Protein by Kjeldahl Method

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Price of the test:

$100 per analysis

Acceptable Matrices:

Virtually all foods and food products

Limit of Detection:

0.14% Nitrogen

Sample Size Requirements:

20 grams


Protein (Kjeldahl) digestion unit and glassware. Automated titration using pH electrode

Reportable Units:


Turn Around Time:

15 Business Days

Is Rush Available?


Method Reference:

AOAC 2001.01 and 984.13; AACC 46-11A

Method Description:

The sample is digested in hot sulfuric acid in the presence of a copper catalyst. As a result, all nitrogen-containing compounds are converted to ammonium salts. The resulting ammonia from the digestate is steam-distilled under caustic conditions. The distillate is captured in a buffered solution and titrated to a pH 5.3 endpoint with hydrochloric acid. Protein is then calculated from the nitrogen content using a published conversion factor (e.g. 5.70 for wheat, 6.25 for most foods, etc.).

Additional Information:

Available Protein Factors:
6.25 - general purpose food products/ingredients (Default) except as noted below
6.26 – All cereal grains and oilseeds except wheat
5.70 – wheat, wheat flour, and wheat flour breads
6.38 - dairy
5.46 - peanuts and brazil nuts
5.18 - almonds
5.30 – Other tree nuts coconuts (butternuts, cashews, chestnuts, hazelnuts, hickory nuts, pistachios, walnuts, pecans.)