the total nitrogen economy of humans and animals. Thus, determination of nitrogen is commonly used to determine the protein content of a sample. Total nitrogen, which is determined by the Kjeldahl procedure, is converted to crude protein by a factor of 6.25, as mentioned earlier. Thus, the conventional measure of "protein" or "crude protein" in foods is N x 6.25, and it is recommended that this one factor be used in nutritional studies in which whole diets contain more than one source of, nitrogen. The Kjeldahl's method is commonly used in estimation of protein content of foods and has been extensively used for protein estimation of various foodstuffs. Although over a period of time many other methods have emerged for determination of organic nitrogen, this method still remains an old favourite because it is reliable and has very well standardized procedures.