Protein content is the measured proportion of protein in a food product, typically determined by the Kjeldahl or Dumas method and expressed as a percentage by weight on a dry or as-is basis, and is a key trading parameter for pulses, grains, oilseed meals and protein ingredients.
In trade practice
Suppliers declare protein content on the certificate of analysis, referencing the test method used, because Kjeldahl and Dumas can give slightly different results and buyers need to know which applies. For wheat flour, malting barley and pulse ingredients, protein content directly affects functionality and end-product performance, so buyers often specify a minimum value and require batch-level testing by an accredited laboratory. A common error is comparing results across methods without a conversion factor, or confusing crude protein with digestible protein for feed applications. Nutritional declarations on finished goods must also align with the tested value.
In a specification
A specification states protein content as a minimum percentage on a defined moisture basis, names the test method (Kjeldahl or Dumas) and references the applicable ISO or AOAC procedure.