Not All Nitrogen Is Protein: Rethinking Protein Analysis in Complex Matrices

Protein content is often estimated by measuring total nitrogen and applying a conversion factor to calculate crude protein. While this approach is well established, it assumes that all nitrogen in a sample comes from nutritionally available protein, which is not always true.

This learning lab looks at cases where nitrogen-based protein determination can overestimate usable protein, particularly in complex matrices such as insect-derived ingredients and processed feed materials. Common sources of non-protein nitrogen, including chitin, are discussed, along with how they influence protein interpretation. The role of Kjeldahl and Dumas methods is reviewed, and practical approaches for improving the interpretation of protein results are presented.