Why Kjeldahl method is not accurate in determining protein content in food?

It should be noted that different foodstuffs require the use of different conversion factors. The method slightly overestimates the true protein content because nonprotein nitrogen is included in the total nitrogen result.

What is the basis of quantitation of proteins using the Kjeldahl method?

In the Kjeldahl method, the nitrogen is released into a strong acid and the content is measured after neutralization and titration. In the Dumas method, the nitrogen is liberated in a gaseous form and is determined with a thermal conductivity detector, after removal of carbon dioxide and water aerosols.

How do you measure nitrogen content in proteins?

On the basis of early determinations, the average nitrogen (N) content of proteins was found to be about 16 percent, which led to use of the calculation N x 6.25 (1/0.16 = 6.25) to convert nitrogen content into protein content.

Which method is best for protein estimation?

Top 5 Protein Quantification Assays

  • Bicinchoninic Acid (BCA) This colorimetric, two-step assay was originally developed in 1985 – making it a baby compared with the 64-year-old Lowry assay!
  • Bradford.
  • Folin-Lowry.
  • Kjeldahl.
  • Ultraviolet Absorption.

What are the limitations of Kjeldahl method?

Limitations of Kjeldahl Method This method measures only nitrogen bound to organic components (proteins, amino acids, nucleic acids) and ammonium in the sample. This method is not suitable for compounds containing nitrogen in azo and nitro groups or in rings (quinoline, pyridine, nitrate, and nitrite, etc).

How do you measure Kjeldahl nitrogen?

Total Nitrogen is defined as the sum of organic nitrogen, nitrate, nitrite, and ammonia:

  1. Total N = Organic N + NO 3 –-N + NO 2 –-N + NH 3-N. N = Nitrogen.
  2. Total N = TKN + NO 3 –-N + NO 2 –-N. The Hach s-TKN Method.
  3. s-TKN = Total N – (NO 3 –-N + NO 2 –-N)