Non-Protein Nitrogen Infographic
What is it?
Protein analysis is typically based on a Nitrogen analysis and assumed factors to calculate protein. Since proteins are not the only source of Nitrogen, Protein analysis can be falsely inflated by a variety of ingredients and other food components. This group of materials are classified as Non-Protein Nitrogen (NPN).
NPN Examples
- Free Amino Acids
- Dietary Ingredients: Creatine, Caffeine, Choline, Carnitine
- Metabolites: Ammonia, Urea, Nucleotides, Amines
- Amino Sugars: Glucosamine, Chitin, Chondroitin
Corrected Protein Calculation
Eurofins can analyze for NPN and calculate a corrected protein value.
Options:
Individual Source Analysis
- Directly measures compounds like caffeine, creatine, and free amino acids
- Calculates nitrogen contribution from each source
- Recalculates protein nitrogen after subtracting NPN
Direct NPN Analysis
- Uses TCA to separate precipitating proteins from soluble NPN
- Measures nitrogen in the soluble fraction (includes amino acids and small peptides)
- Note: Inclusion of small peptides in NPN is not a precisely defined peptide length.
Amino Acid-Based Protein Analysis
- Sums bound amino acids (as dehydrate form) to calculate protein
- Excludes various NPN bias, offering a more direct protein estimate
- Free amino acid and small peptides are included unless specifically excluded
Economic Adulteration
NPN may also be important for economic adulteration surveillance. One of the most consequential instances of food fraud was the widespread use of melamine to boost apparent protein content in milk powder and other products. Measurement for NPN is one way to identify possible fraud in foods with protein claims.
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