Bulletin of the IDF N° 459/ 2012: Collaborative Study on the Kjeldahl Reference Method for Nitrogen Determination of Dried Dairy Products according to ISO 8968-1/2 | IDF 20-1/2
|published date||24 March 2012|
|reference||Bulletin of the IDF No. 459/2012|
Results of an international collaborative study conducted to establish precision figures for the determination of Kjeldahl nitrogen in milk powders, milk protein concentrate, whey protein concentrate, casein, caseinate and infant formulas in order to extend the scope of ISO 8968-1/2│IDF 20-1/2. Twenty eight powder samples, with a range of crude protein content, varying between 11.7 and 92.4%(m/m), were prepared and dispatched to the participating laboratories as blind duplicates. The report gives details of the techniques required to optimize digestion procedures to obtain the maximum nitrogen result for each sample type. The statistical analysis of the results gave a repeatability value, r, of 0.7% of the mean result and a reproducibility value, R, of 1.3% of the result obtained.
Keywords: Kjeldahl nitrogen, milk powders, milk protein concentrate, whey protein concentrate, casein, caseinate, infant formula, interlaboratory study, repeatability