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Elemental analyzers



Learn about the Kjeldahl and Dumas methods for the determination of n/protein in various feed samples, a key parameter concerning quality control and protein declaration. Download the e-book with results on BIPEA proficiency testing samples and a comprehensive comparison of the two techniques.
As stated by international labeling regulations in the Food & Feed industry as well as research facilities, the calculation of the total protein content is key in relation to quality control and protein declaration.

For the determination of the protein content of food and feedstuff, two distinct primary methods have been broadly accepted within laboratory operations. These are Kjeldahl wet chemical method and Dumas high-temperature combustion method.

Protein determination in Feedstuff: Dumas or Kjeldahl method?

To determine the protein content, it is possible to analyze feedstuff samples according to the Dumas method and the Kjeldahl method. Both are primary methods working in accordance with international standards such as AOAC, AACC, ASBC, ISO, IFFO, OIV.

The Dumas method, developed in 1831, is older than the Kjeldahl, 1883, but more convenient in many aspects such as speed, safety, cleanliness, productivity, and cost per analysis. The problem in the past was that it was not easy to reproduce the conditions required by the Dumas method and for this reason, the Kjeldahl technique took the lead and became considered as the classical method for nitrogen/protein determination.

However, the Kjeldahl method uses concentrated sulfuric acid and a catalyst for the digestion of the sample. As stringent standards started being applied in the 1990s with regards to the use of harmful chemicals, many laboratories evalu­ated the Dumas method as an alternative. Numerous comparative studies were then developed, a series of international standards were devised, and also grain inspection services in the US, Canada, and Australia recognized the Dumas method.

Results obtained with the Dumas nitrogen determination are usually a little bit higher than with Kjeldahl since nitrogen compounds like nitrates, nitrites, and heterocyclic compounds are detected. In the Kjeldahl method, such compounds are converted into the ammonium ion incompletely or not at all. The opposite could also happen (rarely) because in this kind of analysis there are lots of variables that could influence the final result.

Download the E-book

Learn more about protein determination in various feed samples with the brand-new dedicated E-book. Read about N/Protein determination comparing the Dumas and Kjeldahl methods, discover all the related results and the VELP solutions.
Download the E-book on N/Protein Determination in Feed
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