Kjeldahl nitrogen analysis as a reference method for protein determinationin dairy products

Measurement of total nitrogen by Kjeldahl analysis is the historical refere nce method for determination of the protein content of dairy products and i s used for both calibration and validation of alternative methods for prote in determination. Accurate evaluation of alternative methods is not possibl e if there is large uncertainty regarding the reference values. When Kjelda hl analysis is used to establish reference values, the performance of the K jeldahl testing must be verified and within established expectations. Advic e is given for Kjeldahl system optimization, evaluation of test results, an d troubleshooting. Techniques for successful Kjeldahl nitrogen analysis of dairy products other than milk are discussed.